The British Army Wireless Set B44 was a post-war military VHF transceiver. It was introduced in the early 1950s as part of the British Army's Larkspur radio communications system. It is an interesting piece of British military radio history, particularly because it was later used by radio amateurs.
Its connection with amateur radio
Surplus B44 sets found their way into amateur hands during the early 1960s. They were adapted for operation on the 70 MHz (4-metre) amateur band.
I had a B44 which had crystals for 70.26 MHz. Mine was the MKI which was single channel. I modified the power supply, which included removing the vibrator and fitting a couple of power transistors in its place. It worked well on a dipole antenna on a pole above my shed roof. A friend of mine had one in his car, a Hillman Imp. We had some good QSOs when he was out and about.
Military use
The radio was designed for short-range tactical communications, particularly within light anti-aircraft regiments. It was a portable VHF radio which could be carried or operated as a small ground station. It was used to communicate between military positions and units in the field.
Technical specifications
| Specification | Details |
|---|---|
| Manufacturer | British military equipment |
| Introduction | Early 1950s |
| Frequency coverage | 60–95 MHz |
| Modulation | AM |
| RF output | Approximately 3 watts |
| Channels | Three crystal-controlled channels |
| Range | Up to approximately 15 miles |
| Power supply | 12 volts DC |
| Radio system | Larkspur |
The valve circuitry
The B44 Mk III used 12 valves, with several different valve types employed in its circuits. The surviving technical documentation identifies the following:
| Valve reference | Valve type |
|---|---|
| V1–V5 | CV138 |
| V6 | CV140 |
| V7 | CV137 |
| V8–V9 | CV136 |
| V10–V11 | CV416 |
| V12 | CV2129 |
The set used separate stages for its receiver and transmitter functions, with crystal-controlled frequency selection.
Receiver operation
The receiver was designed to cover the military VHF range of 60–95 MHz.
Its principal functions included:
- Receiving incoming AM signals.
- Amplifying weak radio-frequency signals.
- Converting received signals to an intermediate frequency.
- Detecting the audio signal.
- Amplifying the audio for headphones.
The receiver was designed to work with the three pre-set channels.
Transmitter operation
The transmitter was crystal controlled, giving the operator three pre-set channels. Its output was approximately 3 watts AM, although some later amateur-radio descriptions quote around 4 watts. The transmitter used valve RF amplification to produce the VHF signal, with the microphone audio modulating the carrier.
I wish I’d kept mine. It was in pristine condition.