[aprssig] unusual Terrestrial APRS propagation

Brett Friermood brett.friermood at gmail.com
Mon Aug 31 19:47:07 CDT 2015


On Mon, Aug 31, 2015 at 6:38 PM, Paul Bramscher via aprssig <
aprssig at tapr.org> wrote:

> No errors in reasoning.  I indeed heard 2m "DX" (Kansas and elsewhere to
> Minnesota) -- but ONLY on 144.390 Mhz.  If 2m was genuinely open to
> tropo ducting, etc. it wouldn't manifest solely on that freq.  This was
> in the daytime over the weekend.  If I truly had a 300-400 mile range on
> 2m, broadly speaking, there would have been many distant phone
> conversations elsewhere on 2m.  Instead, there were none at all.
>
> Likely someone was just re-TX'ing internet traffic locally.


The entire VHF High band has been very wide open the last couple days.
Public Safety systems around here have been experiencing extreme
interference from the enhanced propagation to the point of making some
repeaters unusable. I was hearing so much differing traffic it was hard to
even attempt to figure out who I was hearing.

I heard a number of distant repeaters, and a few stations on 146.52,
however I would agree that 2m was very quiet. I'm sure this was mainly from
few operators being on the air, though, and definitely not from the band
not being open.

As for that site, as I understand it it takes a feed off the -IS and
somehow processes it to determine active paths between digipeaters. As
Stephen mentioned we don't know exactly how that processing is done, so we
really don't have a complete picture. We also don't get the complete
picture because any system that attempts to do so is inherently flawed if
using an APRS-IS feed because of the fundamental structure of the -IS. A
separate network would need to be used to bypass the duplicate filtering of
the APRS-IS and generate a more accurate depiction of the current
propagation situation.

Brett KQ9N
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