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

[Bob Shohet, KQ2M]

I had a problem on 20 meters similar to that.  I could not figure out what it was – back and forth to the tower with burnishing the relays in the relay box, replacing certain cables, etc.  No help.  I swapped amps and radio – no difference.  I swapped relay boxes – no difference.  Then I checked the only thing left  to check – the coaxial connectors on each of the yagis in the 3-stack.  On one of them I noticed a tiny bit of black on the outside of the center conductor pin on the PL259 and I immediately realized what it was – my tower had been hit by lightning (again) and there was some arcing in the center conductor pin on one of the pl259’s from on one of the antennas.
I scraped the black off with a utility knife, then did the same thing with the other PL259’s in the three-stack and did the same thing for the inside of the slightly arced SO239 in the relay box (I could reach a small part of it), screwed everything back in and problem GONE!  Full audio again – solid with no cutouts!
So check EVERY coaxial connector that is involved between the radio and the antenna feedpoint.  It is likely that one or more of them either have some moisture/condensation buildup and/or grit, arcing or something else affecting the connections between the radio and the antenna.
If that does not solve the problem for you, then check all relays and control cables from the antenna to the shack.
And If that doesn’t solve the problem then it is likely your antenna – and in one or more of the elements. 
SOMEWHERE there is an intermittent – it is just a matter of systematically checking every possible that might be involved until you find it.  Eventually you will.  Hopefully it is just a connector – that will be the easiest and most cost effective thing to diagnose and fix.
73 & GL!
Bob KQ2M