1. CECOM LAR Operation Course
AN/TRC-170 SIGNAL FLOW
CECOM LAR Course
Logistics Assistance Division
Fort Monmouth, New Jersey
This is a critical part of this class. Understanding the flow will help you in the operation and troubleshooting the AN/TRC-170.
Signal Flow

2. CECOM LAR Operation Course
V2 SEP Location
The AN/TRC-170(V)2 /3 has two Signal Entry Panels (SEP).
The signal entry panels are the way we interface with the local subscribers.
The SEP in both versions of the terminals are identical.
However they are in different locations.
Here we see the V2 SEP 1 & 2
SEP #1 is located on the bottom as shown in your LAR Handbook on page 4-2
SEP #2 is located on the top.
Signal Flow

3. CECOM LAR Operation Course
V3 SEP Location
Here we see the curbside of the V3 TRC-170.
SEP #1 is located on the right, closest to the door of the shelter.
SEP #2 is located on the left, nearest the front of the shelter.
Signal Flow

4. CECOM LAR Operation Course
Signal Entry Panel 1
SEP-1
GM-1 Connects to CX Coaxial cable and to the right of it there is a surge protector assembly labeled GM-1.
GM-2 Connects to CX Coaxial cable and to the right of it there is a surge protector assembly labeled GM-2.
LGM-1 Can handle 16, 4 wire subscribers, digital or analogue, which can be brought in via 16 sets of quad push binding post that have surge protectors attached: or the 26 pair cable can support the first 13 subscribers. Subscribers 14 through 16 must be brought in through the binding post.
Signal Flow

5. CECOM LAR Operation Course
Signal Entry Panel 2
SEP-2
GM-3 Connects to CX Coaxial cable and to the right of it there is a surge protector assembly labeled GM-3.
GM-4/LSCDM Connects to CX Coaxial cable, and to the right of it there is a surge protector assembly labeled GM-4/LSCD. NOTE the surge protector must be changed if the LSCDM is used.
LGM-2 Can handle 16, 4 wire subscribers, digital or analogue, which can be brought in via 16 sets of quad push binding post that have surge protectors attached: or the 26 pair cable can support the first 13 subscribers. Subscribers 14 through 16 must be brought in through the binding post.
ROCU- Two sets of quad binding post are also provided for connection of the ROCU.
Signal Flow

6. CECOM LAR Operation Course
V2 Block Diagram
Now lets take a look at the Signal Flow of the AN/TRC-170V)2. Please refer to FO 4-1.
Follow Signal Flow
Multiplexer TD-1235 (LGM) 6A2, 6A5. The two Loop Group Multiplexer will multiplex up to 16 four wire, 16 or 32 KB/s conditioned diphase digital, or voice frequency analog inputs into one balanced NRZ digital group on the equipment side.  
Digital data Modem MD-1026 (GM) 6A3. The main purpose of the GM is to change the cable format to a balanced NRZ signal and vice versa. It contains 4 separate pairs of Group Modem cards. These are referred to as GM 1 through 4. In addition to mission traffic, each individual group of the diphase GM interfaces a 2 KB/s data orderwire (DOW) and a 16 KB/s digital voice orderwire (DVOW) or an analog voice orderwire (AVOW).
Cable Driver Modem TD-1023 (LSCDM) 6A5. The Low Speed Cable Driver Modem (LSCDM) interfaces a repeated CX coax cable system on the cable side with the AN/TRC-170 system on the equipment side. The optional equipment is not installed in any Army TRC-170 and will not be discussed.
Baseband Patch Panel 6A1. The Baseband patch Panel is used to interface the DGM gear and the Tropo Modem.  
Signal Flow

