[Elecraft] OT: Re: KPA500 mobile?

[Matt Zilmer]

I think that both XM and Sirius were/are using 2.2 GHzor thereabouts.  
It's not MSS territory, but it works if you have enough power behind it.

73,

matt W6NIA


On 4/15/2017 4:32 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
>
>
>
> On 4/15/2017 10:40 AM, Clay Autery wrote:
>> I would think it would depend almost entirely on the orientation of the
>> tunnel...   (and satellite reception azimuth).
>>
>> First, the longest of those two tunnels is only 425 feet or so. The
>> other is significantly shorter (southbound).
>> The tunnels are oriented generally north/south which is the preferred
>> direction IF you have to monitor geosynchronous satellite transmissions
>> from overhead...  sort of).
>> You are right on the edge of a large body of water, which while not
>> brine, has better conductivity than the soil around the lake.
>> Significant potential for reflections off the high ground on almost all
>> sides....
>>
>> Don't know where that first tunnel is, so I can't comment.  But if you
>> gotta hear in a tunnel.... those two would be great candidates...
>>
>> 73,
>>
>> ______________________
>> Clay Autery, KY5G
>> MONTAC Enterprises
>> (318) 518-1389
>>
>> On 4/14/2017 10:47 PM, Fred Jensen wrote:
>>> Semi-related curiosity regarding shielding.  My wife's car has
>>> Sirius/XM radio.  It usually loses contact with the satellite driving
>>> under Interstate bridges and the like.  Likewise in the garage.  OTOH,
>>> at our previous home there was a tunnel through a small hill, perhaps
>>> 1/4 mi long.  The XM worked fine through it. There are a pair of
>>> tunnels at Cave Rock next to Lake Tahoe through a granite mountain.
>>> XM works fine through them too.  Anyone know why?
>>>
>>> 73,
>>>
>>> Fred ("Skip") K6DGW
>>> Sparks NV USA
>>> Washoe County DM09dn
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>
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-- 
"A delay is better than a disaster."
-- unknonwn

Matt Zilmer, W6NIA
[Shiraz]