When I returned from GW a couple of weeks ago, I reinstalled my
station and was puzzled that it took a very long time to get any
amount of current into the antenna. I initially thought it was the
effect of the leaves that had appeared on the nearby trees whilst I
was away. Things got worse. Every time I transmitted the current
was different, and usually no better than 65% of normal, though
long periods of transmit improved it. Tuning was very broad so I
suspected that something was lowering the Q of the system.
I renewed several joints, especially where long periods of RF
caused some heating, but this had no effect (though of course
worth doing anyway from time to time). Having gone over every part
of the system at ground level, I began to suspect the inductor at
the top of the mast. I was hoping it wasn't that, as it is quite
difficult to lower the mast and at this time of year there is a risk of
the top wires becoming entangled in tree branches 12m above
ground.
Having lowered the mast, the cause was immediately obvious. The
plastic cola bottle used as a light-weight coil former had several cm
of water in it! I presume that a small amount of water would dry out
with the RF when the station is used every day, but leaving it alone
for two weeks whilst away caused a build-up. Needless to say I
now have better waterproofing and some drain holes, and my report
from DQ0KBM has gone up an S-point.
Mike, G3XDV (IO91VT)
http://www.dennison.demon.co.uk/activity.htm
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