100W Medium Frequency Transmitter

Posted on Feb 5, 2014

The 100W4 is a two tube medium frequency transmitter with provision for pre-tuning to three frequencies in MF band and for type A1, A2 and A3 emission. For type A1 the two tubes operate as parallel oscillators and for A2 and A3, looking at the set from the front, the left hand tube serves as a oscillator and the right hand tube as a modulator. The

100W Medium Frequency Transmitter
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oscillator is directly coupled to the antenna and antenna itself is therefore a main part of the oscillator LC circuit. With approximately 200 watts input the output is approximately 100 watts and therefore the efficiency is approximately 50%. (slightly over 55% on CW and somewhat less on RT and TT). Generator. Cumulative compound DC two armature windings. One armature winding terminates at a commutator at one end of the generator to provide from approximately 10 - 15 volts at a maximum 12 amps approximately 150 watts. The other winding terminates at the other end of the generator at a commutator having more and finer segments than at the 12 volt end and has a maximum output of. 4 amps at 1000 volts (400 watts). There are two series fields one in the 12 volt circuit and on in the 1000 volt circuit. The generator also is provided with a common 12 volt shunt field in series with which is a hand controlled field rheostat. The motor and generator are coupled together by means of a semi flexible coupling. Normally there are four flexible leads running from the wave change switch on top of the transmitter to the main tuning inductance which is about a foot in diameter and has 44 turns of heavy flat copper winding (provision is made for a fifth lead which is only used when a counterpoise is necessary in the antenna system). For each frequency to which the transmitter is to be tuned a set of four detachable jacks is necessary....

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