> Complex yes, but probably less complex than two sets of
elements and trying
> to deal with the interactions. Essentially, you'd wind up
with a big
> multipole relay to switch between two sets of tuning
networks. Does he
> really need to run two bands simultaneously? If so, it's
a bit trickier,
> but then again, it would be no tougher (probably easier,
in fact) than a
> diplexer for the 600 kHz spacing on a repeater.
A duplexer allows simultaneous reception and transmission
with one receiver and one transmitter at the same time, a
diplexer allows multiple receivers or multiple transmitters
to be used on one antenna. Repeaters use duplexers.
To use just four elements, we would need a controlled phase
shift two-band diplexer at each element (with about 100dB
isolation) and then AFTER that we would need a two band
phasing system. Everything would be phase-critical.
It would be MUCH less complex to do what he originally
thought of, and that would be to use two antennas. That
would only require simple traps and pass systems that were
not phase-critical. Two bands in four phased elements is
workable one band at a time, but a complex nightmare
(although it could be done with limited bandwidth) on two
bands at the same time.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list