SWR changes

[white devil]

Need some help with an SWR problem.
Antron 99 mounted to the chimney
Astron RS 35 A power supply
Uniden 78
KL 200 power supply

Switched radios this week. SWR's have always been 1.2 to 1.4 across all 40 channels. Never measured them without the amp on. Unhooked the amp and now SWR is off the scale. Took the radio out to the truck and checked it out there and no problems. Changed SWR meeters and get the same results. With the amp hooked up and on still get low SWR. Could this be a grounding problem with the radio? Any help appreciated.

[white devil]

Did some more checking and find that my SWR on channel one is 1.6 and stays under 2 until I get to channel 19. At that point it jumps up over 3 and stays there until channel 40. Back down to 1.6 at channel 1.

[231]

Sort of sounds to me like maybe you got water in your coax. Have you had any heavy rains lately?

I had that happen just a few weeks ago with one of my dipole antennas. It must have migrated through a weak spot that I didn't quite seal up well enough. It did almost exactly what you described. SWR wasn't real bad, but bad enough to get my attention compared to where it was when I installed it.

[white devil]

We were inudated with several inches of rain last week and strong wind. Guess I will climb up on the roof and take it apart and make sure everything is dry. Re-seal things and see what happens. Thank you for your help. I am assuming that is what it took to get your swr back in place.

[231]

Yea it solved the SWR problem, but I simply replaced the coax...not just sealed it up better. If you have water in the coax like I did, sealing it up may not be a long term solution. The water currently inside the coax still has to have a place to go, and sealing it up better might mean you just trap the water in there.

The coax I had up was fairly new (less than 6 months old). So I just cut off the ends and have it hang drying inside the tool shed. I'll use it again down the road...but not any time soon. In the mean time it was a good excuse for me to do some minor antenna upgrades and seal it up even better than before...which I think I did. Time will tell though.

BTW, it's easy to mistake water in the coax for something else...like other antenna reflection, wet ground, etc. (like I did). I found my problem totally by mistake while attaching the dummy load to my ICE remote switch box. I had that particular coax dangling with the PL-259 hanging down. I looked down and saw a small 3" puddle and a drip from the connector. It was then I knew without a shadow of doubt why my standing wave had jumped from 1.2:1 to about 1.7:1 (+/-). Even dumb guys like me get lucky once in awhile. :D

[white devil]

Thanks again for your help. Picked up some more coax today and a spare antenna. Going to put everything together and check it before I climb on the roof and put it up. Will pull the old coax and antenna down and see what I can make out of it.

[BtyMONSTER]

here's a article on waterproofing RF connectors ,

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[LYVWIRE#61]

THANKS for posting that BOOTY ! Great info , basic stuff that can driver you nuts when you have problems !