[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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