.. oc 'S 101. 20 •l./ . ' 4-21 ···~ FM.s.24-21r -----:--------- DEPARTMENT OF THE ARMY FIELD MANUAL FIELD RADIO ,~ :RELAY TECHNIQUES HEAD'QUARTERS, DEPARTMENT OF THE ARMY . DECEMBER. 1966 SUNY Al bUt·H\LO TAGO 6864C ~ · THE LIBRARY * FM 24-21 FIELD MANUAL } HEADQUARTERSDEPARTMENT OF THE ARMY No. 24-21 WASHINGTON, D.C., 23 December 1966 FIELD RADIO RELAY TECHNIQUES Paragraph Page 1-5 3 CHAPTER 1. INTRODUCTION--------- 2. RADIO RELAY SYSTEMS Introduction________________ 6,7 5Section I. Methods of operation________ 8-10 8 II. Systems____________________ 11, 12 11 III. CHAPTER 3. EMPLOYMENT OF RADIO RELAY SYSTEMS Tactical applications ________ 13-16 19 Section I. II. Typical use in area-typewide-front situations______ 17,18 26 CHAPTER 4. SYSTEM PLANNING Introduction________________ 19-22 31 Section I. Siting techniques_____________ 23-28 34 II. III. Computing radio relay paths_ 29-34 40 IV. System reliability~----------35-37 51 CHAPTER 5. RADIO FREQUENCY -.,, MANAGEMENT AND 6-SELECTION Section I. Frequency management _____ 38-45 58 II. Frequency selection_________ 46-51 65 CHAPTER 6. SYSTEM OPERATINGTECHNIQUES Introduction________________ 52-54 84 Section I. System lineup______________ 55-60 85 II. III. Noise and interference_______ 61-63 89 *This manual supersedes FM 11-8, 22 August 1957. AGO 63640 SUNY Al buH-t-1L\J 1 THE LIBRARY Paragraph PageCHAPTER 7. MAINTENANCEOPERATIONS Section I. Introduction________________ 64,65 93 II. Preventive maintenance______ 66-69 95 III. Overall and sectionalizingtest for trouble clearance__ 70-74 98 CHAPTER 8. ANTIJAMMING Section I. Characteristics of jamming operations_________________ 75,76 102 II. Antijamming instructions____ 77-81 103 CHAPTER 9. FIELD EXPEDIENTS Section I. Introduction________________ 82,83 107 II. Connections and antennas____ 84-88 108 III. Power source expedients_____ 89,90 110 IV. Operational expedients_______ 91-94 112 CHAPTER 10. DESTRUCTION OFRADIO RELAY EQUIPMENT------------95-98 116 APPENDIX A. REFERENCES____________ 119 B. PHYSICAL SECURITY____ 125 c. DISPLACEMENT OFRADIO RELAYFACILITIES INDIVISION AREA________ 130 D. RADIO RELAYCOMMUNICATIONSDURING PHASESOF TACTICALOPERATIONS __________ 133 GLOSSARY-------------------------------· 138 INDEX-----------------------------------145 2 AGO 63540 CHAPTER 1 INTRODUCTION 1. Purpose This manual is a guide for field radio relay personnel in the employment of radio relay equipment under tactical conditions. 2. Scope This manual provides information on the tactical employment of radio relay, system planning, siting and installation, frequency selection, antijamming, system maintenance, and related subjects. 3. Use This manual presents material that may be used without modification for both nonnuclear and nuclear warfare. 4. References Publication and other reference material pertaining to subjects within the scope of this manual are listed in appendix A. 5. Comments and Recommendations Users of this publication are encouraged to submit comments or recommended changes for the improvement of the manual. Comments should be AGO 6354C keyed to the page, paragraph and line of the textto which they apply. Reasons for the commentsmust be included to insure complete understandingand proper evaluation. Comments should be forwarded to the Commanding General, United StatesArmy Signal Center and School, ATTN: SIGDTL2 Fort Monmouth, N.J. 07703. 4 AGO 63540 CHAPTER 2 RADIO RELAY SYSTEMS Section I. I.NTRODUCTION 6. General a. A radio relay system consists of a series of radio stations operating in tandem on frequencies above 30 me (megacycles). When used in conjunction with multiplexing equipment, a radio relay system provides communication channels for telephone, teletypewriter, facsimile, and data. (1) When radio equipment having a s~fficiently wide baseband is used, transmission of data and television signals may be obtained. (2) Every radio relay system has two terminals--one at each end of the system. Radio terminal sets often are installed as part of, or adjacent to, the carrier terminal. ·The maximum distance between radio terminal sets (without intermediate radio relay sets) is governed by the type of equipment used. (3) Radio relay sets are installed, where necessary, to retransmit the signals from the preceding radio terminal or, in multiple hops, from the preceding radio relay set. AGO 6354C 5 b. Radio relay systems operate in the VHF(very high frequency) or UHF (ultrahigh frequency) bands. The VHF band covers frequenciesfrom 30 to 300 me, and the UHF band covers frequencies from 300 to 3,000 me. Radio propagationin these bands may be considered to be confinedto direct waves which travel in nearly a straightline between the transmitting and receiving antennas. Useful transmissions between radio sets inthe VHF and UHF bands are generally limited torelatively short distances, 25 to 30 miles ( 40 to48 km (kilometers)). Longer distances may bepossible, however, when the antennas are sited onhigh hills. Meteorological conditions, such as thetemperature and humidity of the troposphere*,may have the effect of greatly extending the distance over which usable field intensities are received. Such conditions-which may be presentfor varying periods of time-are encounteredmost frequently where radio sets are located nearthe shore of an ocean or other large body ofwater. c. Radio waves in the VHF and UHF bandstravel in nearly straight lines, and operation inthese bands normally requires a radio line-of-sightpath between the transmitting and receiving antennas. This does not mean that one antenna cannecessarily be seen from the other antenna, butrather that there is an unobstructed path betweenthe transmitting and receiving antennas. When .the transmitter is separated from the receiver by • The atmosphere below the stratosphere. In the troposphere.temperature dec.rea.ses with altitude. a distance greater than 30 miles ( 48 km), the curvature of the earth will have an effect on the • transmission path. Even if there are no hills or other obstructions in the path, the curvature of the earth may preclude the establishment of a straight line transmission path between the transmitter and the receiver. d. A greater operating range may be obtained if antennas are properly oriented and correctly elevated over flat terrain. Locations where the transmission path is blocked by hills, buildings, cliffs, densely wooded areas, or other obstructions should be avoided. Depressions, valleys, and other low places are poor locations for radio reception and transmission, because the transmission path is more likely to be obstructed by the surrounding terrain. Normally, transmission over water is better than over land. Transmission over open paths, along open river valleys, or from elevated sites that overlook jungle growth is recommended. Weak or undesirable signals may be expected if the set is operated close to steel bridges, underpasses, and high-tension lines. Undesirable signals also may be expected if the antennas are positioned where the transmitted or received signal must pass over the power generator at either terminal. 7. Use of Radio Relay Systems Radio relay systems may be used as a primary communication facility or to supplement/complement an existing cable and open-wire carrier system. Specifically, radio relay systems may be used- AGO 6364C a. Tactically, to establish initial trunk line communications in a rapidly moving situation. b. As a multiple-channel primary facility-thenumber of channels will depend on the bandwidthof the radio sets and the type of multiplexingequipment used. c. As a multiple-channel system to supplementor extend a wire system. d. In combination with multiplexing equipmentto provide a combination of telephone, teletypewriter, facsimile, and television or telemeteringdata transmission (with certain equipments) overa single radio path. Section II. METHODS OF OPERATION 8. Introduction Radio relay equipment may be operated in oneof two methods a. One-way operation without a break-in capability, referred to as one-way reversible (simplex)operation. b. Simultaneous two-way transmission, calledduplex operation. 9. One-Way Reversible One-way reversible operation is two-way communication between two stations, but in one direction at a time. While one station is receiving atransmission from the other station, the operatorcannot make the transmitting station hear himuntil it stops transmitting. That is, he cannot 8 AGO 63540 TERMINAL STATION TERMINAL STATION ------l ~--------l m 8 I \f a 2! I ANTENNA ANTENNA RECEIVER RECEIVER RADIO RADIO TRANSMITTER TRANSMITTER I I 1------UP TO 48 KM-'1 I RADIORADIO RECEIVERRECEIVER ANTENNAINPUT I ______ j L ____ _ J L__ RADIO TERMINAL SETRADIO TERMINAL SET FM 24-21-1 Figure 1. Use of radio relay set as a one-way reversible oO single-channel field radio set. TERMINAL STATION TERMINAL STATION -0 r-------------, ,------------, I ~ I I I Sl7 : HANDSET I I A I I I I I I I I RADIO I I RECEIVER I I RADIO I TRANSMITTER I ANT. INPUT III '-up TO 48 KM___..I CONNECTING I CONNECTINGCABLE.__...... I CABLE---.. II I F2 IIII RADIO I RECEIVER I I I RADIO I ANT. INPUT o+---J I TRANSMITTER I I I II I I L---------------~ L---------------~ RADIO TERMINAL SET RADIO TERMINAL SET 0~ FM24-21-2 .......g: Figure 2. Use of a radio relay set as a duplex single0 channel field radio set. "break in." The advantage of one-way reversible communication is that just one operating frequency is required and each transmitter carrier is on only while the operator is talking. Singlechannel one-way reversible operation requires the use of only one antenna system. Figure 1 is a block diagram of typical components of two radio terminal sets, used for ordinary single-channel one-way reversible voice communication between two stations. 10. Duplex Operation Duplex operation, which is communication in both directions simultaneously, permits the operators to talk to each other as in normal conversation. Figure 2 is a block diagram showing typical components of two radio terminal sets as an ordinary duplex single-channel field radio set. This arrangement requires the use of two antenna systems, and provides one voice channel in each direction. The provision of auxiliary teletypewriter terminal equipment or facsimile equipment at each station makes it possible to send facsimile or teletypewriter signals. Both transmitters may be left on continuously during voice communication between two stations, or each transmitter carrier may be turned on by pressing the pressto-talk switch of the handset. Section Ill. SYSTEMS 11. Multihop Systems Multihop systems may be either one-way reversible (fig. 3) or duplex (fig. 4) in design. In AGO 6354C 11 multihop systems the communication distancesbetween radio terminal stations may be greatlyincreased by interposing radio relay stations between the terminal stations for the purpose ofrelaying the communication in both directions.The total distance that can be covered is dependent upon terrain conditions and the type andquantity of· traffic to be handled. a. One-Way Reversible Relay System. (1) The one-way reversible relay communication system, which permits only onechannel of communication in one direction at a time, is limited to one radiorelay station (fig. 3). In this system, thetransmitter carrier at the relay stationnormally is controlled by the receiver,which turns the carrier on only when anincoming signal is received. (2) Since the relay station must receive theincoming signals and retransmit themsimultaneously, the transmitter and receiver must have "separate antennas andthe sending frequency must be differentfrom the receiving frequency. (3) This system is limited in its traffic capabilities and distance coverage. Use ofthis system to send teletypewriter orfacsimile signals is not practical becauseit would require constant manual switching from send to receive at the terminalstation. This system requires two operating frequencies, and the carriers are on 12 AGO 6354C A B RELAY STATION TERMINAL STATIONTERMINAL STATION 8 r----------, r----------, r----------,I r fJ I II ,f-4I I I I I HANDSETHANDSET I •"'0 I I II RADIO II RECEIVER IECEIVE!t II U.DtOTIANSMITTER II I / I CONNECTING I CABLES I I I I I HANDSU I I I I I I I I I I I 1 I 1 I I IADIO I I IADIO I I RECEIVER I I lECEIYEl I I I I I RADIO I I I 1 ""'· '"'u' or-1 ' TlANsMmu 1 I ANT. '"'u~ 1 I I I1 1 I I ~--~: ~~-t-~: ~~..1 IIL----------~ L----------~ L---------~ IADIO TERMINAL SET RADIO TERMINAL SETRADIO TEIMINAL SET - FM24-21-3 w Figure 3. Type one-way reversible single-channel radio relay communication system. only during periods of actual communication. b. Duplex Relay System. (1) Duplex operation, which permits communication in both directions at thesame time, is accomplished by usingseparate antenna systems for each transmitter and receiver (fig. 4). The transmitter and receiver at each location musthave a frequency separation specified inthe manual accompanying the radioequipment. In a system of this type, asmany as nine stations may be spaced atintervals of 25 to 30 miles (40 to 48 km)to extend communications to greater distances. By operating the transmitter carriers continuously, it is practical to usethis system for teletypewriter, facsimile,or multichannel voice communication. (2) In this system, all transmitter carrierssending communications in one direction may be on only while communications are being sent; or, they may be lefton continuously, depending on the desired method of operation. 12. Multichannel System a. A tactical multichannel communication system usually provides 4 or 12 VF (voice frequency)channels between two points separated by distances as great as 150 miles (240 km) for a 4channel system and 200 miles (320 km) for a12-channel system. (With the use of new multi 14 AGO 6354C plexing equipment, 24, 48, or 96 VF channels may be employed.) A typical system is shown in figure 5. (1) The two-or four-wire line connected to the teletypewriter terminal and its associated teletypewriter equipment enables either 1, 4, 8, or 16 teletypewriter communication channels to be placed on any one VF channel of the telephone terminal, depending upon the type of teletypewriter equipment used. (2) The radio terminal set may be located at any distance up to 5 miles (8 km) from the 4-channel VF carrier equipment and is connected to the carrier equipment by loaded spiral-four cable. 12-channel VF carrier equipment may be located at any distance up to 1 mile (1.6 km) from the radio terminal set without intermediate attended repeaters), and is connected by use of nonloaded spiral-four cable. Terminal B at the distant location includes identical equipment in an arrangement similar to that at terminal A. (,3) The number of radio relay sets that should be used as relay stations will depend on the type of radio equipment employed, the RF (radio-frequency) noise at any receiving site, the length of the communication system, the design of the system, and the signal loss due to the AGO 6354C 15 0. - A TERMINAL STATION B RELAY STATION r------l r----------, RELAY STATION TERMINAL STATION ~---l ,-----l I I " I --,1',,--:,z__-+1---SV I HAHosn I I l " I SV 1 I I I RADIO ANT. • RADIO ANT.I(! I RECEIVER RECEIVER• I II I RECEIVER RECfiVU RADIO I~ I I I RADIO RADIO I I I I ANT. INPUT UANSMITTU TIANSMITT£1 ANT. INPUT CONNECTING CONNECTING L __'0;~'l':: __ J L -___£A!!!,_ -CONNECTINGCABLE-RADIO TERMINAl SET -_j RADIO lUMINAL SET CAIU ,-------, ~w ~~w RADIO I I I I I I r:;:NT. . I " r I " RADIO RECEIVER ANT. I RECEIVER RECEIVER I I RECEIVU IAOIO TIANSMITTEI RADIO I I I I TRANSMITTER TIIANSMITTEI I I CONNECTING 1-~::~-i : UPTO I CONNECTING L _ _J L CAllE CAllE -41KMJ U.DIO TERMINAl UT -_j L L ____ ...J RADIO TERMINAL SET RADIO lUMINAL SU RADIO lUMINAL SIT FM24-21-4 0~ Figure 4. Type duplex single-channel radio relay ~ communication system. ~ 8 UUlYPIWllfU TERMINAL A ~ I "'~ I ~~:~~E~~ I.ADIO lUMINAl Sll CHAN\ r-~ r------, ====I I y--.-,-~ ~~~~: I I I CHAN 3 I I TO TEIMINA~= ===I I lHAY TIHO fEU-CHAN 4 I STATION l'fPEWllfEI (!f REOUIIED) = = ==t I= t = ====I I 2-WIII ='~~~I I {Nl~~: I) EQUIPMENt CHAN 5 I AND THEN .AT UlMIHAl CHAN 7 I I====, I -'~~~~ I ----L _ _j~ fiELD WilE (NOtE 2) 1. NOT TO u:cnO A 7-01 lOU. 2. NOT TO EXCUD A 4-DI LOSS. '----v------1 UUPHONU Figure 5. Type multichannel radio 'relay communication system. -.... terrain over which the signals will betransmitted. b. The multichannel system provides 4 or 12voice channels that are capable of being operatedin both directions simultaneously between terminals A and B. The number of VF channels varyin accordance with the type of radio and carrierequipment used. (1) An order-wire channel. is provided asthe system service channel. All operators in the system can communicate witheach other by using this channel. (2) The traffic channels cannot be enteredinto the radio relay stations withoutsuitable telephone terminal equipment. c. When any of the channels on the line sideof the telephone terminal are used for voice, andnormal 20-cycle signaling is required, those channels must be passed through ringing equipment asshown in figure 5. Any channel used for facsimile• equipment must be bypassed around the ringingequipment. 18 AGO 6364C I 3 CHAPTER EMPLOYMENT OF RADIO RELAY SYSTEMS Section I. TACTICAL APPLICATIONS 13. General Because of the versatility and flexibility of radio relay equipment there can be no set rules for the application of such systems to tactical communications. In each instance, the amount of radio relay equipment to be used will be dictated by the Signal Plan, which results from the estimate of the signal situation made by the signal planner. 14. Specific Considerations a. Radio relay circuits always are operated point-to-point; that is, from terminal to terminal or, if radio relays are used, from terminal to terminal through the relays. b. Normally, higher headquarters will provide the entire radio relay system, including the terminal equipment at the subordinate headquarters and the necessary relay station. Signal plans must provide for radio terminal sets and teams to be attached to subordinate units, particularly when such units are not authorized these terminals and teams. Under normal conditions, operational con- AGO 63540 19 trol for attached terminal teams remains underthe command of their parent organization or asdirected in the operation order. c. Communication planners also must consider (1) The type and quantity of radio relayequipment available. (2) The characteristics and proposed possible use of the equipment. (3) The usability of assigned operating frequencies. ( 4) Capabilities of existing and proposedwire systems. (5) Integration of the radio relay systemwith the wire system. (6) The consolidation of relay stations wherecommunications systems are adjacent toor intersect each other. This will simplifylogistical support and security requirements and will reduce the number of personnel. (7) The possibility of air-transporting radiorelay equipment to provide communications for special situations, such as areadamage control following a nuclearstrike. (8) The possibility of communication security since the enemy may interfere withor disrupt communications. (9) Accessibility of selected sites, which requires consideration of administration 20 AGO 6354C and logistics that may affect supply, maintenance, and transportation. (10) Geographic and terrain characteristics. 