[ARC5] An "Extra Class" Question:

[Bill Fuqua]

Modulation inductors were used to improve fidelity and remove DC bias from 
the plate transformer which would cause the core to saturate
at low modulation frequencies. I suspect they are referring to a 
monitoring  device such as a peak reading AC volt meter capable of 
measuring 1.414 times the RMS value
of the voltage across the secondary. Or an oscilloscope. Or any device that 
would indicate when the plate voltage plus audio voltage swings negative 
(over modulation condition).
   Just a note. Asymmetrical modulation was accepted by the broadcast 
industry and also articles were in the handbooks as well where
a diode was used to prevent the HV to the class C final from swinging 
negative. However, to prevent splatter an audio lowpass filter
had to be placed between it and the amplifier. This solution sounds too 
complex to be the answer.
    Spark gaps were used to prevent breakdown of the transformer's 
insulation. They would naturally generate loads of splatter.
   Spark gaps were needed to protect the secondaries of the modulation 
transformers in case of light loading or an open filament
in the final amplifier. With out the load of the final on the modulation 
transformer the modulation transformer voltage could swing many times
what is should. I have seen this happen in a Viking 1 transmitter with a 
bad final. A spark flew from the B+ bypass capacitor to ground.
   What year was this question in the license manual?
73
Bill wa4lav