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[aprssig] 9600b UHF APRS IS THE FUTURE OF APRS

Bob Bruninga bruninga at usna.edu
Mon Oct 9 17:57:15 UTC 2006


>> It's not the coverage that's the problem,  it's the 
>> number of users in the collision domain and the 
>> size of the  aloha circle vs. digipeater location...
>
> Don't forget "packet time" is also part of the equation.  
> A 9600 baud network with packets 1/4 the size of a 1200 
> baud network can handle 4X the number of users in its 
> Aloha circle.

BUT, in order to make 9600 baud work at UHF, you first have to make up a 9 dB RF link penalty, and a few dB decoding penalty.  This requires you to have to install 4 times as many digipeaters for the SAME performance.

Now, once you have installed 4 TIMES the number of digis, you now have much smaller CELLS and can stuff in 16 times as many users.  BUT WITH THE DENSITY OF APRS AND HAM USERS, there just arent that many users to require this tremendous
effort.

Again, I am not opposed and I welcome the effort if people want to do it, but to me, the effort far outweighs any 
benefit unless somehow we get 100% of hams to routinely run APRS so that APRS can become what it was intended to do.

That is, to keep an APRS user fully informed of EVERYTHING in HAM radio that is going on around him.  This "informed" process is simply a single packet in most cases of a position, or a status of what is happening in his local
VHF range.

Bob, Wb4APR





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