15. System Procedures a. Preoperation. (1) Reliable radio relay operations can best be realized when based upon a clear and detailed signal SOP (standing operating procedures) and a well-planned and clearly written SOl (signal operating instructions) and SSl (standing signal instructions). The signal SOP should include a statement that directs all signal operations to conform with instructions in the current SOl and SSI. (2) Extracts of the SOl will be issued to each radio relay team chief. These extracts will contain the prearranged message code, call signs, frequencies, the map-coordinate code, and the unit authentication system. Arrangements must be made in advance to insure timely delivery of new SOl extracts as required. (3) Each radio relay team chief will be issued tactical maps covering the probable area in which the team will operate. b. Tactical Employment. During operations any orders for tactical employment must be given in code, in accordance with the SOl extracts. The team chief who receives the message must authen- AGO 6364C 21 ticate the transmission. Conversely, the personoriginating the instructions also should be required to authenticate. c. Clear-Text Information. Transmission of thefollowing types of clear-text information overorder-wire circuits (engineering channels) mustbe prohibited. (1) Radio relay station locations. (2) Movement instructions to stations. (3) Identification of stations with units. (4) Instructions regarding future tacticaldeployment. d. Changes in Circuitry. Information regardingchanges in a circuit must be transmitted in both directions-from higher to lower headquartersand vice versa. Orders regarding the system willcome from the terminal servicing the higher head quarters. e. Equipment Considerations. (1) :Circuits must operate exactly on assigned frequencies. (2) Correct antennas must be used. (3) Transmitting and receiving antennasmust be oriented properly. When two ormore systems utilize the same site, frequency separation between transmit andreceive antennas on different masts becomes a critical consideration. f. Security. Radio is the least secure meansof communication; therefore, radio security isa constant consideration. The enemy obtains 22 AGO 6854C information merely by knowing that radio sets are operating. The enemy's analysis of the number of sets in operation, the volume of traffic, or the location of the sets is particularly valuable. Radio transmission may be restricted or prohibited for security reasons. An important measure for defense against the enemy gaining intelligence from radio transmissions is radio silence (also listening silence) . However, radio transmissions are not prohibited when the need for radio communication outweighs the value of the information the enemy might gain. Consequently, radio sets usually are not silenced in units that are in contact with the enemy. g. Radio and Listening Silence. Radio silence is that period specified by the commander during which the transmitters and receivers of all radio sets are kept inoperative. Listening silence is that condition when the receivers are permitted to remain operative to monitor net frequencies and the transmitters are shut down. 16. System Flexibility a. Geneml. Radio relay systems are extremely flexible and furnish a variety of communication capabilities. These systems may be used in the following ways: (1) To extend the lines of communication in a fast-moving situation, mobile equipments may be employed in jumpteam operation. These teams can displace to forward, rear, or lateral locations prior to the actual displacement of head- AGO 6354C 23 quarters, thus insuring continuous communications. By maintaining communi • cations at the old CP (command post)with duplicate radio relay equipment orwith wire systems, the circuits may beswitched to the new CP when the oldcommand post closes. (2) A radio relay system may be insertedinto a wire system without reducing wirecapabilities. Where the terrain, such asdense forests, swamps, jungles, deepravines, steep grades, large streams, orrugged valleys, makes wire constructionimpractical or impossible, radio relaywill be installed. (3) At times it may be desired to drop orinsert certain traffic channels at a radiorelay point. A block diagram of a radiosystem in which some traffic channelsare dropped at a radio relay point isshown in figure 6. At the radio relaypoint, each radio set (transmitter andreceiver) is connected to a separate telephone terminal. The two telephone terminals are then operated back-to-back withthe desired traffic channels dropped atthe back-to-back connection. Trafficchannels can be dropped at radio relaypoints in radio systems that are usedwith the 4-or 12-channel telephone systems. However, the telephone terminalsthat are used to drop the traffic channelsat the radio relay point must be the 24 AGO 6354C RADIO TERMINAL SET RELAY STATION RADIO TERMINAL SET ,-----l g .-------l I --------, "'.,. I w---, I en I~ I I 1 TO HlEPHON£ SPIRAl·0 AltMT AUA SIGNAL CfNTEit MULTICHANNEL RADIO IELAY SYSTEMS ---{ ~ NOTE: LEGEND: SPIRAl·fOUR CABLE CARRIER SYSTEMS CORPS CIRCUITS SIMILARLY PROVIDED COMMAND SIGNAL CENTU (INSTAlLED WHEN PRACTICABLE) FM24-21·1 Figure 8. Type corps tactical communication system. division main CP and its echelons with the major subordinate commands of the division. b. Figure 8 shows one application for a corpstactical communication system as integrated withthe communication systems of field army anddivision. c. Figure 9 shows a type field army area communication system. The number of area communication signal centers varies in accordance with thecommunication requirements. Figure 9. Type field army a1·ea communication 8ystem. (Located in back of manual) 30 AGO 6354C CHAPTER 4 SYSTEM PLANNING Section I. INTRODUCTION 19. General a. System planning includes the overall layout of radio relay circuits, locations of sites, choice of equipment, and frequency asssignment. b. The factors to be considered in planning radio relay systems are (1) Circuit requirements as determined by traffic studies and/or previous experience. (2) Capabilities of the radio relay equipment in conjunction with the associated multiplexing terminals. (3) Propagation characteristics and terrain features over which the radio system will operate. (4) Siting of radio sets and antennas. (5) Power-balance calculations, such as required inputs, noise levels, and power outputs. (6) Interference reduction by frequency selection. (7) Advantages gained by using crosspolari- AGO 6394C 31 zation, separate masts, and antenna directivity. (8) Field methods of minimizing interference. (9) Limitations of spiral-four cable in aradio system. (10) Availability of frequencies for assignment. (11) Location and mobility requirements ofsupported elements. (12) Remoting requirements. 20. System ConsiderationS/ a. A radio ·relay system may be used directlyfor primary trunks, or as a link in an existingwire system. The installation may be temporaryor permanent. With some types of radio relayequipment, channels may be dropped betweenterminals and made available at some intermediate point (fig. 6). b. The permissible number of hops depends onthe type of equipment and terrain. Distortion,noise, and the possibility of circuit failure due toinoperative equipment increase as the number ofhops increase. 21. Multiplexing Equipment Connections a. Terminal Connections. Through the use ofmultiplexing equipment, channels may be brought out as either two-wire or four-wire circuits. Thesecircuits are connected to voice terminal equipment or to carrier teletypewriter equipment. 32 AGO 6354C b. Through Connections. Where systems are to be extended, patch-through connections between multiplexing equipments should be made on a four-wire basis, if possible. The standard signal levels specified in the equipment technical manual should be retained for circuit quality. c. Baseband Connectio'IJ,S. In interconnecting radio relay and wire carrier systems, the baseband connections must be made on a four-wire basis. Baseband connections between certain equipments may require limited lengths of coaxial, spiral-four, or other special cable. Baseband connections, as well as the required signal levels, are covered in appropriate equipment manuals. 22. Separation of Radio Terminal From Carrier and Multiplex Equipment a. At the terminal installations of systems using wire carrier, the carrier equipment may be located with the radio terminal equipment or centralized near the telephone switching central. b. At division and lower levels, carrier equipment usually is married to the radio equipment in the same vehicle. Such an arrangement maintains the tactical identity of the radio carrier terminal, and reduces emplacement and teaT-down time. However, the length of the wire lines to be constructed between the carrier terminal and the loop equipment is limited, and differs with the type of equipment used. c. At higher echelons (corps and above), carrier equipment frequently is centralized near the AGO 6354C 33 telephone switching central. This permits greaterflexibility of employment for the available carrierequipment. In such installations, a spiral-four orother suitable broad-band wire facility is used tofeed the radio terminal output to the telephone carrier terminals; however, the wire lines to theswitchboard are greatly reduced in length. Section II. SITING TECHNIQUES 23. General There are many factors that must be taken intoconsideration in planning the sites of radio relaystations in a radio relay system. a. Physical security must be considered as a factor in the selection of a radio relay site-this isparticularly true in isolated areas. A guide fororganizing a perimeter defense is given in appendix B. b. In engineering a radio relay system, especially where continuous operation is essential, considerable attention must be given to the locationof the radio relay station, particularly in rollingterrain or in areas where scatter or reflection mayintroduce problems. c. Radio relay sites usually follow a zigzagcourse. One reason for this pattern is that the terrain seldom lends itself to a straight line of radiorelays without having some of the hops unnecessarily short and others too long for satisfactory reception. Also, hills rarely are spaced so that therelays are in a straight line, and still have adequate elevations. However, there are exceptions to 34 AGO 63540 every rule and zigzagging is not always necessary. It is possible and practical to site the relays in a straight line and' still have reliable reception. Cross polarization of antennas and/or alternate frequencies may be used to give satisfactory reception. d. Siting may be done by a number of methods or by combination of separate methods. Contour maps, military topographic maps, aerial photographs, and surveys may be used satisfactorily. Usually, sites are chosen tentatively from military topographic maps, and a field trip or aerial survey is made to verify the choice. 24. Field Inspection a. The initial contour map reconnaissance to select terminal and relay sites should provide several alternate locations for each proposed installation. Some of the alternate sites will be discarded on the basis of profiling, and the balance must be checked by actual on-the-ground inspection. b. A field trip should be made for the purpose of locating accessible roads; determining whether the ground is suitable for vehicles and the erection of antennas; and determining the amount of clearing needed to prepare the site. Under ideal conditions, where portable beam-antenna equipment and sufficient time are available, a further check on signal attenuation may be made between adjacent sites. 25. Siting by Radio Altimeter a. In areas where accurate contour maps are AGO 6354C 35 not available, the altimeters on AmlY airplanesand helicopters may be utilized to profile a proposed VHF (very high frequency) hop. Either theaneroid (pressure) or the radio altimeter may beutilized for this purpose. Initial readings shouldbe taken at each end of the hop. Subsequent readings taken at significant terrain features in astraight path between the two ends of the hopthen may be plotted on 4/3 earth radius paper(DA Forms 11--47 and 11-48). In using thesedata, just as with profiles developed from contourmaps, the curvature of the earth and the averagerefraction may be computed. The earth's curvature plus atmospheric refraction will effectivelyelevate an obstruction several hundred feet higherthan it actually appears on flat earth, or on a rectangular coordinate profile. This is especially truewhere a long hop is involved. b. Aerial photographs are useful in determining locations of roads, power lines, or other details which may affect the choice of the site. In thefinal analysis, however, an on-the-spot inspectionof the site is most desirable, since this will revealproblems which would not otherwise be apparent. 26. Ac.cessibility of Sites a. One of the most important considerations inselecting radio relay sites is accessibility. Whereno road exists to a proposed site, a field trip willbe required to determine the amount of worknecessary to establish accessibility. For rollingterrain, road construction may not be too difficult;whereas in rocky, hilly, terrain more serious prob 36 AGO 6354C lems will be met. Often it may be more advantageous to select another site less desirable from a radio standpoint, rather than attempt to establish accessibility at the best site. Such problems, however, involve both tactical and logistical considerations. In hilly country, landslides and washouts hamper operations and provide a hazard for operating and maintenance personnel. The quality of the access road and the terrain in which it is located will determine the amount of use it will receive. b. Emergency and routine supply by helicopter is worthy of consideration in cases where tactical requirements justify sites located in otherwise inacessible locations. The three significant questions are: Will a helicopter be available when needed? Can a helicopter land? If not, can it approach the site close enough to drop supplies? 27. Power Considerations The reliability of the radio relay-and therefore of the entire system-is dependent upon the source of power. Maintenance and operating procedures, as outlined in SOP's and equipment manuals, should be rigidly adhered to for reliability of operation. If a power line is available at a proposed site, it should be carefully appraised to. determine whether the line is capable of carrying the additional load of the radio relay. The power should be regulated, both in frequency and voltage, and the wires should be large enough to carry the added load without excessive voltage drop. In any case, standby engine generators must be available AGO 6354C 37 and in operating condition, and must be regardedas the primary source of power. 28. Polarization of Antennas a. General. For practical purposes, radio wavesin the VHF range transmitted from a vertical antenna usually are regarded as being verticallypolarized, while those from a horizontal antennaare regarded as being horizontally polarized.Either type of polarization may be used for VHFtransmission. Selection of the type of polarization to be used will depend on frequency availabilityand operating conditions. For best results, thepolarization of the distant receiving antenna must be the same as that of the local transmitting antenna. b. Advantages of Vertical Polarization. (1) Simple vertical dipole or whip antennasare omni-directional in a horizontalplane. This feature is advantageous whengood communication is desired in all directions from a radio set. (2) Where antenna elevations do not exceed10 feet (3 meters), vertical polarizationin the 50-to 100-mc (megacycle) bandresults in a stronger signal than can beobtained from horizontal polarizationusing antennas of the same height. However, this difference is negligible whenusing frequencies higher than 100 me. (3) For transmission over sea water, verticalpolarization is better than horizontal po 38 AGO 63540 larization when antennas are below a certain elevation. This elevation is about 50 feet (15 meters) at 85 me and lower at the higher frequencies. This means that with ordinary antenna mast heights of 45 feet ( 13.7 meters), vertical polarization is better at frequencies lower than 100 me. At higher frequencies, there is little difference. c. Advcdages of Horizontal Polarization. :O) The inherent directivity of a horizontal antenna can be used to advantage as a means of minimizing intereference. A simple horizontal antenna with its axis pointed east and west transmits and receives best in north and south directions, and performs poorly by comparison in east and west directions. '(2) Horizontal antennas are less apt to pick up man-made interference, which ordinnarily is vertically polarized. '(3) When antennas are located in fairly dense forests, horizontally polarized waves usually suffer lower losses than vertically polarized waves; this is especially true in the higher portion of the VHF range. For any small change of antenna location in moderately wooded areas, the standing wave effects of vertically polarized antennas will cause relatively large changes in field intensity. Under the same conditions, these 39 AGO 6354C adverse effects are not so pronouncedon antennas horizontally polarized. Invery dense jungles, performance generally is poor for both types of polarization. Section Ill. COMPUTING RADIO RELAY PATHS 29. Procedure The procedure to be followed in planning asingle-route radio relay system is outlined in bthrough g, below. When planning a system ofinterconnecting or parallel routes, follow this procedure for each route in the system. a. Determine specific locations of the terminalpoints of the radio relay system. These points willbe based on tactical and geographic considerationsand by the location of the equipment connectedto the radio terminals. b. For each radio relay system, draw a sketchon paper as shown in figure 10. Label the radioterminal at the higher headquarters "A" and theother point "B." Assuming a 30-mile ( 48-km) radius as a yardstick for propagation distances,use A as the apex and draw an arc of that radiusabout terminal A and in the general direction ofterminal B. Use of an air chart permits rapidvisual identificaton of possible line-of-sight paths,since the color contours are easily evaluated. c. Choose a site with high elevation on ornear the 30-mile ( 48-km) radius arc drawn aboutterminal A. Label this site "radio relay 1" and 40 AGO 6354C 2 ~ ""~ FM24-21-19 ,. Figure 10. Selection of intermediate radio relay points. - draw a profile graph of the ground between terminal point A and radio relay 1. d. Use the procedure outlined in paragraphs29 and 30 to determine if a line-of-sight pathexists between terminal A and the first relay station. If the site chosen does not give a line-ofsite path, discard the site and select another. Labelthe site selected "radio relay 1." e. If it is impossible to obtain a line-of-sightpath between terminal A and any proposed radiorelay 1, shorten the hop distance by selecting a suitable site that is closer. f. When a site has been provisionally selectedfor a radio relay, determine by power-balance calculations whether the site selected is adequate. Ifthe calculations indicate that the site is not adequate, discard it and select a new site; repeat theprocedure. If very high obstacles are located inthe path, refer to paragraph 34. g. Use the procedure outlined above to determine the sites for all radio relays in the systemuntil the distant termial is reached. The maximumallowable number of relay points will be deter mined by the equipment used. Such informationis contained in the equipment manual. 