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Re: [TowerTalk] Antenna shift, VHF/UHF matching unit burning out

To: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>, "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Antenna shift, VHF/UHF matching unit burning out
From: Scott <scottb@radios-online.com>
Date: Mon, 21 Apr 2014 06:18:23 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
My suggestion is throw the Diamond antenna off the tower and put something up worthwhile. Those things are useless imo.

Scott
N1CX

At 10:23 PM 4/20/2014, Roger (K8RI) on TT wrote:
I think that I've lost a ground. The SWR has gone sky high on the Diamond 144/440 repeater antenna. As the antenna is only rated at 200 watts the matching network is pretty light duty. Also, the AV640 which originally was very easy to match, is now difficult to find the resonant points.

I believe this is due to a DC bias through the matching transformers putting the cores into, or near saturation.

I keep using, I think and I believe as I really don't know, but it sounds logical.

The new AV840 just arrived and I need to work on the Diamond antenna, so I need to find the problem before going any farther with the antennas.

I had been talking to N8ERF on the repeater when he mentioned I was getting noisy. I immediately stopped transmitting, came in, got the SWR bridge, took it to the shop and put it in the line. The SWR had gone from 1.2:1, to off scale. I think the finals are OK. I certainly hope so.

So tomorrow, I'm going to add one of those grounding plates that tie everything together and to the station ground. The space behind the desk out there is a mass of wire, that could be neatened up, so I can see at a glance what is connected to what.

That and all the projects need to be finished up so I have an organized shop in which to work.

Any thoughts on the grounding would be appreciated

73

Roger (K8RI)

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