Tom,
All you have to do is make sure it's not resonant on one of the operating
bands. If it is, you can park that frequency somewhere else by adding or
subtracting a few turns of wire. To check its resonant frequency, short the
coil with a jumper, then use a grid dip meter to measure it. The main thing is
that the choke has to have enough inductance at the lowest frequency to block
the RF.
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/25/05 at 2:44 PM KD7QAE wrote:
>So, Are you telling me that at every operating frequency of the amp I
>have to design the plate choke so that it has a parallel resonance?
>That is impossible without adding some sort of tuning mechanism, which
>clearly isn't done in practice. You cannot count on parallel resonance
>for the general wide band plate choke design. I agree w/ Rich's analysis.
>
>Tomm, KD7QAE
>
>R.Measures wrote:
>
>>On Aug 25, 2005, at 4:52 AM, Roy Koeppe wrote:
>>
>>
>>
>>>If...
>>>
>>>"Reactance at 1.8MHz = 3099 Ohms"
>>>
>>>Then,
>>>
>>>With 3 kv on the plates, circulating current through the choke winding
>>>and through the by pass cap is 1 amp?
>>>
>>>
>>
>>With a 3kV anode supply, The peak change in anode potential is c.
>>2700v-pk 0.707 x 2700v = c. 1900V-rms, so the circulating current
>>through the HV-RFC is 1900v / 3099-ohms = 0.616A-rms
>>
>>
>>>You see, this is a useless parameter.
>>>
>>>
>>
>>Not quite since the HV bypass C must be able to carry 0.616A at 1.8MHz
>>without overheating and igniting.
>>
>>
>>
>>>Circulating current is limited by
>>>parallel resonances in the winding,
>>>
>>>
>>
>>At 1.8MHz, with a typical Ham amplifier - I don't think so.
>>
>>
>>
>>>which present a much higher
>>>effective resistance to the tank circuit.
>>>
>>>73, Roy K6XK
>>>
>>>_______________________________________________
>>>Amps mailing list
>>>Amps@contesting.com
>>>http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>>
>>>
>>
>>Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>>
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>>
>>
>>
>>
>
>
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