back to 2025.07.06 K0DV beam troubleshoot

1 evaluation on 2025.07.06:


Doug's first suspicion was a problem with the lightning arrestor that's inline with the coax, about halfway up
the tower. But then he tested it with an MFJ-259 to see how far it was to the open, and it looks like about
175 feet. We don't have any exact numbers, but that's probably pretty close to the total length of the coax.
His estimate was around 175 feet, and he has 25 feet of coax left. He doesn't have any record of how much coax
he bought for this run, but 200 feet sounds like a nice even lenght of coax to buy, and adding 175+25 gives 200.

Opinions vary, but Doug suspects a problem in the rotor loop for the beam turning. I personally suspect what
looks like a sealed coupler under the boom (halfway between the balun on the front and the tower) or possibly
the connection to the front end of the antenna where the balun connects to the ends of the double boom.

The antenna has other issues as well. One of the elements broke off awhile ago (doesn't seem to be affecting
tune on any band though) and one of the elements is bent a little. I think we can reinstall the missing element
if Doug orders a replacement section, but bending the other element is a risky maneuver since tubing can suddenly
fold when you try to bend it.

We discussed options for repair, and there's the possibility of lifting the beam up on the mast stub sticking
up from the center via a rope, disconnect the boom/mast plate, and rotate the antenna so the front (balun) end
is facing downward, and the antenna booms are in parallel to / laying against the side of the tower. This may
be a job for two people, since that's a huge antenna to be wrestling around. I think I can replace the broken
element from the tower if that's all the farther down the antenna we need to get to.

I think the next step will be to get out there with a quad and get some close-up pictures and video of the rotor
loop, the coupler below the boom, and most importantly, a top view with close-up of the balun and where it
connects with the boom ends. Also, if I climb the tower and disconnect the coax at the arrester, he can measure
the length to the break again. If it doesn't get shorter, then the problem is actually there. But if it DOES get
shorter, we'll then have an accurate measure of the feed coax and can make a much more accurate estimate of
where the open is at. (I also need to bring out my 42x optical zoom camera and big binoculars)


media



last updated 07/07/2025 at 21:33:02 by make_www_index.command version 2025.06.28.A