-----Original Message-----
From: Bob & Linda McGraw K4TAX <RMcGraw@blomand.net>
To: measures <2@vc.net>
Cc: Wt8r@aol.com <Wt8r@aol.com>; AMPS <amps@contesting.com>
To: <amps@contesting.com>
Date: 03 May 2000 03:23
Subject: Re: [AMPS] Practical PI Nets
>
>I seem to recall being told to "tune the plate capacitor to the right
>side of resonance". This gave a plate current indication of slightly
>off of the true dip in current. As I recall, this produced a noticeable
>increase in efficency. Hence, the tank was not tuned at resonance but
>slightly higher in frequency as the capacitor was reduced in C as it was
>turned to the right or clockwise.
>
>Is this what you guys are speakin of? This appears opposite of what
>Dave indicated.
As you adjust the anode cap. from lower to higher C, the load presented to
the tube anode goes from a mix of resistance and inductance through pure
resistance, to a mix of resistance and capacitance. The highest impedance
occurs at the pure resistance setting, and this is where you see the anode
current 'dip'. Provided there is negligible feedback from anode to input,
any other setting normally results in higher anode current and/or lower
output, i.e. lower efficiency.
The setting of the load cap. and the value of the Pi inductor define what
the anode resistance will be. Once the anode cap is set, the load cap can be
adjusted very slightly - more C gives a higher anode resistance for higher
efficiency, less C gives lower anode resistance for better linearity.
All done without mention of resonance :-)
Steve
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