7. CECOM LAR Operation Course
V2 Block Diagram
Multiplexer TD-1236 (TGM) 6A4. The Trunk Group Multiplexer (TGM) multiplexes up to 4 data groups into 1 super group. The TGM is capable of controlling a TSEC/KG-94A Trunk Encryption Device (TED) on both the group and super group side.
Trunk Encryption Device TSEC/KG-94A (TED). The TED performs full encryption/decryption of group or super group mission traffic. One or two TEDs are used, as required. TED 1 (5A1A1) is used on the radio (super group) side while TED 2 (5A1A2) is used on the cable (group) side.
2 KB/s DOW- Coming out of each GM you will notice a 2 KB/s DOW. This orderwire is only used by the Air Force. We will discuss it very briefly. The DOW is extracted and patched to the 7A1 Level converter. The level converter changes the level of the signal required for the KG-84. The signal is then sent to the DLED (KG-84) it is unencrypted and sent to the CESE. The CESE adds the status of the local terminal and sends it to the next DLED. There it is encrypted and sent back to the 7A1 level converter. Here the levels are changed back to the requirements for the Tropo Modem.
16 KB/s DVOW- A 16 KB/s is received by the GM and with the exception of GM-4 is routed directly to the 7A3 TOCU. Here the signaling and voice traffic is processed. Secure voice is provided by the KY-58. These orderwire signals are routed to the Tropo Modem for transmission.
Signal Flow

8. CECOM LAR Operation Course
V2 Block Diagram
AVOW- The TRC-170 has the capabilities for a non-secure Analog Voice Orderwire. This is only sent across the cable side of the system. This used to talked to cable repairmen and to the TD-1234 (RMC).
Demodulator-Modulator Group OM-71 (Tropo Modem). The TM has two sections, a Modulator and Demodulator. We will first discuss the 5A3 Modulator 5A3 section. The Tropo Modem takes the 2 orderwire signals and the super group data and multiplexes it onto one data stream. This data stream is then modulated unto a nominal 70 MHz IF and sent to the two up converters.The TM sends a Modulated 70 MHz signal out to the 7A5 IF Test Panel for internal loop back testing. The TM also sends two 10 MHz Reference signals to the Frequency Synthesizers. 
Frequency Synthesizer 5A4 & 5A5. The synthesizer provides stable outputs in the 4.47 to 5.07 GHz ranges. These outputs supply local oscillator signals to the two Up Converters and two Down Converters. The synthesizer is phased locked to the 10 MHz signal from the Tropo Modem.
Transmitter Amplifier-Converter AM-7027 (Up Converter). The Up Converter mixes the nominal 70 MHz IF with 4.47 to 5.07 GHz from the Synthesizer to produce the 4.4 to 5.0 GHz output signal. The converter has tow modes of operation, LOS and Tropo. 
Signal Flow

9. CECOM LAR Operation Course
V2 Block Diagram
RF Amplifier (HPA). In the LOS mode of operation, the signal from the Up converter is routed through a filter in the HPA and no amplification is performed. In the Tropo mode the signal is routed through a 5 cavity klystron. There the signal is amplified and routed to the diplexer. kW, air cooled amplifier. It operates in the 4.4 to 5.0 GHz band. The klystron and High Voltage Power Supply is not used when operating in the LOS mode.
Diplexer. This device is used in the V2 terminal only. It enables the transmitter and receiver to operate from a common antenna port.
Waveguide Entry Panel- This panel on located on the outside of the shelter. Here we connect the four external wave guides which connect to the antenna.
Antenna- The V2 uses two 9.5 foot parabolic antennas.
Signal Flow

10. V2 Waveguide Entry Panel
CECOM LAR Operation Course
V2 Waveguide Entry Panel
Wave guide Entry Panel #1 (Shown on the left, three ports)
ECCM The top port is not used. It was intended to be used with a ECCM (Electronic Counter-Counter measure up grade.
XMT/RCVR 1 Is located on the left. This connected the HPA #1 and Down Converter Receiver #1.
RCV-4 Is located on the right of Entry Panel #1. This a receive only port and is connected to Down Converter Receiver #4.
Waveguide Entry #2(Shown on the right, two ports)
XMT/RCV 2 Is located on the right side. This connected to HPA #2 and Down Converter Receiver #2.
RCV-3 Located on the left side of Wave guide entry Panel #2. This is a receive only port and is connected to Down Converter Receiver #3.
Signal Flow