30. Plotting Profiles on Nonlinear Graph Paper a. To determine that a line-of-sight path existswhen choosing a site, draw a profile map (fig. 11) of the terrain between the two proposed sites.Nonlinear graph paper, such as DA Forms 11 47 and 11-48, may be used for plotting profiles 42 AGO 6354C from terrain maps. When using nonlinear graph paper, follow the procedure in b through i below. b. Determine from the terrain map the scales used for the distances involved. c. Draw a line between the two proposed sites (E or H, fig. 11). Measure the length of this line and convert it to the distance between two points. d. Determine the elevation of each site as indicated by the contour lines. Add the height of the antenna mast to this elevation to determine the total elevation. For example, station N at path D (H, fig. 11) is 1,350 feet (411 meters) high.(15 Assuming an antenna height of 50 feet meters), the total elevation is 1,400 feet (427 meters). This point is marked off on the vertical scale of the graph above the zero-mile point (J, fig. 11). Station 0 has an indicated elevation of 1,400 feet ( 427 meters). This height plus an antenna height of 50 feet (15 meters) gives a total elevation of 1,450 feet (442 meters). This point is plotted on the vertical scale (J, fig. 11) above the 27-mile (43-km) point, because 27 miles (43 km) is the distance between the two proposed sites. e. Draw a straight line between these two points on the profile chart. Check this line and note its lowest point. f. Draw a complete profile of the terrain between the two sites. Follow the line drawn on the terrain map and pick up high and low points. Plot AGO 6354C 43 Figure 11. Plotting profile8. (Located in back of manual)these points on the graph paper and join them. Allpoints that are above the straight line on the graph (I, fig. 11) represent intervening ob structing terrain. g. If intervening hills exist between the twoproposed sites, as in path C (I, fig. 11), or if thesite line is below the curvature of the earth, asin path B (G, fig. 11), poor communications willresult. If possible, therefore, use paths such asD (J, fig. 11) where intervening obstructing hillsdo not exist, and good communication probablywill be obtained. h. A quicker method of determining line ofsight sometimes may be used. After the straightline has been drawn on the profile chart, scan theline and determine the elevation of the lowestpoint on the line. Next, scan the correspondingline on the contour map and determine whetherany point is at a higher elevation that that ofthe lowest point of the profile-chart line. If thereis none, as on path D, a line-of-sight path exists between th!:J end points of the line, and it is notnecessary to plot the profile of the interveningterrain. If there are elevations above the point oflowest elevation, as on path C, draw a completeprofile to determine whether these high pointsrepresent obstructions. For example, the point oflowest elevation on the profile-chart line for pathA (F, fig. 11) is 10 feet (3 meters). On the terrainmap, note that path A passes over a portion of terrain that exceeds 10 feet (3 meters) in elevation. 44 AGO 6354C Therefore, it is necessary to plot the profile chart before deciding that path A will provide a line-ofsight path. i. If the proposed site is intended for a radio relay station, the transmission paths to such site, and from the site to the next radio relay or terminal station, must be considered. It usually is necessary that line-of-sight paths exist in both directions. 31. Plotting Profiles on Linear Graph Paper If profile graph paper is not available, a profile may be plotted on linear graph paper and then corrected for the curvature of the earth. Use the following chart; then proceed as indicated in a through e below. Conver~;ion of Sea-level Elevations to Line-of-sight Elevation~; D (distance from D (distance from reference point) Elevation reference point) Elevation correction correction miles km (ft) (k = 1) miles km (ft) (k = 1) 2 3.2 3 20 32.0 266 4 6.4 11 22 35.2 323 6 9.6 24 24 38.4 384 8 12.8 43 26 41.6 450 10 16.0 67 28 44.8 522 12 19.2 96 30 48.0 600 14 22.4 130 32 51.2 682 16 25.6 170 34 54.4 771 18 28.8 217 36 57.6 865 Note: The corrected elevation in feet equals n• H=--- 1.5k, where k is the ratio of the effective radius of the earth to .AGO 6354C 45 the true radius of the earth and D is the distance in milesfrom the reference point. Using 1 for k in this formula does not correct for the effect of refraction of the radiowave. When the value for k is 4;3, the formula becomes v• H=-- 2 When the distance is in kilometers, the formula forcorrection in meters is v• H=-- 17These formulas correct for both the curvature of theearth and the 15-percent increase in· transmission distancedue to refraction. Note. Convert feet, yards, and miles to meters andkilometers as follows: Number of feet x 0.3048 = meters Number of yards x 0.91 = meters Number of miles x 1.6 = kilometers a. Determine from the terrain map the scalesused for distances and elevations. Draw a. line onthe terrain map between the two proposed sites. b. Pick out high and low points along the lineand plot these to scale on the linear graph paper.A sample profile is plotted as a broken line curveon this type of graph paper (fig. 12). c. Draw a line on the graph paper between terminal points A and B. d. Correction must be made for the curvatureof the earth to obtain a true picture of the lineof-sight path. A, high point is selected as near aspossible to the ·halfway point between the terminals, in this case R. Next, by means of the fig 46 AGO 6354C ures shown in the conversion chart above, thE: heights of all prominent points in both directions from this central point must be corrected (shown as a solid-line curve). For example, point P shown in figure 12 is 6 miles (10-km) from reference point R. After correction, P becomes P t, 24 feet (7.3 meters) lower than the original point. e. Some profile maps will indicate a line-ofsight path with the drawing uncorrected. With correction, however, intervening objects may become apparent. 32. Determining Line-of-Sight Profile Graph After drawing the profile graph for a particular path, and correcting for the earth's curvature (if linear graph paper is used), check the graph carefully to see that a true line-of-sight path exists. The path should not be obstructed in any way nor should it come closer than 200 feet (61 meters) to any intervening obstructions. If the path is obstructed, discard the site and choose a new one, if possible. If it is still impossible to achieve a lineof-sight path, determine the adequacy of a path from the power-balance calculations. 33. Power-Balance Calculations a. Power-balance calculations are made when planning a system to determine if the estimated loss over a particular path does not exceed the allowable loss for the path. If the estimated path loss is greater than the allowable path loss, either the path should be changed, the hop length should be shortened, or an intermediate radio relay AGO 6354C 47 .. CD 1-"' "',. FEET (/) A ffi lpoO/l 1 w "ll,op41!~ . ' ::;; .. 1'-,, •IVr (fiVe N 6f111(f!:s z0 rl!tiit..~"io/f..!!,GJ.tr flo,':'iiiJ w ....1 400 PROFILE CORRECTED FOR EARTH'S CURVATURE w ~~'"'1'1±1:1 PROFILE OBTAINED FROM CONTOUR MAP l:tr.: c;; 200 + > "'0 1 c:'l0 MILES 0 10 15 20 g: KILOMETERS 5 10 20 30 40 ..~ FM24-21-12 Figure 12. Plotting profiles on linear graph paper. should be used. If it is not possible to do any of these things, the hop may be established even though calculations indicate that there will be excessive loss. However, in a system where one or more hops have a greater estimated loss than allowable loss, these hops will ·limit the operating effectiveness of the radio system. Every effort should be made to reduce path attenuation while planning before the actual establishment of the radio relay system. b. Power-balance calculations performed while planning a radio relay system give only an approximate indication of the system performance. The only dependable way to determine system performance is to set up the system and test it. If the loss of any particular hop is difficult to determine from power-balance calculations, the equipment may be installed and tested. 34. Use of Obstacles to Obtain Long Trans,mission Paths Successful VHF and UHF communications have been reported over extremely long paths across mountainous terrain, where a knife-edge obstacle was near the center of the transmission path. In mountainous terrain where such obstacles are encountered, the following procedure may be followed: a. Place antennas on each side of the obstacle, at equal distances and not too close to the obstacle (signal attenuation increases as antennas are moved closer to the obstacle). b. Set up a radio set at each end of the hop and AGO 6354C 49 test the quality of transmission. Vary the heightand position of one antenna until a position andheight is found where the signal of maximum intensity is received. c. Use figure 13 to obtain an approximate indication of the path loss due to a very high obstacle. For path lengths 50 and 150 miles (80 and TRANSMITTING AND RECEIVING ANTENNA HEIGHTS: EACH 100 FEET ABOVE THE SURFACE "0 r---t--+--+-++-l+t+----+--t-+--H-+t+ttt+tttttH ~ 120 ;!! ., 130 3 0z 140 WITHOUT OBSTACL~J ~ 100 \ j ~z 160 1-.. .. 170u;;; , ; 100 OBSTACLE GAIN 190 200 210 220 2!0 I 240 2~,o~o~-.~o~o-73o~o-L~.~oo~~LL~I,oLoo-~e~.oo~o--L-~~o~oo~LL~L~o~o~o~~2o~poo h0, HEIGHT OF OBSTACLE ABOVE SEA LEVEL IN FEET FM24·21-I! Figure 13. Theoretical obstacle gains at 100 MG. 50 AGO 6354C 240 km), the chart shows the free-space transmission loss and the smooth earth transmission loss when using the principle of diffraction over high obstacles. The antenna heights are given as 100 (30.48 meters) above the surface. Also shown is the path loss at 50 and 150 miles (80 and 240 km) plotted against the obstacle height. Section IV. SYSTEM RELIABILITY 35. Estimate of Reliability a. There are many factors others than the possibility of equipment failures to be considered in estimating the reliability of a radio relay system. Transmitter output, distances between stations, and receiver sensitivity are some of the characteristics that will affect reliability of a system. Other factors, such as reflected or refracted signals, fading due to ionospheric storms, and even seasonal changes in the terrain can affect the signal strength, and hence affect the reliability. Many of these variables may be eliminated or controlled, however, by careful choice of sites, use of proper equipment, and allowance for fading. b. One way of obtaining higher reliability is to decrease distance. between radio relays. Relay spacing of 30 to 50 miles (48 to 80 km) generally will be satisfactory for frequencies below 10,000 me, provided good path clearance is available. c. A signal will affected by the receiver antenna gain and the transmission line loss between the antenna and the receiver. In order for the output signal from a receiver to be intelligible, it must be AGO 6354C 51 stronger than the receiver noise level. Manufacturers of the receiving equipment determine a signal level for their equipment which depends onthe type of modulation used and the receiver design. This level is called the threshold level, andrepresents the lowest signal level that will be intelligible. Although a received signal may be onlybarely above this level, satisfactory transmissionwill result if there is no fading. Since fadinglowers the signal strength at the receiver, it isnecessary to have a much stronger signal arriveunder normal conditions, in order that an intelligible signal may be received under expectedfade conditions. The difference between the fieldstrength of the level normally received and thethreshold level is called the fade margin. Thefield-strength to be expected for any radio sitecan be calculated within -+-5 db (decibels) byusing information from the equipment manualand data taken on the individual hops of a radiorelay system. d. Radio relay equipment is designed to operatewithin one section of coaxial cable (issued withthe equipment) between the antenna and radio.The addition of more sections of cable increasestransmission line loss between the antenna andthe equipment. The antenna must be located asnear the equipment as possible, since the use oftwo or more section of coaxial cable reduces theoutput signal by more than 50 percent. 36. Acceptable Reliability a. Reliability is determined by the percent of 52 AGO 6354C the time that tp.e signal strength at the receiver is above a predetermined level. This level is the signal strength to be expected 90 percent of the time, and is independent of the receiver characteristics and fade conditions expected in the area where the radio relay sy~tem is to be installed. Should the signal strength be equal to the threshold level of the receiver, the outage time would be 10 percent, and obviously not acceptable. No radio relay system should be planned to operate at the receiver threshold level, since a fade of any magnitude would immediately result in circuit outage. b. By planning the hops so that the signal is higher than the threshold level of the receiver, higher reliability is obtained. This acts as a cushion to absorb fading. For example, if the received field strength at the receiver is -10dbm (decibels reference to 1 milliwatt of power), and the receiver threshold level is -50 dbm, the difference, 40 db, is the fade margin for that hop. On the basis of previous experience, it has been found that a 40-db fade may be expected not over .01 percent of the time, so that the 40-db fade margin gives a reliability of 99.99 percent. The relationship between reliability and fade margin usually is given in applicable technical manuals, so that the radio relay system can be engineered for whatever reliability is desired. In most instances, path attenuation will be the greatest source of attenuation, so that, where a low reliability is acceptable, the relay stations may be spaced further apart. c. In calculating the reliability to be expected AGO 6354C 53 from a radio relay system, the simplest and safest · method is to assume that outages in the various hops will not occur simultaneously. For example, if a radio system has 10 hops, with an efficiency of 99 percent for each hop, it is safe to estimate that each will be out 1 percent of the time. However, since outages are assumed to occur at different times, the total outage time for the entire 10hop system then should be 10 percent, so that the system as a whole would have a reliability of 90 percent. As the number of hops increase, however, the likelihood of the outages occurring simultaneously also will increase. 37. Factors lncreasin.g Range of Reliability There is no method of simply evaluating the effect on a VHF or UHF system of such factors as changes in weather or terrain conditions. However, the effect of many other important factors can be evaluated. When installation of radio relay stations beyond the radio line of sight is necessary, the following factors tend to improve performance on either the normal or the obstructed circuits a. Proper Antenna Orientation. Terrain in the vicinity of either the transmitting or receiving antenna can distort the antenna pattern; therefore, antennas should be experimentally rotated to arrive at the best orientation. Such rotation frequently will reduce the effects of indirect (reflected) signals caused by rough terrain features, such as river valleys or near-by high mountains. Conversely, however, sharp terrain features may AGO 6354C be capitalized upon to provide usable indirect radio paths when both transmitting and receiving antennas are properly oriented. Normally, propagation by indirect paths is inferior to that of direct paths, but .in some instances circuits can be established through use of such indirect paths where no circuit normally can be realized. b. Radiation of Strong Signals. (1) After the site is selected and the proper antenna orientation determined, the signal level at the receiver will depend on the strength of the radio signal directed toward the receiver location. VHF or UHF systems should be established with the minimum amount of power required for good reception, while at the same time allowing sufficient power to overcome fading due to atmospheric disturbances. This procedure also will minimize adjacent and cochannel interference, reduce the amount of interference between adjacent or interconnected VHF or UHF systems, and lessen the possibility of enemy interception. (2) If a high-gain antenna is used, the effect will be the same as if transmitter power were increased. (3) Losses between the transmitter and the antenna may be minimized by using a high quality transmission line as short as possible and properly matched at both ends. AGO 6354C (4) When a circuit is subjected to enemy jamming, the change from multichannel to single-channel operation allows more of the transmitter power to be concentrated in the single channel, and thereby improves the signal strength of the channel. (This procedure should be used only under emergency conditions.) (5) On marginal circuits, it may be necessary to use a separate RF amplifier unit to increase the transmitted power. c. Use of Lower Level Signals at Receiver. (1) The ability of the receiver to operate on a weak signal is direct1y dependent on the ability of the receiving antenna to capture as much of the signal as possible without picking up excessive noise interference. High-gain antennas, properly oriented toward the signal source and situated away from noise sources, will provide better reception than simpler antenna types. The amount of noise picked up by any antenna will increase unless local sources of interference, such as high-voltage transmission lines, ignition systems, or other electrical equipment, are eliminated. In many installations, nearby communication equipment may generate spurious signals which merge into a high background noise level. In some installations, adjacent channel or cochannel interference will determine the lowest useful signal at the receiving site. 56 AGO 6354C (2) In addition to external noise, the received signal must compete with noise generated within the receiving set itself. High quality receivers, located in an area free from interference and connected to a high-gain antenna by a short highquality transmission line, will provide the best signals. AGO 63540 57 CHAPTER 5 RADIO FREQUENCY MANAGEMENT AND SELECTION Section I. FREQUENCY MANAGEMENT 38. General The radio frequency spectrum is a limited resource which must be shared, worldwide, by civil,government, and military users in both peace andwar, and only portions of the spectrum are available for each user. The internationally controlledradio frequency spectrum extends from 3 kc (kilocycle) to 40,000 me, and the nations of the worldmeet periodically to permit equitable sharing ofthe spectrum on a worldwide basis for the mutualbenefit of all. Frequency management at variouslevels down to division is discussed briefly in thefollowing paragraphs. 