[TowerTalk] Sigma 180-S / 280-S

[Grant Saviers]

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?

Grant  KZ1W

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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