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Re: [TowerTalk] VSWR Changes with Power

To: ed_richardson@shaw.ca
Subject: Re: [TowerTalk] VSWR Changes with Power
From: RCM <robrk@nidhog.net>
Date: Mon, 21 Oct 2019 21:29:51 -0400
List-post: <mailto:towertalk@contesting.com>

> On Oct 21, 2019, at 18:37, ed_richardson@shaw.ca wrote:
> 
> 
> I did some more testing today and found out the there are indeed out of band 
> oscillations that are occurring.  They did not occur everywhere in the band, 
> only when the antenna load was slightly inductive +9<X<+3. 
> 

You note that you get no oscillation at full power, then funny stuff at low 
power.

I’m a bit thin on solid state amps, so I try a possible tube amp idea and terms.

Tube amp tank circuits are designed for a particular plate voltage and plate 
current, hence plate load impedance.

Tune up at high power for the designed Zp. All is happy.

Drop just the drive, for lower power, and the tank circuit and input circuit 
values are out of the park.

That plus some other weak component (L connector) might be the cause.




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