11. CECOM LAR Operation Course
V2 Block Diagram
Receiver Amplifier Converter AM-7026 (Down Converter). The Down Converters contain a LNA and a mixer which converts the 4.4 to 5.0 GHz to a 70 MHz IF. Two Down Converters are used for space diversity and two for frequency diversity reception.
IF Test Panel 7A5. The IF Test Panel contains a loop back circuit and an antenna alinement circuit. The loop back circuit provides a calibrated means of applying the Tropo Modem modulator IF output to any one or any combination of Tropo Modem demodulator inputs.
Tropo Modem-Demodulator 5A6. The demodulator performs the inverse function of the modulator. Specifically, it recovers the Baseband data from the 4 receiver IF inputs.
Orderwire Control Unit C (VOCU) 7A3. The Voice Orderwire Control Unit (VOCU) provides a means of interfacing a VINSON, KY-58 secure voice instrument, with the 16 KB/s/s Digital Voice Orderwire. The connection is made on first come first served party line basis.
Signal Flow

12. CECOM LAR Operation Course
V2 Rack Layout
Point out locations of the equipment discussed
Signal Flow

13. CECOM LAR Operation Course
V3 Block Diagram
Now let’s take a look at the Signal Flow of the AN/TRC-170V)2. Please refer to FO 4-1.
Follow Signal Flow
Multiplexer TD-1235 (LGM) 6A2, 6A5. The two Loop Group Multiplexers will multiplex up to 16 four wire, 16 or 32 KB/s conditioned diphase digital, or voice frequency analog inputs into one balanced NRZ digital group on the equipment side.  
Digital data Modem MD-1026 (GM) 6A3. The main purpose of the GM is to change the cable format to a balanced NRZ signal and vice versa. It contains 4 separate pairs of Group Modem cards. These are referred to as GM 1 through 4. In addition to mission traffic, each individual group of the diphase GM interfaces a 2 KB/s data orderwire (DOW) and a 16 KB/s digital voice orderwire (DVOW) or an analog voice orderwire (AVOW).
Cable Driver Modem TD-1023 (LSCDM) 6A5. The Low Speed Cable Driver Modem (LSCDM) interfaces a repeated CX coax cable system on the cable side with the AN/TRC-170 system on the equipment side. The optional equipment is not installed in any Army TRC-170 and will not be discussed.
Baseband Patch Panel 6A1. The Baseband patch Panel is used to interface the DGM gear and the Tropo Modem.  
Signal Flow

14. CECOM LAR Operation Course
V3 Block Diagram
Multiplexer TD-1236 (TGM) 6A4. The Trunk Group Multiplexer (TGM) multiplexes up to 4 data groups into 1 super group. The TGM is capable of controlling a TSEC/KG-94A Trunk Encryption Device (TED) on both the group and super group side.
Trunk Encryption Device TSEC/KG-94A (TED). The TED performs full encryption/decryption of group or super group mission traffic. One or two TEDs are used, as required. TED 1 (5A1A1) is used on the radio (super group) side while TED 2 (5A1A2) is used on the cable (group) side.
2 KB/s DOW- Coming out of each GM you will notice a 2 KB/s DOW. This orderwire is only used by the Air Force. We will discuss it very briefly. The DOW is extracted and patched to the 7A1 Level converter. The level converter changes the level of the signal required for the KG-84. The signal is then sent to the DLED (KG-84) it is unencrypted and sent to the CESE. The CESE adds the status of the local terminal and sends it to the next DLED. There it is encrypted and sent back to the 7A1 level converter. Here the levels are changed back to the requirements for the Tropo Modem.
16 KB/s DVOW- A 16 KB/s is received by the GM and with the exception of GM-4 is routed directly to the 7A3 TOCU. Here the signaling and voice traffic is processed. Secure voice is provided by the KY-58. These orderwire signals are routed to the Tropo Modem for transmission.
Signal Flow

