[Amps] Fwd: Pi-L In-circuit Adjustment Question

[R.Measures]

On Feb 23, 2005, at 8:54 AM, Bill Fuqua wrote:

> At 11:11 AM 2/23/2005 -0500, you wrote:
>
>      Ok that is fine. For reasonable values of Q the "1" is on the 
> order of
> variables you have no control over such as tolerances, parasitic
> reactances, variations in tubes etc. That is why I simplify things to
> Ri/Ro=Q^2.  Ri being the High-Z. end of the L network. Maybe it would 
> be
> better to say Rhi/Rlow=Q^2. For a Q of 10 the difference is 1 percent. 
> Not
> something to worry about in terms of SWR (1.01:1.00).  I have used a Q 
> of
> 10 because the output network not only is used to match impedance but 
> to
> reduce harmonics.
> For a single PI network you will probably want a Q of 20.

Eimac recommends a Q of 10 - 15.  Since tank circulating-I is roughly Q 
x Idc-anode, and conductor heating is I^2 x R,  a Q of 20 causes 4x the 
bandswitch conductor dissipation than does a Q of 10.

> So the "+1" even
> becomes less significant.
>      For those that have tried the amplifier resonance test, the 
> apparent
> shift in resonance most likely due to the change of input impedance 
> shift
> of the input of the amplifier as you change the tune capacitance. You 
> may
> notice a change in the grid current or exciter to amplifier SWR as you
> change plate tuning capacitor.

This argument does not hold water in my opinion
>
> 73
> Bill wa4lav
>
>>
>> Hi Rich,
>> Before getting into this discussion too deeply, are we all in 
>> agreement  that
>> the fundamental parallel to series equivalent and series to parallel
>> equivalent mathematics are correct and accepted by everyone?
>>
>> Specifically:
>>
>> Rs=Rp divided by (Q^2+1)
>>
>> Rp=Rs multiplied by (Q^2+1)
>>
>> Q in a parallel circuit= R divided by X
>>
>> Q in a series circuit=X divided by R
>>
>> Xp=Rp divided by Q
>>
>> Xs=Rs times Q
>>
>> Rs=series resistance
>> Rp=parallel resistance
>> Xs=series reactance, + for inductive, - for capacitive
>> Xp=parallel reactance, + for inductive, - for capacitive
>>
>> Stopping at this point for now. Any disagreement so far?
>>
>> 73,
>> Gerald/K5GW
>>
>>
>>
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>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org