<html><body><div style="color:#000; background-color:#fff; font-family:Courier New, courier, monaco, monospace, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1441112402151_2858" style="font-family: Courier New, courier, monaco, monospace, sans-serif; font-size: 16px;"><div id="yui_3_16_0_1_1441112402151_2857" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"><div id="yui_3_16_0_1_1441112402151_2856" dir="ltr"><font id="yui_3_16_0_1_1441112402151_2855" face="Arial" size="2"><b id="yui_3_16_0_1_1441112402151_4040"><span id="yui_3_16_0_1_1441112402151_4039" style="font-weight: bold;">Sent:</span></b> Monday, August 31, 2015 8:47 PM<br> <b id="yui_3_16_0_1_1441112402151_4042"><span id="yui_3_16_0_1_1441112402151_4041" style="font-weight: bold;">Subject:</span></b> Re: [aprssig] unusual Terrestrial APRS propagation<br> </font> </div> <div id="yui_3_16_0_1_1441112402151_2867" class="y_msg_container"><br><div id="yiv0416169969"><div id="yui_3_16_0_1_1441112402151_2866"><div id="yui_3_16_0_1_1441112402151_2865" dir="ltr"><div id="yui_3_16_0_1_1441112402151_2864" class="yiv0416169969gmail_extra"><div class="qtdSeparateBR"><br><br></div><div class="yiv0416169969yqt4229474359" id="yiv0416169969yqtfd62827"><div id="yui_3_16_0_1_1441112402151_2863" class="yiv0416169969gmail_quote">On Mon, Aug 31, 2015 at 6:38 PM, Paul Bramscher via aprssig <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:aprssig@tapr.org" target="_blank" href="mailto:aprssig@tapr.org">aprssig@tapr.org</a>></span> wrote:<br clear="none"><blockquote id="yui_3_16_0_1_1441112402151_2862" class="yiv0416169969gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">No errors in reasoning. I indeed heard 2m "DX" (Kansas and elsewhere to<br clear="none">
Minnesota) -- but ONLY on 144.390 Mhz. If 2m was genuinely open to<br clear="none">
tropo ducting, etc. it wouldn't manifest solely on that freq. This was<br clear="none">
in the daytime over the weekend. If I truly had a 300-400 mile range on<br clear="none">
2m, broadly speaking, there would have been many distant phone<br clear="none">
conversations elsewhere on 2m. Instead, there were none at all.<br clear="none">
<br clear="none">
Likely someone was just re-TX'ing internet traffic locally.</blockquote><div id="yui_3_16_0_1_1441112402151_2868"><br clear="none"></div>Hi Paul<br></div></div></div></div></div></div><div id="yui_3_16_0_1_1441112402151_3264">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.</div><div id="yui_3_16_0_1_1441112402151_3280"><br></div><div dir="ltr" id="yui_3_16_0_1_1441112402151_2974">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.<br></div><div id="yui_3_16_0_1_1441112402151_2997"><br></div><div id="yui_3_16_0_1_1441112402151_3013">The use of RF that is "always on" (APRS, WX Radar, etc) allows for easier visualization of the event.<br></div><div id="yui_3_16_0_1_1441112402151_3014"><br></div><div id="yui_3_16_0_1_1441112402151_3076">I've attached three graphics to illustrate. They were just captured a moment ago and are...<br></div><div id="yui_3_16_0_1_1441112402151_3015"><br></div><div id="yui_3_16_0_1_1441112402151_3031">Untitled00 = 144-MHz APRS-based propagation maps<br></div><div id="yui_3_16_0_1_1441112402151_3033">Untitled01 = 9-GHz NWS Radar propagation maps<br></div><div id="yui_3_16_0_1_1441112402151_3072">Untitled03 = NWS surface maps</div><div id="yui_3_16_0_1_1441112402151_3135"><br></div><div id="yui_3_16_0_1_1441112402151_3817">The "geometry" of the inversion layer determines what frequencies it will affect.<br></div><div id="yui_3_16_0_1_1441112402151_3833"><br></div><div id="yui_3_16_0_1_1441112402151_3136">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. :-)</div><div id="yui_3_16_0_1_1441112402151_3438"><br></div><div id="yui_3_16_0_1_1441112402151_3440" dir="ltr">'hope this is helpful.</div><div id="yui_3_16_0_1_1441112402151_3441" dir="ltr"><br></div><div id="yui_3_16_0_1_1441112402151_3442" dir="ltr">Kind regards,</div><div id="yui_3_16_0_1_1441112402151_3443" dir="ltr">Ev, W2EV</div><div id="yui_3_16_0_1_1441112402151_3444" dir="ltr"><br></div></div> </div> </div> </div></body></html>