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AZIMUTH tracking of LEO's



This was an earlier post that did not make it through AMSAT-bb.  So by now
I have already said it again... sorry for the repeat...

>On Thu, 29 Aug 2002 owner-AMSAT-BB@AMSAT.Org wrote:
>
>> My research on the net seems to indicate that most people on
>> UO-22 are using gain antennas and az-el rotors, especially on
>> receive.
>
> (only because they already have them).  Elevation is NOT required for
> LEO except for 2% of the time.  Not worth it.  So you can do it all with
> only a radio shack rotator and a short UHF beam...
>
> My APRStk (a dos program) does full automatic LEO tracking with only a
> $20 interface between the Radio shack rotator (any 3 wire rotator) and
> the LPT1 parallel port.  And if you happen to use the Kenwood D7 or
> D700, it also fully tracks and tune the radio to each satellite as it
> comes in view and accoutns for doppler...
>
>See http://www.ew.usna.edu/~bruninga/rotator1.html
>
>> Has anyone out there had experience using a modest cross yagi
>> for UO-22 receive?  I'm thinking about 5 or 6 elements,
>> switchable RHCP/LHCP with a good preamp, something on the
>> order of 60 degrees/3db beamwidth with a gain of 9-10 dBi.
>
> Absolutely perfect.  My THD7 handheld can receive UO-22 9600 baud using
> only a handheld 3 element UHF yaggi (rotated by hand to match immediate
> polarity), so a 5 or 6 element is perfect...
>
>> If that leaves me too much of a hole directly overhead, I > might
>> supplant it with a Moxon turnstile array (switchable RHCP/LHCP, ~5.5 dBi
>> gain).
>
> the 2% of the time that the satellite is above 60 degrees is just not
> worth it.  Besides, you are also in the NULL of the satellites antenna
> anyway since most of them are vertically polarized...
>
>> For transmit, I'm thinking 3 or 4 el. yagi, vertically
>> polarized.
>
> Yes, sinec this will help on ISS and PCsat downlinks, but 50W into a
> OMNI WHIP is more than enough to hit ANY LEO amateur satellite (except
> for QRM).  And when there is a collision, then netither one of you gets
> in anyway....  the BIG beams on the uplink are only "required" if your
> obnjective is to step on everyone else and try to be 13 dB stronger and
> maybe capture the receiver...  (I am NOT saying that is bad.  It can be
> said that it is better to let the big guys hammer their traffic through
> and then clear the channel, then everyone coliding and no-one getting
> through... )
>
>Ah, I ramble...
>
>Bob
>
>
>
>> > I'd
>appreaciate hearing your comments, suggestions. >
>> Thanks,
>>
>> John Pfeifer - KLWN
>> Kodiak, Alaska
>>
>>
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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://www.toad.net/~wclement/bruninga/mic-lite.html

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