Dear all.
Last night whilst the tx was sending a QRS call on 71.8 I went outside to
check that there was no corona discharge from the antenna, easy to see in
the dark.
No problems were seen but I noticed a crackling noise behind me. Closer
investigation revealed that it was coming from the ground at the base of the
antenna support mast which is strapped to a fir tree. Small sparks could be
seen amongst the undergrowth where the mast touched the ground. This was
obviously a waste of valuable energy!
I decided to earth the pole, then at least it would no longer be a lossy
structure, just some additional capacitance. After I had done this three
things happened, the resonant frequency went down, the match changed and,
when the ATU was re-adjusted, the antenna current rose by 10% for the same
power input. This must be due to higher Q because of less loss.
Well worth doing. Fire-risk reduced and power increased!
Look out for lossy structures near the antenna and either insulate them
they will then be live... ) or earth them solidly.
73, Dave G3YXM.
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