Re: [TowerTalk] 4 SQ arrays

[Jim Lux <jimlux@earthlink.net>]

At 04:51 PM 11/19/2004 +0100, Jan Erik Holm wrote:
> Now I see my error. I checked at .35 wl spacing
> and that will give about .5 wl on the diagonal.
> Don´t know why I wrote 1.5 wl and 2 wl below,
> my fingers are to fast for my brain.
> Anyway, at .35 spaceing the F/B doesn´t seem
> to get better, what I wrote below will happen.
>
> Jim SM2EKM
> -

Tiny fractions of a dB difference in forward gain (11.56 vs 12.04) Big 
difference in F/R (20+ vs 10-15 dB)

I suspect that the "real" performance will be much more affected by the 
changed mutual coupling with the elements at a different spacing. More to 
the point, the different impedances will affect what phases that hybrid 
really produces (and, if you're 0.25 WL from the center on the diagonal, 
that means your feedline must be somewhat longer than the nominal .25 WL 
called out in the Comtek instructions, so that's yet another factor that 
would have to be considered.)

I haven't tried it, but it should be possible to model the Comtek box (or 
any "Collins hybrid") in NEC with NT and/or LD cards. Then, you'd get all 
the interactions properly modeled.



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