TRA967
In general I do not have too much interest in VHF/UHF equipment but when the opportunity arose to add this VHF Manpack to my collection I decided to take it.I am happy to report that I am pleased that I did
The TRA 967 is a compact, for its age, VHF FM Transceiver covering the range 36-75.975 Mhz. It has 1600 channels spaced at 25 khz.and is powered by 12V from either the MA968A Ni-Cad battery pack , the MA968B Dry Cell Pack or a Vehicle Supply , although obviously a suitable mains PSU can be used.There are two versions the TRA967/1 with 1Watt output or the TRA967/3 with 3 Watts output..
Audio output is 50mw into 50 ohms and 10mw into 300 ohms
There is an inbuilt Matching Unit for the 1M whip that is used with the set and it can also give band switching info for the MA972 Remote ATU and like the TRA931 it uses beta emitter lights for "backlighting " the frequency selection knobs.
To the top left of the set we have the mounting for the 1M Whip, below this a 'Ground' Connector, and below this a BNC connector for an "external" Antenna.The four rotary switches on the top row select the operating frequency and below these the 'Mode' switch and 'Audio Gain' Control.To the right of these are the two 'audio' sockets, one 6 pin , one 7 pin.
Unlike the TRA931 this set has a metal case and therefore no screening covers over the mainboards.
The mode switch has the following functions.' Off', 'On' (!), 'Whisper', 'Rebro', and 'Noise'
"Off" and "On" I think are quite self explanatory..!.
"Whisper" increases the microphone sensitivity by some 20db.
"Rebro" is a "Re-Broadcast" facility whereby two TRA967 may be used with the MA4009 'Rebroadcast Control Unit".This offers a number of useful functions ,but mainly, enables the two sets to act as a form of repeater.For this the set emits a standard 150 hz pilot tone.
'Noise' just basically opens the squelch. The squelch level being pre set within the set itself.
The battery pack clips on to the bottom of the set and that's it..!
Operation.
In use the set is just put on the operating frequency , the volume is set to the required level, and transmission is by use of the handset. A "Power Save" circuit is used when the squelch is closed and a series of "pips" can be heard in the headset. If an incorrect frequency is set, that is outside the operating range of the unit it lets you know by "beeping" at you., it also "beeps" when the battery pack starts to run down. The inbuilt AMU takes care of antenna matching when the 1M whip is used.
Circuit Description.
The receiver is a single superhet that down converts to 10.7Mhz for the IF.The Rf amplifier incorporates input and output matching networks.These are tuned by Varicap Diodes from a voltage generated on the Synthesizer Board.The amplified signal is applied to the mixer where it is combined with the 'Channel Oscillator' and the difference frequency is selected by the 10.7 Mhz crystal filter unit.The audio is recovered by an integrated IF Amplifier and Limiter and this is fed to an Audio Amplifier.
The Transmitter has a microphone amplifier and limiter which applies the audio to the modulator on the Synthesizer. Here a 150hz pilot tone is added to the audio signal. The FM RF signal is amplified by a three stage wideband amplifier and passes through a lowpass filter to the transmit/receive changeover relay
It looks relatively straight forward to replace the 10.7 Mhz IF filter with a narrower unit if required.Because of its 25 Khz steps this set is of limited use to amateurs on Four and Six Metres.Even for use listening outside the Ham Bands 25khz steps are unsuitable .None the less if you can find a frequency that won't upset the Band Plan then this set makes a nice little box to either carry around in the car with you or to place on a convenient shelf in the shack to monitor your favorite frequency.
The lack of an external squelch control is a nuisance although it looks more than possible to change the volume control for a dual concentric version and have a squelch control that way. Audio output is quite low and some arrangement needs to be made here.I have used a small external speaker with a built in amplifier on the TRA931 and no doubt , if I still had it, it could be used on the TRA967 with good results.
Brief Specifications.
| Frequency Range | 26 to 75.975 Mhz |
| Channels | 1600 |
| Channel Spacing | 25 Khz |
| Mode | F3 Narrow Band FM Simplex |
| Power Supply | 12V 1.4A TRA967/3 TX 120MA RX (signal) |
| Transmit Power Output | TRA931/1 1Watt --- TRA967/3 3 Watt |
| Peak Deviation | 5 Khz |
| Sensitivity | 12db for 1uv emf with 3khz deviation at 1khz |
| Weight | 3.5 kg complete kit |
| Dimensions | 285D x 166 W x 76 H with battery |
Control Panel.
To the left is the underside of the Synthesizer Board to the right the Transceiver board and in the middle a general view of the set.
These views show the main boards hinged upwards. Left the Synthesizer Board and to the right the Transceiver Board.
A view showing the Battery Box and Main Case.
A view of a recently acquired MA968B Dry Cell Battery Box. The set works quite happily with 10 Ni-Cads (C Type)
Accessories.
There are a large number of "Add On's" listed for this equipment. I have listed a few below.
| MA968A | Rechargeable Battery |
| MA968B | Primary Battery Pack |
| MA988 | Loudspeaker Amplifier Unit |
| MA4009 | Rebroadcast Control Unit |
| MA989E | Mounting Frame |
| TA970 | 25W VHF Amplifier` |
| MA972 | Antenna Matching Unit |
| MA978 | Battery Charger |
| CA4001 | VHF Test Set |
| MA985B/MA986 | Local/Remote Control Boxes |
Conclusion.
The set is limited by having 25 Khz channel spacing. Reducing the deviation to below 3 Khz is possible but with the UK 4M and 6M Amateur Band Plans 25 Khz stepping is not compatible. It looks like it may be possible to add a repeater shift but again this would be limited because of the steps.Not having an adjustable squelch is a nuisance. Adjusting the level at which the squelch opens for a lower input is possible but then you have to put up with the set spluttering due to noise etc.Obviously the set is tough so you can cart it about to your hearts content.The two "Audio" sockets connect you to the Audio Output, Microphone and Power Lines so mobile use is very easy if you make up a wiring harness of some sort and use the BNC antenna socket for some type of mobile whip.Using the set in "Noise" mode will enable you to keep an ear on the channel in use, although this is not really very useful in a quiet car..! For me the set finds its use monitoring a local channel where the signals are very strong. I use a "Multiple Dipole" ie one cut for 4M and another for 6M and use a common 75 Ohm coax feeder. I have not bothered with a Balun at present.
I have not yet looked to see if any of the components fitted to this set are difficult to get hold of but this is something that must be faced with sets of this vintage. At least getting in to replace them is as straight forward as you could expect. Racal do seem to have made their tactical equipment easy to maintain , and, like the TRA931 , the manual is very "hands on."
15/02/2002