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Re: Interference on AO-51

>That sounds like a good idea (What's the total bandwidth?) 

We suggest four possibly adjacent 2m 15 KHz channels:
- FM repeater downlink
- APRS Packet (FM) (has been .825)
- PSK-31 (FM downlink, 10m linear uplink)
and then the linear transponder also only being
15 KHz to support up to 5 simultaneous SSB

>and with a  series of Low Earth Orbiting satellites 
>it's effectively implementing "time  division multiplex"
> - Just wait a little longer and you have a continuation 
>of service when the next satellite comes within range.
>Although,  I wonder how the proposal will fit in with 
>HEO orbiting  satellites?   Any HEO bird would be 
>QRMed by the LEOs which presumably  would need to 
>avoid any existing downlinks.  

It could be argued that we should not be using our
very precious and narrow 2m for any HEO projects:

a) The 2m satellite band is just too narrow to be 
consumed  by one HEO satellite.
b) HEO's QRM almost half the planet at a time but
there can be many LEO's using the same frequency
at the same time over different areas.
c) The lack of doppler tuning on 2m is ideal for LEO's
and not needed on HEO's.
d) HEO's move slowly and are stabilized and can point
gain antennas at Earth, LEO's cannot.  THus HEO's
should concetrate on higher frequencies to take
advantage of pointing gain.
e) LEO's are the only satellites that can easily close 
the link to a mobile whip antenna on 2 meters and so 
we should not be using those valuable frequencies
for HEO's which have other options.

At least that is how it seems to stack up to me...

de Wb4APR, Bob

In a message dated 04/05/2006 12:47:01 GMT Standard Time, bruninga@usna.edu  

One of  our school's proposed projects is to suggest six 2m 
downlinks on the  ISS.  One for FM voice,  one for SSTV, 
one for packet (APRS),  one for 30 simultaneous PSK-31 
users and one for 30 KHz wideband  transponder (10 SSB
users).  And then to also  encourage other  satellites 
supporting those same 6  channels.  As more and more  
satellties got added, soon we would have near continuous 
coverage of  these 6 comon modes. 

All easily heard on an HT or mobile with no  tracking and
no tuning.  And NO problems from the interlopers  and
illegal 2m QRM in some areas.
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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