[time-nuts] GPS through windows

Chris Albertson albertson.chris at gmail.com
Tue Jun 5 01:36:07 EDT 2012


Part of the problem of using a window would remain even if the glass where
removed.  This is the antenna can not "see" the entire sky from a window.
 You can do "ok" if the window faces South (assume you are in the Northern
Hemisphere)  With a good timing GPS receiver you only need to see a very
small number of satellites.  So the window can work but you would get
better results if you can see the horizon all 360 degrees around.

Is there no access to the roof?  What about the roof of some other
building.  Place the antenna and the receiver on the roof and send the data
back via some kind of link.

Using a higher gain antenna might (make up for any attenuation cause be
coating on the glass. So it might work.



On Mon, Jun 4, 2012 at 10:24 PM, Hal Murray <hmurray at megapathdsl.net> wrote:

>
> Does window glass have significant attenuation at GPS L1?
>
> What if it's a big window on a modern green office building and has some
> sort
> of coating/content to reduce IR transmission?
>
> Google found an (expensive) paper from IEEE where the abstract said:
>  At average, about 30 dB attenuation is observed from 800 MHz to 6 GHz
> so I assume the answer is mostly "sure does".
>
> Does anybody have more info?  Is there a rule of thumb?  (maybe X dB, or X
> dB/inch)  Does it vary wildly from brand to brand of glass?
>
> ----------
>
> Context is that I took some low cost consumer GPS toys when I visited a
> friend who had recently moved into a new office building.  He's on the 4th
> floor, well above anything else on that side, so we had a clear view for
> half
> of the sky looking West or slightly North of West.
>
> We tried a SiRF III and a Sure demo board.  I had forgotten to update the
> Sure clock the night before so it was having a hard time getting off the
> ground.  We took everything outside where they locked up within a few
> minutes.  Back inside with the antennas on a window sill, both just barely
> worked some of the time.
>
> The glass below the sill was a different color, slightly less yellow.  We
> tried the lower (floor level) sill but didn't notice any difference.  That
> wasn't a serious test with numbers and error bars, but we probably would
> have
> noticed if it had suddenly started working much better.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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-- 

Chris Albertson
Redondo Beach, California



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