[aprssig] IS-to-RF alternate proposal - 'marked beacons'

Georg Lukas georg at op-co.de
Fri Dec 30 12:07:58 EST 2011

* Andre <aprs at pe1rdw.demon.nl> [2011-12-30 10:56]:
> my direct range for home stations is about 50 km to 80 km and 2 hops
> can easely get me 150 km out, now if 500 km gives a 100% load on
> 9k6, 150km would probably still be beyond the acceptable load on 2
> meter.

You have to consider that by halving the radius you reduce the area (and
thus the potential number of data sources) to 1/4th. Thus, by going from
500km to 150km you reduce the potential traffic to 9% (which is still a
little too much for 1k2, but at least in the right order of magnitude).

> setting the range to half the next RGATE has the problem that
> they are not going to be evenly spread, it could be 10 km to the
> east and 50 km to the west and 30 km north, now what range do you
> have to set? 5 km would leave a huge gap to the west, 25 km would
> give a huge overlap to the east and probably overload the channel.

Yes, this (preventing duplicate injects) is something we have to worry
about instead of adding more unneeded complexity. However, it can only
be solved by either

 * providing complex geometric functions for rgate range filtering
   (which probably would need a google earth addon to configure the
   coverage polygon)

 * or tolerating duplicate injections by multiple rgates (which is maybe
   a possibility if they are both using a no-repeating path.

 * or, define an rgate priority, where low-priority rgates delay the
   packet to be injected and listen if it was already rgated on their
   local RF (this is complex and might go wrong in many ways)

 * or, as you suggested, define which one of the multiple igates should
   be an rgate as well, leaving the other ones for RF-to-IS only.

> I'm also wondering how you are going to define local, local on 80
> meter or Zugspitse  is a lot further then local on 23 cm simplex.
> Right now we appear to define local as the aloha circle or in most
> cases 2 hops, wich is not a circle either.

Of course it is. Defining arbitrary area filters is an easy thing in
software, but you can not burden an rgate operator with too much
complexity. Some of them already fail to make the simplest things
correct, like adding a > in front of the "status" packet. :(

73 de Georg DO1GL
APRSdroid - Open Source APRS Client for Android ++ http://aprsdroid.org/m
     ++ https://market.android.com/details?id=org.aprsdroid.app ++
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