Medium Wave broacasters usually have a big RF choke to ground on their output,
installed in the ATU, especially for series fed towers. It is typically called
the 'static drain' and sold by Harris, LBA, Kintronics and others
manufacturers. These chokes are made from
fairly heavy magnet wire, 18 AWG or better, solenoidal style on a large
diameter form. Without them, a lot of the current crop of solid state
transmitters will kick off when thunderclouds build up due to the voltage
induced on the output feeder.
Back when tubes were used, of course, these chokes doubled as a safety choke
for failed blocking capacitors.
I usually install quarter wave coaxial stubs on VHF and UHF transmitters that
don't change channels much, as a lightning/static protection device for
monopole antennas, esp in New Mexico in rural installations. Its for same
reason.
73
John
K5PRO
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