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Re: [Amps] Plate Impedance, ARRL

To: craxd1@verizon.net, amps@contesting.com
Subject: Re: [Amps] Plate Impedance, ARRL
From: jkearman@att.net (Jim Kearman)
Date: Wed, 26 Apr 2006 16:56:41 +0000
List-post: <mailto:amps@contesting.com>
From: "Will Matney" <craxd1@verizon.net>

> I'm not knocking using 1.8 as that's what I use and it works. The reason I 
> broought all this up is that they do not make it clear from what I read that 
> these factors are for triodes only that I seen. 

I suspect that when that section was written, the League was publishing only 
triode amplifiers. For many years until George Daughters published his 4CX1600B 
amplifier, all Handbook amps used triodes.

I got the insight into the differences from reading Rich Measures's site. It's 
interesting to read the history of his Handbook chapter, which was presumably 
rejected mainly for political reasons. As load impedance calculations are based 
on the plate-voltage swing, it seems intuitive that the k factors for triodes 
and tetrodes/pentodes would be different. 

> Also, the terms differences that 
> we use where they say the plate load resistance is the same as plate 
> impedance.

Assuming the load is matched, the plate is looking into a non-reactive 
impedance, so the terms could be interchanged. Considering the load as an 
impedance, though, is more in line with the fact that we are dealing with ac 
and reactances, not dc and pure resistors. My guess is the confusion stems 
mostly from erratic editing of the Handbook. Certain chapters are chosen for 
revision and updating each year. Other chapters, even though they may contain 
known errors, are not touched. It might pay to take several years' worth of 
Handbooks, cut them up, and reassemble them to produce one relatively 
error-free copy! 

73,

Jim, KR1S
http://kr1s.kearman.com/
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