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Re: Dish Formulas ?



Thanks Joe.

Unfortunately, I can only get an indication of return
loss on a single frequency with my homebrew setup, so
I may have to abandon my plan to use a circular patch
as the coax-to-waveguide transition for my dual-mode
feed shown at
http://www.qsl.net/va3rr/dualmode/dual_mode.htm

I tried modelling a helix inside the dual-mode, but I
think the smaller waveguide section needs to be
longer, or I get too much "squint".

I'm having a ball with 4nec2, though.  I was an EZNEC
user for a long time, but 4nec2 lets me use patches
and has a great build facility for parabolas, disks
and other structures.

I think I've found a way to clean up those nasty helix
sidelobes somewhat.  Gotta make a trip to Wal-Mart to
find the right bowl. If I get time on Tuesday, I'll
put my latest NEC2 model on my webpage.  My main goal
is to get the satellite antenna on the tower before
the snow flies...


 --- Joe Ennis <joe@whiskey7.net> wrote: > Yup,
> 
> My round patch was a real bear to tune. Got the 'W'
> on
> the bench w/ VSWR: 1.05:1, 1.2:1, 1.05:1 but, after
> mounting it on the feed strut, the best I could get
> for
> return loss was ~13db for 1.5:1 VSWR. Could not find
> a "sweet" spot that would yield better results.


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