[aprssig] First digi versus last digi?

Robert Bruninga bruninga at usna.edu
Tue Jan 20 15:49:00 EST 2015

To me, FIRST digi is the most important.  It allows NATIONAL tracking for
weeks with nothing but a tracker an 6 AA cells (no GPS).

Here’s how:

Use any timer/pic porocessor/tracker and simply transmit a short STATUS
text once every 10 minutes.

APRS.FI and/or FINDU.COM plot the location of this first
heard-no-posit-beacon and plots it as a “VICININTY” plot showing the
nearest digipeater that heard it.  FINDU does this now, I am not sure about

This gives you a plot anywhere in the country where that tracker has been
(to the nearest 10 miles or so).  And at one packet every 10 minutes at  5
Watt output, then the average power is 0.01W or at 7 volts (6 cells) at 1.4
mA which should last 2000 hours on a AA alkaline cell or about 3 months.

No, it is not precise tracking, but for tracking something all over the
country with no access to anything but 6 AA cells, it is a great technique.

ALSO of course, knowing the first digi while messaging is useful for
assuring that digi gets a copy of any messages to that station.

Bob, WB4APR.

*From:* aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] *On
Behalf Of *Andrew P.
*Sent:* Tuesday, January 20, 2015 3:26 PM
*To:* TAPR APRS Mailing List
*Subject:* [aprssig] First digi versus last digi?

Greetings, all.

I'm looking at adding some more path analysis features to my APRS program,
and was wondering what the consensus was regarding plotting path from
original sender to first digipeater/Igate versus path from last digi/Igate
to receiver. Which has more value to the user?

I ask this because my original implementation supported last digi, but this
never seemed to be useful. And now I'm adding functionality to identify and
guesstimate-locate stealth first digis.

Is there any need to keep last digi identification, filtering, etc.?

Just wondering how people woukd feel about that.

Andrew Pavlin, KA2DDO

author of YAAC
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