[AMRadio] The Manual Sez

[Donald Chester]

>From: "James M. Walker" <chejmw at acsu.buffalo.edu>

>the is
>just one pair(ie two leads) that go to the transformer, there is in fact
>a 600 watt heater coil (cone shaped) with a light bulb base that is
>switched into the circuit when the transmitter mode is changed from FONE
>to CW.

The purpose of that heater cone is to reduce HV plate supply voltage and 
serve as a current limiting resistor to the transformer primary in the 
"tune" mode.  The transmitter runs full plate voltage on CW and reduced 
plate voltage on phone.  The series resistor would be unsatisfactory in 
"phone" because, with the variations in class-B modulator current, a series 
resistor in the transformer primary would result in extremely poor voltage 
regulation.  You would have the same problem in the CW mode, as the voltage 
would soar with the key in the "open" position.

Don K4KYV

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