Subj : Satellite Antenna
To   : Kusho
From : Spaceman Spiff
Date : Mon Aug 23 2004 10:00 pm

  Re: Satellite Antenna
  By: Kusho to Spaceman Spiff on Tue Aug 24 2004 12:17 pm

 >   Re: Satellite Antenna
 >   By: Spaceman Spiff to Angus Mcleod on Mon Aug 23 2004 04:20 pm
 > 
 >  > The Birds I will be looking at are in a polar orbit, I believe you can ge
 >  > about 4 pictures a day, usable pictures that is from a couple different b
 > Yea, then you aren't gonna want a parabolic antenna.  You would have to know
 > the point of aquasition, (which changes every day) and then swing across the
 > sky to track it.  That is dificult.  I do satellite communications with the
 > military, and it can be rough following some of their geosync sattys.  I
 > wouldn't want to even try on a polar satty.  You also will need a very clear
 > look at the sky.  Since the satty will be going across the whole thing, you'
 > need a pretty open area for it, or a really high antenna.
 > 
 > Kusho
 > 
Very true. I work in Cable TV, about 22 years now. I know the problems if one
of our big dishes (parabolic antenna) move just a little. We even have a few
SIMULSAT dishes capable of holding several LNB's at the same time to point at
several birds in GEOSYNC, all are fixed and not intended for tracking a moving
object from horizon to horizon. About 2 weeks ago I was having lots of fun
(not) with satellite dishs at work.The Weather Channel didn't like our small
3.7 meter dish giving us a signal quality 5o (marginal) we needed something
like a 85-100. We moved to an LNB on the big 5.3 meter simulsat and reoriented
an LNB and bingo we had signal quality of 90 on the Motorola receiver.

I remember seeing the Russian's using helic wound antennas, let me rephrase
that, I remember seeing pictures and video of Russian helic antennas for work
with thier satellites and space program. Old stuff, but interesting.

Back to the point, I could imagine trying to use a parabolic antenna to tracka
moving object, would take a system very sophisticated. I would imagine NASA and
the military may have stuff like that that could handle microwave type stuff.

It might not be that bad with freqs down at 137 MHz, but the gain from even a
10 foot dish at 137 MHz wouldn't be that great, It would be better to set up an
array of Yagi's and a tracking system like Angus mentioned.

My thought is possibly a couple of arrays covering two parts of the sky, having
each array set so several YAGI's would allow a wider beam pattern. It is going
to be a fun project. The only trying part is you have to wait for a bird to see
if the design is good and tweaking the system could take many days.

I am lucky, I am ata very high location, on the same ridge that US Navy chose
to build the Johnville Naval Air Warefare center (now closed) but it was chosen
becasue it was one of the highest locations in the county North of
Philadelphia, they used to test Jets and other stuff, it was also a training
sight for the Mercury, Gemini and Apollo astronauts. it is only 10,000 feet
from my home, so hieght is no problem. With 35 watts i can transmit on 2 meters
and talk simplex to shore points over 70 miles away from New York, New Jersey
down below Cape May and across into Deleware using only a Colinear J-Pole.

Thanks for the input and thank you for your service to our country.
73 Mark

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