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I read with interest the message from
Dick/PA0SE, regarding his antenna system and fire.
Earlier this year I had a similar problem, when
running at high power. At first I used my
antenna wire with its plastic insulation only.
This ran through a hole drilled in the hardwood
window frame. However once I ran the rig up
to 5 amps, there was a crisp crackle and the
antenna current dropped down to almost zero.
Using my Variac, I gradually ran up the power
again and again, but once I would get to
about 2.5 amps the insulation would break down.
The more I tried it , the lower the level became
for the flashover to occur.
I then added some plastic over the insulation ,
but I had an interesting result. Rain water ran
down the antenna wire and
between the two insulations, with the result that at 5 amps
output
the outlet hole in the hardwood window frame would suddenly
start emitting puffs of white
smoke in time with the morse code. I could read the morse by
smoke signals ( no blankets
required ). If I kept the key down long enough I could dry out
the water.
Eventually I found a ceramic standoff with a hollow
centre and drilled out a bigger hole in
the window frame for it. I also now put a drip turn in the
antenna wire to prevent rain water
running into the feedthrough. Mind you, I have drilled that
hole at an angle. I also stuffed the
ends of the ceramic insulator with 'Blu-Tac'. Stops the
wind blowing into the shack in Winter.
As they say "No smoke
without Fire"
73's
Finbar
EI0CF
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