Id use one of the 1mh pie wound transmitting chokes often found on Ebay and
elsewhere. There are many different current ratings to choose from.
Carl
KM1H
----- Original Message -----
From: "Vic K2VCO" <vic@rakefet.com>
To: <amps@contesting.com>
Sent: Tuesday, June 28, 2011 11:49 AM
Subject: Re: [Amps] PA choke design
> Regarding the option of making the choke part of the circuit:
>
> Many commercial amps actually do this, because the reactance of the chokes
> they use is
> comparable to the load impedance of the tube. My thought is that this is
> NOT a good idea,
> because what you are doing is making a very low-Q component -- the
> choke -- part of the
> tank circuit. So I expect it will heat up from the circulating current and
> waste power. It
> could even burn out if it's not husky enough.
>
> This could be one reason why some commercial amps make the most power on
> 40 meters,
> dropping off when you go higher or lower in frequency.
>
> On 6/28/2011 8:26 AM, pc5m, Carel wrote:
>> Hi, I know it has been discussed before, but can't find any good
>> pointers.
>> For my single band 160mtrs PA I would like to design the plate choke
>> inductor. I would like to get the group opinion on
>> - using a long/big normal air wound coil to get around 1 mH (coil not
>> involved in "matching" i.e. impedance well above circuit impedance at the
>> anode. 1 inch wide/several inch long/500turns)
>> - using a smaller air wound coil such that the choke will become part of
>> matching circuit, RF currents flowing in this case.
>> - using a ferrite core to get a smaller package. Not sure how big a
>> ferrite
>> core I would need to keep 1mH of inductance even when several amps of DC
>> current are present (saturation).
>>
>> In this case I am not too concerned (I think..) of parasitic resonance's
>> of
>> this coil, as long as it is a good inductor at 2 MHz : - )
>>
>> Any ideas ? pro - con's ?. Tnx, Carel.
>>
>>
>>
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>
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
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