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Re: [TowerTalk] 40m Beam: Problem - Attenuation and Static

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40m Beam: Problem - Attenuation and Static
From: Richard Thorne <rthorne@rthorne.net>
Date: Thu, 21 Mar 2019 21:06:10 -0500
List-post: <mailto:towertalk@contesting.com>
The WX cooperated yesterday evening so I could climb the tower.

I disconnected the coax to the balun as well as disconnecting the balun from the feed point, then reconnected both.

During the disconnection process I did not notice anything unusual. I also opened the balun and everything looked normal.

Since and SWR analyzer was not useful for identifying the problem I took my Elecraft KX2 up the tower with it's own coax to connect to the balun.

After reconnecting the balun to the feed point I connected the KX2 to the balun and found WW0Y CQing.  The beam was pointed in the wrong direction but he did hear me for a very brief QSO.

A picture of the KX2 setup is on my qrz page.

I wonder if this is the first qso made at 120' on a tower?

At any rate the problem is now resolved.  I guess the disconnect/reconnect solved the problem.

Thanks for all the suggestions.

Rich - N5ZC

On 3/17/2019 3:00 PM, Richard Thorne wrote:
I've had a strange problem develop with my JK 404C 4 element tribander.

 - The signal is sometimes attenuated.  Per my Flex 6600, I'll show a noise floor of -130db, when I transmit a bit the noise floor increases to -120db.

- After transmitting and the noise floor increases, I get a lot of broad band static, which appears to be random and comes and goes.

- The SWR on the antenna is excellent and doesn't change, which seems to be strange with symptoms described above.

- I'm using a 2 antenna WX0B stack match to combine the JK404c and a F12 2 element delta 240 40m yagi.  I have absolutely no issues with the F12 delta 240 going through the same feed line (from the stack match) to the transceiver when the Delta 240 is the only antenna selected on the stack match.

Here's what I've done to attempt trouble shoot the problem:

- disconnected the JK 404C feedline from the stack match and attached an Elecraft KX2 directly to the feed line.  Same issues as described above.

The feed line is LMR-600 from outside the shack to the tower.  The coax is direct buried, no pvc pipe.

- From the shack to the base of the tower a run of LMR-600 about 195' long.  RG-213 from the LMR-600 via SO-239 / female N adapters to another length of LMR-600 (with the same adapters)

- The LMR-600 goes from the base of the tower up to the where the antenna is mounted.  The LMR-600 is attached to the tower leg inside the tower, not outside.

- RG-213 jumper from the LMR-600 to the balun/feed point of the antenna.  At this junction I'm using a DXEngineering grounding block with a 2" barrel so-239.

All that being said has anyone come across the same symptoms of an attenuated signal and static that was caused by coax adapters, bad coax or a balun at the feed point?

This particular antenna has a phasing line between two driven elements with 1:1 current baluns at each feed point.

I'm stumped at this point.  I climbed the tower this morning and didn't see any obvious mechanical issues.

Any ideas or other things to check?

Thanks in advance.

Rich - N5ZC
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