[aprssig] unusual Terrestrial APRS propagation

Robert Bruninga bruninga at usna.edu
Wed Sep 2 08:09:13 EDT 2015

Another possible “experiment” is to listen to the 435.350MHz downlink from
PSAT which is relaying down ANY PSK31 signals heard on ten meters
(28.120).  An interesting study would be to look for stations heard by the
satellite OVER the horizon from its current position.

But when it is over the usa and you can hear the UHF downlink then you are
in the same footprint as most of the senders, but if you look at their
positions AND the satellite footprint, in real time, it should be
interesting to see who is getting in frokm outside the footprint.

Bob, WB4aPR

*From:* aprssig [mailto:aprssig-bounces at tapr.org] *On Behalf Of *Ev Tupis
via aprssig
*Sent:* Wednesday, September 02, 2015 7:07 AM
*To:* pfbram at comcast.net; TAPR APRS Mailing List
*Subject:* Re: [aprssig] unusual Terrestrial APRS propagation

Indeed.  That's a good example of knowing how to interpret what is being

On the web-map, when hovering over a "blob" and clicking you are presented
with vectors that represent the direct routes that were being traversed
along with an estimate of the area around those vectors that may
(conjecture) also be experiencing enhancement.

It is the basis for that conjecture that is not stated on the web site.
Therefore the site includes some "fuzzy" logic in addition to actual data.

On the local rig, apparently the APRS network loses absolute endpoint
determination so as long as you are hearing an IGate that is participating
in the opening there is an assumption that your station is an endpoint?
Again, that makes the data simply an "indicator" rather than an
"absolute".  Still...it is enough to motivate DX chasers and experimenters
to actually pick up a mic and actually call CQ themselves.

Here's where I'll again advertise "The PropNET Project" (
http://www.PropNET.org) where every station is an endpoint and constantly
probes 10 meter propagation by individually IDing (using APRS [GR##id]
format) and when another PropNETer decodes the transmission a true-plot
vector is generated and placed on the map.  If there is a vector to/from
your station you can be assured that your station was an endpoint in the
communication circuit.

The *next* revision of the client software will include text alerting from
your own station...to alert you that YOUR station is experiencing 10-meter
DX.  As an aside, each client has a "robot" that will reply to a human
operator if interrogated; which is a GREAT feature if the band is open as
evidenced by the presence of PropNET ID's but nobody is around to QSO with.

Again, this is very powerful as it does not rely on derivative data from
other stations that may be better equipped and experiencing an opening.

There's more, but you get the idea.  The PropNET project (APRS' cousin)
brings another level of utility and precision to the hobby.

Anyway..."back to the regularly scheduled program, already in progress". :-)


Ev, W2EV


*From:* Paul Bramscher via aprssig <aprssig at tapr.org>
*To:* pfbram at comcast.net; TAPR APRS Mailing List <aprssig at tapr.org>
*Sent:* Tuesday, September 1, 2015 9:38 PM
*Subject:* Re: [aprssig] unusual Terrestrial APRS propagation

I checked the paths of some of the stations recorded by my rig and it looks
like a nearby station, N0HOY-10, was bringing in some distant 2m traffic
mid-late August.  Some in the 75-200+ mile range (as seen on aprs.fi also).

73, KD0KZE / Paul


*From: *"Paul Bramscher via aprssig" <aprssig at tapr.org>
*To: *"Robert Bruninga" <bruninga at usna.edu>, "TAPR APRS Mailing List" <
aprssig at tapr.org>
*Sent: *Tuesday, September 1, 2015 12:25:23 PM
*Subject: *Re: [aprssig] unusual Terrestrial APRS propagation

Wow -- I thought it too unusual, didn't believe what I was seeing.  I wish
I'd left the igate on -- will put it into full-time service tonight.  I
knew there was at least some enhanced propagation.  Direct hits from
digipeaters 50+ miles away that I could confirm and some apparently much
further.  I had to zoom APRSISCE's map outward, the lines drawn were much
longer than normal.

The D710 was giving its trademark blip, a slightly different sound, on a
periodic basis for hearing "DX" stations.  I'll have to set aside HF for
awhile and experiment with 2-6m if this is still going on.  As for not
hearing other 2m phone stations for the short time I looked, I was part of
the problem myself: I only listened, but didn't call CQ.

73, KD0KZE / Paul


*From: *"Robert Bruninga via aprssig" <aprssig at tapr.org>
*To: *"TAPR APRS Mailing List" <aprssig at tapr.org>
*Sent: *Tuesday, September 1, 2015 10:07:06 AM
*Subject: *Re: [aprssig] unusual Terrestrial APRS propagation

I agree, there is no better tropo indicator (or meteorscatter) detection
system than APRS.  With 20,000 transmitters all over the country running
continuously, even a few seconds of enhanced propogation will appear on the
APRS network while the Voice Operators may be waiting72 hours for the

Of course, someone in a rural area that can only hear one local digi will
hear a LOT more tropo than someone in a busy APRS area where the channel is
always busy…

In fact, people is remote APRS areas my feel lonely with the lack of
activity, but any activity they DO see can be very exciting with enhanced
propogation…  And now is the season for tropo.  I hear it every day in
Maryalnd in the mornings when I hear the FM radio stations all jumbled
coming to work…   bob

*From:* aprssig [mailto:aprssig-bounces at tapr.org] *On Behalf Of *Ev Tupis
via aprssig
*Sent:* Tuesday, September 01, 2015 9:20 AM
*To:* TAPR APRS Mailing List
*Subject:* [aprssig] unusual Terrestrial APRS propagation

*Sent:* Monday, August 31, 2015 8:47 PM
*Subject:* Re: [aprssig] unusual Terrestrial APRS propagation

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.

Hi Paul

It is common for people to trust only their own observation.  In this case,
the lack of distant phone conversations on other frequencies is likely
because there were no phone conversations taking place at the instant that
you scanned for them.

What is being observed here is a classic tropospheric anomaly that occurs
when a high pressure system sets up on the East Coast USA.  The phenomenon
has been documented and observed for decades.  In fact, when it occurs over
the Western Atlantic, it is referred to as a "Bermuda High" and hams that
are East of the Appalachian Mountains benefit from it nicely.

The use of RF that is "always on" (APRS, WX Radar, etc) allows for easier
visualization of the event.

I've attached three graphics to illustrate.  They were just captured a
moment ago and are...

Untitled00 = 144-MHz APRS-based propagation maps

Untitled01 = 9-GHz NWS Radar propagation maps

Untitled03 = NWS surface maps

The "geometry" of the inversion layer determines what frequencies it will

By the way...see that "green patch" in the NWS map?  That indicates a
MASSIVE inversion in progress.  If you were to scan for 10 GHz ham signals,
you'd hear "ssssssssssssss" only because I doubt there are any QSO's taking
place. :-)

'hope this is helpful.

Kind regards,

Ev, W2EV

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