>
>
>
>>>When the plate blocking cap fails, this puts the HV across the antenna
>>>terminal. The purpose of the safety RF choke is to trip the primary CB's
or
>>fuses to
>>>remove the HV from there WITHOUT destroying itself. If it is not robust
enough
>>>to take the "hit" and fails open, the lethal HV is STILL on your
>>>antenna!
>>>(Not good!)
>>>
>>With an ordinary Load C, this is not going to happen.
>
>
>I guess the load C's in my amps are in the extrordinary catagory.
>They are 1000 pf 5kv vacuum variables.
? A 5kV Load-C clearly belongs in a tetrode with handles amplifier.
> No arcing with full HV
>applied, much less a smaller voltage from a leaky C/block.
>
? I have never seen a leaky C-block. When barium titanate dielectric
starts to breakdown, a short is virtually certain within mS.
>The safety RF choke in my amps does two things; it protects
>more expensive components from carbon build-up an damage,
>and it keeps me from being published in QST in the "Silent Keys"
>column!
>
? For the Silent Keys scenario to take place, C-block would have to
short, the amplifier would have to be in TX mode, and C2 would have to be
clearly overinsulated -- and then the operator would have to grab the
ungrounded side of the antenna. .
- later, Phil
-
- Rich...
R. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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