OK, I have this problem...

[LeoG]

I have no adapters in my house system other than the ones on the SWR meter 239>N.  I do have a PL239 to Male N 90º on my repeater system to allow the coax to get to the back of the repeater.

 

I'm over 90% confident there is water in a fitting or coax then when it freezes negates the problem of the water.  It's 40ºF right now but I'm at work so I can't test it.  It's not going below freezing tonight I believe so the SWR is likely to be at 2.09 again when I get home.  Contacted the wife and it sounded better than I thought it would being as warm as it is.  So maybe I'll be proved wrong.

I'm doubting it though.

[LeoG]

So weird.  21ºF seems to be the magic number, or so I assume.  That's when it happened when I was monitoring it.  And last night I was monitoring it because the temps were suppose to fall also.  But by the time I went to bed at 1am the temps had only gotten to 24º and the SWR remained at 2.06.  The coax had more than enough time to freeze since it got below freezing about 6pm and was dropping about 1º per hour.  It hit 21º about 5am.  I wasn't up to see that but when I did check about 8am (20º) the SWR was at 1.16.

The lightning arrester is near the entry point of the house so maybe the warming effect of the coax in the house is slowing the freezing down.  The attic isn't heated so it's not like the cable is 65º on the other side of the wall.  And there's no guarantee the issue is at the lightning arrester and not the antenna.

Just more to the mystery.

[SteveShannon]

9 minutes ago, LeoG said:

So weird.  21ºF seems to be the magic number, or so I assume.  That's when it happened when I was monitoring it.  And last night I was monitoring it because the temps were suppose to fall also.  But by the time I went to bed at 1am the temps had only gotten to 24º and the SWR remained at 2.06.  The coax had more than enough time to freeze since it got below freezing about 6pm and was dropping about 1º per hour.  It hit 21º about 5am.  I wasn't up to see that but when I did check about 8am (20º) the SWR was at 1.16.

The lightning arrester is near the entry point of the house so maybe the warming effect of the coax in the house is slowing the freezing down.  The attic isn't heated so it's not like the cable is 65º on the other side of the wall.  And there's no guarantee the issue is at the lightning arrester and not the antenna.

Just more to the mystery.

If the problem is water, it is possible that it’s a weak solution with some contaminant.  That would depress the freezing point.

Or maybe it’s not water but some physical change, a contraction of some component along your feed line that results in a change in impedance somewhere.

Do you have a dummy load you could use to isolate portions of your feed line to see where the issue is taking place?

[LeoG]

Of course I do.  But I'm not tearing my system up until it gets warmer out.  I might have the opportunity to heat up the lightning arrester and fittings to see if the SWR moves when I thaw the water in that connection if it even exists there.  If nothing happens it's at the antenna.

I'm tending to think that is going to be the problem area because the antenna fitting was wrapped on the ground and it has that aluminum shroud over it for protection.  It seems like it would be the hardest to be infiltrated.

While the lightning arrester is down stream and the water would flow down the cable.  I have my drip loop and did what I could so the arrestor wasn't at the bottom of the run.  But my bet is the issue is there if it's not a defect in my antenna.