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Re: Speaking of big ears...



Margaret -- you might be interested to know that the site at Rosman NC was
originally built by NASA to be a satellite tracking facility in the 1960's and was
turned over to the spooks in the late 70's. With my colleague Larry Brown, I made
some Radio Astronomy observations using Rosman in the late 1960's at ~2 GHz.

One of the Rosman 85' antennas is the twin of the antenna my group operates as a
geodetic VLBI station at Fairbanks AK (see http://lupus.gsfc.nasa.gov and click on
Brochure. See especially the photo ~2/3 of the way down in
http://lupus.gsfc.nasa.gov/brochure/bintro.html). This antenna is unusual in that
it uses an "X-Y" mounting. When pointed straight up to the zenith, both drive axes
are horizontal with no "zone of avoidance" overhead (you have a hard time tracking
overhead thru the zenith with an Az-El mount). Also either axis has only 180
degrees of tracking range. With this drive system, it can get from any part of the
sky to any other in under 2 minutes. These antennas cane really fly!

When the spooks upgraded Rosman from hydraulic to electric motors in the mid-80's,
we gathered up all their old hydraulic motors, valves, etc and the Fairbanks
antenna continues to run on them -- replacements for all the old Vickers hydraulic
widgets are made of that rare metal Unobtanium.

BTW -- The Alaskan twin of Rosman has been on both 70 & 23 cm EME as W3IWI/KL7 and
KL7RA. With work we've done on the antenna, we get ~45% aperture efficiency at 9
GHz. The cryogenic LNAs we use give us a total system temperature (LNA + losses +
God's 3K universe + atmospheric attenuation) of 40-50K at both 2.3 GHz and 8-9 GHz.

Also today, Bob Bruninga (WB4APR)  posted some AO-40 .WAV files obtained with the
40' ex-NASA antenna that was moved to the US Naval Academy some years back. The 40'
antenna is a clone of the 40' antenna at Goldstone that I developed for VLBI that
we used in the 1980's.

It was an interesting surprise and nostalgia trip to see two the "distant cousins"
of my "children" mentioned on the same day on AMSAT-BB.

73, Tom


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