[time-nuts] GPS through windows
Hal Murray
hmurray at megapathdsl.net
Tue Jun 5 05:24:30 UTC 2012
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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