...it's not really added. Like Terman said, it's feedthrough power.
Remember power in depends on the input RESISTANCE, not impedance and it has
to go somewhere, by virtue of the conservation law. Going in, coming out! it
so happens that in a common grid - as in common base for that matter- there
is no phase inversion between input and output so that actually the power at
the output is fed in phase with the input power, added vectorially and the
sum goes out.
It's not that complicated, at least at the conceptual level.
Alex 4Z5KS
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Paul M Dunphy
Sent: Thursday, March 05, 2009 11:34 PM
To: amps@contesting.com
Subject: Re: [Amps] An Extra Thank You!
At 05:22 PM 3/5/2009, you wrote:
>I didn't add the drive back in on mine, so I'm off by that 20W.
>
>I'm not sure I completely understand why the drive is added back. You
>could write a thick, thick book with what I don't know about tubes,
>because when I went to school they weren't taught anymore.
>
>Jeff/KD4RBG
Jeff,
I'm pretty sure it's because in a grounded grid amplifier the
input drive signal is passed straight through, so you get it plus
whatever the tube(s) squirt out.
I'm sure there is a better "electrical engineer" answer, but
that's how I understand it.
73, Paul VE1DX
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