[NLRS] Dear Dishers

Thu, 29 Aug 2002 10:18:14 -0500

Hi Jon,

I did not have the advantage of Paul Wade's book when  I got the 18" dishes.
I did have the LNA.   I measured the center of the point of the LNA and
plotted a line  was the center of the LNA feed.   I did not know the
location of the phase center  of the LNA.   I built a mount that would allow
my feed horn to be on the same center line as the LNA  with the ability to
move my  feed horn back and forth.   Put it on the antenna range and max the
gain  and determined the phase center for my horn.  I seems to work ok.

Paul Wade has technique with a string from the top and bottom of the off set
dish which also indicated the phase center.  My technique was  and Paul's
techinque were the same.  But Paul's gave you the point before you  anything
was constructed (easier).
73  Bob  W�AUS
----- Original Message -----
From: "Jon Platt" <[email protected]>
To: "NLRS" <[email protected]>
Sent: Wednesday, August 28, 2002 9:01 PM
Subject: [NLRS] Dear Dishers

Dear 10 GHzers.

Several weeks back, during Bloomingtons clean-up days, my neighbor across
the street set out a microwave dish in their garbage pick-up pile.   I was
over there in a flash, and in the good tradition of bartering, we traded
"garbage".   The dish is an elliptical design, gray in color, aluminum,
looks fairly flat, and is without any markings of any kind.   It measures
26" high by almost 24" wide with an off-center feed point that has a feed
arm about 17" in front of the dish.   The mounting hardware is in good shape
and it looks like it should be a snap to install on a tripod.

Is anyone familiar with this type of dish and have a suggestion as to how to
feed it (for 10 GHz).   I do have a couple of the "small" 10 GHz horns ....
I think that they are in the 8 or 10 dB range or so (they measure about 1"
high by 2" long by 1" deep) ... quite a bit smaller than the 17 dB horns
.... would these work as a feed for this dish ??   I suppose I would need a
transition to mount to the backside of the small horn.   When I hold this
small horn on the dish feed arm at what I think should be the feedpoint, it
visually looks like it should/would illuminate the full dish.  Thoughts?

I also have an old style 18" dish (solid) that I could design my 10 GHz
antenna around, but I would have to construct the feed point arm and dish
mount ..... perhaps I can use some of the mounting hardware off the
elliptical dish.   However it appears that most people are using bigger
dishes (than 18").  Would it be better to go with this smaller, "classic"
dish or should I plan my system around the elliptical dish discussed above ?

73, Jon
W0ZQ

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