I'm considering the 180S or 280S also, likely the shorter (not Magnum)
versions. The Tornado variable pair of inductors at the feed point
(squeeze/expand the coils) appears to be a good idea at least for the
dipole, and should be easy to set, using SWR.
It would also seem to be possible to make a pair of Tornados work for
the 2L beam, but with two sets of variable inductors the tuning might be
a nightmare to figure out. Moving around the 70Khz bandwidth would be a
real plus. With enough L range, it might tune to some other band, but I
won't even go there, other than to suggest it might provide some
detuning/decoupling from adjacent yagis.
So, are there any Tower-Talkians with experiences or models with either
of these setups?
Jim Thomson wrote:
> If anybody owns either a F-12 Sigma 180-S or 280-S.[ both 80m ants].. or
> knows somebody who does own
> either one, perhaps you could stick a few watts into it on 20m, and see
> what kind of swr
> you have on 20m. If you have the time, perhaps sweep it with a MFJ/etc,
> and see where it
> does resonate. Not all these ants will resonate on their 3/5th harmonics.
> The F-12 340-N [3-el 40m yagi]
> does not resonate on 15m.... it resonates just below the 12m band.
> What baffles me is 3.5 x 3 = 10.5 mhz. 10.5/14.2 = .74 The 80m
> ant, on it's 3rd harmonic is
> 26% lower in freq than 20m. I have heard several horror stories now of
> 80m arrays completely
> screwing up 20m yagi's that are in close proximity. Rotating the 80 + 20m
> arrays , so their booms are
> 90 deg to each other does not always work. The 35' booms used on both the
> 280-S and 340N will screw
> up 20m real fast.
> I noticed that Optibeam uses decoupling rods on their 4-el 40m yagis. They
> won't screw up a 15m yagi, nor
> another HF array. Does anybody know how this is done ? Can this technique
> be adapted to an 80m array ?
> Jim VE7RF
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