The R4187 Communications Receiver

 This fine old receiver, bearing the badge "Standard Radio", now rather battered, was one of the last military sets to use valves, and was fitted in the Avro Vulcan aircraft. The receiver weighs in at just 26 pounds and is used operationally with a mixture of other equipments, including the T4188 transmitter, Power and radio unit 4192, Control unit 4189/4190/7216, Junction box 4191, Aerial tuning units 7106/7180, Selector unit 7003, Impedance matching units 7949/7949A/9541

The Vulcan was one of the trio of H-Bombers developed in the 50s to replace the Canberra which in turn had replaced derivatives of the WWII piston engined aircraft of Bomber Command.

The Vulcan's stable-mates were the Vickers Valiant and the Handley Page Victor.

In those days Britain led the world in aircraft design. We had lots of independent manufacturers that had been producing aircraft from the very earliest days and each manufacturer had plans to move into the commercial sphere and was developing a prototype airliner based on their military plane.

The Avro Vulcan with its huge delta wing was to become the Avro Atlantic, the Handley Page Victor was to be the VC9 and the Valiant the V1000. Just before these types was the DH106 Comet/Brabazon IV which was to be a tail-less turbo jet airliner. Unfortunately none of these civil aircraft were ever built to be put into service and before too long Britain lost its lead to the US, although Concorde, the sonic boom of which I hear every day at around 10:15am (I initially wrote this a good few years ago), actually made it with help from the French.

I suppose the decline of Britain's hopes and aspirations started with the demise of the Bristol Brabazon. Who remembers seeing this plane on its round-Britain goodbye flight which must have been around 1953 or 54?

 click to see API

 

 

 Here is the R4187 lump out of its case and pictured next to its controller; the part used by the aircraft crew.

In those days the V-Bombers were supposed to be able to fly to Vladivostok and back and of course needed HF radio in order to maintain contact with base. I can't imagine that any of the aircraft would ever have been able to get back from a mission, if ever called to deliver an atom bomb, as once air defence systems had improved, only intercontinental missiles would have been viable.

Interestingly the Vulcan was actually called into active service during the Falklands conflict, but to deliver conventional rather than A-bombs I might add!

Was this the only time the V-bomber force was used in anger? I have a suspicion that at the time they had already been sold as scrap and a deal had to be struck with the purchaser to borrow them back!

The receiver shown above is quite interesting as it uses a large bank of crystals to define 12 sub-bands. The desired sub-band can be selected by the CHANNEL selector switch from A to M (excluding I). As you can see above, receive modes are R/T, MCW, CW1 and CW2. Fine tuning within the selected band is accomplished by synchronous motors. An Intercom position is also available.

 Below is a collection of pictures of the set

You'll see about as many gear wheels as valves. I counted 16 valves (one is hidden away on tthe main chassis).

The receiver tunes 24 pre-set channels in three bands viz.

2.8 to 5.2MHz, 5.2 to 9.7MHz and 9.7 to 18.1MHz

Using plug-in crystals in the ranges corresponding to the three bands viz.

4.95 to 7.35MHz, 7.35 to 11.86MHz and 7.55 to 15.95MHz.

The receiver is a double-conversion superhet and the RF design follows standard practice but the set has a main chassis and front panel plus seven detachable modules. Remote control facilities are fitted which use electric motors. The first IF is 2.15MHz and the second IF is 100KHz. Although crystal controlled the 2nd oscillator can be tuned plus or minus 7KHz so this might be a good place to start if a wider tuning range was to be required?

There's broad filter for R/T, and a narrow band filter together with a BFO set to 99KHz is provided for CW reception.

The RF amplifying unit uses 6 valves

V1 CV140 limiter, V2 CV454 1st RF amp, V3 CV454 2nd RF amp, V4 CV453 1st mixer, V5 CV454 IF amp, V6 CV453 2nd mixer

The IF amplifier uses 9 valves

V1 CV138 2nd oscillator, V2 1st 100KHz IF amp, V3 2nd 100KHx IF amp, V4 CV138 cathode follower, V5 CV140 Audio detector & AGC detector, V6 CV138 BFO, V7 CV138 AF amp, V8 CV136 Audio output, V9 CV140 noise limiter

The main chassis has a single valve

V1 CV455 1st local oscillator.

Below, I've interspersed circuit diagrams of the receiver as follows:

Unit 4207 Receiver front end; Unit 4208 Receiver back end; Unit 4211 Receiver crystal selector unit, band switching etc;; Unit 4190 Control unit.

 

 Below, bottom centre is the cover to the crystal oven and amongst the valves you can see a B7G crystal for the BFO.

 

 

 HT is supplied from a rotary converter seen below, bottom left.

 

 

 

 

 

 

 

 

 

 

 

 

 I have three examples so I should be able to refurbish at least one...

 

 

 

 

 

in progress...

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