This was supposed to have been sent to aa4nn@juno.com in regard to an
insulator problem he had instead of TT.
<<
As I said in previous E-mail, the more the end loading, the shorter the
resonating stub and the higher the Q and voltage on the resonating stub on
the end. I had the Latten Lab 200 uh loading coils at the ends of a 40M
dipole and only 3' of wire to resonate it on 75M. I worked with narrow
bandwidth on 75. He dropped the 3' wire vertically down with no
insulator--it was hot. Latten's design ran a rope from the end of the coil
insulator to the support. He advertised this antenna in QST 30-40 years ago.
You have longer wires at the end of the loading coils on 160 in terms
of wavelengths but you have far more power. The manufacturer apparently
didn't know of the potential voltage on the insulator or he didn't go quite
far enough in reducing the amount of loading. But as I pointed out, the less
inductance requires larger wire on the band it is used as a choke. Hold the
key down for 1 minute and drop the coil to the ground quickly and see if it's
hot.
I came up with a way to cool the voltage at the end of the 3' wire that
cracked insulators at 300 W. Extend 2 wires from the end of the wire and
insulator hole beyond the other end of the insulator at about 60 degrees
about 2" and make a loop at the end connected to these 2 wires. It takes the
high voltage end beyond the end of the insulator and distributes it around
the loop instead of a small loop in the insulator.
K7GCO >>
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