This is a test made for the Marines by Codalex for testing the digital Bit Error Rate (BER) on the X-mode connector of field radios like the RT-524/VRC, RT-524/VRC, RT-442/VRC, RT-841/PRC-77, MRC-135A and others. This is in support of the TSEC/KY-57, KG-84A and similar voice cipher equipment that needs a digital data format in a voice channel and multichannel telephone systems using radio links. The case for the F91120 test set may be the same size as a TSEC/KY-57 and some of the internal parts may be the same. There is a place on the case bottom for a BB-588/U or BA-5588/U battery. My 68BA should work here.
Maybe the PRC-68 series of radios can be tested in support of the TSEC/KYV-2A?
This unit can be powered from normal 115/230 Volt mains power, an internal battery or an external DC source.
F91120 Test Unit
NSN <none> Ser. No. 001
Contract No. M67854-94-C-2009 P/N F91120 CAGE Code 96344
96344 gives Codalex Ltd, Montreal, Quebec, Canada
- INTL - Internal battery
- EXT - External, either through the Fig 9 IEC line cord (115 or 230 VAC selectable via internal toggle switch or DC using the Fig 10 DC power cord with alligator clips.
- CHG - Charge the internal battery
- Green 2 digit 7-segment display of the number of errors out of 2x10E33 bits when multiplied by the RANGE
- OVFL - If the Overflow light is on increase the RANGE to a higher number
- SYNC - indicates that the Base Band clock has been recovered and the receive counter circuit is locked to it
- CHG - indicates that the internal battery is being charged
RANGEA multiplier of 1, 10 pr 100 applied to the ERRORS that are displayed.
POWERThe ON or OFF switch.
- OFF - ?
- AUD - Audio, How different from Data
- DATA - what signal?
- TEST - Continously runs the self test and injects 94 errors when RANGE is set to X1.
- INT - uses an internal clock
- EXT - requires a clock from the radio (like on SINCGARS)
- BB - the data format is Base Band
- DP - DiPhase (requires twice the bandwidth but works better than base band)
- 1.2 Kilo Bits Per Socond - standard audio rate (test time = 80 seconds)
- 2.4 Kilo Bits Per Socond - standard audio rate (test time = 40 seconds)
- 9.6 Kilo Bits Per Socond - standatd audio rate (test time = 11 seconds)
- 16 Kilo Bits Per Socond - used with the KY-57 type voice scramblers (test time = 6 seconds)
- 32 Kilo Bits Per Socond (test time = 3 seconds)
Wire Binding Posts
- XMT - data out
- GND - ground
- RCV - receive data
- TRIG - to oscilloscope to see the "eye" diagram for the channel being tested
STARTWill start a BER test, although the set is continously testing so you can just wait for the next result. The first result after making a change will be in error and a few seconds can be saved by pressing START.
UUTThis 26 socket connector allows cabling the test set to various radios to facilitate testing them.
- Select an appropriate POWER MODE ( INTernaL battery, EXTernal AC or DC)
- RANGE switch is set to X1
- POWER to ON
After a few seconds the ERRORS will display 94. This display will blink on and off once every few seconds. If the RANGE is set to X10 the self test will show 19 and on X100 it will display 1. These numbers come about because in self test mode a known number of errors are added to the data stream.
Internal BatteryThis appears to be the same as is used on the PRC-68 series radios, like the BB-388 or others that are used in the battery box.
Two Test SetsFor most of the tests you need two of these test sets, one to send the data pattern and the other to check it for errors.
The transmit and receive portions of the F91100 are seperate, so you can run a test with a single unit. For example the F91100 output in the audio mode could be used to modulate a signal generator which could drive a receiver and the receiver X-mode digital output could be tested for errors. Or a wire line system could be tested if there was a loop back capability at the far end. Another way is to use two radios whose antenna ports are connected by an attenuator and use the X-mode connector for input to the Tx radio and the X-mode connector on the Rx radio.
- RT-841 Power Connector: A - Gnd, P - Wideband Output
- RT-524 X-mode Connector: F- Gnd, A - Wideband Output (!- BC this seems backwards?-)
- RT-1523/RT-1439 Data Connector: A - Gnd, B - Receive Data
Description Radio Figure BER Test Unit Connector UUT Connector(s) BER Test Unit F91120 1 & 2 Canvas Bag "96344/F91100" 12 Cable Ass'y A 96344/F91100 RT-524/VRC RT-841/PRC-77 6 MS 3116J16-26P MS 3116E12-10P
Cable Ass'y B 96344/F91100 J-4961/GCC
7 MS 3116J16-26P MS 3111J14-19P Cable Ass'y C 96344/F91100 TA-1042
KY-90 data port
8 MS 3116J16-26P MS 27467T17835S Cable Ass'y D 96344/F91100 RT-1523
9 MS 3116J16-26P M 55116/4-4 (U-183) Cable Ass'y PWR 96344/F91100 24 VDC 10 MS 3116J10-6S 9/16" Alligator Clips Cable Ass'y DC 96344/F91100 115 or 230 VAC
50, 60 or 400 Hz
11 IEC Line Cord American 3 prong Plug
J1 Connector Pin OutA = same as RCV bind post, B = same as XMT bind post, C = Code Word
The FUNCTION switch has three wafers whose contacts are brought out to J1. This allows controlling an external devices mode of operation. In order:
Wiper = E, P, G, OFF = D, N, T, AUD= C, M, S, DATA= B (= XMT), M, R, TEST= (nc), (nc), (nc)
K (may=) same functin as TRIG?
Related to Z1 (data generator) are: u, F (Ext Clock In), H (Bipolar Tx Clock), J
+5 VDC = b
Module FunctionsZ1 = 100 K bit/frame data generator, Z2 = RCV clock Phase Lock Loop, Z3 = Error Counter, Z4 = Power Supply, Z5 = Baud Rate Generator, Z6 = Error Counter Range divider, Z7 = LED Display
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