MUSEUM "WAALSDORP"

The transmitter circuit consisted of an oscillating power triode delivering 2 W to the antenna with anode modulating by a power pentode. Of particular significance was the application of a coaxial low loss tuning arrangement (at the time called "Kolster self inductance" 1, 2) for the oscillator which must have contributed considerably to the frequency stability. The receiver contained an "acorn" miniature triode as super regenerative demodulator preceded by an "acorn" pentode to prevent the oscillation reaching the antenna. This was followed by the above power pentode as low frequency amplifier. The front panel shows the tuning dials for transmission and reception and in between a current meter with switch. Below a switch for off, receive and transmit. This transmitter- receiver formed one unit of some 20 kg. and the range was 10 - 15 km under the specified conditions.

The second unit (17 kg) contained a Ni-Fe battery delivering low voltage power to the filaments and to a vibrator-rectifier for anode voltage. This provided 10 hours of operation for equal transmission and listening time.

A third unit in the form of a long tube (5,5 kg.) contained the collapsible 3 element Yagi antenna, the mast sections for up to 2,2 m antenna height, microphone and telephone head-set.