From: R. Measures <r@somis.org>
Date: February 20, 2005 2:31:57 AM PST
To: TexasRF@aol.com
Subject: Re: [Amps] Pi-L In-circuit Adjustment Question
On Feb 19, 2005, at 9:12 PM, TexasRF@aol.com wrote:
> Hi Mike, in answer to cold tuning the output network:
> The tube contributes a significant part of the total C1 value; for this
> reason, it needs to be in the circuit. If this causes a problem
> connecting your
> load resistor, the resistor can be placed across the rf choke with
> nearly the
> same results, especially on the bands between 160 and 20m,
>
> C1 resonates the network and C2 adjusts the output impedance.
A Pi-network is not resonant because it is two L-networks in series,
and L-networks never operate at resonance.
>
>> Therefore, in
>> your cold test C2 should be used to provide 50 ohms output. C1
>> resonates the
>> network and you should be able to remove or null the reactance
>> reading showing
>> on your bridge. There is some interaction between C1 and C2 but the
>> network
>> should act as described. Said another way, C1 will also change the
>> 50 ohm
>> reading but not as much as C2, C2 will change the resonance/reactance
>> but not
>> as much as C1
>>
>> The method you are using is a wise move to confirm all is as
>> expected. I
>> have used this method as high as 432 MHz with good results.
>>
>> Happy tuning!
>>
>> 73,
>> Gerald K5GW
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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