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Re: [Amps] IM distortion and such

To: "'Gary Schafer'" <>, <>
Subject: Re: [Amps] IM distortion and such
From: "Joe Subich, W4TV" <>
Date: Thu, 29 Jun 2006 23:35:53 -0400
List-post: <>

Gary writes: 

> That is exactly Rich's point. The degree of loading has no 
> effect on VHF energy.

Gary, you make the same mistake Rich does ... the voltage is 
not necessarily due to parasitic oscillation at VHF frequencies.
An unloaded tank can generate voltages several times that of the 
applied (plate supply) voltage depending on the Q and impedance 
transformation.  Since the tube is not operated in class A, 
harmonics will be generated and, particularly at 10 meters, 
some of those harmonics will certainly extend to VHF (3 x 28 
= 84, 5 x 28 = 140).  Again, that is expected behavior.  

What is important is that the tank be properly loaded, the 
components be designed to withstand the normally generated 
voltages and reasonable care be taken to prevent the tube 
from turning into a TPTG oscillator at some unknown frequency.


   ... Joe, W4TV 

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