[aprssig] 30M APRS and digipeaters...

Bob Bruninga bruninga at usna.edu
Fri Jul 13 08:50:05 EDT 2012

> The whole problem with (explicit digipeater) idea 
> is knowing the available explicit paths.

You look at your screen and you SEE who is the strongest and who has been
heard the most reliably.  This is ham radio, I think, and I assume there is
an operator.  

You seem to be talking about continued unattended blind transmission via
every possible digipeater all the time 24/7, then that is exactly the QRM
mess we are trying to avoid.

> Perhaps the stations could report their directly-heard 
> "adjacent" stations in their beacons.. 

The can!  That is fundamental to APRS.  Its called a HEARD QUERY.  If you
hear a station, you can just send a HEARD QUERY and find out who and how
often he has heard other stations.

> The only issue now is the size of the beacon messages 
> as the heard lists grew and deciding how long until heard history expires.

In APRS dos I think it was maybe 6 hours in general, though I woiudl
receommend 4 hours or less for HF.

> 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.

You bet.  I think all the tools are in place.  And with IGates listening all
over, it should be fun to do.


------Original Message------
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
> book.

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
antenna systems with 10 dB more gain than most stations on HF. (Unless you
a big-gun contest or DX station with a full-size 30M yagi on a 75'
[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
and time in the solar cycle.      At one time or another, virtually anyone
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
Skype:        WA8LMF
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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