Jim White, K4OJ wrote:
> I am modeling a "stack" for ten meters and am debating about rotating
> multiple yagis simultaneously from one rotor "sidemounted" which is very
> "tall".
>
> There would be twenty some odd feet in between the yagis, and the tall mast
> would have a rotor at its "base".
>
> The antennas would be little 4 element jobbies, very lightweight short
> boomed yagis to clear the guys, etc.
>
> Question, why couldn't I use a lightweight galvanized tube for this mast?
I just did that, using water pipe. Pair of Cushcraft 4 el 10s
at 40'/60' connected by two 10' galvanized sch. 40 1.5" water
pipes, with one support collar in the middle (at the splice),
and of course one near the top antenna (actually, just below
the top one).
The sch 40 pipe, in this particular application, seems more
than adequate for the task. Galvanized fence posts would be
fine I'm sure, but water pipe is cheap, and you can tighten
clamps on it without flattening it. Since the first collar
is 10' above the rotator, you don't need to go crazy trying
to center the mast in the rotator, there is plenty enough
slop in the system. The important thing is to get the rotator
in line with the collars.
BTW, the element spacing on the Cushcraft yagi is such that when
rotated around Rohn 45 on a sidearm, you just barely have enough
clearance. It would never work on a 20" face width tower.
The stack is working so well that I plan on doing another
pair at 80'/100', and treating each pair as a single antenna
in the standard simple upper/lower/BIP switch.
73, Steve K8LX
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