Wireless Set No.31 A.F.V.

 This example of a Wireless Set No.31 appears to be an early version. The set emerged, after some modifications, as the Mk2 and in fact many earlier models were modified as the Mk1/1 to bring them to the same standard as the later model. This example appears to follow the original design so I'll assume its a Mk1 design although it's actually marked as an A.F.V. (Armoured Fighting Vehicle) version. The transceiver was introduced in the period 1945-1947 as a manpack, probably to replace the ubiquitous 18 Set, but operated in the VHF range 40-48MHz instead of 6-8MHz which, following WW2 became jam-packed with hgh power short-wave broadcasts. A little later of course and the low VHF band was used for television making its use a little tricky. Maybe experience with the 17 Set may have influenced the choice of frequencies for the 31 Set, then again the similarity with the very successful US radio the BC1000 indicates that the latter may have guided the choice of frequency ? Was a Requirement Specification ever raised for WS31 or did someone just tell the Army that this was what they would be given?

Click the picture to see its circuit diagram.

 

 The WS31 operated on narrow-band FM rather than AM and was a close copy of the US-made SCR300/BC1000 (see below)

 

 

 The WS31 is so similar in certain areas that I think the same drawings were used to make the parts. Take for example the chassis detail pictured below. The UK Plessey plug has been fitted over the hole for BC1000 plug suggesting the basic chassis was made exactly to the US drawings.

 

 The tropicalising coating covers everything except the tuning trimmers. How was this done?

The label on the front of the set tells me it was made by M.R. (Murphy Radio) and all over the set are inspection stamps recording M.R. What about dating evidence? I looked at a selection of valves and found several are of US manufacture, but the majority carry CV numbers and probably British. But maybe the set has been refurbished or overhauled (the mod strike label tells me it has visited a maintenance depot once). There are two crystals and one carries the date 4-54 which is likely to be April 1954. The cover for the main tuning gang and the rear of the metal tuning dial have the number "3894" pencilled on them which matches the serial number on the identification label. The power connector has a fine thread and is identical to that fitted to the R216 receiver.

The evidence points to the fact that this example was manufactured around mid-1954 to drawings originating from the Mk1 design but amended to cater for A.F.V. use.

 

 Note the five trimmers which are used to align the unusual five gang tuning condenser.

 

 
 V1 CV807/DL93 Power Amp V6 CV785/DF91 RF Amp   V11 CV785/DF91 3rd IF Amp  V16 CV784/DAF91 Noise Amp/Rectifier
 V2 CV807/DL93 Tx Mixer/Xtal Osc  V7 CV1758/DF92 1st Mixer  V12 CV1758/DF92 1st Limiter  V17 CV1758/DF92 DC Amp
 V3 CV785/DF91 Doubler  V8 CV785/DF91 1st IF Amp  V13 CV1758/DF92 2nd Limiter  V18 CV784 Squelch Osc/Amp
 V4 CV785/DF91 Master Osc  V9 CV785/DF91 2nd IF Amp  V14 CV753/DA90 Discriminator  XL1 4300KHz; XL2 6815KHz
 V5 CV1758/DF92 Reactor/AFC  V10 CV782/DK91 2nd Mixer/Xtal Osc  V15 CV784/DAF91 AF Amp/Discriminator  LP1 6V 0.15A

 

 
  Above a BC1000, dating from 1944, which is very similar to the 31 manpack set but has a hinged lid and a few other mechanical differences.

 Up to now I've only described the WS31 itself, but this example, the AFV version, is designed to be used in conjunction with other equipments. It was manufactured at the time WS19 was in service and this transceiver connects into the AFV electrical system to allow it to operate alongside the WS19 via a set of other equipments. Firstly, the set requires power for its battery valves. Power comes from Power Supply No.3 which not only supplies 3.9 volts, 90 volts and 150 volts, but also includes audio amplification for the WS19 moving coil microphone and headphones which are shared with the 31 set. To handle the connections to these a control unit is required, either a Type 16 for use with the WS19 A Set (HF) or a Type 17 with the WS19 A and B Sets (HF + VHF).

In order to integrate into the WS19 environment a number of modifications were made to the original manpack design. Some are pretty obvious viz. the fitting of the Plessey plug to the rear of the chassis and a coax plug to the front panel, and some, not obvious including internal wiring changes to the way transmit/receive/calibration switching is made and a permanently lit dial lamp.

 Wireless Set No.88

 

 Although the black case indicates that this version of the set might be a Type B, supplied to infantry mortar platoons, I purchased it as a modified Type A designated as the A.F.V.version designed for fitting alongside a Wireless Set No.19 in tanks and other amoured vehicles. As such it's supplied with the amplifier and 12 volt power supply shown further below which was needed to overcome high ambient noise levels and to dispense with the usual WS88 battery pack. However, it's obvious to those who know about such things that this is a demobbed 88 set supplied to the Army Cadet Force, probably in the vicinity of London Band I TV transmissions. The clue is a pin preventing channels A & B from being selected. Why not just pop open the case and switch the crystals round? You may also note the screws securing the case are the type for which you need a special tool, so without this, reconfiguring the channels wasn't an option.
 
 
 
   The identification plate has been removed and the part number D2395 written in its place. What looks like a "ZA" number is completely obscured.
 because of its last intended use this example had security screws securing the chassis into the case. These were tightened to the point the head of the screw broke off and so the dome-shaped nuts needed to be sawn off to reveal the chassis in the pictures below.

 

 The aluminium plate marked with the main parts can be detached by removing seven screws to reveal the wiring etc.

 

 There are lots of battery valves plus a set of crystals under the cover on the right.

 

 

 To prevent operation on local TV channels you can see that besides the channel selector limit peg two of the four crystals have been removed.
 

 Below is the Power Supply/Amplifier for the AFV version of WS88 mentioned above.

 

 

Below, pictures of the PSU/Amp removed from its case. 

 

 

 
 

Below, a typical layout for the WS88AFV co-located with a WS19 and Control Units No.16 and 17.

 

 Note the cable connected to PL2. This was part of the AFV modification.

Two versions of the manpack set were in use, the Type A and the Type B. Their channels are listed here.

 TYPE A

 MHz

 Crystal KHz

 TYPE B

 MHz

 Crystal KHz

 Channel A

 42.15

 6525

 Channel E

 39.70

 6117

 Channel B

 41.40

 6400

 Channel F

 39.30

 6050

 Channel C

 40.90

 6317

 Channel G

 38.60

 5933

 Channel D

 40.20

 6200

 Channel H

 38.01

 5835

Power consumption for the manpack set is as follows..

 Battery

 1.5volts

 90volts

 Receive

 770mA

 13.5mA

 Transmit

 1050mA

 40mA

WS88 Valve lineup

 Circuit Ref

 Type

 Equiv.
  

 Circuit Ref

 Type

 Equiv.
  

 Circuit Ref

 Type

 Equiv.

 V1

 CV807

 3A4
  

 V6

 CV1758

 1L4
  

 V11

 CV1758

 1L4

 V2

 CV785

1T4
  

 V7

 CV1758

 1L4
  

 V12

 CV753

 1A3

 V3

 CV1758

 1L4
  

 V8

 CV785

 1T4
  

 V13

 CV753

 1A3

 V4

 CV1758

 1L4
  

 V9

 CV785

 1T4
  

 V14

 CV784

 1S5

V5

 CV1758

 1L4
  

 V10

 CV785

 1T4
      

 Return to Reception