[VHFcontesting] Getting beginners interested in VHF Contesting

Tom Carney tomc at carneysugai.com
Sat Mar 6 15:19:07 PST 2010


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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