On Apr 2, 11:52 am, Bob Dixon wrote:
My 40M beam works only intermittently. Typically under normal
conditions, the received signals are weak and the SWR is very high.
If I rotate the antenna, it "comes alive" in some directions and works
fine for a while, then dies again. In all cases, if I transmit into it
with a KW is comes alive and works fine for a while (few minutes) and
then dies again. A single dit will fix it. 100W does not do it.

I replaced the coax which runs around the rotator and it made no
difference. I just recently learned that a local friend also has an
intermittent antenna which can be restored by transmitting a KW into it.

Is this a common problem? is there a generic solution? Any hints
would be appreciated. Note that it is not too easy when up on the tower
to jiggle things while someone on the ground tries to watch the SWR and
shout back and forth. We tried that when we replaced the coax.

Thanks!

Bob W8ERD

What you have is an electrical connection that is physically an
electrical
circuit but has a corrosion build up at the joint. A poorly connected
pressure
on the coax is often the cause. Change to a soldered connection and
make
sure the connection is tight. If you have twisted wires on the antenna
put
wire nuts on them.to increase pressure on the joint.
The antenna itself can create similar problems if you have not used a
conductive grease
at telescopic joint connections
Have fun
Art