Microphona Superdual MK305

Microphona Superdual MK305

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Brand and type: Microphona Superdual MK305. The "super" doesn't mean frequency-changing as in a super-heterodyne radio: it has no oscillator/mixer tube.

Produced: Tsechoslowakia 1935/1936

Cabinet: Wood with bakelite front. The back is a solid wooden plank.

Tubes: All side contact (European P-base): AZ1 (full wave rectifier) - AF7 (HF) - ABC1 (detector and pre-amp) - AL1 (output stage). The filaments take 4V.

Power: Mains supply from 120 to 240V AC in 5 steps.

Bands: Long and medium waves. The dial shows mainly stations from Eastern Europe.

Controls: The usual, and a few knobs and switches of which I don't know what they are supposed to do. A knob on the back shows this sign: O-|--< in ASCI.

Obtained: In 1982. I swapped it wih a museums conservator for a sort of home-built transmitter from WWII, which I found on a flea market.

Condition/working: It looks good and is complete. Some time ago I got a few weak stations, but lately it is dead. This is a TRF or reflex-receiver. Probably I will have to replace many leaky capacitors. The schematic was sent to me from Tsechoslowakia.