15. CECOM LAR Operation Course
V3 Block Diagram
AVOW- The TRC-170 has the capabilities for a non-secure Analog Voice Orderwire. This is only sent across the cable side of the system. This used to talk to cable repairmen and to the TD-1234 (RMC).
Demodulator-Modulator Group OM-71 (Tropo Modem). The TM has two sections, a Modulator and demodulator. We will first discuss the 5A3 Modulator 5A3 section. The Tropo Modem takes the 2 orderwire signals and the super group data and multiplexes it into one data stream. This data stream is then modulated unto a nominal 70 MHz IF and sent to the up converter.The TM sends a Modulated 70 MHz signal out to the 5A4 IF Test Panel for internal loop back testing. The TM also a 10 MHz Reference signal to the Frequency Synthesizer. 
Frequency Synthesizer 3A2. The synthesizer provides stable outputs in the 4.47 to 5.07 GHz ranges. These outputs supply local oscillator signals to the Up Converter and two Down Converters. The synthesizer is phase locked to the 10 MHz signal from the Tropo Modem.
Transmitter Amplifier-Converter AM-7027 (Up Converter). The Up Converter mixes the nominal 70 MHz IF with 4.47 to 5.07 GHz from the Synthesizer to produce the 4.4 to 5.0 GHz output signal. The converter has two modes of operation, LOS and Tropo. 
Signal Flow

16. CECOM LAR Operation Course
V3 Block Diagram
RF Amplifier (HPA). In the LOS mode of operation, the signal from the Up converter is routed through a filter in the HPA and no amplification is performed. In the Tropo mode the signal is routed through a 5 cavity 1 kW, air cooled amplifier klystron. There the signal is amplified and routed to the diplexer. It operates in the 4.4 to 5.0 GHz band. The klystron and High Voltage Power Supply is not used when operating in the LOS mode.
Waveguide Entry Panel- This panel on located on the outside of the shelter. Here we connect the three external wave guides which connect to the antenna.
Antenna- The V2 uses two 6 foot parabolic antennas.
Signal Flow

17. V3 Waveguide Entry Panel
CECOM LAR Operation Course
V3 Waveguide Entry Panel
Wave guide Entry Panel #1 (Shown on the left)
XMT Is located on the left. This connected the HPA .
RCV Is located on the right of Entry Panel #1. This a receive only port and is connected to Down Converter Receiver #1.
Waveguide Entry #2(Shown on the right)
RCV Located on the right side of Wave guide entry Panel #2. This is a receive only port and is connected to Down Converter Receiver #3.
ECCM The top port is not used. It was intended to be used with a ECCM (Electronic Counter-Counter measure up grade.
Signal Flow

18. CECOM LAR Operation Course
V3 Block Diagram
Receiver Amplifier Converter AM-7026 (Down Converter). The Down Converters contain a LNA and a mixer which converts the 4.4 to 5.0 GHz to a 70 MHz IF. Two Down Converters are used for space diversity reception.
IF Test Panel 7A5. The IF Test Panel contains a loop back circuit and an antenna alinement circuit. The loop back circuit provides a calibrated means of applying the Tropo Modem modulator IF output to any one or any combination of Tropo Modem demodulator inputs. The two 70 MHz IF signals are split and routed to the 4 inputs in the TM.
Tropo Modem-Demodulator 5A6. The demodulator performs the inverse function of the modulator. Specifically, it recovers the Baseband data from the 4 receiver IF inputs.
Signal Flow

19. CECOM LAR Operation Course
V3 RF Rack
Point out the equipment.
Signal Flow

20. CECOM LAR Operation Course
V3 Baseband Rack
Point out the equipment.
Signal Flow

21. CECOM LAR Operation Course
Summary
The most important part to becoming a good Tropo Communicator is understanding the path the signal travels through your equipment.
Recap Slide
Signal Flow

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