39. International International frequency management emanatesfrom the ITU (International TelecommunicationsUnion), which is a specialized control agency ofthe United Nations. Periodic international conferences are called to conclude treaties regulatingthe use of the radio spectrum, obtain standardization of methods and procedures, and minimize interference. Most ITU member countries impose 58 AGO 6354C additional regulatory measures beyond those required by international treaty. a. The international radio regulations specify the details governing the operation of internationa~ communications, and. the tables of frequency allocations are the basis for all international frequency usage. b. For the purpose of frequency allocations, the world is divided into three regions. A type of service may be the same in all regions or may vary between regions in accordance with international agreement. These allocations are used throughout the world for the control of electromagnetic radiations. c. The International Frequency Registration Board, which is a working group of the ITU, maintains a register of frequency assignments in the international frequency list. It is this regulation that insures international protection of frequency assignments.' All United States registrations are made through the FCC (Federal Communications Commission). 40. National Within the United States and its possessions, the authority and procedures used to manage radio frequencies were established by the Communications Act of 1934. This act established separate control procedures for government and nongovernment users. a. The IRAC (Interdepartment Radio Advisory Committee) was established to advise federal government departments in the area of radio opera- AGO 6354C 59 tions, and to make assignments of radio frequencies to federal government users. b. The FCC was established to regulate all nonfederal government radio communications. c. To avoid mutual frequency interference, coordination is effected by these agencies prior to an assignment. 41. Department of Defense a. At the DOD (Department of Defense) level, frequency management is handled by the J/FP (Joint Frequency Panel) of the MCEB (Military Communications-Electronics Board). Neither the board nor the panel has executive status, but were established to serve in an advisory capacity to the Joint Chiefs of Staff. (1) The function of the MCEB is to assist in the preparation and coordination of joint and combined directives and/or agreements in various communications-electronics activities, including frequency allocations and assignments. (2) The J /FP of the MCEB coordinate, allocates, and assigns frequencies for the military departments, and coordinates with allied military communications boards and committees as required. (3) Each military department maintains a staff for planning and administering the use of the radio frequency spectrum. b. As a tool of frequency management, the DOD established a large computer analysis facil 60 AGO 6354C ity to predict the interference potential of existing or proposed electromagnetic environments, based on spectrum signature and environmental data. 42. Continental United States and Overseas a. Within the CONUS (Continental United States), the Office of the Chief of CommunicationsElectronics obtains frequencies from the Inter department Radio Advisory Committee for CON US Army commands. The Chief of Communications-Electronics authorizes lists of frequencies and call signs to satisfy routine CONUS tactical and training requirements. Coordination and assignment procedures have been established to afford greater flexibility in meeting the tactical and training requirements. These procedures include coordination with the FCC to asure noninterference to civil operations, and with the Federal Aviation Agency to assure noninterference with their activities. b. For frequency requirements outside the United States, the Joint Frequency Panel of the Military Communications-Electronics Board coordinates and assigns frequencies for use between oversea commands, or between oversea commands and the CONUS. 43. Department of the Army As one of the major users of the radio frequency spectrum, the Department of the Army has a vital interest in all facets of frequency management. It must share the spectrum with the AGO 6354C 61 other military services, government departments,and civil operations. The focal point for staff advice and coordination of all army communicationselectronics activities is the Chief of Communications-Electronics. This advice and coordination encompasses the assignment, allocation, and controlof army frequencies, and the negotiations for newfrequencies to meet ever-increasing requirements. 44. Field Army a. The army signal officer is responsible for providing frequency support to all units of the fieldarmy. This includes: (1) Providing representation at frequencyconferences of higher headquarters asrequired. (2) Coordinating with adjacent armies andsubordinate units on the assignment offrequencies to flanking or supportingunits. (3) Preparing appropriate army SOl andSSI items for the purpose of: (a) Allocating frequency lists to the corpsand divisions in accordance with thedisposition of forces and the tacticalmission. (b) Allocating lists of call signs in thesame manner as frequencies. (c) Assigning frequencies and call signsto army headquarters and army troopnets. (4) Resolving interference problems of subordinate units. 62 AGO 6354C ( 5) Maintaining records of all frequency assignments within the field army area. (6) Receiving, processing, and forwarding to higher headquarters the radio frequency requirements for all communicationselectronics operations in the field army area. b. Radio relay requirements can be expected to exceed the available channels, particularly in areas with extensive television and aeronautical facilities in use. The ABM plan (para 49) or another effective plan should be used to obtain maximum use of each available frequency. Radio relay frequency usage must be controlled at army level. in any assignment plan employed. The importance of multichannel radio relay communications in the army area demands strict control. Assignment of frequencies to corps and divisions may be decentralized, but assignments must be forwarded to army frequency branch of the anny signal section. 45. Corps and Division At corps and division level, frequency control is the responsibility of the corps signal officer and the division signal officer, respectively. a. Radio relay frequencies are obtained from the anny SOl, which contains a radio relay list for the entire field army. This list is common to all field armies. b. The following procedures are established for radio relay frequency control and assignment- AGO 6354C (1) Centralized control. Corps and divisions submit their radio relay system plans to the army frequency branch. The plans, in system diagram form, identify and locate terminals, relays, and distant terminals with grid coordinates from a standard map. Terminals or relays located on prominent hills will also indicate hill numbers. Signal centers are designated by an identifier selected from the identifiers allocated to each unit in the army SOL '(a) Upon receipt of all radio relay plans, the army frequency officer plots all circuits on a situation map, and assigns frequencies to each circuit, present and proposed, employing various radio relay frequency assignment techniques. (b) After units have received their radio relay assignments, all further coordination is conducted directly between the unit concerned and the army frequency branch. (2) Decentralized control. If the availability of radio relay frequencies permits, sublists of radio relay frequencies may be prepared at army level and allocated to the subordinate units, using adequate geographic separation between identical sublists. Acting for the corps signal officer or the division signal officer, the radio officer at corps or division assigns the frequencies to each circuit in his respec- AGO 6354C tive relay complex, both present and proposed, employing the most effective assignment technique for his system. Upon implementation, the complete radio relay system plan, with assignments recorded, must be forwarded to the Army frequency branch. Section II. FREQUENCY SELECTION 46. Methods of Frequency Selection a. The methods of frequency selection depend primarily on the kind of equipment used and the physical makeup of the radio relay network. The method for each equipment is described in the technical manual covering the equipment. b. The information in paragraphs 48 and 49 outlines procedures to follow in using the twoblock method for assignment of frequencies to a simple isolated route and the ABM method for assignment of frequencies to a complex system. The two methods to be discussed are intended to be used for systems employing Radio Set ANI TRC-24. c. The information in paragraphs 50 and 51 outlines procedures to follow in using the double ABM and XY methods for assignment of frequencies to routes having heavy traffic. 47. Interference Between Transmitters and Receivers The purpose of any frequency plan is to minimize the effects of mutual interference between •AGO 63540 65 transmitters and receivers, and between receivers.With a radio set operating full duplex, the transmitter power is usually millions of times greaterthan the power of the received signal. The receiver must be able to reject the powerful transmitted signal and select the weak signal to whichit is tuned. The sensitivity and selectivity of aradio receiver can be determined and predicted. a. In order to accomplish effective rejection ofa transmitted signal, a receiver must be separatedfrom the transmitter (fig. 14). A receiver can beseparated from a transmitter by distance or byfrequency spacing. b. Cross polarization may be employed (fig. 15)to reduce the required frequency separation whenvertical polarization can be used without excessive signal loss. c. The following chart shows the minimum fre- SAME MAST RECEIVER TO RECEIVER ~ + + 1 Fl -r- F2 F3 r---F4 TRANS-RECEIVER TRANS- MITTER RECEIVER MITTER t j DIFFERENT MASTS FM24-21-14 Figure 14. Transmitter and receiver separation. 66 AGO 6354C SAME AS 01 FFERENT MASTS I 1 I I TRANSMITTER (NOTE I) RECEIVER (NOTE 2) NOTES: I. VERTICAL POLARIZATION 2. HORIZONTAL POLARIZATION FM 24-21-15 Figure 15. Cross polaTization. quency separations required for Radio Set AN/ TRC-24. Minimum separations required (MCS) On different mast, near Two by, or on same mast receivers On same mast cross polarized nearby Band 1 A 9 8 B 18 10.5 1.52 c 28 11 3 D 40 12 AGO 63540 67 48. Two-Block Frequency Assignment Plan The two-block plan is used for the assignment of frequencies to a simple isolated system (fig.16). The system used in this discussion consistsof two terminals and three relays (fig. 16), withthe radio sets operating in the C band and theantennas having horizontal polarization '(para47c). Proceed as follows: a. Arrange the frequencies in a numerical sequence. Divide the frequencies equally into twolists (blocks) while maintaining a minimum of 28mcs separation between the highest frequency inblock I and the lowest frequency in block II (fig.17). The 28-mcs separation is the requirement for transmitting and receiving antennas on thesame mast for C band operation (para 47c). Referring to the chart in paragraph 47c, it must beremembered that this separation changes withthe band being used. b. Assign transmitting frequencies through thesystem. Beginning at terminal A, alternately select a frequency from block I, then block II (fig.18). When these assignments are completed, assign frequencies in the same manner from B to A(fig. 18). A B FM 24-21-16 Figure 16. Simple i.~olated 1·oute. 68 AGO 6354C BLOCK I BLOCK II ONLY 14 MCS 265(NOTE) 225 270 230 272 232 273 235 274 236 276 238 279 240 28 MCS 280 242 (NOTEl251 285 NOTE: THESE TWO FREQUENCIES CANNOT BE USED BECAUSE THEY DO NOT PROVIDE THE 28-MCS SEPARATION REQUIRED. FM24-21-17 Figure 17. Frequencies divided into two blocks. TERMTERMINAL INAL RELAY RELAY RELAYNO.I N0.2 N0.3 B 21o R . 23o R 'L0 A n~~~ ~ T T 2~' ~ ~3 T FM24-21-18 Figure 18. Two-block frequency assignment. c. At each relay or terminal where two or more receivers are located, make certain that the minimum required receiver-to-receiver separations are AGO 63540 69 maintained (2 mcs for C band). For this reason,frequencies from a specific block may not alwaysbe assigned consecutively. d. Since blocks I and II are separated by 28mcs for same mast separation, the 11-mcs separation requirement for different masts, and crosspolarization for same mast, is already considered. e. The two-block plan also may be used for asimple parallel system (fig. 19) where there arenot more than two transmitters and two receiversat each terminal to be considered. In any system,however, frequency assignments are consideredtentative, and reassignment may be necessaryafter testing the system. 49. ABM Frequency Assignment Plan The ABM plan is used for assignment of frequencies to a complex system (fig. 20) where thereare more than two transmitters and receivers atthe same location. a. The ABM plan designates each terminal or TERMINAL TERMINAL A B FM 24--21-19 Figure 19. Simple parallel sy8tem. 70 AGO 6354C relay location with the letter A, B, or M (fig. 20). The established rule is that the same lettered locations will NOT be interconnected (fig. 21). Following this rule, location A can establish shots with locations B or M, location B with A or M, and location M with B or A. b. Considering all possible shots, a triangle can be drawn as shown in A, figure 22. In the AN/TRC-24 radio relay system, there is no transmitter-to-transmitter separation required. Therefore, all transmitter frequencies at any lettered location can be placed in one group or block without regard to interference problems. X XX Figure 20. Complex system. AGO 63540 71 CORRECT INCORRECT FM24-21-21 Figure 21. Interconnection of location.~. c. Considering transmitter frequencies only,six groups or blocks of frequencies are requiredfor the triangle (A, fig. 22). These blocks of frequencies are numbered from I through VI. Relative to location A, I and II are the transmittingfrequencies and IV and V, in this case, are thereceiving frequencies. d. Analyzing the triangle situation, you willsee that in order to set up a system between Aand M, the transmitter frequencies at A must befrom block I, and the receiver frequencies at Amust be from block IV. Each system has a designated block from which the frequencies must beused (B, fig. 22). e. To set up a system from B to M, find theblock where B transmits and M receives. In thiscase it is Block VI (B, fig. 22). 72 AGO 6354C A. LOWEST HIGHEST FREQUENCY FREQUENCY LOCATION I I II m IV v IVI I II I I I A T R B. 8 R T I I T M 0 0 FM 24-21-22j Figure 22. Triangle situation and corresponding chart. AGO 6364C 73 f. Now, the frequency separation required between the transmitter and receiver, same mastand different masts, must be applied to the blocksof frequencies. Looking again at the triangle,consider the frequencies at location A (A, fig. 23). (1) The transmitter-to-receiver, same mast,frequency separation is 28 mcs; therefore, block II and V, and I and IV, mustbe separated by 28 mcs. (2) The transmitter-to-receiver, differentmast, frequency separation is 11 mcs;therefore, blocks I and V, and II and IV,must be separated by 11 mcs. (3) Upon inspection you can deduce that,since blocks I and IV are separated by28 mcs, then blocks I and V must beseparated by an amount greater than 28mcs. Logically then, the block I and Vseparation has been accomplished andneed not be considered again. g. At this time, examine the separation required for the circuits at locations B and M (Band C, fig. 23). Analyzing the separations requiredat B and M, and applying them to the blocks inB, figure 24, it is evident that seven separationsare required as shown in C, figure 24. h. It has been determined that six blocks orgroups of frequencies are required by consideringthe six transmitter frequencies from the trianglesituation, and the necessary separations requiredbetween the blocks. Now, it is necessary to determine the number of frequencies required in each 74 AGO 6354C T A. II MCS LOCATION A R B. LOCATION B RT C. II MCS LOCATION M FM24-21-23 Figure 23. Frequency separations at locat·ions A,B, andM. block. To accomplish this, an analysis must be made of the system requirements (fig. 25). AGO 6354C 75 28MCS A. I II ill N v VI II MCS II MCS 28MCS B. I II m IV v VI II MCS 28MCS28MCS 128MCS + ~ c. I II m N v VI tiiMCS f t· LIIMCS J IIMCS '----IIMCS - FM 24-21-24 Figure 24. Frequency separation, as applied to blocksof frequencies. 