High-Efficiency Feedhorns for Prime-Focus Dishes

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The Professor
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High-Efficiency Feedhorns for Prime-Focus Dishes

Post by The Professor » Mon Mar 19, 2018 10:57 pm

High-Efficiency Feedhorns for Prime-focus Dishes
VE4MA and Chaparral feeds with Septum Polarizers

Paul Wade W1GHZ ©2006
Tommy Henderson WD5AGO

This started out to be a simple project – optimize the VE4MA feedhorn1 with a septum polarizer2 for
circular polarization. Some unexpected results have led to a larger analysis with conclusions that may
differ from the prevailing wisdom, but have been verified by measurements made by WD5AGO.
Some improved variations of the VE4MA and Chaparral feedhorns are described which show some of
the highest calculated and measured efficiencies to date for a prime-focus dish.

What we often call a “feedhorn” includes several separate elements: an antenna which shapes the
beam for improved dish illumination, a waveguide section (round, square, or rectangular), perhaps a
circular polarizer, and an excitation region (waveguide, probe transition to coax, or other transition).
While these elements may interact, each has a separate function and may be analyzed independently.
It is not necessary to exactly replicate all the dimensions from end-to-end, but it would be foolhardy to
make changes without considering possible interactions....

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PhD in TVROSat

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