[aprssig] 9600 APRS
whsander at gmail.com
Wed Apr 1 22:43:12 EDT 2009
My increasing involvement in Emergency Management in NJ has gotten me back
into APRS with a vengeance, and my Kenwood rigs are running hot. Running
slow 1200 baud with random packet intervals and packet collisions seems kind
of static. The newer rigs will run 9600 APRS, but there is no 9600 network
We have better features built into the Kenwood radios than we actually get
to use because the network at 144.39 is still 1200, hence very little 9600
ops- mostly satellite spotting. Since we allow these features to languish
unused or at least under used, no other radio manufacturers seem to feel the
need to incorporate them in their product lines. Now we have lost the
TH-D7s. ( I don't really believe that decision was made because of toxic
chemicals in the PCBs... Do you?)
How about something a bit different? Suppose, as an experiment, here in
Central NJ where there is a pretty dense signal cluster, we were to set up a
440 UHF 9600 APRS digi at as high a point as we can get, running as much
power as we can manage.
Instead of having a conventional digi, have a computer hooked to 2
radios/TNCs, one running at 1200 on 144.39, the other at 9600 on 440 UHF.
Have the computer APRS application record all the received packets over a
three minute period of monitoring 144.39 1200 operations, compile them into
one long data stream and at the end of that 3rd minute transmit that three
minute take from 144.39 1200 onto the 440 UHF band 9600 channel in one long
burst. In the intervening minutes between that digi-burst and the next, 9600
UHF APRS units can transmit position packets, which will not be digipeated
immediately but will be scooped up by the computer and incorporated into the
next data burst, and can be cross banded to 144.39 at 1200 as well.
If I am correct, this will cut packet collisions way down, and on the UHF
9600 channel the air will be clear, allowing for greater distance RX and TX
in between digi-bursts, at least until a large number of people start
running APRS at 9600 on UHF and we eventually get QRM. And even if a large
number of people eventually do run 9600 on UHF, the capacity of the channel
is as much as eight times that of 144.39 because of the speed increase. That
gives us room for more content, larger packets, longer messages, in short-
More room to play with.
I am not a programmer, and so I can't make this happen by myself. All I have
is some money for equipment and the desire to see this happen. One of the
talented APRS programmers out there would have to get interested in this.
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