I am trying to be "scientific" in my approach here. The only common relays
or switches in the system ate in the tuner as the amp is new and the
condition predated it. The tuner is an AT5K plus with vacuum relays and a
roller inductor. I have the issue even when I put the tuner into "bypass".
This leads me to believe that the issue isn't in the inductor. The second
antenna is also connected to the same tuner, I have no problems with this
antenna so perhaps I should switch antenna ports and see if the problem
follows the antenna....
I have switched coax from the back of the tuner to the antenna with no
change in behaviour, that leaves the connector at the DX Engineering plate.
Could this be my issue? Maybe the flashover is a result of a short here? Is
there any way to test it? Should I get another one and see what happens?
73,
Bruce Beard
AB1KC
brucebeard@gmail.com
---------- Forwarded message ----------
From: Pete Smith <n4zr@contesting.com>
Date: Thu, Oct 6, 2011 at 7:37 AM
Subject: Re: [TowerTalk] Strange HV-18T HyTower issue
To: Bruce Beard <brucebeard@gmail.com>
Definitely sounds to me like a relay or switch somewhere in the signal path,
or (less likely) a connector. Many relays and switches can develop an oxide
coating on the contacts sufficient to attenuate signals on receive, but when
you pass just a bit of power through them the oxide temporarily burns off.
73, Pete N4ZR
The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000
On 10/6/2011 7:18 AM, Bruce Beard wrote:
> The Antenna
> 3 year old Hy Gain Hy Tower. Optional MK-17, 17M stub installed,
> MK160A,160M long wire installed .
> DX Engineering radial plate.
> Fed with Andrew Heliax hardline.
> 4000+ feet of radials.
>
> The Installation:
> Mounted in concrete. Located in heavily wooded area. lots of leaves
> and debris, constantly cleaning stuff from base of antenna, never seems to
> make any difference.
>
> The problem:
> First noticed that while working on 75M and 160M, after
> transmitting, the antenna would go quiet. It is as if the attenuator is
> coming on or the antenna is being disconnected. If I put just a small amount
> of RF into the antenna system it "wakes up". This condition is more apparent
> on 160M than 75M.
> SWR is fine under power; however, I have noticed that SWR (indicated on my
> LP 100A) sometimes begins rising, in ssb while keyed but without drive (i.e.
> keyed but not speaking). Speaking and thus putting power into the system
> brings SWR back down.
>
> Now I believe I am getting a flashover somewhere. Plate voltage will spike
> on the amp after transmitting with power thus shutting off the amp. My OCF
> dipole is fine with the same radio/amp/tuner combination. My Yagi is fine
> with no symptoms although I don't use the tuner for the Yagi.
>
> Replaced coax last year with no apparent change. Dropped antenna for
> visual inspection and saw nothing that looked unusual.
>
> I am at a bit of a loss here and I need suggestions as to where my problem
> might be or how to diagnose this (these) issue (s).
>
> 73,
> Bruce Beard
> AB1KC
> ab1kc@arrl.net
>
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