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RE: Feeding 1.2 meter offset dish for AO-40,



Beautiful job Pieter! Let us know your results as soon as possible.
This is the best looking antenna I've seen for AO-40 S band. You
would help a lot of us by writing an article on how to build one and
match the feed to 50 Ohms. The preamp might yield better results
located right at the feed connector. Let us know if there is any 
measurable difference.

I'm working on a similar offset dish. The helix is only 3 turns because
of the illumination requirements for the dish. Four turns is only
about 55 deg beam width and this isn't enough to illuminate 90%
of the dish I'm using, which has a lower f/d ratio than the one
you show in the pictures (.6?)

How did you determine where to put the helix in relation to the
focal point? You mentioned "phase center at .7 inches from the reflector" is where the
focal point would be placed. I haven't 
been able to find a reference to this subject anywhere and had
planned to post a question on this BB about this.

Ken  K5MBV
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