At 11:09 PM 8/7/01 +0000, K3KO wrote:
>
>Bill,
...
>It is problematic with triband beams. It also indicates the problem
>in obtaining a decent spacing for 3 bands. In reality, it will be a
>compromise. There are many articles on stacking of tribanders. At
>least one is in the ARRL antenna handbook.
I did some modeling to try to determine the best compromise spacing, using
the "scoring" technique I outlined in NCJ for January-February 2001. The
bottom line is that different stacking distances, as you'd expect, weight
the compromise in favor of one end or the other of the frequency range.
Given where radio conditions are heading, I feel that seeking a good
compromise between 15 and 20, and letting 10 take third place, is probably
as good a solution as any. That led me to 28 feet for short-boom
tribanders like my C-3Es, and 30-32 feet for bigger antennas like the TH-7,
Skyhawk, etc. Essentially, I wound up in the same place by mdeling that
others did through experience.
1X/2X and 1X/2X/3X spacing also looks good, at least in models. It seems
to work well to reduce high angle lobes.
73, Pete N4ZR
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