[aprssig] 30M APRS and digipeaters...
andrewemt at hotmail.com
Thu Jul 12 22:35:23 EDT 2012
Gee, that routing concept sounds exactly like the original raw AX.25 packet concept with explicitly addressed digipeating, before anybody invented generic aliases, way back in the early 1990's. ;-)
The whole problem with that idea is knowing the available explicit paths. People published connectivity charts then (I remember seeing maps of the entire EASTNET northeast United States VHF/UHF AX.25 packet net in 1997), but the paths were fairly static; on HF, the paths would change too frequently for static webpages or hard-copy.
Perhaps the stations could report their directly-heard "adjacent" stations in their beacons.. We have enough computer power now to build connectivity maps dynamically and derive routes from them (good old Routing Information Protocol from the Internet). The only issue now is the size of the beacon messages as the heard lists grew and deciding how long until heard history expires. On the other hand, combining network adjacency and geographical position data would provide a near-real-time map of.propagation as a side-effect.
Actually sounds like kind of a fun project. Anybody want to try to define a message format for the routing beacons?
Andrew Pavlin, KA2DDO
From: Stephen H. Smith
To: aprssig at tapr.org
Sent: Jul 12, 2012 9:07 PM
Subject: Re: [aprssig] 30M APRS and digipeaters...
On 7/12/2012 6:37 PM, Bob Bruninga wrote:
> I have always personally thought it would be useful to have a few MEGA
> STATION digipeaters but as soon as we open that pandora's box, EVERYONE
> becomes a digi. That is why I had hoped that the "mega stations" of most
> advantage to operators would be obvious to the operators and then people
> would use them (not generically) but by specific callsign, which is OK in my
How do you define "MEGA-STATIONS"? Unlike VHF the distinction between
fill-in and true WIDE is essentially non-existent.
Being up on a hill really doesn't make your sky wave coverage significantly
greater, as it does for line-of-site on VHF. You are unlikely to encounter
antenna systems with 10 dB more gain than most stations on HF. (Unless you are
a big-gun contest or DX station with a full-size 30M yagi on a 75' tower.)
[I've been dreaming of building a crossed-dipole turnstile-type antenna for
30M, complete with the 1/4-wave phasing line between the dipoles, that would
optimize NVIS as well as long-haul propagation.]
The stations heard strongly by any given user (i.e. your potential mega
stations) will vary wildly with the user's location, time of day, time of year
and time in the solar cycle. At one time or another, virtually anyone on
30M may become a "mega station" to another particular station.
I think it would far more useful to just try to get everyone to enable
digipeating under their OWN CALL ONLY so that users can then exploit any
station that happens to appear as "mega" to them at a given moment.
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.net
Build This Compact 30-Meter Magnetic Loop Antenna
HF APRS Operation
"APRS 101" Explanation of APRS Path Selection & Digipeating
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