76 AGO 6354C FM 24-21-25 Figure 25. Analysis of system requirements. i. From figure 25, it can be seen that three transmitter frequencies are required for the A to M shots. Thus, a minimum of three frequencies are required in block I for A to M. Continue the analysis of the system-the requirements for the entire system should conform with the listing below. AGO 6354C 77 A-M_____ Block I _____3 frequenciesA-B _____ Block II _____6 frequenciesM-B _____ Block III _____2 frequenciesM-A _____Block IV _____3 frequenciesB-A _____Block V _____6 frequenciesB-M_____Block VI _____2 frequencies 22 Total frequenciesrequired j. Divide the allocated frequencies into sixblocks (see chart below) to include as many foreach block as require (i above). There is no definite procedure for this division other than trialand error. Separations between respective blocksmus.t be checked, or the method will fail; i.e., 28mcs separation for I and IV, II and V, and IIIand VI; 11 mcs separation for I and III, II and IV,III and V, and IV and VI. The following chartis an example of frequency division for C bandoperation. 225 252 300 227 259111 303 228 I 260 312 231 262 316 v 234 268 324 235 269 IV 331 237 II 271 338 239 274 347 VI 244 280 348 246 283 356 250 290 78 AGO 6354C k. At this time, frequencies may be assigned to the system (fig. 26). The transmitter frequency is always located next to the terminal or relay symbols. If this entire procedure has been followed exactly, then transmitter-receiver separation is taken care of; however;care must be taken X FM24-21-33 Figure 26. Assigned frequencies in a type radio relay system. AGO 6364C 79 at relays and multiterminals to assure that receiver-to-receiver minimum separations (2 mcs)are observed. 50. Double-ABM Plan If the traffic load on a particular route is sogreat that an additional radio link must be established and an additional frequency assigned, useof the ABM plan becomes difficult, and the doubleABM plan should be used. a. The double-ABM plan uses the same six frequency blocks as the single-ABM plan. The doubleABM plan uses symbols A, B, and M for theseblocks, and also three more symbols-A', B', andM'. Figure 27 shows all six symbols in use. Also,the figure shows that a station labeled A cancommunicate with a station one hop away labeledA'. Four of the six frequency blocks can be usedfor communication between A and A' (two blocksin each direction). Thus, a heavy traffic routecould be made up of radio stations labeled A, A',A, A', etc. Similarly, B and B', or M and M',could be used. b. Suppose that symbol A is assigned to a station S. Then, on a heavy traffic route, that stationone hop away from S could be assigned A'. On alighter traffic route, the station one hop awayfrom S could be assigned B or M. c. The series of symbols with prime and nonprime letters (A, A'; B, B'; M, M') need not beused for heavy traffic routes only. However, thesingle-ABM series or the single A', B', M' series 80 AGO 6354C FREQUENCY I :r BLOCKS: WAYSOFUSE A T R a R T T M o=J o:J A' R T I T R a· { M' R CD I T R I T R {: I a R T T { a' R M T { R M' FM24-21-26 Figure 27. Double-ARM plan. is better for the lighter traffic routes because it permits a greater number of interconnections. d. A route can be made up partly of one series of symbols and partly of another, such as A', A, B', M'. Symbol shifts of this kind help in making interconnections. AGO 6354C 81 51. XY Plan The XY plan is used when planning a veryheavy traffic route. This plan is not as flexible asthe previous plans (ABM and double ABM); forflexibility, it relies on interconnection with them.Interconnection between the XY plan and theABM or double-ABM plan can be worked out bythe planning officer. a. The XY plan (fig. 28) uses the same six frequency blocks as the ABM and double-ABM plans.Stations labeled X and Y can communicate witheach other (without mutual interference) by usingVHF channels in four frequency blocks (two ineach direction). b. If adjacent broad bands of frequencies aredivided into six blocks each, it is necessary toavoid transmitter-to-receiver interference betweenblocks VI and VII (VII is block I of the adjacentgroup). A station using way X in one of the broadbands of frequencies should use way Y in the ad- FREQUENCYBLOCKS: I II m DZ lZI WAYS OF USE X T R y R T FM24-21-27 Figure 28. XY plan. 82 AGO 6354C jacent broad b~;tnd, and vice versa. This would practically eliminate interconnection possibilities with ABM plans, if both XY and ABM plans were used in both broad bands of frequencies. However, interconnections can be made by placing a guard between the two bro~d bands of frequencies and by using way X at the same stations in both bands, or by using the XY plan in only one of the two broad bands of frequencies. AGO 6364C 83 CHAPTER 6 SYSTEM OPERATING TECHNIQUES Section I. INTRODUCTION 52. Operating Practices Uniform operating practices must be established throughout the communication system toassure efficient use of signal personnel and facilities. SOP's must be distributed to all points inthe system where personnel operate and maintaincommunications. 53. Circuit Control Facilities a. A circuit control facility must be designatedfor each system to simplify circuit managementproblems and to insure orderly control of operations. The terminal serving the higher, or larger,headquarters usually is designated as the locationfor the control facility. The control facility is responsible for supervision of initial and overalltests, coordination and maintenance effort fortrouble location and clearance, and temporary circuit reassignment to meet emergency conditions. b. The control facility must maintain a log toshow which circuits are out of service, the reasonfor such outage, and the prospects for restoral.The log also must show when permission has been 84 AGO 6354C granted radio relay stations to remove the circuit for routine tests, to patch in spares, or to perform any operation affecting circuit performancP.. Copies of all circuit orders must be sent promptly to the control facility to insure that control personnel have accurate information on the condi· tions of assigned circuits. 54. Use of Order Wires a. To carry out necessary testing functions, order wires usually are required between the control facility and subordinate facilities. Normally, maintenance operations and instructions are transmitted over order-wire circuits which usually are an integral part of the communication equipment. b. Order-wire circuits are required as a communication means during the system lineup. Therefore, it is important to complete the lineup of the order-wire circuit before attempting the lineup of the other channels. Section II. SYSTEM LINEUP 55. General The overall system must be lined up by adjusting transmission levels at all points in the system, where such adjustments are possible, in accordance with instructions contained in the appropriate equipment manual. The overall system lineup consists of the radio-system lineup, which is accomplished first, and the carrier-system lineup, which is accomplished after the radio- AGO 6364C 85 system lineup is completed. Procedures for lineupof both equipments are detailed in the equipmentmanuals. 56. Control of Lineup a. All lineups are supervised by the controlfacility, designated terminal A; the remainingterminal in the system being designated terminal B. Where carrier equipment is physically separated from the radio-terminal equipment, the carrier attendants at terminal A will supervise theoverall system lineup. b. During system lineup, intermediate relay orrepeater stations (radio or carrier) report allreadings to the control facility. c. Permission to make lineup adjustments mustbe obtained from the control facility. If telephoto,facsimile, or other transmissions that requirecritical signal levels are being transmitted overthe system, the control facility must insure thatno more than a 2-DB change will result in thesystem as a result of any one lineup. 57. Radio-System Lineup a. The radio-system lineup is performed onlyafter the starting procedures have been performedfor each radio set of the radio system, as outlined in the appropriate equipment manual. Thelineup insures that the radio system is operatingat maximum efficiency prior to superimposing thelineup. If connections to the carrier system havebeen made, the control carrier terminal must beinformed when the radio-system lineup is com 86 AGO 6354C pleted, so that overall system lineup may be accomplished. b. The radio lineup procedure is accomplished first in the A-B direction, and then in the B-A direction. When performing the lineup, the controls of the transmitter at radio terminal A are adjusted first. When this has been accomplished, the control radio-terminal attendant directs the attendant at the next receiver in the A-B direction to adjust his receiver control appropriately. When this has been accomplished, radio terminal A then directs that the next transmitter in the A-B direction be adjusted. Each successive receiver and transmitter in the A-B direction is lined up in sequence until the receiver at terminal B is lined up. At this point, radio terminal B assumes temporary control, and directs the lineup in the B-A direction. c. After all stations have reported readiness for overall system lineup, the control carrier facility is notified. 58. Overall System Lineup a. The overall system lineup is performed for both the carrier system and the radio system. This lineup is controlled by the carrier terminal designated as the control facility. As in the case of the radio-system lineup, the carrier-system lineup, is accomplished first in the A-B direction and then in the B-A direction. The procedure followed is the same at both terminal and repeater stations. AGO 6354C b. The carrier-system lineup adjustments aremade in accordance with the procedure outlinedin the equipment manual or SOP's. The step-bystep process for lining up the carrier system issimilar to that for the radio-system lineup (para57). 59. Monitoring and Operating Checks Monitoring and operating checks must be performed at periodic intervals. These checks normally are performed while the system is operating and should not interrupt the normal use ofthe radio and carrier equipment. Equipment manuals and SOP's provide a list of checks to be performed. 60. Circuit Order Tests a. Overall circuit order tests are required afterinstallation tests have been completed and beforethe systems, trunks, and circuits are placed inservice. These tests are made on trunks that area part of new installations, are additions to anexisting system, or which have been rerouted bywiring changes or by patching. They are made onan overall system basis, from switchboard toswitchboard (or, if available, from testboard totestboard). b. All circuit order tests are under the direction of the control facility. The tests includeoverall signaling and talking, with supervisorychecks being made to assure efficient operation.Adjustment and alinement checks also are madeto determine whether facilities meet established 88 AGO 6354C performance requirements. Noise measurements are made on long distance networks. Ifthe overall performance requirements are met, the trunks are released for use in the communication network; if not, they are subjected to sectionizing tests to bring the system up to acceptable standards. Section Ill. NOISE AND INTERFERENCE 61. General The amount of noise or interference at the receiver location limits the length of gaps between radio relay equipment-the more noise or interference present, the shorter the distance that can be spanned satisfactorily. The most objectionable results of high noise level are reduced intelligibility in telephone circuits and errors in carrier teletypewriter circuits. Unshielded electrical equipment, powerlines, motor vehicle ignition systems, certain hospital equipment, and power units are sources of radio noise. Normally, all receiving equipment is set up away from heavy motor traffic routes, and vehicles are not permitted within 200 yards (182 meters) of receiver antennas. Harmonic radiation from other transmitters also may cause considerable interference. The prime requirement for good communication is a high signal-to-noise ratio. 62. Mutual Interference a. The various ways in which mutual interference can occur are- AGO 6364C 89 (1) Transmitter fundamental radiation toreceiver fundamental response. (2) Transmitter spurious radiation to receiver fundamental response. (3) Transmitter fundamental radiation toreceiver spurious response. (4) Transmitter spurious radiation to receiver spurious response. (5) Receiver radiation to receiver fundamental response. b. Spurious radiation refers to signals radiatedfrom the transmitter on many frequencies otherthan the fundamental or carrier frequency. Whilethese spurious radiations are weaker than the fundamental or carrier frequency, they may bestrong enough to cause interference (noise) innear-by receivers. Noise is strongest when the receiver is tuned to a frequency corresponding toone of the spurious transmitter radiations. c. If these other signals above and below thefrequency to which the receiver is tuned arestrong enough, they may be amplified to the pointwhere they will render the desired signal unintelligible. It is possible for the local oscillator ina super heterodyne-type receiver to radiate asignal which can cause interference. This isknown as receiver radiation. d. When receivers are situated close to transmitters, the frequency separation must be greaterthan normal. e. Interference caused by spurious radiations 90 AGO 6354C of the transmitter being picked up by the spurious responses of the receiver need be considered only when a large number of transmitters and receivers are operated at one site and the received . desired signal is weak. No interference of this type will be encountered in a communication &ystem where transmitters and receivers are operated with antennas separated by at least 60 feet (18 meters) and with the receivers operating on strong signals. 63. Operation with High System Noise a. Occasionally, traffic channel noise is excessive. This may be caused by a higher noise level at one or more radio hops than at others. A hop may have relatively high path attenuation due to a long transmission path or line-of-sight obstructions. A high noise level also may be caused by external sources such as ignition or radio interference. b. Under such conditions, it frequently will be possible to improve the overall system signal-tonoise ratio. Better reception may be obtained by increasing the signal output of the transmitter and reducing the gain of the receiver where the high noise level occurs. c. There are limits to signal-to-noise improvement, however. Changing four-channel output to one-channel output (or 12-to 4-) will increase the relative signal-to-noise level. This assumes that all of the transmitter power that was used in the higher number of channels is applied to the lower number. AGO 6354C 91 d. When a particular hop is operating with excessive noise, follow the procedure outlined in the equipment manual. 92 AGO 6354C CHAPTER 7 MAINTENANCE OPERATIONS Section I. INTRODUCTION 64. General a. Maintenance operations are assigned to specific levels of command in accordance with the primary mission, characteristics, and mobility of the level involved, and the economical distribu tion of resources. b. Repair parts allowances and initial guide quantities are selected and allocated to organizational, direct support, general support, and depot maintenance organizations in accordance with the provisions of AR 700-18. The supply of repair parts at direct support level and below will be accomplished by maintenance support organizations. 65. Categories1 of Maintenance There are four broad categories of maintenance (fig. 29) that have been defined by the Department of Defense for all services. They facilitate the assignment of maintenance missions and responsibilities within the Department of Defense. a. Organizational Maintenance. Organizational maintenance is that maintenance normally auth <\GO 6354C 93 CATEGORIES' OF MAINTENANCE OPERATOR OF~--USINGUNIT ORGANIZATIONAL ~ MAINTENANCE UNIT MECHANICOF USING UNIT DIRECT SUPPORT MAINTENANCE GENERAL SUPPORT MAINTENANCE SEMIFIXED REPAIR SHOP .. DEPOT MAINTENANCE AI~~~ I =-%' FIXED REPAIR SHOP FM24-21-28 Figure 29. Categories of maintenance. orized for, performed by, and the responsibilityof a using organization on equipment in its possession. This maintenance consists of functionsand repairs within the capabilities of authorizedpersonnel and is performed by using organizational tools and test equipment. Maintenance exceeding the authorized scope of maintenance maybe performed when authorized by the next highermaintenance support commanders. 94 AGO 6364C b. Direct Support Maintenance. Direct support maintenance is that maintenance normally authorized and performed by mobile repair teams from designated maintenance activities in direct support of using organizations. This category of maintenance is limited to the repair of end items or unserviceable assemblies in support of using organizations on a return-to-user basis. c. Geneml Support Maintenance. General support maintenance is that maintenance authorized and performed in semifixed or permanent shops by designated organizations in support of the Army supply system. Normally, general support maintenance organizations will repair or overhaul materiel to required maintenance standards in a ready-to-issue condition based upon applicable supported Army area supply requirements. d. Depot Maintenance. Depot maintenance activities, through overhaul of economically repairable materiel, augment the procurement program in satisfying overall Army requirements and, when required, provide for repair of materiel beyond the capability of general support maintenance organizations. Section II. PREVENTI.VE MAINTENANCE 66. General Preventive maintenance is the systematic care, inspection, and servicing of equipment to maintain it in serviceable condition and prevent breakdowns. It is accomplished by equipment operators and organizational maintenance personnel. AGO 6364C 95 a. Radio operators, who are highly trained inoperating techniques, perform only those simpleroutine maintenance operations that can be performed by men with a limited technical background. Each appropriate technical manual coverst~1ese preventive maintenance measures in anoperational checklist. b. Organizational maintenance personnel provide maintenance backup support to the operator,and are responsible for organizational maintenance that requires limited technical training.Each appropriate technical manual contains equipment performance checklists and other organizational maintenance information. 