[aprssig] unusual Terrestrial APRS propagation

pfbram at comcast.net pfbram at comcast.net
Tue Sep 1 12:25:23 CDT 2015


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 

----- Original Message -----

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 weekend. 



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 affect. 





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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