T4188 Transmitter

This is the companion transmitter for my R4187 receiver. I acquired it from Martin Wilens in Holland and it's in excellent condition. A complete aircraft installation requires several boxes, these are the R4147 and T4188 plus the 4192 transmit power/modulator unit and control box.

Below are various views of the chassis. The set is designed to be remotely controlled when installed in an aircraft, but manual controls are provided making it a useful piece of kit. As the transmitter runs in class C it won't work too well as a linear amplifier unless the biasing of the valves is changed. Cooling air for the pair of PA valves is provided by a small blower.

Below you can see in the centre the CV428 (5B254M) driver (this valve is very similar to the 807 except it's physically a lot smaller and uses an IO base). To it's left is the CV2127 (6CH6) buffer amplifier valve.

Below the pair of CV2519 (4X150A) valves, wired in parallel, operating in Class C with 600V of amplitude modulated HT.

The transmitter tunes from 2.8Mc/s to 18.1Mc/s in 3 bands viz. 2.8-5.2Mc/s, 5.2-9.7Mc/s and 9.7-18.1Mc/s) and driven by 1 of 24 crystals delivers 100 watts of carrier power. Below the circuit diagram... not really very complicated as it's basically an amplifier followed by a driver then a pair of power amplifier valves. It's an AM transmitter using plate modulation with the high power audio amplifier mounted on another chassis. The thing operates in Class C which is ideal for this type of transmitter and quite different to a linear amplifier. The unit would however make a really useful linear amplifier if the valves were biased differently. One use for a modified T4188 might be as a power amplifier for a WW2 transmitter such as a WS19. A complication of the T4188/R4187 set-up is the requirement for the thing to be remotely controlled. On an aircraft, one can select a crystal then have the receiver and transmitter automatically tune to that frequency using a set of motors and gear trains. The original idea behind the T4188/R4187 was communication between base and an aircraft which would have been sent on a bombing run. A typical aircraft would have been a Vulcan bomber and somewhere like Vladivostok would have been the target. No doubt the US would have had a similar radio for use in their B52 aircraft and the USSR in their TU-95 Bear. Back in the 50s and early 60s the UK had no less than three V-bombers. The Avro Vulcan (that huge delta wing aircraft), the Handley Page Victor (later used as a tanker aircraft) and the Vickers Valiant. These three had taken over from the English Electric Canberra which didn't have sufficient range and payload. Interestingly, manufacturers of the V-bombers planned to develop commercial airliners from their military versions. These were the Avro Atlantic, the V1000 and the VC7, HP97 and HP111. None ever materialised but the Victor did get developed into the B1, B2, K1 and K2 versions.

Click the circuit to download a hi-def printable document

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