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Re: Echo PL tone

At 03:32 PM 5/30/2004 -0400, Pete wrote:
>  Bill, Ever use UO-14? Possibly to eliminate any taxi cab dispatchers 
> causing
>QRM during their illegal use of 2 meters. 73 Pete NA2P

I'm not sure PL tone is going to help that much any more Pete.  The illegal 
2m transmitters in Baja California are so strong now that knock us right 
out of the FM satellites, including SO-50 which does have a PL.  They just 
come right over the top of us and the satellite shuts off.  Howard, K6IA 
was still getting knocked out even after cranking the power up to 100W into 
a 9 ele 2m KLM beam.

If you want to demonstrate the effect, do this simple simulation.  Set up a 
50W station and an HT to transmit on a repeater that you know you can get 
into with the HT.  Turn the PL tone on the 50W station off, then key 
it.  Then try to get in with the HT.  It won't go in because the stronger 
signal is overloading the front end of the repeater receiver.  It seems to 
be the same thing that is happening with SO-50.

So it is likely the same thing will happen with Echo - PL tones are good 
for protecting the satellite batteries - but from what we can see here on 
the west coast it does nothing to improve FM capture in the face of a huge 
linear in the hands of a illegal user.

Some good news is that Echo is not sitting on a 25KHz tuning step (145.920) 
so it's possible that we've avoided being right on top of illegal 
transmissions by people who never think to go in and change the tuning 
step. I just wish they would have moved it to something like 145.915 so it 
would be less than 6khz away and made it NFM, but it's a good step in the 
right direction.

One other piece of good news is that I didn't need nearly as much power as 
Howard (though I still was putting 25W into a 5ele beam).  I'm computer 
controlled, so my transmitter was compensating for doppler - the illegal 
transmitter is not.  So this could be a strong argument for computer 
controlling even on FM satellites.



W0EEC - CM87tm
AMSAT Area Coordinator - San Francisco Bay Area
http://www.projectoscar.net    http://www.PlanetEmily.com 

Help Launch Echo - http://www.amsat.org/amsat/sats/echo/index.html

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