Topband: Antenna Question

[Roger D Johnson]

I'm planning a dual band 80/160m vertical. My idea
is to make the antenna 1/4 wave on 80m and switch
in top loading with a vacuum relay for 160m. I'd
like a sanity check on my reasoning. This will
eventually be part of a 4 square system but I did
the figuring for a single vertical as a worst case
scenario.

The antenna will be made of 3in irrigation pipe and
will be approx 67 ft high. With 1500 watts, I figure
232 volts RMS at the base. Computed surge Zo of
antenna is 310 Ohms. TL and ON4UNs programs both
show a voltage of slightly over 2000 volts RMS at
the top of the radiator. My first thought was to
buy Russian vacuum relays from QRO-stuff but I
checked Alan Bond's site and he has Kilovac K47A
relays rated at 8 kv for only $19 each.

Any comments?

Thanks, Roger N1RJ

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