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[aprssig] APRS on 144.99 MHz

Robert Bruninga bruninga at usna.edu
Wed Sep 29 20:16:26 UTC 2004


While debating if 144.99 is available for packet, here
is a new thought to ponder....  WHile reading this, think
of an application like tracking all low-power-tracker-
hikers in the Smokie Mountain National Park...

**  Given that the "ideal dual channel input APRS digi" is
more complex than just hooking up a TNC and radio.

**  Given that APRS growth more often than not, is based
on quickie digis in some cases,

Therefore, one could consider the following optional
application of 144.99  *** IN RURAL AREAs ONLY***
to easily provide plenty of low-power tracker coverage
while only having to configure one "ideal dual input
channel digi:

That is, put up one "central IDEAL dual channel input" digi
to get the 144.99 data over to 144.39 with CSMA, but then
you can put up several low power out-lying digis in the
boonies to link VIA *one-and-only-one* hop on 144.99
to get the packets to the central dual-freq digi.

*  The advantages are:
    1)  simplicity and large coverage for low power trackers
    2)  Alternate channel for passing LOCAL connected
         emergency traffic with ONE HOP ONLY...

*  The DISADVANTAGES ARE:
    1) immediately doubles the probabily of collision with
        other low power trackers
    2) Makes 144.99 impossible to share with other users
        who now can ALL hear EVERY tracker ALL the time
        instead of only one in a blue moon (when a tracker 
        happens to get within a mile or so of someone)
    3) Popularity of great success on uncongested channel
        may invite too many people which immediately kills
        the Golden Goose...

NOTICE how this can only work in remote areas to simplify
growth.   It MUST be understood that this will NOT work in 
populated areas with lots and lots of low-power mobiles on
the alternate channel because it will be far overloaded
completely killing the alt-channel concept in the first place.

So, its just an idea *FOR UNIQUE APPLICATIONS***

For example.  Say you wanted to track hikers in the smokies
National Park.  Existing 144.39 digis that cover the area
also hear traffic from the surrounding 10 states.  They cant
hear low-power trackers.   BUT!  Put up one dual-input
digi with CSMA listening also on 144.99 (if available in that
area) and then scatter 3 or 4 144.99 low-power solar powered
digis around the corners of the park and you can track the 
shirt-pocket trackers with no QRM everywhere with no
QRM.   This could work well.

It would be impossible to work on 144.39.

de WB4APR, Bob





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