[NLRS] 10 GHz feed

Wed, 29 Jan 2003 12:13:25 -0600

Hi Gerry,
No argument.  Its NOT "optimal."  But it works very well; more than enough
to offset the trouble of making a new feed and mounting it.

My 18" dish with a W1GHZ optimized feed measures between 32-33 dB gain at
10.368GHz, and that's with a weekend spent building it and an hour or more
spent optimizing the mounting position.

My 18" dish with the original feed and the guide drilled out to 0.75" dia.
measures 31+ dB at 10.250 GHz.  Total time involved was about an hour.  I
suspect I could get a bit more out of it by optimizing the probe: diameter,
position, and length.  But I'm not sure its worth the effort for non-EME.
(And 18" aint an EME antenna!!)

73 Donn
WA2VOI/0

-----Original Message-----
From: Dr. Gerald N. Johnson, electrical engineer
[mailto:[email protected]]
Sent: Tuesday, January 28, 2003 10:06 PM
To: Donn Baker
Cc: Ed Marciniak; NLRS
Subject: Re: [NLRS] 10 GHz feed

It might be that a feed optimized for 13 GHz would be a little small and
have a bit of excess spillage at 10.368 GHz. Beam width from a horn feed
is inversely proportional to the horn aperture in wavelengths. A 30%
change in wavelength should make a significant change in feed pattern.
Possibly not beyond usability, but probably a bit away from optimum.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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