The tunnel on Taylor Road, Newcastle, CA, which is the best candidate
for a tunnel on a road that may have been part of the old US Route
40.... as it officially ends in Utah now. :)
That tunnel runs ENE to WSW or therabouts...
0.103 km or 544.6 feet....
62 degrees 49 minutes from south to north....
Seems off axis unless the satellite is way off-axis.... but I had to use
a seriously off-axis sat once when I lived in CA.... Had to aim the
dish almost due east near the horizon...
We just renewed for her for another 3 years... She's happy, I'm happy.
Waveguide.... I don't know enough to hazard a guess.... But at a an
approx 13 centimeter wavelength, sat sigs can certainly travel down a
large tunnel if it enters at a small enough angle of incidence....
AND, maybe that water is helping contain the signal in the "guide".
#5.... cool to know.
73,
______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
On 4/15/2017 6:32 PM, Fred Jensen wrote:
> Well, one of the side benefits of this list ... lots of smart and
> knowledgeable people. A summary and then it can pass into the archive
> ...
>
> 1. The first of "my" tunnels is in Newcastle CA [between Auburn and
> Sacramento on the old US40 and Lincoln Hwy route] and was constructed
> sometime around the end of the 19th/beginning of the 20th centuries.
> It's not quite 1/4 mile long. There is no visible wire or radiax in
> it. The hill it runs thru is full of water and you get leaked on when
> driving thru it, even in summer.
>
> 2. In the early 80's, the company I worked for then had a contract to
> rehab the communications for the Bay Area Rapid Transit system. We
> used a 300 ohm twinlead with a hollow core about 2 1/2 in in diameter
> along the ceiling of the tunnels and underground sections. It was 150
> MHz land mobile stuff and the twinlead was fed from a combiner that
> put 5 or 6 transmitters into it [train control, fire, security, etc.]
> It worked very well. Aligning the combiners [which actually looked a
> bit like a still [:-) ] was a bear in the equipment spaces in the tube
> under SF Bay but it worked well. They also wanted 800 MHz simulcast
> throughout the service area, a requirement probably still waiting for
> a real solution.
>
> 3. Other than under bridges, in canyons, beside heavily forested
> roads, and in the garage, where it's obvious the path to the
> satellite(s) is blocked, we don't experience any XM drop outs. She's
> going to drop the subscription, it's expensive and my new Honda
> Ridgeline has become our travel vehicle, but she's had it since 2013.
>
> 4. I've wondered if there wasn't some sort of waveguide effect in
> tunnels. For BART, one of the many problems we had with simulcast was
> that it leaked into the tunnels, even as far as the bottom of the
> Transbay tube. I don't know the XM satellite frequencies but I
> thought they occupied some spectrum abandoned by the Cellphone industry.
>
> 5. [Bonus Factoid]: The pine forests of the Southeast US are opaque to
> 800 MHz.
>
> Thanks for all the ideas and peripheral info.
>
> 73,
>
> Fred ("Skip") K6DGW
> Sparks NV USA
> Washoe County DM09dn
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