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Re: [aprssig] Re: GPS data from PCsat



On Tue, 15 Jan 2002, Jeff King wrote about dual use of 144.39:

> OK... thanks for the explanation. Kind of a layer cake approach. I like it.

And for what it is worth, there was actually another idea for channel
sharing for an APRSAT  that we designed to go to a near geostationary
orbit.  It RECEIEVD on 144.39.

THis seems ludicrous at first blush, becasue the frequency in north
america is jammed with dozens of collided packets per second (and a
satellite would hear all of them at once)....  But these are all aimed
more or less at the horizon and using 50W or less stations.  And the
satellite is up at about 45 degrees over the central USA, where  all of
this energy is about 6 dB or more down.

So we theorized that a mobile with a 300W amp and a roof mounted turnstyle
antenna with a main lobe straight up, would be able to just hit the bird
(40,000 km away) and still be at least 16 to 20 dB stronger than the noise
level of all the other 144.39 traffic... (whcih could not possibly be
decoded)..

The advantage being that those special mobiles would be transparently able
to hit the terrrestrial system and/or the satellite without any operator
intervention..

But that was the mission we got bumped off one week before integration...
(And also back when we thought there was no way we would ever get a 2m
frequency from AMSAT in the satelltie sub-band and so we were looking at
other ways to share frequenceies)

 Bob


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