[aprssig] APRS in caves! (mammoth map) & HF

[Andrew P.]

Hmmm.... The old LORAN-C navigation system used 90 to 110 kHz. Too bad they shut it down a couple of years ago.

So, in theory, we could build some LF transmitters synchronized by GPS on the surface and carry a LORAN receiver underground. Considering how old the LORAN-C technology was, it shouldn't be hard to re-implement small versions of the transmitters with modern hardware. But it would be a lot of work, and the receivers are hard to find (I unloaded mine at a hamfest 13 years ago).

Just my $.02.

Andrew Pavlin, KA2DDO
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Greg Dolkas <ko6th.greg at gmail.com>
Date: Tue, 20 Nov 2012 04:06:12 
To: <aprssig at tapr.org>
Subject: Re: [aprssig] APRS in caves! (mammoth map) & HF

HF penetrates wet rock?  Cool.  Now if we can figure out a way to correlate multiple HF signals, maybe build a poor-man's underground-capable GPS?  Sort of like what SSTV is to NTSC...

Ok, crazy thought.  But so far the only location information you're going to get is either a manually entered coordinate, or a guess based on your path to the exit node.
 
Greg  KO6TH



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