Inhaltsverzeichnis
Wireless Set No. 31 AFV
Used by the Royal Signal Corps.
The British Wireless Set No.31 was developed as a lightweight manpack radio for communication between infantry units; the W.S.31 AFV (Armoured Fighing Vehicle) version was also intended to be installed in armoured cars and vehicles.
The set, which was intended to replace the low power radios W.S.18, 68 and 46, was based on the technically closely related American set SCR-300-A (BC-1000). The first prototypes were ready at the end of 1945/46, production started in November 1946 and the set was delivered to the infantry between 1947 and 1949.
The successor version Wireless Set. No. 31 Mk 2 as a manpack radio dispensed with the squelch circuit, the volume control was moved to the top left corner of the front panel.
Technical data
- Frequency range: 40 - 48 MHz, 41 channels with 20 kHz channel spacing
- Frequency display: Analogue dial
- Frequency memory: none
- Features: squelch
- Transmit power: FM 0.3 watts
Power supply
- Batteries: Heater voltage 4.5 V; anode voltage 90 V and 150 V
- Vehicle operation with separate power supply (Power Supply and L.F. Amplifier No. 3): 12 or 24 V vehicle battery
Dimensions
- 305 x 432 x 152 mm, weight 10.2 kg
Accessories
Operation
Technically is the W.S.No.31 based on the widely used american SCR-300A (BC-1000). The manpack radio consists of a transceiver unit which was strapped onto a battery box with dry batteries Battery Dry No.1 or No.2 (90/60/4.5 V). A mains power supply was developed in the USA, but was not introduced to the troops. In Great Britain, the W.S.31 AFV version was operated in armoured vehicles with the Power Supply and L.F. Amplifier No. 3, and an external power supply unit for the W.S.31 was also developed in France.
The manpack radio operates in the military VHF range 40 - 48 MHz and used frequency modulation, in contrast to the single-channel set BC-611 which used amplitude modulation. Thanks to the FM mode, the radio link was less susceptible to interference from ignition sparks of all kinds. As another plus, a free channel could be selected from 41 channels, in contrast to the BC-611 which had to be realigned after the single channel was changed.
The tuning knob / channel selector switch with a mechanical lock is located on the left of the front panel, channels 0 - 40 have 200 kHz spacing, four channels for communication with the Wireless Set No.88 are labelled A - D. The set can be calibrated in the CAL positions at 43.0 / 47.3 MHz. At the bottom left is the volume control and next to it the connector for headphones / headset with transmit/receive switch, which has been modified on the set shown.
At the top right is a pushbutton for calibrating the transceiver, the dial window with the channel display (with a mechanically adjustable calibration mark) and the aerial connector.
The Wireless Set No.31 AFV shown here is the version for light armoured vehicles, in which role, the set partially replaced the Wireless Set No.19. The battery compartment and a hinged cover to protect the controls of the manpack W.S.No.31 were omitted, the set was usually connected directly to the vehicle installation with the on-board intercom system, the socket for the headset on the front panel was reserved for test purposes. The aerial socket was converted to a coaxial socket and the output impedance was adjusted to 50 ohms.
The Wireless Set. No.31 was replaced around 1958/59 by the Wireless Set A41 and the AFV version around 1959/69 by the Larkspur set B42.
Technical principle
The receiver operates as a double conversion superhet with preamplifier stage, the receiver oscillator oscillates at half the operating frequency and then passes a doubler stage, only the early Mk I sets have an automatic squelch. By pressing the Calibrate button, the 10th and 11th harmonics of the 4300 kHz oscillator are fed to the second mixer tube and can be tuned to „zero beat“.
In transmit mode, the modulator signal is mixed with the main oscillator (17.85 - 21.85 MHz) and then fed to a frequency doubler stage; after mixing with the 4.3 MHz oscillator signal, the signal is fed to an RF output stage and the antenna.
Components
The set is equipped with tubes:
- V1 CV807 (3A4): Power amplifier, power amplifier
- V2 CV807 (3A4): Mixer, crystal oscillator
- V3 CV785 (1T4): Doubler
- V4 CV785 (1T4): Oscillator
- V5 CV1785 (1L4): AVC
- V6 CV785 (1T4): HF amplifier
- V7 CV1785 (1L4): 1st mixer
- V8, V9 CV785 (1T4): IF amplifier
- V10 CV782 (1R5): 2nd mixer, crystal oscillator
- V11 CV785 (1T4): IF amplifier
- V12, V13 CV1785 (1L4): Limiter
- V14 CV753 (1A3): Discriminator
- V15 CV784 (1S5): Discriminator, NF Amplifier
- V16 CV784 (1S5): LF amplifier
- V17 CV1785 (1L4): DC amplifier
- V18 CV784 (1S5): Squelch Oscillator
Technical documentation
Development
In 1940, the Galvin Manufacturing Company, the predecessor of Motorola, developed the BC-1000 or SCR-300, the first portable multi-channel frequency-modulated manpack radio. It underwent troop trials in 1942 and from 1943 it was used as the first „walkie talkie“, an FM portable radio, in the Second World War theatres, for example in the Pacific, Normandy and (southern) Italy. One problem was the supply of the necessary special batteries.
Great Britain built the set as Wireless Set. No.31, and soon a version for armoured cars was introduced with a power supply unit that could be connected to the on-board system and was of course no longer dependent on batteries for power supply. The W.S.31 was introduced from 1947.
