[TowerTalk] Weird High VSWR

[John Caracciolo]

I stumbled upon your site while researching a VSWR problem I am having.  I 
was hoping you could post this on your site and maybe someone in your group 
has experienced something like this and can point me in the right direction.

I maintain two FM's on a community tower.

FM 1 single bay, 440 Haat, 1 5/8 line TPO 2000
FM 2 two bay half wave spaced, 300 Haat 1 5/8 line TPO 2500

Last week FM 1 tripped off with a high VSWR  I was able to fold back RF out 
and get 1500 out with about 90 coming back.  There is another low power FM 
on the tower with us at the 490 Haat, I noticed his box was in VSWR fold 
back as well, he had 50 going out and about 10 coming back.  My second FM 
was fine.

Since it was 3am, and cold and snowy, I figured, maybe ice on the bay, 
(mine and the other station), and my lower FM was unaffected.  Two days 
later and no real ice, I sent a crew up the tower to inspect the bay.  No 
ice, no burns, connectors good, ( on mine and the lp).  With that check 
done, we pulled the bay and swept the line.  Line looks great.  We put the 
bay back and same thing.

What's my next step?  Two independent stations have the high VSWR, both 
started at the same exact time. Both of our lines are fine.  Both bays are 
near the top of this tower.  There is a lot of other two way, paging, and 
some PD stuff up there, but no real high power stuff.

VSWR seems steady, no real change.  Up until last week this was a great 
install, no problems, good match, brand new antenna, (about two years old 
now).

Not sure what I should be looking for.
Any guidance would be appreciated.
Thanks in advance
John C.