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Bob:<br>
I can report similar experiencess, although contrary vhf vs uhf.<br>
<br>
Specifically, our 2m and 70cm repeaters in Hampton, VA were on the
top of the Chamberlin hotel, on Ft. Monroe, adjacent the Hampton
Roads Bridge/Tunnel. I had noted for years that the 2m propogated
several hundred feet int the tunnel at each end. I speculated that
it was a waveguide effect, and predicted deeper coverage when we put
the UHF on. Sure enough, you could talk on the UHF repeater, <i>all
the way through the tunnel</i>, unless there were a bunch of large
trucks in the tunnel.<br>
<br>
I suspect that your different observations relate to waveguide
conductivity --- the metal in the walls, or at least rebar in the
concrete, had to be more conductive than the rock you were in.<br>
<br>
All good fun!!<br>
<br>
73,<br>
Jim<br>
<a class="moz-txt-link-abbreviated" href="mailto:wb4gcs@amsat.org">wb4gcs@amsat.org</a><br>
<br>
<div class="moz-cite-prefix">On 12/9/2012 8:59 AM, Robert Bruninga
wrote:<br>
</div>
<blockquote
cite="mid:CALdCfNJizSSPG3RuC1PyAHoanYxHk1GVTjU95ZzEPXrYovVmBg@mail.gmail.com"
type="cite">
<blockquote type="cite">
<pre wrap="">Bob. I discovered years ago installing radio comms on large cruise ships
that VHF radio signals propagated up down and through the ships where
the passages acted as waive guides. The caves possibly do the same.
</pre>
</blockquote>
<pre wrap="">
Good point. During my 3 year tour on the LCC-19 in Westpac in the
early 80's, I hooked up an autopatch to an unused telephone in a radio
room and then carried my HT. The XO could call me anywhere on that
phone (even if I was in the rack). My longest phone call was over 75
miles from the top of Mt FUJI back to the wardroom to make
reservations for supper.
The waveguide theory works because everything is a conductor. From
what I read, caves operate more like perfect dummy loads since the
walls are more like the absorbers in an anechoic chamber.
Even if the range is only a hundred feet, some may wonder why bother.
The reason is that some caves, just getting in that first 100' may
take hours. THen once in, they can walk around freely. Being able to
communicate from a base camp on the inside to the outside is valuable
during cave rescue.
Come to think about it, a few hundred feet of light wire to link
between two digipeaters through very circuitous crawl passages might
also be a handy tool in the tool box.
Also, come to think about it, for carrying these digis, I need to come
up with a lighter weight housing instead of 4" PVC!
Bob, WB4APR
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</pre>
</blockquote>
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