Might I make a simple suggestion.
Analog Devices gives away a free program called LTSpice
(http://www.linear.com/designtools/software/ltspice.jsp) which is a
great tool for understanding how circuits work. Just model the tube,
build the PI or PI-L network, and measure every voltage and current for
every level of drive. Efficiency can also be measured easily.
This tool should be on just about everyones PC who does any design or
who wants to understand how circuits work. LT SPice also has a Yahoo
usergroup that is extremely helpful.
73, Larry, W0QE
Bill, W6WRT wrote:
> ORIGINAL MESSAGE:
>
> On Sun, 30 Aug 2009 10:12:31 -0400, "Joe Subich, W4TV" <lists@subich.com>
> wrote:
>
>
>> If you change the network by changing the plate load impedance
>> as you do when you run 1000 watts in the high voltage position
>> the VALUES of the capacitors must change since the value of the
>> inductor is fixed.
>>
>
> REPLY:
>
> There is your fundamental error. Simply by reducing the drive (without
> retuning), you DO NOT change the impedance the network presents to the tube.
> The
> impedance is the same and the Q is the same. Only the amount of energy fed to
> the network changes, and of course the efficiency. Basic physics.
>
> You can easily prove this for yourself. Tune up at max power, measure any RF
> voltage or current anywhere in the output network, including the antenna, and
> then reduce the drive. The RF voltage and/or current will decrease linearly
> with
> the reduction in drive. That's why they call them "linear" amplifiers.
>
> To insist that circulating current INCREASES when drive is reduced is utter
> nonsense. Period.
>
> 73, Bill W6WRT
>
>
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