There are many variations of the BC348 and the receivers differ in frequency range and design. The H K L and R models cover the range .2 -.5 MHz and 1.5 - 18.0 MHz. Others cover 2 - 18 MHz.
The BC348 is the 24v version of the BC224, which runs off 12V. Ground based receivers of similar design but much heavier in weight are the BC312 (12V) and the BC342 (117V AC). These sets have low frequency counterparts in the BC314 (12V) and the BC344 (117V AC).
Note that the valve line up for different models varies. Later models featured single ended tubes and should have had enhanced performance.
The IF frequency for the BC348 is 915 kHz.
The sets had 4000 or 300 ohm headphone outputs. Unfortunately they lack audio gain and a very useful modification was to add a triode between the detector and output valve to remedy the situation.
They are easy sets to work on and are very well built.
Some models use a back bias system around the audio stage and care should be taken to return this negative HT lead to the appropriate position and not to deck.
Most sets have been converted to 6.3V AC heater operation. High tension of 200 - 300V is required.
© Ian O'Toole, 2009. Page created: 28/04/03 Last updated: 27/10/2012