67. Responsibility Commanders are responsible for insuring thatpersonnel under their command comply with procedures and instructions dealing with preventivemaintenance and that they fill out the requiredmaintenance records as provided by TM 38-750. 68. Preventive Maintenance Services a. Daily Service. Preventive maintenance services are performed by the radio operator eachday the equipment is operated. The equipment isinspected and serviced in accordance with procedures outlined in the applicable equipment technical manual. Deficiencies and shortcomings thatare not corrected by the operator, or that are corrected by replacement of parts, are recorded onan appropriate maintenance form (TM 38-750). b. Periodic Services. These inspections and 96 AGO 6354C services, prescribed by appropriate technical manuals, are performed by organizational maintenance personnel. At the time of service, organizational maintenance personnel, assisted by the operator, systematically inspect and service the equipment. All deficiencies and shortcomings, as well as the corrective action taken for each, are recorded on an appropriate maintenance form (TM 38-750). If repairs by a higher category of maintenance are required, an appropriate maintenance form will be prepared and forwarded with the equipment to the supporting maintenance activity. 69. Electric Shock Hazards and Safety Precautions a. General. High voltages may be required in the operation of radio sets. Therefore, radio operators and maintenance personnel should first become familiar with the equipment manual before operating the equipment. Warning: DEATH ON CONTACT may result if operating and maintenance personnel fail to observe safety precautions. b. Precautions. Whenever radio sets use high voltages, the radio operator should observe the following operation and maintenance precautions: (1) Be careful not to contact high-voltage or power connections. (2) Avoid contact with transmission lines and antennas that have radio frequency voltages. (3) When working inside radio sets, be sure AGO 6354C 97 that the power source is disconnectedand that high-voltage capacitors are discharged. (4) Check the equipment manual for a list ofcomponents that contain high voltages. Section Ill. OVERALL AND SECTIONALIZING TESTS FOR TROUBLE CLEARANCE 70. Multichannel Systems a. A standard multichannel radio relay system(fig. 5) basically consists of the following: (1) Radio-terminal sets. (2) Radio-relay sets. (3) Telephone carrier sets. (4) Teletypewriter carrier sets. (5) Ringing equipment. b. Trouble in the system can be localized bytesting the following: (1) The radio circuit between terminal stations in both directions. (2) The spiral-four circuit between theterminal radio stations and terminalcarrier stations at each end of the system. c. A step-by-step procedure for sectionalizingtroubles in b (1) and (2) above is shown infigure 30. Figure 30. Overall and sectionalizing tests on trunksof radio relay systems. (Located in back of manual) 98 AGO 6354C 71. Long Distance Network A long distance network comprises the long distance trunk or radio link with its associated central office equipment. Overall tests are used to verify the transmission ang signaling features of communication trunks associated with new installations, with additions to the existing plant, and with reassignment of circuits. 72. Overall Tests a. The overall talking, signaling, transmission, and other tests should be made from switchboard to switchboard under the supervision of the control station. If trouble is encountered, the faulty channels should be removed from the switchboard, and further tests continued from patching panel to patching panel. b. Once a trouble is suspected or reported, overall tests should ~e conducted to verify the trouble condition. Sectionalizing and localizing tests then should be made to identify and locate the failure point. 73. Station Operation and Maintenance Overall tests of communication channels include initial and periodic tests to assure serviceability. Adequate testing equipment is required at terminals and intermediate points to perform overall and sectionalizing tests. Under the supervision of the control facility, overall signaling, talking, and transmission tests from terminal to terminal should be made first. These are followed by sec- AGO 6354C 99 tionalizing tests between control facilities and,finally, between relay stations. 74. Tests on Trunks of Radio Relay Systems a. Standing operating procedures must be setup to insure orderly control of maintenance andother work for those long distance circuits whichpass through several test or carrier and radiorelay stations in different administrative areas. b. Overall and sectionalizing tests on trunksof a radio relay system are shown in figure 30. Order-wire circuits often are a built-in feature of military radio relay equipment, as indicated in the figure. The order wires may be extended toorder wires of connected systems in the circuitlayout. c. Maintenance personnel are required at allstations in a system to permit coordination oftesting activities on long distance trunks andtransmission systems. Control and subordinatefacility procedures must provide for orderly analysis of troubles, and should designate responsibility for placing and maintaining circuits inservice. Once a trouble is located, corrective maintenance procedures must be carried out. d. The areas of responsibility for the activitiescomprising an integrated radio relay and wirecommunication system are shown in figure 30. Inaddition, the procedure and sequence of operations for testing and troubleshooting is outlinedin steps 1 through 8 (fig. 30). SOP's must beformulated for forward, intermediate, and rear 100 AGO 6354C area radio relay communication systems, so that specific responsibilities are assigned to the separate activities of the system. By this means, troubleshooting and testing procedures may be established and preventive and corrective maintenance performed in a minimum of time and effort. AGO 63540 101 CHAPTER 8 ANTIJAMMING Section I. CHARACTERISTICS OF JAMMING OPERATIONS 75. General Enemy jamming is the transmission of disturbing radio signals to interfere with the receptionof the desired signal. The effects sought by theenemy are to disrupt our system and deny its useto our forces. Techniques employed to minimizethe effect of enemy jamming are called antijamming. The term electronic counter-countermeasures (ECCM) encompasses antijamming. a. All radio relay equipments are vulnerable tojamming activity, and it must be assumed thatjamming operations will be conducted by theenemy whenever it is to his advantage. b. Prior to jamming, the enemy searches thefrequency spectrum to locate radiated signals.After identifying a transmission, the enemytunes a transmitter to the same frequency andtransmits a jamming signal. In so doing, thejammer attempts to prevent the effective reception of desired signals on the frequency. 76. Defense Against Jamming In most instances, ECCM measures will go be 102 AGO 6354C yond the effort.s of operators. Most radio relay equipment has been designed with built-in antijamming features. Special frequency assignments, frequency changes, the use of alternate communication routes, and operational adjustments are techniques that may be used to overcome enemy jamming. If possible, the enemy jamming station should be located and destroyed. Additional preventive measures include proper siting, use of alternate frequency assignments, code words, and a frequency change system. Section II. ANTIJAMMING INSTRUCTIONS 77. General Operator skill and confidence are essential for maintaining communications during enemy jamming. These can be developed by individual, team, and unit training in which simulated enemy jamming is used to approximate actual field conditions. The operator must be familiar with antijamming instructions in the equipment manual. 78. Instructions for Commanders and Staff Officers a. If possible, study and plan all operations in advance; use brevity codes to direct plans. b. Keep messages as short as possible. c. Stress radio discipline and security. d. Destroy enemy jamming stations, if possible. e. Always inform the next higher headquarters of enemy jamming activities. AGO 6364C 79. Instructions for Signal and Communication Officers a. Initial siting is probably the most importantand effective antijamming measure that can betaken-it becomes more important the closerradio relay is brought to the enemy location.Where possible, locations for forward area terminals and relays should be chosen with a welldefined land-mass to shield them from possibleenemy interception and jamming. In addition toterrain mass, foliage and man-made structures canbe used in achieving this protection. b. When directional antennas are employed,they can be rotated to minimize the strength ofthe jamming signal in relation to the strength ofthe desired signal. c. Mobile facilities should be relocated to sites where the jamming signal is received at minimum strength. d. Polarization of antennas may be changedfor maximum signal strength. e. Antenna heights may be changed. f. Where possible, alternate frequencies shouldbe available, and by using spare equipment, thecircuit should be re-established on the new frequency, with the original equipment continuing tooperate on the original frequency. g. Circuits should be established on minimumpower requirements, consistent with circuit quality; high power should be used during jammingto attempt to override the interference. If there 104 AGO 6354C are many radio sets in a given area, the SOl should specify, on priority basis, the circuits which will switch to higher power. h. Generally, forward area radio relay circuits should not be installed in a line perpendicular to the line-of-contact with the enemy. This may be prevented by installing radio relays to permit approach to a forward area at an angle. Such equipment utilization must be weighed against all other requirements. i. Filters should be used, if available, to minimize unwanted signals. 80. Instructions for Operators a. Site the station and antenna to minimize enemy jamming. b. Learn to recognize enemy jamming; report all details to the officer-in-charge. c. Learn to readjust the set to minimize the effects of jamming. d. Operate with minimum power until jammed; then increase the power. e. Shift to alternate frequencies and call signs as directed. f. Authenticate all transmissions over the order wire. g. Keep the order wire transmissions as short as possible. h. When jammed, keep calm, keep trying, keep operating-a skilled operator may at times be able to work effectively through such interference (FM 24-150). AGO 6354C 105 81. Reporting Enemy Jamming A prompt, accurate, and complete report ofenemy jamming is important, since an enemyjamming attack is usually part of a well-organizedplan and frequently precedes important tacticalmaneuvers. The reports from the individual radiooperators, which frequently provide intelligenceon the extent and importance of enemy actions,are normally compiled at division or corps headquarters by electronic warfare (EW) personnel.Properly correlated jamming information mayserve as a warning of impending enemy action ina sector or on a broad front. 106 AGO 6364C CHAPTER 9 FIELD EXPEDIENTS Section I. INTRODUCTION 82. Definition a. A field expedient is a positive action that can be taken by personnel to maintain, facilitate, or expedite communications under unusual conditions. These conditions may originate as a result of normal wear or use of equipment, accidental damage, or enemy action. Employment of field expedients requires the application of common sense and ingenuity on the part of personnel immediately concerned. b. Because of the many possibilities of equipment failure, complete and comprehensive solutions cannot be formulated; however, certain of the more common field expedients are presented in this chapter. 83. Use of Printed Material a. Certain expedients which have proved themselves during field operations and are adopted as official operating procedures are described in Department of the Army publications. Examples of this type literature are TB SIG's. These bulletins are published to acquaint Signal Corps personnel with difficulties encountered with equipment in the AGO 6354C field and to suggest methods of overcoming suchdifficulties. Usually, they are interim measuresand describe corrective action for equipmentsprior to final publication of MWO's, which aredesigned to improve the equipment permanently.Such MWO's are official Department of the Armypublications which direct and describe in detailphysical alterations to be made to Army equipment by trained technicians. b. Published TB SIG's and MWO's are listedin DA Pam 310-4. Communication personnelshould familiarize themselves with these publications and take the necessary action. Section II. CONNECTI.ONS AND ANTENNAS 84. Coaxial Cable a. Coaxial cable should be kept off the ground,using non-metallic supports. It may be temporarily placed directly on the ground only when thetactical situation demands such action to expeditecommunications. The use of the proper cablelength, as specified in the equipment manual, isa critical factor and should not be altered exceptin cases of emergency. Generally, the use ofshorter cable lengths are preferable to longerlengths. Be careful to avoid coiling or kinking thecable. Spiral-four cable or field wire may be usedfor temporary repairs to broken cable elements,but their use as substitutes for coaxial cable generally results in excessive line loss and equipmentdamage. 108 AGO 6354C b. Cable connections and fittings on equipment must always be kept clean and dry. 85. Vehicular Expedient for Coaxial Cable For ease in running the cable from the vehicle to the·antenna, an appropriate reel unit may be mounted on the rear of the vehicle antenna trailer, and a ground rod may be used as an axle. By using this method, a length of cable, as short as possible, may be payed out, and the coupling may be taped and connected with ease. This facilitates installation and also helps to prevent knotting and kinking of the coaxial cable-kinked coaxial cable has extremely high RF loss. 86. Effective Protection for Coaxial Couplings An effective protective covering for coaxial couplings is %-inch, nonadhesive, polyethylene rubber-and-rosin composition tape. Coaxial couplings protected by this tape can be submerged in water or subjected alternately to freezing and thawing temperatures without adversely affecting transmission qualities. The use of ordinary friction tape generally is unsatisfactory. 87. Antennas The following are some of the expedients that may be used in installing antennas: a. Install antennas on a tree, building, house, or similar structure in an emergency. b. Use field wire, rope, or any similar material to replace lost or damaged guy wires. AGO 6354C 109 c. Where the site is located at high elevations,use a shorter mast than is normal. This facilitatesmaintenance and orientation, and also any alteration in antenna settings which may be requiredby change of operating frequency. d. Use a standard dipole antenna that is cutto proper length. This however, reduces the gainand directivity due to the absence of reflector anddirector elements. 88. Storage for Antenna Guys Antenna guys may be wound and stored on a1-by 6-by 24-inch board by making semicircularcuts at each end for winding the guys lengthwisearound the board. The guy lengths may be indicated on the board and several guys may bewound on each board. These boards may be-madeto fit the appropriate antenna parts case. Thismethod eliminates fumbling and groping forantenna guys, and facilitates locating guys ofappropriate length. Section Ill. POWER SOURCE EXPEDIENTS 89. Method of Reducing Unit Noise at Forward-AreaSites The procedure outlined below is designed to re duce power unit noise by approximately 90 percent. a. Construct a dugout with adequate clearancealong the sides and top to provide sufficient spacefor maintenance and ventilation. 110 AGO 6354C b. Locate the dugout preferably on a slight rise or hill so that accumulations of water and rain will be drained off. Construct drainage ditches from the low side of the dugout. c. Reinforce the sides of the shelter with sandbags, or a wooden or steel framework, to provide support and to prevent cave-ins. d. Erect a roof of available material to provide protection from the weather. Allow space for a ventilator shaft to carry exhaust fumes away. (An exhaust system may be improvised by using flexible metal pipes or carrying cases for 155 millimeter shells.) e. Drape empty sacks or canvas along the roof overhang to muffle generator noise. f. Camouflage the dugout with available material that matches surrounding terrain. 90. Other Expedient51 for Power Sources a. Power unts that are recommended for specific equipments usually give the best results; in emergency situations, however, use any power unit of appropriate output -voltage, current, wattage, and frequency. Sometimes spare equipments are available to provide additional output power; in such cases, it is recommended that only as many units be used as are required to carry the load. b. In case of emergency, turn off all equipment and lights except those actually required to keep the circuits in operation. AGO 6354C Section IV. OPERATIONAL EXPEDIENTS 91. Proper Antenna Orientation for Improvement of Marginal Circuits Terrain in the vicinity of either the transmitting or receiving antenna can seriously distort the antenna radiation pattern so that a weak instead of a strong signal will be received (A, fig. 31). Often the strong signal can be obtained only by trial and error methods. During experimental orientation, advantage often may be taken of indirect radio paths utilizing adjacent obstacles such as high mountains. In B, figure 31, antennas are oriented for a direct path, and a weak signal is obtained because of intervening hills. In addition, part of the signal is reflected by the adjacent obstacle, thus canceling the direct signal. In C, figure 31, the transmitting and receiving antennas are oriented for the indirect path which results in a relatively stronger signal than that obtained by the direct path. 92. Improvement of Marginal Circuits Normally, operating sites should be selected as outlined in chapter 4. Under certain situations, however, it may not be feasible to locate them within line-of-site distances. Marginal circuits may result from operation beyond line-of-sight distances. To increase the sensitivity of marginal circuits follow the procedure outlined below. a. Check and tighten cable couplings and connections. 