>
>> > > since 1995, the Handbook has had an inaccurate method of calculating
>> > > RF current in a DC blocking cap. My guess is that it will remain there
>> >> until sometime around 2040. .
>> >
>> >What is the correct method?
>>
>> ? Calculate the difference between instantaneous anode potential at max.
>> conduction and anode supply potential. Divide by 2^0.5 to convert peak v
>> to RMS v. .
>
>OK, you found the RMS anode voltage for a sinewave at the anode.
>
> > Disconnect the C1 side of the blocking cap. Measure anode-C.
>> with tube in socket Calculate capacitive-reactance in ohms.
>> Current=volts/ohms.
>
>I'm sorry Rich, something appears to be seriously missing in your
>"improved" method.
>
? indeed. . . and the missing something is assumption.
>You have determined anode RMS voltage, and then assumed that
>voltage drives the anode capacitance of the tube and that is the
>current through the blocking cap.
>
>Let's try the "improved" method with a 3CX1200.
>
>Let's assume the RMS voltage is 3000 volts. The anode
>capacitance is about 14 pF.
? Let's not. To accurately calculate peak and RMS anode-potential, it
is a mistake to assume that all tube types have the same minimum anode
potential at max. conduction.
>.......
- later, Tom
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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