[TowerTalk] 40m Beam: Problem - Attenuation and Static
Jim
jimw7ry at gmail.com
Sun Mar 17 20:57:09 EDT 2019
Things to check? Yes. Every connection in the chain from the radio to
the antenna.
I too have had this issue on antennas and all types of things with
connections and relays.
Thanks
73
Jim W7RY
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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