112 AGO 6354C I " I THEORETICAL I ACTUALPATTERN ---t>\ PATTERN\ \ '' A ~ WEAK DIRECT ~ SIGNALWEAK INDIRECTSIGNAL RCVR B ANT. & XMTR ~\\ANT. ADJACENT OBSTACLE FM24-21-31 Figure 81. Orientation of transmitting and receiving antennas for indirect signal paths. AGO 63540 113 b. Retune all transmitters and receivers in thecircuit. c. Check to see that antennas are adjusted forproper operating frequency. d. Try changing the heights of antennas. e. Try changing locations of antennas. f. Separate transmitters from receiving equipment, if feasible. 93. Transmission and Reception of Strong Signals a. After an adequate site has been selected,and the proper antenna orientation obtained, thesignal level at the receiver will be proportional tothe strength of the transmitted signal. b. Excessive signal strength may result in adjacent and cochannel interference. If a high-gainantenna is used, a stronger signal can be obtained. Most of the current high-gain antennascontain a parabolic reflector for the higher frequencies. Losses between the antenna and theequipment can be reduced by using a high qualitytransmission line, as short as possible and properly matched at both ends. When traffic conditions permit, the change from multichannel tosingle-channel operation will allow more of thetransmitter power to be concentrated in thesingle channel. This will relatively increase thestrength of the signal. 94. Operation in Extremely Mountainous Terrain Useful information based on operational experience in mountainous terrain is outlined below: 114 AGO 6354C a. It is recommended that skid chains be used on vehicles operating on unpaved roads, regardless of the weather conditions. b. Personnel should be well trained in the use of ropes and pulleys. c. In hauling and lowering, equipment must be well packaged to prevent damage. d. At times, radio relay equipment can be operated through masking hills. e. As a general rule, for every man at the top of a mountain, three will be required for his logistical support. AGO 6354C 115 CHAPTER 10 DESTRUCTION OF RADIO RELAY EQUIPMENT 95. General In some tactical situations, it becomes impossible to evacuate all radio relay equipment. It isimperative, therefore, to destroy all equipmentthat cannot be evacuated to insure that it willnot be used by the enemy. Equipment captured bythe enemy may be of use to him or may reveal information that was not previously known by him. 96. Destruction Priorities a. Instructions for the destruction of equipmentin the combat zone must be adequate, uniform,and easily followed. b. Destruction of equipment must be as complete as time, equipment, and personnel will permit. Since the complete destruction of equipmentwill seldom be possible because of the time required, priorities must be established to insurethat the higher classified items are destroyedfirst, followed by items of a lower classification.Unclassified items are destroyed last, in the orderof their importance to the enemy. All essentialcomponent parts must be destroyed to prevent theenemy from constructing one complete set fromseveral damaged ones. 116 AGO 6354C 97. Destruction Plan a. The destruction of equipment that is subject to capture will be accomplished only upon orders of the commander, and the destruction plan will be uniform throughout the command. b. To provide uniformity all personnel must be familiar with the destruction plan, including the priority of destruction. In addition, they should be trained to use uniform procedures in destroying equipment. 98. Methods of Destruction The methods of destruction outlined below will prevent the enemy from using, salvaging, or identifying the equipment. a. Smash. Use sledges, axes, handaxes, pickaxes, hammers, crowbars, heavy tools, or other heavy objects to smash the crystals, tubes, meters, controls, headsets, dynamotors, microphones, storage batteries, relays, switches, ~esistors, dials, and coils. b. Cut. Use axes, handaxes, machetes, or other sharp instruments to cut cables and wiring, and to rip out wiring from the chassis. c. Burn. Use gasoline, kerosene, or oil to burn the technical manuals (or instruction books), diagrams, cables, wiring, carrying bags, and capacitors. d. Bend. Bend the panels, cases, mast sections, and chassis. e. Explode. If explosives are required in de- AGO 6364C struction work, use firearms, grenades, primacord,composition C, or TNT. f. Break. Break all operating components, suchas loudspeakers, headsets, microphones, and keys. g. Dispose. Bury or scatter the destroyed partsin slit trenches, foxholes, or other holes; or throwthem into streams or lakes. 118 AGO 63540 APPENDIX A REFERENCES 1. Publications (C) ACP 110 _____ Tactical Call Sign Book (U). ACP 118(D) ______Visual Call Sign Book. (CM) ACP 121(D)_Communications Instructions General (U). (C-NOFORN) ACP 121 (B)-LCommunications Instructions General (U). (CM) ACP 12.2(B) Communications Instructions Security (U). (CM) ACP 124(B)_Communications Instructions, Radiotelegraph . Procedure (U). (C) AGP 125 ______Communications Instructions, Radiotelephone Procedure (U). (CM) ACP 126 ____Communication Instructions, Tt.letypewriter Procedure (U). ACP 1.29A ________Communication Instructions Visual Signaling, Procedure. ACP 131(B) ______Communication Instructions-Operating Signals. AGO 6354C (C) JANAP 201 (E) ________Status of Noncryptographic JANAP's and ACP's (U). AR 105-31 _______ Message Preparation. AR 320-5 ________ Dictionary of United States Army Terms. AR 320-50 _______Authorized Abbreviations and Brevity Codes. AR 380-5 ________ Safeguarding Defense Information. AR 750-1 ________ Maintenance Concepts. DA Pam 108-1 ____Index of Army Films, Transparancies, GTA Charts, and Recordings. DA Pam 310-1 ____Military Publication, Index of Administrative Publications. DA Pam 310-3 ____Military Publications, Index of Doctrinal, Training, and Organizational Publications. DA Pam 310-4 ____Military Publications, Index of Technical Manuals, Technical Bulletins, Supply Bulletins, Lubrication Orders, and Modification Work Orders. DA Pam 750-1 ____Preventive Maintenance Guide for Commanders. FM 5-20 __________Camouflage, Basic Principles and Field Camouflage. 120 AGO 6354C FM 11-9 _________ Signal Radio Relay Company. FM 21-5 _________ Military Training Management. FM 21-6 _________ Techniques of Military Instruction. FM 21-11 ________ First Aid For Soldiers. FM 21-26 ________ Map Reading. FM 21-30 ________ Military Symbols. FM 21-31 ________Topographic Symbols. FM 21-40 _________ Small Unit Procedures in CBR Operations. FM 24-1 _________Tactical Communications Doctrine. FM 24-16 ________ Signal Orders, Records and Reports. FM 24-17 _________Tactial Communications Center Operation. FM 24-18 ________ Field Radio Techniques. FM 24-19 ________Communications-Electronics Reference Data. FM 24-20 ________ Field-Wire and Field-Cable Techniques. FM 31-25 ________ Desert Operations. FM 31-30 ________Jungle Training and Operations. FM 31-71 ________ Northern Operations. FM 31-72 ________ Mountain Operations. TM 9-1345-200 ___.Landmines. TM 11-459 _______.International Morse Code (Instructions). AGO 6354C 121 TM 11-486-6 _____ Electrical CommunicationsSystems Engineering -Hadio.TM 11-486-.11 ____ Electrical CommunicationsSystems EngineeringEngineering Definitionsand Abbreviations.TM 11-661 ________ Electrical Fundamentals(Direct Current).TM 11-662 -~-----Basic Theory and Application of Electron Tubes.TM 11-665 __ ____ CW and AM Radio Transmitters and Receivers.TM-11-666 _______Antennas and Radio Propagation.TM 11-668 _______ FM Transmitters andReceivers.TM 11-681 _______ Electrical Fundamentals(Alternating Current).TM 11-2651 ______Antenna Groups AN/GRA4 and AN/GRA-12.TM 11-5820348-15 _________Organizational DS, GS, and Depot MaintenanceManual: Antenna Equipment RC-292.TM 38-600 _____..__Administrative Use VehicleManagement. T.M 38-750 ________Army Equipment RecordProcedures.TM 38-750-1 _____Maintenance Management:Field Command Procedures. 122 AGO 6354C 2. Training Films TF 11-1342 _______Tuning Transmitters- Part I: Setting Fre quency. TF 11-1425 _______Preventive Maintenance Practices for GroundSignal Equipment. TF 11-1632 _______The Effects of the Ionosphere on Radio Wave Propagation. TF 11-1776 ______ Operation and Maintenance of Communication Equipment in Extreme Cold. TF 11-1831 _______Tuned Circuits. TF 11-1976________Radio Transmission Security. TF 11-2069 _______Basic Principles of Frequency Modulation. TF 11-2091 _______Tuning Transmitters -Part II: Amplifier and Antenna Tuning. TF 11-2487 _______Radio Interference, Part I. TF 11-2488 _______Radio Interference, Part II. TF 11-2553 _______Radioteletype Procedures, Operation. TF 11-2851 _______Fundamentals of Radio Troubleshooting-Part I -Principal Technique. TF 11-2852 _______Fundamentals of Radio Troubleshooting -Part II-Troubleshoting a Radio Receiver. AGO 6354C 123 TF 11-2853 _______Fundamentals of RadioTroubleshooting-PartIII-Troubleshooting aRadio Transmitter.TF 11-2854 _______Fundamentals of RadioTroubleshooting-PartIV-Additional Devicesand Techniques. 124 AGO 6354C APPENDIX B PHYSICAL SECURITY 1. Security Factors Radio relay stations in isolated areas must have adequate security to insure continuous operation. This security can best be attained by establishing a perimeter defense to prevent intrusion of unauthorized personnel into the site area. Security factors to be considered are outlined in a through c, below. a. Terrain. Defense against enemy attack may be improved by taking advantage of natural terrain features. b. Vulnerability. The location of the site with relation to its proximity to enemy forces will influence the extent of the defensive measures required. c. Tactical and Logistic Requirements. Tactical requirements, such as the availability of personnel and materials, must be considered when planning perimeter defenses. If the site cannot be reached by vehicle, then airdrops may be required. 2. Preparations for Defense a. Immediately after occupying a site, personnel not engaged in establishing communications should start the preparations for perimeter de- AGO 6354C 125 fense. A reconnaissance of the area must be madeto determine the best location for the perimeterdefense line. Some of the factors that affect thislocation are- (1) Critical terrain features around or nearthe site. (2) Locations for good observation and fieldsof fire. (3) Locations that offer the best camouflageand concealment for personnel and equipment. ( 4) Advantageous locations for obstacles. (5) Protection against the best avenues ofenemy approach. b. Obstacles that may be used in the perimeterdefense are- (1) Tactical barbed wire (double-apron andconcertina). (2) Trip-firing devices attached to grenades,flares, or dynamite. (3) Antipersonnel and antitank mines. (4) Barricades and other applicable fieldfortifications. c. Augmentation of the defense personnel byinfantry (or other available troops) may be necessary. Such .an augmentation would permit radiorelay operation personnel to devote full time toprimary duties. 3. Example of Typical Radio Relay Site Assume that a team of six men is assigned to 126 AGO 6354C operate a radio relay site only a few miles from enemy territory. The site is subject to raids from guerrilla or enemy patrols and is situated at the top of a l:igh ridge, where there are many avenues of approach for enemy attack. This arrangement is depicted in figure 32. Defense positions are located so that personnel may be rotated to defend the sector under attack. A roving sentinel is assigned to alert the remainder of the crew in event of attack. Note that emplacements are located so that guns and personnel may take up positions to defend any sector. Through the proper arrangement of obstacles and deployment of personnel, the six-man crew may be capable of resisting enemy attack from any direction for a limited time. The use of bunkers for protection against grenades and mortar fire; mines and boobytraps well out in front of position; and pits and holes, cleverly concealed, afford maximum physical security. 4. Camouflage, Cover, and Concealment Strict compliance with the principles established in FM 5-20 is mandatory. In certain cases complete camouflage is impossible; for example, camouflage material may seriously attenuate antenna signal strength. Antenna masts and guys may be camouflaged with no adverse effects. 5. Defense Against Air Attack 'Ground defense against air attack includes both active and passive measures. AGO 6354C 127 LEG EN o: In UNOCCUPIED POSITION 1: RADIO STATION OCCUPIED POSITION +++ROVING SENTINEL CREW POSITION(NOT UNDER ATTACK) 50 t 50 CAL MACHINE GUN ~MINEFIELD 'it ANTIPERSONNEL MINES ""1RflP-CONCERTINA WIRE Q OPERATIONAL VEHICLE FM24-21-32 Figure 32. Physical security for radio relay sites. a. Active measures against air attack consistof concentrated fire from small arms and machineguns. Since attacking aircraft are a target for 128 AGO 6354C only a few seconds, all available weapons must be brought into action promptly. b. Passive measures against air attack include- (1) Dispersal of facilities within an area. (2) Camouflage of vehicles and equipment by concealment or deception. (3) Use of terrain features to provide concealment. (4) Rigid blackout discipline. (5) Control of the use of fire to avoid disclosing positions by smoke or flames. AGO 6354C 129 APPENDIX C DISPLACEMENT OF RADIO RELAY FACILITIES IN DIVISION AREA 1. General Radio relay facilities within the division areacommunication system must be able to displacewithout interrupting the continuity of service tousers of the system. The task of providing uninterrupted communication is made easier by intelligent, detailed advanced planning on the partof the division signal officer and his close coordination with the division staff, particularly G-3.Type methods of displacing radio relay facilitiesat division main, division alternate, and the forward areas are discussed below. 2. Division Main Radio relay equipment from the reserve poolis moved to and installed at the new location. Existing division main radio relay circuits then aremonitored and taken over by the advance group when the command post moves forward. Old division main closes down and its radio relay equipment reverts to the reserve pool at the new location. 3. Division Alternate Radio relay facilities are displaced by moving 130 AGO 6354C the reserve equipment to the new division alternate location, monitoring the present radio relay system, and taking over at a predetermined time. After the radio relay system has been taken over at the new location, the released radio relay terminals at the old division alternate represent a .reserve pool of equipment for use during future displacements. 4. Forward Areas Radio relay facilities at a forward signal center may consist of three radio terminals (two in operation and one in reserve). Figure 33 indicates that one terminal is used as a single terminal in system TAN 51-61 and another terminal is used as a double terminal in a systems TAN 60-61 and TAN 61-62. Methods of displacing radio relay facilities at a particular forward signal center (in this case, center 61) are described below. a. The reserve terminal moves forward to establish a new area signal center (TAN 61 JUMP). b. System TAN 51-61 JUMP is established by using one-half the reserve terminal that displaced to 61 JUMP. c. System TAN 51-61 is closed out, and that terminal is displaced to 61 JUMP to establish systems TAN 60-61 and TAN 61 JUMP 62. d. Systems TAN 60-61 and TAN 61-62 are closed out when the command closes, and this AGO 6354C 131 ',' ' ,,.q,._ ~, '"'"-~t.o ~.;>' ', TAN61-62~ .~ .,. ,.- ~~v F"M 2 4-21-34 Figure 33. Type diagra!ln for displacement of forwardarea radio relay facilities. equipment is displaced to forward signal centerTAN 61 (formerly 61 JUMP) and is held in reserve for the next displacement. 132 AGO 6354C APPENDIX D RADIO RELAY COMMUNICATIONS DURING PHASES OF TACTICAL OPERATIONS 1. General The information that follows describes briefly the employment of radio relay in the various phases of tactical operations. That is, in the assembly area and during a. Marches. b. Movement to contact. c. The offense. d. The defense. e. Retrograde movements. f. Passage of lines and relief in place. 2. Assembly Area In the assembly area, where units of a command gather in preparation for further tactical operations radio communication is normally restricted or silenced. Radio relay teams may be deployed throughout the area, but normally do not operate. Exceptions to this are warning broadcasts and transmissions from reconnaissance forces in con tact with the enemy. All radio sets are serviced and tested on channels prescribed for the planned operation by the current SOl and SSI. AGO 6354C 3. Marches Marches are classified as either tactical or administrative. They may be made in one or morestages, in one or more columns, and over one orseveral routes. Communications are used for column control, for contact with reconnaissance andsecurity elements, and to communicate with supported and higher units. To insure that minimumessential communications are provided, the signal(or communications) officer must receive advancebriefing on the march plan. When practical, thesignal officer should make a reconnaissance of theroute of march to determine whether radio relaystations are needed to maintain continuous communication. When air vehicles are available forcolumn control, communications facilities for contact with such vehicles should be dispersed withinthe column. During periods of radio or listeningsilence, prearranged visual signals may be usedfor communication between air and groundvehicles. a. Tactical Marches. Radio relay may be employed during the tactical march if it does notcompromise security or hamper the speed of movement. Normally the employment will be along asingle axis oriented along the march route. Toestablish radio relay communications, a base station should be installed on the most commandingheight. Such a station should be self-sustainingbut may require assistance for defense. b. Administrative Marches. This type of marchis made when no enemy ground interference is 134 AGO 6354C anticipated. Radio and mounted messengers are the principal means of communication; however, radio security must be maintained to reduce or deny information to the enemy. 4. Movement to Contact In movement to contact, during the early phases of deployment, radio relay is not operational. Radio relay teams, however, should be spotted at positions that can best support the ensuing operation. 