500 WM3 LF-MF Transmitter


Modes: CW, MCW and  AM when fitted with a voice adapter
MCW tone : 500 Hz
Frequency Range: 125 KHz to 500 KHz (2400 to 600 metres)
Power Output:  500 watts
Frequency Control: MOPA
Dimensions: 24"W x 36"D x 66"H
Circa: 1928

The  500 WM3 is a transmitter designed for shipboard use.  It operates on any of four wavelengths in the range of 600 to 2400 meters when used with an antenna resonant for 250 meters and a capacitance of .0007 mfd. All four channels are controlled by a common, front panel wave change switch. The set is normally wired up to permit two wavelengths in the band 600 to 1300 metres and two in the band 1200 to 2400 metres.

Power was provided by two motor-generator sets; one delivered high tension DC (2000 volts @ 750 ma) while the other provided low voltage DC for heating the tube filaments.

The transmitter itself was comprised of a pair of T-250 tubes, wired in parallel and in MOPA fashion. Each tube was rated for 250 watts dissipation.  A voice adapter comprised of a UX-210 speech amplifier driving an MT-12A modulator triode. As a system, the 500 WM3 was used with the MST2 Tuner and the MSA5 amplifier combination.

500 WM3 transmitter. (Courtesy Laval Desbiens via Spectralumni)
500 WM3 Operator's Manual. (Courtesy Laval Desbiens via Spectralumni)

Contributors and Credits:

1)  Spectralumni  http://www.spectralumni.ca
2) Laval Desbiens <desbiens.laval(at)videotron.ca>

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May 11/08