[AMRadio] Odd tuning on 160M

Jim WB5OXQ inb Waco, TX wb5oxq at grandecom.net
Sun Jul 19 14:51:27 EDT 2009

Sounds like something in your antenna circuit is overheating and causing the 
resonance to change.  I had that same thing happen with a trap antenna and 
finally a coil in the antenna burned up.  I was running about 500 watts on 
160.  So I build an inverted L for 160 and I am using that will good results 
when my rotator dial starts turning and the control box smokes.  New I am 
buying a new rotator and i am not planning to run power on 160 any more.  I 
cannot afford it.
----- Original Message ----- 
From: "M. K. Hess" <mkhess at kias.org>
To: <amradio at mailman.qth.net>
Sent: Saturday, July 18, 2009 12:16 PM
Subject: [AMRadio] Odd tuning on 160M

> Hi Folks,
> Here's a question that may need to get filed under "dumb", or maybe not, 
> but
> here goes!
> I have a V-Beam, a Vertical, and a Dipole, all capable of 160M operation. 
> I
> use a K3 as my exciter, an Alpha 91B as an Amp, and
> a Palstar AT-Auto for the tuner. The following happens with any of these
> antennas, including my dummy load (Heath CanTenna)...
> I have the Alpha in Stby, and key up the K3 w/ 10w through the Palstar to
> "whatever" load.... If finds a 1:1 match and all is well.
> If I advance the K3 to 120W all remains well... Can Xmit all day and 
> night,
> without issue. NOW....
> I fire up the Alpha 91B, and begin to tune it.... after a couple of 
> seconds,
> the Palstar starts to "re-tune" the load. I wait until it settles, and
> start the Alpha load again, same thing... this happens a few times until
> finally the Palstar thinks it's got a match, AND the Alpha thinks it's
> happily loaded...
> Finally, I hear someone calling.... I call back... as I'm talking, the
> Palstar starts re-tuning again and the Alpha usually goes into Hi-SWR
> shutdown...
> I fiddle with them for a bit, and try the call again.... Sometimes it 
> stays
> stable, most times it goes haywire several times during the QSO...
> WTF is going on!?!?!?!
> I have grounding out the ying-yang, and no RF back to the station, I have
> heavy duty parts from the shack to the antennas.. (See my web 
> www.n3eaq.net
> for details)
> This mostly seems to happen on 160 and 80 and DEFINITELY on 1885 when I'm
> trying to do AM!
> Any ideas!?!?!?! All help is appreciated!
> Mike - N3EAQ
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