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Re: Ao-40 site questio



On Mon, 8 Sep 2003, DC wrote:

> I've been given the opportunity to put a [satellite] recieve station on
> the top of a tall building here on campus.  (In Houston) [under
> computer control so we can hear all the satellites in view...]

I have several comments:

1) Yes, AO-40 always follows the Geostationary arc +/- 10 deg or less and
so is always in the direction you asked about.

2) All other satellites (LEO's) do NOT need any elevation tracking 98% of
all of the time they are in view.  THus a simple $50 Radio Shack rotator
is perfect for automated station to use LEO's.

3) Yes, your discone will hear most satellites when they get close enough
(say above about 30 to 40 degrees).

BUT!  Of all the time that a LEO is in view, they spend over 65% of their
time below 20 degrees, and 95% of their time below 50.   This means two
things related to #2 and #3 above:

 *** The discone will only hear 10% of any given satellite (#3)
 *** for the 5% above 45 degrees the satellites are 10 dB stronger!
 *** You dont need any EL rotator for 98% of all satellite passes (#2)

    See my http://www.ew.usna.edu/~bruninga/rotator1.html

for the details.  I wish more satellite programs would recognize this fact
and give us the TWO-BIT parallel port out put for these simple
rotators!!!!

LAST THOUGHT:  If you don't use the simple beam, then the LAST place you
want to put an omni satellite receive antenna is on the top of a building
in a metropoliatan area!  You will get so much intermod you wont hear
anything anyway...  See #2.  Since you wont hear anything unless the
satellite is say above 30 deg, then this means you can mount it on the
ground well out of the high RF at altitude as long as it can see above 30
degrees or so of surrounding buildings.

just some thoughts...

Thanks
Bob, WB4APR

> I'm putting an autotracking primestar dish w/ downconverter and wideband
> 100-1000mhz discone on the roof of a 10 story building.  These will be
> connected to a PCR-1000 via a relay for antenna selection.  The reciever
> will be attached to a computer on the roof that will stream the audio
> over the campus network as well as accept/display tuning/positon
> commands via the network (eventually a web page).  My goal is to
> automate much of the tracking/tuning (not to hard with today's software)
> so that wheneven AO-40 comes above the horizon people will be able to
> listen live to an ?!amateur radio communications satellite!?!  If the
> university agrees, prehaps the streams will be available over the
> internet as well.  I'd like to be able to listen to/track all the sats
> but as I'm footing the bill for this thus far I can't afford all the
> antenna/rotator/switching hardware to make that happen yet.  I decided
> to go with the discone because it enables me to utilize the huge tuning
> range of the PCR-1000 to show off a bit of amateur radio beyond just the
> sats (they're only above the horizon for limited amount of time).  Just
> curious, will a 0db discone without a preamp be able to hear any of the
> LEOs?  That would be cool.
>
> The complexity of this project is starting to run away from be a bit.
> One thing that's got me scared is lightning.  I'm putting antennas and
> quite a bit on my (expensive) equipment on a tall building where I won't
> be able to disconnect it during a storm.  There are several other tall
> buildings around as well but my antennas will still look like a good
> lightning rod.  I've been doing quite a bit of reading about lightning
> protection.  Thus far all its done is make an already expensive project
> even worse.  I've been checking out rf protectors by PolyPhaser but
> that's as I under stand it only one small part of my system.  It sounds
> like I need protection on my network lines, my coax, my rotator control
> lines, my power supply lines and my antenna switching relay lines.  In
> addition I thought it might be a good idea to have a coaxial relay that
> would enable me short the center conductor of my reciever's input to
> ground in threatening situations.  My is situation complicated by the
> fact that all this will be on top of a building where grounding might be
> more difficult howeverlightning rods already are installed (and they
> might be a decent ground).  Do any of you have any experience/advice here?
>
> Thanks for hearing out my long winded post.  I'd love to hear some
> suggestions and comments...
> -David Carr
> KD5QGR
>
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de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://ssdl.stanford.edu/mims/


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