Interesting discussion. I am primarily a rover and face somewhat a
similar requirement to simplify the antenna situation. For me, it's
more the desire to minimize the time to put up and take down the
antennas than the cost.
First comment, since the 706 (and FT-100) have two antenna connectors,
I'm not convinced it worth the trouble to go for a single feedline. If
you do, you end up with some form of duplexer at the radio end of the
coax. Or at the least, a coax switch. I have a similar problem in
feeding a 2M and 432M antenna from the single antenna connector of the
radio and tried a switch at first but would frequently forget to switch
the antenna. A duplexer is similar in cost to the extra feedline up to
50/60 feet. More if you use RX-8X for 6M.
I've tried modeling several different antennas just to get 2M and 432 on
a single boom without much success. The presence of the 2M elements
seems to distort the 432 pattern. At least that what EZ-NEC predicts.
For example, I recently modeled a dual band yagi that appears to be a
Cushcraft A270-10S. This antenna has five elements on each band. The
elements for one band are mounted above the boom, the other band below.
Cushcraft quotes 10bdi gain for each band, but EZ-NEC predicted only
about 8 dbi on 432. Remove the 2M elements from the model and the gain
jumps over 2db.
Perhaps some form of quad might be a solution, haven't tried that. The
N6NB pack uses a three element multiband quad for 2, 222, and 432 and
Wayne quotes a gain of 7-8 DB over a dipole.
73,
Tom K6EU
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