The BP-3 was a valve-basedspy radio transceiver, developed during WWII by Tadeusz Heftman of the Polish Military Wireless Unit (Polski Wojskowy Warsztat Radiowy) in Stanmore (UK). It was introduced in 1943 and was intended for use by Agents and Resistance Organisations in Europe.
The ‘B’-series of radio sets (from 1943 onwards: ‘BP’) were produced alongside the ‘A’-series and featured increased power output. The sets were housed in a black wrinkle-finished metal box with a lid, and were labelled in Polish or English.The BP-3 covers 2-8 MHz and is built around 6 valves, all of which are mounted internally. It the field it was powered by a 12V DC converter with rotary transformer, but it could also be powered by the external 120/220V AC Power Supply Unit (PSU) that was connected to the 5-pin socket on the front panel, just like on the other ‘BP’ models.
The BP-3 measures just 28 x 21 x 9.5 cm and weights no more than 4 kg. It uses a long wire or dipole antenna and comes with a set of accessories, such as power cables, crystals, antenna and counterpoise wires, external morse key, a mains power supply unit (PSU) and a 12V DC converter.The transmitter produces an output power of 50 Watts in CW, which is more than its much larger and havier British counterpart theB2. Apart from the Polish Resistance in occupied Europe, the BP-3 was also used by the SOE (both in Europe and Asia), and the French, Czech and Yugoslavian Resistance. For a long time, the Polish spy radio sets were superior to their British counterparts. The BP-3 was followed by theBP-4, which had a different frequency range (4-16MHz) and finally in 1944 by theBP-5, which covered the same 2-8 MHz but had a built-in AM (voice) modulator.