5. The Offense The basic forms of offensive maneuver are the penetration and the envelopment. The exploitation is an offensive operation that may follow a succesful penetration or envelopment. a. Penetration. Prior to enemy contact, radio communications are usually restricted to listening silence to preserve the element of surprise. After an attack is launched, special restrictions on radio and radio relay operations normally are removed and they become a primary means of communication. Radio security must be maintained, since radio traffic is a prime source of intelligence to the enemy. b. Envelopment. In the envelopment, the attacking force avoids the enemy's main defense areas and reaches for objectives in his rear area by way of his flanks. Communication distances, therefore, will be greater, and, since the need for speed of tactical actions and surprise increases, periods of radio silence may be longer. With this AGO 6364C 135 exception, radio relay communications are similarto those described for the penetration. c. Exploitation. The rapid rate of advance during the exploitation limits the use of radio relay.When possible, radio relay systems will be installed by using a plan similar to the one used fora tactical march (para 3a). 6. The Defense During the defense, radio communications aresubordinated to multichannel wire facilities andmessengers. Radio nets remain open, but onlistening silence, to supplement the multichannelwire facilities if interrupted. During the initialphases of a defensive operation, where securitypermits, radio relay systems may be employed tosatisfy the larger circuit capacity required. 7. Retrograde Movements Retrograde movements include withdrawals, delaying actions, retirements, or a combination ofthese. Radio communications are regulated duringall disengagements. Listening silence may be enforced until the withdrawing unit reaches a designated position or has been committed against theenemy elsewhere. 8. Passage of Lines and Relief in Place a. Passage of Lines. Radio relay equipment ofunits making the passage through friendly linesshould not be employed until the passage is complete. However, the unit in occupancy of the position should maintain a normal radio relay traffic 136 AGO 6354C pattern. It may be possible for the unit passing through to use the multichannel facilities of the occupying force. b. Relief in Place. Radio relay employment for a relief in place is governed by the same guidelines as for a passage of lines. AGO 63540 137 GLOSSARY Absorptz~on-The loss of radiated energy due todissipation in a conducting medium.Amplification-The process of increasing the electrical strength of a signal.Antenna-An electrical conductor or a system ofconductors used to radiate or receive radiowaves.Array (antenna)-An arrangement of antennaelements to achieve desirable directional characteristics.Attenuation-The reduction in strength of a signal.Authentication-A security measure designed toprotect a communication system againstfraudulent messages and other transmissionsoriginated by the enemy.Axis of communication-The line or route onwhich lie the starting position and probablefuture locations of the command post or aunit during a troop movement. The mainroute along which messages are relayed orsent to and from combat units in the field.Band of frequencies-The range of frequenciesbetween two specified limits.Carrier frequency-The frequency of an unmodulated radio wave.Channel--An electrical path over which transmissions can be made from one station toanother. 138 AGO 6354C Circuit-A communication link between two or more points, capable of providing one or more communication channels. Coaxial cable-A transmission line consisting of two conductors, one inside the other, and separated by insulating 'material. The inner conductor may be a small copper tube or wire; the outer conductor may be metallic tubing or braid. Radiation loss from this type of line is practically zero. Coaxial cable is also called concentric line. Command post (CP)-The headquarters of a unit or subunit where the commander and staff perform their functions. In combat, this headquarters often is divided into echelons. Communication center-A communication agency charged with the responsibility for receipt, transmission, and delivery of messages. It normally includes a message center, crypto center, and traru;mitting and receiving facilities. Conductivity-The relative ability of a material to allow the flow or passage of an electrical current. Cross-modulation-Modulation of a desired signal by an undesired signal. Decibel (db)-The standard unit of power ratio measurement. Normally it is the ratio of output power to the input power. Demodulation-The process of recovering the audio component (audible signal) from a modulated RF carrier wave. AGO 6364C 139 Dielectric-An insulating material between theplates of a capacitor. Dipole antenna-Two metallic elements placed endto end, each approximately one-fourth wavelength long. Direct path--A path that has no intervening obstacles and is said to be line-of-sight. Distortion-Distortion exists when the outputwave form is not a true reproduction of theinput wave form. Distortion may exist because of transmission or amplification irregularities in amplitude, frequency, or phase. Duplex operation-The operation of radio equipment in conjunction with equipment at another location in which the process of transmission and reception are concurrent. Electromagnetic field-The magnetic field that anelectric current produces around the conductor through which it flows. Facsimile-A system for the transmission of stillpictures or printed matter by means of electrical impulses that are controlled by a photoelectric cell and reproduced at the receiver bya mechanical device. Fading-Variations in the strength of a receivedradio signal caused by changes in the characteristics of the propagation or transmissionmedium. Frequency-The number of complete cycles persecond existing in any form of electrical orsound wave motions. 140 AGO 6354C Frequency distortion-Distortion that occurs as a result of failure to amplify or attenuate equally all frequencies present in a complex wave. Frequency modulation-The process of varying the frequency of an RF carrier wave in' accordance with the amplitude and frequency of an audio signal. Ground-A reference value for a voltage or potential; usually the earth or a conductor that is common to other circuits. Hop-The terrain distance separating a radio transmitter from the receiver that receives its transmission. Ind·irect path-Any path other than a direct path between two stations. Interference-Any electrical disturbance from a different source which causes undersirable responses in electronic equipment. Ionosphere-Highly ionized layers of atmosphere (between the altitudes of approximately 35 to 250 miles) that affect the propagation of radio waves. Jamming-Deliberate blocking or impairing of radio reception by means of interfering electrical radiation. Means of signal communication-A medium by which intelligence is conveyed from one person or place to another. Mega-A prefix meaning one million. AGO 6354C Micro-A prefix indicating one-millionth. Modulated carrier-An RF carrier, the amplitudeor frequency of which has been varied in accordance with the intelligence to be conveyed. Modulation-The process of varying the amplitude or the frequency of a carrier wave inaccordance with other signals to convey intelligence. The modulating signal may be anaudio signal, a video signal (as in television),or electrical pulses or tones. Network-A designated system consisting of twoor more stations able to communicate witheach other. One-way reversible (simplex) operation-A method of operation in which communicationbetween two stations takes place in one direction at a time. Path-That part of the atmosphere through whichthe radiated wave passes. Point-to-point circuit-A nonswitched circuit permanently connected between two radio terminal sets or other terminal equipments. Radiate-To send out energy into space, as in thecase of RF waves. Radio frequency (RF)-Any frequency of electromagnetic and electrostatic fields capable ofenergy propagation into space. Radio frequencies (10 kc to 10,000,000 me) are usuallyhigher than those associated with soundwaves. 142 AGO 6364C Radio relay system-Two radio terminals and as many radio repeaters as are required (consistent with the technical capabilities of the equipment) to span the distance between the two terminals. Radio repeater set-Radio set designed to give two-way service as a receiving and retransmitting unit between two terminals (or a terminal and another radio repeater set). Radio terminal set-Radio set designed to give two-way service as a receiving and transmitting terminal (to or with a radio repeater or other terminal). It may contain necessary wide-band modulation or associated carrier multiplexing equipment. Reflection-The turning back of a radio wave from a metallic object, the surface of the earth, or the ionosphere with the angles of incidence and reflection equal and lying in the sane plane. Refraction-A phenomenon which causes a wave that enters another medium obliquely to undergo an abrupt change in velocity in the medium and also in direction. Also, the bending of radio waves in the troposphere or around an object. Relay-A process of retransmitting intelligence through an intermediate station. Repeater-A combination of apparatus for the reception and retransmission of signals that are either amplified, or reshaped, or both. AGO 6364C Siting-Properly locating an antenna (or radioset) to obtain optimum performance. Transmission line-Any conductor or system ofconductors used to carry electrical energyfrom its source to its load. Tuning-The process of adjusting a radio circuitto resonance with the desired frequency. Wave length-Tb.e distance in meters traveledby a wave during the time interval of onecomplete cycle. It is equal to the velocity inkilometers per second divided by the frequency. 144 AGO 63540 INDEX Paragraph Page ABM' frequency assignment plan 49 70 Antenna expedients ------------------87 109 Antenna guys, storage ________________ 88 110 Antenna orientation ------------------37a,91 54,112 Antennas, polarization ________________ 28 38 Calculations, power-balance ___________ 33 47 Carrier-system lineup -----------~----58 87 Categories of maintenance ___________ 65 93 Circuit control facilities ______________ 53 84 Circuit order tests ____________________ 60 88 Coaxial cable -----------------------84-86 108 Communications during tactical operations ------------------------App D 133 Computing radio relay paths ------·---29-34 40 Conversion of sea-level elevations to line-of-sight elevations ______________ 31 45 Corps radio relay system _____________ 18b 30 Defense against jamming ____________ _ 76 102 Depot maintenance ------·------------65d 95 Destruction of equipment: 95 116 General ------------------------M'ethods -------------------------98 117 Plan ----------------------------97 117 Priorities ------------------------96 116 Direct support maintenance __________ _ 65b 95 Displacement of radio relay facilities __ AppC 130 Division radio relay system _________ _ 18a 27 Double-ABM' frequency assignment plan 50 80 Duplex operation ____________________ 10 11 Electric shock hazards ----------------69 97 Enemy jamming, reporting ____________ 81 106 Estimate of system reliability _______ _ 35 51 AGO 6354C 145 Paragraph Page Field army radio relay system ________ 18c 30Field expedients --------------------82-94 107Frequency management -------------38-45 58Frequency selection: ABM plan ----------------------49 70Double-ARM plan ---------------50 80 Methods ------------------------46 65Two-block plan ------------------48 68 X)' plan ------------------------51 82 General support maintenance ________ 65c 95 Harmonic radiation ------------------61 89 Interference between transmitters and receivers ---------------------47 65Interference, mutual -----------------62 89 Jamming: Defense against -----------------76 102 General ------------------------75 102Instructions --------------------77-80 103Reporting enemy -----------------81 106 Line-of-sight profile graph ____________ 32 47Listening silence --------------------15g 23Long transmission paths _____________ _ 34 49 Maintenance categories --------------65 93Monitoring checks --------------------59 88Multiplexing equipment connections ___ _ 21 32Mutual interference -----------------62 89Noise and interference ---------------61-63 89Operating checks -------------------59 88Operational expedients --------------91-94 112Order wires, use ---------------------54 85Organizational maintenance __________ _ 65a 93Overall system lineup ---------------58 87Plotting profiles: Linear graph paper --------------31 45Nonlinear graph paper ___________ 30 42Polarization of antennas --------------28 38 146 AGO 6354C Power-balance calculations ------------Power considerations -----------------Power source expedients --------------Preventive maintenance -------------- Radiation: Harmonic ----------------------Spurious ------------------------ Radio relay facilities, displacement ___ _ Radio relay paths: Computation ~------------------- Plotting: On linear graph paper ________ On nonlinear graph paper ____ Procedure -----------------------Radio relay systems: Division, corps, and army _________ Employment --------------------Flexibility -----------------------General ------------------------- Methods of operation ____________ Multichannel -------------------Multihop -----------------------Procedures ----------------------Use ----------------·-------------Radio security ----------------------Radio silence -----------------------Radio-system lineup -----------------Receivers and transmitters, interference between _______________ Safety precautions ------------------Sectionalizing troubles ---------------Security: Physical ------------------------- Radio ----------------·-----------Shock hazards, electric --------------Sites: Accessibility ---------------------Field inspection __________________ Power considerations _____________ Paragraph Page 33 47 27 37 89, 90 110 6'6-69 95 61 89 62 89 App C 130 29-34 40 31 45 30 42 29 40 18 27 13-18 19 16 2~ 6 5 8-10 8 12 14 11 11 15 21 7 7 15/ 22 15( 23 57 86 4'! 65 6J 97 70c 98 App B 125 15/ 22 69 97 26 06 24 35 27 37 AGO 6354C Siting by radio altimeter --------------Siting techniques ---------------------Spurious radiation -------------------System considerations -----------·----- System flexibility ____________________ System lineup: Carrier -------------------------Control ------------------------- Overall -------------------------- Radio --------------------------System procedures ----·--------------System reliability --------------·----- Acceptable ---------------------Estimate. -----------------------Factors -------------------------Tactical operations, communications during ---------------------------Transmission paths, long -------------Transmitters and receivers, interference between _______________ Trouble clearance tests: Long distance network ___________ Multichannel systems ____________ On trunks of radio relay systems __ Overall -------------------------- Station operation and maintenance ___________________ Two-block frequency assignment plan __ Warning notice, electric shock _________ XY frequency assignment plan ________ Paragraph 25 23-28 62 20 16 58 56 58 57 15 35-37 36 35 37 App D 34 47 71 70 74 72 73 48 69 51 Page 35 34 89 32 23 87 86 87 86 21 51 52 51 54 133 49 65 99 98 100 99 99 68 97 82 AGO 6354C 148 By Order of the Secretary of the Anny: HAROLD K. JOHNSON, General, U'nited States Army, Chief of Staff. Official: KENNETH G. WICKHAM, Major General, United States Army, The Adjutant General. Distribution: To be distributed in accordance with DA Fonn 12-11 for Field Radio Relay Techniques. -trt~.s. Government Prlntlnc Office: 1966-250-530/6354C 149 AGO 6354C NEAR -END TERMINAL I ---~ --ll CONTROL STATION I '--------------~~~~~RO~E:T~~~~~ II. I --------~ADMINISTRATIVE AREA OF CONTROL STATION -----11 --+---- ~-~--~---l-_ADMINISTRATIV~ I AREA _ _.._ :ADMINISTRATIVE AREA I r ~ -------~ I I OF CARRIER SECTION I OF RADIO RELAY SECTIONI I I i PART OF PART OF I I I I I CAI>RIER AND RADIO I CARRIER 8 RADIO I RADIO RELAY I I I I II SUBCONTROL I SUBCONTROL STATION I I 1 II STATION I STATION I I IORDER II I I ' olol_ o 0 II o r+-o I I ..---!-=::r 11 I' --~~j 1I OVER·ALL TALK ANOI.OVER-ALL TALK} I' SIG TESTS WITH I AND SIG TESTS II ~~~~-~~DTJtRc~T I ~t~~NEAR-END ol ___l ' OVER-ALL NET LOSS OVE R·ALL TRANS MEAS WITH FAR illU I OVER·ALL NET LOSS}f' MEAS WITH NEAR-I TESTS OF TRK I END TERM USING END TERM. USING I 1 TRANS MEAS CKT I MTR MEAS CK T 1 3 STEP ~ECTIONALIZING I SECTIONALIZING ~ I ~SECTIONA~~~ TALK TESTS TO TALK TESTS TO TALK TESTS TO I TALK TESTS WITH I CHECK CONTINUITY RADIO IN SUB-I RADIO IN SUB-j I CONTROL STA I TO SUBCONTROL CONTROL STA I CONTROL STA I STA I I I STEP 4 l(! ECTIONALIZ lNG I SECTIONALIZING : r:u II 1 1 'll~lSECTIONALIZING 1SECTIONALIZING} I I TALK TESTS TO TALK TESTS TO END 8 FAR-END TESTS OF NEARTALK TESTS TO TALK TESTS TO NEAR-END TEST BD 1 NEAR-END TROUBLE II I I I I FAR· END TROUBLE I FAR-END TEST BD POS DR SWBD US-1 II I I I POS OR SWBD US· IDROPS I lNG 4W TEL CKT I II I I I I lNG 4W TEL CKT I ~ SECTIONALIZING :~ [I -----; I I ~~SECTIONALIZING 1 TEST. OF TEL II SIG. TESTS TOWARD I II 1 I 1 ! SIG TESTS TOWARDI ·soG CONV EQUIP LINE OR TOWARD 11 I 1 I : LINE OR TOWARD 1PNR~sul~~~TB1~1LT-1 11 1 1 1 ft:'ofEs~SIN~K~u:~T-1 I TEL SIG CONY EQUIP I II I I : : TEL SIG CONY EQUIP: STEP 6 I SECTIONALIZING }P ii , ~~ r :4SECTIONALIZING , TEST OF LINE TALK TESTS WITH II I TLK TESTS WITH FAC ILl TIES I FAR-END TEST BD I 1 1 : NEAR -END TEST-I I , 1 I! 1 1 11 I I I BD I STEP 7 I I ECTIONALIZING ij ~SECTIONALIZING ~-TESTS OF I I TESTS OF CARR TESTS OF CARR I CARRIER ECT USING BUILT-Ill SECT USING BUILT· 1 SECTION I I ~N TEST EQUIP I IN TEST EQUIP I I I STEP 8 mroF II ~~~~~O~A,LI~~~~O ~~~~~~~~L~~~~~ 11 SECT USING BUILT· I SECT USING BUILT-STATION II IN TEST EQUIP. 1 IN TEST [QUIP. RADIO NOTES' I. TESTS AT FRONTIER STATION ARE SIMILAR TO THOSE PERFORMED AT SUBCONTROL STATIONS. 2. THE ORDER WIRE IS THE VOICE FREQUENCY CHANNEL OF THE CARRIER SYSTEM AND THE RADIO RELAY SYSTEM. 3. OW IS ORDER WIRE. FM24-21-29 Figure 30. Overall and sectionalizing tests on trunks of radio relay systems. E LOWEST ALTITUDE1,280 FT 1 LOWEST ALTITUDE 10FT F LOWEST ALTITUDELOWEST ALTITUDECURVATURE BELOW CURVATURE 1,360FT OF THE EARTH OF THE EARTH JG FM24-2HI Figure 11. Plotting Profiles. xxxx------------------------------------ i.. p X XX i.. i.. xx------ LEGEND : MULTICHANNEL RADIO 6 ARMY AREA SIGNAL CENTER ~ RELAY SYSTEMS SPIRAL-FOUR CABLE CARRIER SYSTEMS D COMMAND SIGNAL CENTER FM24-21-9 THEATER ARMY COMMUNICA TACS TIONS SYSTEM Figure 9. Type field army area communication system.