[TowerTalk] Mounting 10m/15m/20m monobanders -- single mast.

[W2RU - Bud Hippisley]

At 04:47 2005-04-05, KT2Q wrote:
>Any additional suggestions on mast mounting distance for monobanders would 
>be greatly appreciated. 

I have one data point to contribute.  From 1986 until 2000 I had a Cushcraft 20-4CD at 122 feet (one foot over the top plate on my Rohn 25 tower) and a Cushcraft 15-4CD five (5) feet above it, at 127 feet over extremely flat farmland in upstate NY.  The spacing between the beams was set very "scientifically" -- namely, by how far I could reach to tighten U-bolts on the 15-meter bracket while standing on the tower top plate and hanging on to the mast for dear life with one arm and my climbing belt.

It was the first time in my life that I felt like I had a "real signal" on 20 meters.  And despite my initial misgivings that the 15-meter beam might be "too high", that antenna was a "band opener" and "band closer" -- something I had never owned previously.  

Yeah, the beams were too close together.  Yeah, the SWRs weren't exactly perfect (but that's what the pi-network on my SB-220 is for).   Yeah, maybe my F/B on one or both beams was degraded (but it sure wasn't obvious to me).  Yeah, if I'd had EZNEC or something similar back then, I might have paralyzed myself into spending the first two years analyzing the optimum spacing instead of getting the antennas up and playing.  But, you know what?  Those beams WORKED!!!!

I'm sure there ARE optimum spacings for stacked monobanders.  And the differences are probably worth spending some time on in multi-tower super stations with 22-foot masts and climbing steps.  But if you can't optimize, it isn't the end of the world, as I found out, to my great delight.

GL Tony.

Bud, W2RU