<html><head></head><body bgcolor="#FFFFFF">A few hundred feet?  Really?  One reference I found measured about 0.7 dB/foot attenuation in limestone at 1.65 MHz. At 300' you're into moonbounce-like path loss on 80m, which isn't going to work with FT-817s using FM. Shorter distances might work -- how deep are the tunnels?<br><span></span><br><span> -Les W6VN</span><br><span></span><br><span></span><br><span>On Nov 19, 2012, at 6:03 PM, Robert Bruninga <<a href="mailto:bruninga@usna.edu" x-apple-data-detectors="true" x-apple-data-detectors-result="2">bruninga@usna.edu</a>> wrote:</span><br><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>HF VERTICAL LINKS:  I just realized that since HF penetrates a few</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>hundred feet vertically, we can use HF to link up to the surface every</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>7 hops or so.  Just an FT-817 with a DIPOLE above and below ground</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>hooked to a TNC can provide the link  Once above ground, then hops</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>continue on VHF.</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Each vertical link takes up 2 hops, but it sure beats having to do 14.</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>We need some people experimenting with HF packet FM (with squelch) on</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>80m (below ground since it would not be legal above ground)...  I</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>gotta do some research on HF links...</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Also this gets more hams involved.  SOme hams not prone to caving, can</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>man the top side stations.  One of the HF links will be right in the</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Lobby of the hotel and since it has WIFI, then that can be our IGATE!</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>With this map, there's no easy way to separate the above-ground</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>elevation contours from the cave tunnels.</span><br></font></blockquote></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Not sure I follow.  The tunnels are dark black.  Everything else is</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>color.  Its too early to start a huge investmnt in manually crossing</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>over the data to a vector file until I find out "which" path is the</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>MAIN CAVE.  The big portions are easy, but there are many places where</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>there are multiple thin lines.</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Also, is this just the first level of the cave, or is it</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>several vertical levels drawn together?</span><br></font></blockquote></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>all 6 levels.  So crossing black lines do not necessarily mean a connection.</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Bob, WB4APR</span><br></font></blockquote><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Andrew Pavlin, KA2DDO</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>------Original Message------</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>From: Robert Bruninga</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>To: <a href="mailto:APRS@yahoogroups.com" x-apple-data-detectors="true" x-apple-data-detectors-result="3">APRS@yahoogroups.com</a></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Cc: <a href="mailto:aprssig@tapr.org" x-apple-data-detectors="true" x-apple-data-detectors-result="4">aprssig@tapr.org</a></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Sent: Nov 19, 2012 4:58 PM</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Subject: Re: [aprssig] [APRS] APRS in caves! (mammoth map)</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Mammoth cave underlay on local terrain map is now complete.  The map has a</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>LAT/LONG grid on the sides so one can pinpoint one's position into the HT</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>underground to the same 0.01 Minute of LAT/LONG as on the surface.</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>See <a href="http://aprs.org/cave-link.html" x-apple-data-detectors="true" x-apple-data-detectors-result="6">http://aprs.org/cave-link.html</a></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>So far, none of the modern clients seem to do GIF or JPG files.  But as we</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>get closer to the <a href="x-apple-data-detectors://7" x-apple-data-detectors="true" x-apple-data-detectors-result="7">2 March 2013</a> test, maybe someone can develop a vector</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>overlay for the main passage.  Can YACC or APRSIS32 do APRS Overlays?</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span>Bob, WB4APR</span><br></font></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><font class="Apple-style-span" color="#000000"><span></span><br></font></blockquote></blockquote><div><br></div></body></html>