At 09:38 AM 3/3/97 -0500, you wrote:
>In a message dated 97-03-03 08:58:44 EST, you write:
><< Early in the ARRL DX contest I discovered the SWR on my A3S had gone
> on 20M and 15M and was extremely erratic on 10M. Can anyone give me ideas
> on troubleshooting the problem? It was OK two weeks ago in the CW contest.
> It is not the coax or the connection to the antenna -- I hooked my analyzer
> (MFJ-259) -- to the antenna connection at the antenna and got the same,
> high SWR reading. I suppose that either one of the clamps on one of the
> elements has gotten loose -- or it's a problem with one of the traps. Is
> there a way to test a trap and see if it's OK? >>
>Hi, Jay --
> I've got a customer with the same problem. We had one of the trap
>drain holes not quite vertical and we certainly had some water in the trap.
> Then it froze so we might have a damaged trap.
> Other than loose hardware, you may have a bad trap. Here's what I did to
>try and isolate the problem. First, rotate the driven element 90 degrees and
>run your analyzer test again. In a 90 degree position, the DE (or another
>element) won't 'see' the other elements so it won't interact with them. In
>my case, the driven element looked fine so the problem must be in either the
>director or reflector. Put the driven element back in line. Next rotate one
>of the other elements and take another reading. Put it back inline and
>rotate the other, taking a third reading. When the 'bad' element is out of
>position, the antenna should look normal. Take it down and troubleshoot on
>the ground. You can also use your 259 to look at the traps but I haven't
>gotten that far yet. In September and October 1996 QST are a couple of
>articles that go into further uses of the 259 that you may want to examine in
>order to track down a trap problem.
> Since your problem is erratic on 10M as well, you probably have a loose
>connection so the preceeding may be an academic excercise. But the loose
>connection may be in a trap so we'll see.
> Let me know what you find out.
>73, Steve K7LXC
My friend, K0TQ has the same problem on an A4 that was persistant for years.
In fact, he got it from a friend who was done with it and just gave it away
because the SWR was so erratic. TQ replace a couple of the traps and
nothing would clear up the SWR problem. We worked in it for several weeks
and finally we took the whole driven element appart and seperated the
pieces. We found enough water in the driven element, close to the boom,
that had been trapped in the element close to the boom...that the water just
ran out. Apparently, water had gotten into the element but had collected
not in the trap, but in the tube that is attached to the boom. Once the
water was drained and the thing clean up the problem went away. It has
bever reappeared and the beam has been up for about 18 months. There was
not way for the water to drain out and it must have been in there for years.
You would think it would have evaporated, but something was keeping it
in...or water was getting in somewhare. We put some noalox on the tubing
and as I said...the thing has been working great ever since.
My two cents of experience
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com
Sponsored by: Akorn Access, Inc. & N4VJ / K4AAA