CECOM LAR Operation Course IF TEST PANEL CECOM LAR Course Logistics Assistance Division Fort Monmouth, New Jersey The IF TEST PANEL is a major test and troubleshooting tool. This class covers the IF TEST PANEL. Signal Flow

CECOM LAR Operation Course Here’s where it is in the system Point out it’s relationship to Tropo Modem Transmit and Demod sections and the D/C’s Three purposes: Provides a loopback capability for a sample of the Tropo Modem transmit signal. Provides a pass through for the four V2 receive signals. In the V3 there is a power splitter that splits the two receive signals into four to send to the four Tropo Modem Demodulator channels. Although not shown here, it also looks at the signal level from each D/C and provides an RSL voltage to the Alarm Monitor RSL meter. Also not shown here is the mounting panel between the D/C’s and the IFTP. The cables actually run from each D/C to the panel just above the IFTP, and then from there down to the IFTP. Signal Flow

CECOM LAR Operation Course LOCATION V3 TED 1 KG-194 TED 2 KG-194 BASEBAND PATCH PANEL BLANK FOR DELED BLANK FOR DELED DELED PATCH PANEL LGM TD-1235 ALARM MONITOR BZ-250/TRC-170 5820-01-143-6944 Analogue Voice Order Wire 5820-01-143-7683 GM MD-1026 TEST PANEL I.F. ORDER WIRE CONTROL UNIT OCU C-10602/TRC-170 5820-01-142-8007 TGM TD-1236 AC-AC CONVERTER 5820-01-142-6627 HERE’S WHERE IT’S LOCATED: Show where the IFTP is in the V3. Note the physical location in relation to the Down Converters—note that cables must physically run across the van from the D/C to the A5A3 Blank Panel, then down to the IFTP at A5A6. Then from the IFTP, back across the van to the TM Demod section. These cables sometimes get damaged or broken, so this cable path needs to be understood, because you will often be troubleshooting bad cables. The first indication of a bad cable is when the Tropo Modem will not gain equalize on one or more channels. Although there are several other more likely suspects for this problem, bad cables are always a good possibility LGM TD-1235 POWER SUPPLY PP-7904/TRC-170 5820-01-142-8169 Key to lab AN/TRC-170 V3 CURB SIDE Signal Flow

CECOM LAR Operation Course LOCATION, V2 In the V2, the IFTP IS LOCATED IS LOCATED AT 7A5 The cable runs are from the D/C’s in rack 4, over to blank mounting above 7A5, and then to the IFTP at 7A5. Signal Flow

CECOM LAR Operation Course IF TEST PANEL C & I The TEST SIGNAL jack brings out the TM transmit signal sample so we can look at it on a Spectrum Analyzer, Oscilloscope, or measure it with a power meter (-23 dBm). Then it goes to the attenuators for level control. This allows you to simulate a received signal by decreasing the level being sent to the TM demodulator in loopback. From the attenuators it goes to the loopback switches which pass the test signal (along with any signal that happen to be coming in from the D/C’s) over to the Tropo Modem Demodulator. Signal Flow

CECOM LAR Operation Course IF TEST PANEL REAR VIEW This is rear view of a (V)3 IFTP. Note J16 and J17, which accept the D/C inputs and direct them into two power splitters, which develop the four signals to send to the Tropo Modem Demodulator section. If it were a (V)2, J16 and J17 would be empty and J12-J15 would be active. In either case, J11 is input for the tropo modem transmit test signal, and J6-J9 are outputs to the Tropo Modem Demodulator section. Signal Flow

CECOM LAR Operation Course DC1 Directional Coupler D/C 1 D/C 2 D/C 3 D/C 4 70 MHz RCVR 1 IF (70 MHz) J12 RCVR 2 IF (70 MHz) J9 70 MHz RCVR 1 Norm To Tropo MODEM Receivers RSL-1 J6 J15 LB RCVR 3 IF (70 MHz) 70 MHz J7 J14 RCVR 4 IF (70 MHz) 70 MHz DC 2 Directional Coupler J8 J13 RCVR 2 Norm LB RSL-2 DC 3 Directional Coupler RCVR 3 Norm LB RSL-3 DC 4 Directional Coupler A6 Power Splitter FL 2 50 KHz Filter RCVR 4 Norm LB RSL-4 TEST SIGNAL LEVEL AT2 Step Attenuator FL 1 5 MHz Filter 10 DB 1 DB Transmit 70 MHz From Tropo Modem J11 Red RSL-1 1 Antenna 1 Red Cover the three functions of the IFTP as shown in the block diagram. Receive signal pass through—from J12-15 , which come from the D/C by way of the blank mounting panel just above the IFTP, through the Directional Couplers (DC), to J6-J9 out to the Tropo Modem Demodulator section. The loopback function, which takes the transmit sample in through J11, through the attenuator, up to the loopback switches, which apply the test signal through the DC’s onto the receive signal path, which goes to the Tropo Modem Demodulator section. The RSL function, which takes a sample of each receive signal, and applies it to a selector switch that is physically located on the Alarm Monitor Panel. This selected sample is then returned to the IFTP and run through a circuit that provides a dc voltage back up to the meter on the Alarm Monitor Panel. This voltage is proportional to the receive signal level, and is displayed on the meter as RSL. MAJOR POINT: When in loopback, the receive signal is still connected. So make sure you aren’t receiving a signal, because it will degrade the BER reading on the Tropo Modem meter. RSL-4 4 RSL Voltage Out A1 Amplifier K8 Bandwidth Select A2 Log Amp TEST SIGNAL Black To Alarm Monitor 70 MHz RSL-3 3 Antenna 2 Black J4-D RSL-2 2 Note: RSL & Antenna switches are physically located in the Alarm Monitor From Alarm Monitor Bandwidth Select J4-G IF Test Panel (V2 Only) Signal Flow

CECOM LAR Operation Course At any time when the van is powered up, the IFTP can be placed in loopback with any one or all of the loopback switches, and if the Tropo Modem is operational, DEMUX FRAME light should go out immediately, and the BER SHORT should go to 10 neg 5 BER within 60 seconds, assuming the following conditions are met:   1. IFTP front panel attenuators set to zero. 2. CW/NORM switch set to NORM. 3. MISSION data rate set above 64 Kb. 4. Bandwidth switch set to 7.5 if MISSION data rate set above 2304 Kb. 5. No interfering signal being received through the antenna ports Note that the DGM equipment does not even have to be turned on for the above to happen. Signal Flow

AN/TRC-170(V)3 Receive 70 MHz (IF) Signal Flow

CECOM LAR Operation Course SUMMARY TOOL FOR SYSTEM CHECKOUT TOOL FOR TROUBLESHOOTING PROVIDES RSL TO ALARM MONITOR PROVIDES SAMPLE TRANSMIT OUTPUT AT FRONT PANEL PRONE TO CABLE FAILURES Cover above notes. Signal Flow

QUESTIONS FOR YOU What is center freq of TEST SIG out at front panel? What is purpose of front panel attenuators? What position should TM BER switch be in when checking IF Loopback? Where do you select the D/C whose RSL you want to check? On an FTX you’re getting poor BER. You go to loopback and the BER doesn’t come up. Why?