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Re: [Amps] Amps Digest, Vol 42, Issue 67

To: "Tom W8JI" <>
Subject: Re: [Amps] Amps Digest, Vol 42, Issue 67
From: R L Measures <>
Date: Tue, 27 Jun 2006 06:41:28 -0700
List-post: <>
On Jun 27, 2006, at 2:52 AM, Tom W8JI wrote:

>> It occurs to me Ameritron may be trying to compensate for
>> operators who
>> do not 'scope their station. With an oscilloscope you can
>> see how
>> undercoupling
>> the output causes the tube to flat top. That creates
>> distortion, both IM and
>> harmonic. It seems to me that Ameritron, with their
>> suggested tuning method
>> insures the tubes are overcoupled and then underdriven.
> ....and worse yet for the manufacturer, under coupling
> results in high voltages in the tank circuit.

High voltages could also appear in a low-pass Pi-network tank if RF  
energy well above its operating frequency is applied at the input.   
For example, in a TL-922, peak potentials of c. 5000v can appear  
across the Tune-C if and when the 3-500Zs intermittently regenerate  
at the anode's 120MHz self-resonance.

> Besides all
> that splatter, it decreases reliability of the amp and the
> life of expensive tank components.
> The number one cause of operator related field failures is
> underloading the amplifier.
Trio-Kenwood used to claim that the high rate of TL-922A arced  
bandswitch failures were being caused by a large number of amateur  
radio operators "rapidly switching the bandswitch while transmitting  
at full power".

Murphy's Eleventh Law:  It's always the other guy's fault".
> 73 Tom
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R L MEASURES, AG6K. 805-386-3734

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