[aprssig] are write-only APRS-IS clients valid? (dynamic Map?)

Andrew P. andrewemt at hotmail.com
Mon Dec 2 13:13:16 CST 2013

So, to do the mapping that Bob wants to do, we have to get the ISS station temporarily switched to the terrestrial APRS frequencies and bombard the earth with packets so that every IGate and digipeater on the planet hears it by the time a few orbits are done. :-) Would that work?

Andrew Pavlin, KA2DDO
author of YAAC
------Original Message------
From: Tom Hayward
To: aprssig at tapr.org
Sent: Dec 2, 2013 1:59 PM
Subject: Re: [aprssig] are write-only APRS-IS clients valid? (dynamic Map?)

On Mon, Dec 2, 2013 at 10:09 AM, Robert Bruninga <bruninga at usna.edu> wrote:
> If I had the skills, what I would like to see is a map of the USA of all
> digipeaters with their PHG circles shaded yellow.  Then all such PHG
> circles that enclose a 2-way IGate to be shaded green, and all PHG circles
> that do not have a 2-way, but do have a 1-way Igate to be shaded red.

This make a huge assumption that the PHG circles are accurate. Maybe
Lynn could do this for us, but with actual coverage data. He is the
keeper of some valuable data!

You're also assuming there's a way to get a map of all the digipeaters
in the US. I know of digis in my state that don't reach igates or at
least don't always reach igates. This brings us to your next point...

> Then everyone could see how the network is "working".  To me, the lack of
> 2-way Igates in range of most digis is the #1 problem in APRS.

Agreed. Once this problem is solved, paths can be decreased,
alleviating problem #2: channel over-utilization.

> A brute force method might be to have some 2-way CZAR algorithm in the
> middle of the night, originate "messages" to each digipeater in the
> country.  If said Czar then sees the packet heard-on-RF then he can mark
> that digi's area (or nearby IGate) as being two way.
> Of course the digi is not "message capable" so it does not send an ACK,
> but the APRS-IS should be able to see if the local IGate sent the message
> to RF.?

The messages would need to originate on RF. If the message originated
from APRS-IS, it would be gated to RF as a 3rd party packet, and
therefore not passed by any receiving igates. If it did make it back
to an APRS-IS server, dupe checking would throw it out. If these
mechanisms were not in place, every message would loop forever between

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