[TowerTalk] Troubleshooting an A3

[K7LXC@aol.com]

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
haywire
 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

     TOWER TECH -- professional tower supplies and services for amateurs

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