[ARC5] An "Extra Class" Question:

[wb3fau55 at neo.rr.com]

well, there you go,  not a good idea to "weld" with a Viking...
---- Bill Fuqua <wlfuqu00 at uky.edu> wrote: 
> 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
> 
>    
> 
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