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AO-40 reception on a 3m TVRO dish



When I saw On Sat, 15 Dec 2001, Robert Jewell write:

> My C Band dish came with a Chaparral feedhorn.....<snip>

I realized, duh... by just folding a piece of RG-58 into a 2.4" dipole on
the bottom edge of my Chaparral feedhorn, bingo, I get a perfectly
tracking AO-40 3m dish for free!  By using binder clips to hold it and a
reflector plate anywhere along the edge of the feedhorn, I can adjust the
offset angle from about -5 to +5 degrees from the geo arc without
messing at all with the normal mount for TVRO (so the TV still works
fine).. (photos below)...

Since AO-40's path is typically 4 degrees or so above the geo arc, this
makes it trivial to track and find AO40 repeatedly.  Just find the sweet
spot for the dipole, and then all the rest of your tracking is done with
your TV remote control along the longitude arc...

Within 45 minutes of thinking this up, I had it installed complete with
photos!   To see photos, click on "photo1 and photo2" in the
sentence just before the SKY TRACK view on my AO-40 antenna page:

http://www.ew.usna.edu/~bruninga/ao40ant.html  (about mid page)

THe 3m signals are not 9 dB stronger than my 1m dish as I anticipated, but
then I am using 150' of 10 year old RG-59 as the lead in... compared to
10' of new stuff on the portable 1 meter dish.

To help visualize the AO-40 arc relative to my TVRO arc, I wrote a little
program that gives the sky view of the amateur satellites.  This is the
one that did the SKY VIEW on the web page.  You can run it any time and
see what the path looks like.  You can also customize the horizon to match
your yard if you want...(instead of mine.  Just edit horizon.dsh))...

download  ftp://tapr.org/aprssig/dosstuff/APRSdos/skyview.zip

de WB4APR, Bob



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