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G7MRV

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About G7MRV

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  1. Item on right is a Racal MA4073 Fill Gun. Used to set the encryption keys for the Cougar radios such as PRM4515 https://www.cryptomuseum.com/crypto/racal/ma4073/index.htm
  2. None in particular Clive, just wanted to review them out of curiosity
  3. Cheers Clive! I'll check the VMARS lists for them. Ive got copies of the Harness service manuals and had expected the audio gear to have been in those! DO people really pay that sort of money on ebay for a photostat? Martin
  4. Hi, Can anyone inform me as to which EMER contains the circuit diagrams and wiring info for the clansman audio gear - handsets, headsets etc? Cant seem to find it anywhere! Cheers Martin G7MRV
  5. The Clansman PRC344 is a 2W UHF AM transceiver intended for FAC use. As such, there is nowhere within its range that it is legal to transmit. In fact, of all the Clansman equipment, this is the one where transmitting can at best get you into legal trouble, at worst endanger aircraft and lives. But you say, I would NEVER transmit! Well, maybe not deliberately, but who hasnt turned a switch the wrong way accidentally? How easy is it to catch the pressel on a handset? And what about inquisitive fingers from the public at a display when your backs turned? There are no 'power on' lights on this to show your not just playing with a switched off set! It is very easy to ensure you stay legal with the 344, regardless of whether you have a handset, headset, remote radio attached, or select BEACON mode, you simply need to disable the transmitter. So, how do we do this? Surely it needs a technician? Well, no. The PRC344 is a modular system, and provided you take care, this is a very easy fix. We just need to remove a pair of numbered plug-in modules! First, remove the battery! On the larger side cover (not the switch side), remove the 14 hex bolts and lift off the cover. On the plate with the switches underneath, you will see a U shaped section of thick stainless steel wire, clipped over a screw in the middle and with its ends going into two holes. Lift this up with a screwdriver near the screw, and it will come off - this is the module removal tool! Now, locate module 3 (all modules are numbered on their tops), you will see it has holes in the corners. Insert the ends of the tool in these holes, and gently pull. The module will come out. Check it says Amplifier Direct Current on the side (to make sure you havent pulled out the wrong one!), and put it away somewhere safe (so you can put it back if you sell the set). Then, locate module 8, and extract that. Check its says Regulator Audio Level on it to ensure its the right one. Put that in the same safe place as module 3. Replace the extractor tool, making sure it is securely clipped down (if it comes loose inside it will cause big problems!), and refit the lid, making sure to put it back on the way around you removed it, as there are foam pads attached that hold the modules down. This should be easy, as there is a long dessicant canister attached in one corner, and a diagonal cut in another, that matches the diagonal on the body. Tighten up the bolts. Your set will now work just as before, only it will not transmit. Module 3 is the Direct Current Amplifier. It is responsible for providing the control voltages that activate the transmit amplifiers, and switch the antenna relay. It also provides the sidetone on transmit (audio feedback to the headgear). Inside it, there is a logic control gate, which will only activate if it gets a Phase Lock signal from the synthesiser, indicating that the frequency is stable. By removing module 3, there is no logic control, so no control signals to the rest of the transmitter. With only module 3 removed, switching to beacon mode will still activate the Tx RF Oscillator and Driver circuits (these are hard wired into the set). As a result, there will be a slight leakage of RF energy. This is very low level, but may be detectable ( I can detect the emission from my set on a commercial scanner many tens of meters away!) so in order to be absolutely safe, removing module 8 disables the beacon oscillator and Tx microphone audio stages. And after this, you still have an original condition radio, that will still receive properly. It will still look just as good at a display or show, but now you dont have to worry about accidentally calling in an air strike! Martin G7MRV
  6. G7MRV

    RT344

    I am aware this is an old thread, but anyone searching for 344 info will inevitably find it. It is very easy to ensure you stay legal with the 344, regardless of whether you have a handset, headset, remote radio attached, or select BEACON mode, you simply need to disable the transmitter. But you say, I would NEVER transmit! Well, maybe not deliberately, but who hasnt turned a switch the wrong way accidentally? How easy is it to catch the pressel on a handset? And what about inquisitive fingers from the public at a display when your backs turned? This is a very easy fix. First, remove the battery! On the larger side cover (not the switch side), remove the 14 hex bolts and lift off the cover. On the plate with the switches underneath, you will see a U shaped section of thick stainless steel wire, clipped over a screw in the middle and with its ends going into two holes. Lift this up with a screwdriver near the screw, and it will come off - this is the module removal tool! Now, locate module 3 (all modules are numbered on their tops), you will see it has holes in the corners. Insert the ends of the tool in these holes, and gently pull. The module will come out. Check it says Amplifier Direct Current on the side (to make sure you havent pulled out the wrong one!), and put it away somewhere safe (so you can put it back if you sell the set). Replace the extractor tool, making sure it is securely clipped down (if it comes loose inside it will cause big problems!), and refit the lid, making sure to put it back on the way around you removed it, as there are foam pads attached that hold the modules down. Tighten up the bolts. Your set will now work just as before, only it will not transmit. Module 3 is the Direct Current Amplifier. It is responsible for providing the control voltages that activate the transmit amplifiers, and switch the antenna relay. It also provides the sidetone on transmit (audio feedback to the headgear). Inside it, there is a logic control gate, which will only activate if it gets a Phase Lock signal from the synthesiser, indicating that the frequency is stable. By removing module 3, there is no logic control, so no control signals to the rest of the transmitter. And, you havent actually modified the radio, so its still in original condition. Note - with only module 3 removed, switching to beacon mode will still activate the Tx RF Oscillator and Driver circuits (these are hard wired into the set). As a result, there will be a slight leakage of RF energy. This is very low level, but may be detectable ( I can detect the emission from my set on a commercial scanner many tens of meters away!) so in order to be absolutely safe, the beacon oscillator and Tx microphone audio stages should also be disabled. This can be done by additionally removing module 8. Martin G7MRV
  7. Heck, somehow missed those when I looked at the list! Trouble is, im not a VMARS member! I do however have a membership form ready to fill in, just need to get a round tuit.
  8. Pete (I appreciate this is a very old thread and you may have found the answers!) The 12v, 6v, and 3v stabilizer modules have a square black 22uF tantalum capacitor across the supply rail input. These fail either short circuit or extremely leaky, resulting in a dead module/radio. Ive just had to replace them on mine with modern 22uF 50v electrolytics Martin G7MRV
  9. Hi, Im looking to obtain the service EMERs (ideally 2nd and 3rd level) for the PRC344, can anyone help? What I really need are the circuit diagrams, and alignment instructions/test points Ive just resurrected one from dead, which was a nightmare without any circuit diagrams! (luckily it was a PSU fault!) Cheers Martin G7MRV
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