[time-nuts] How can I measure GPS Antenna quality?

Attila Kinali attila at kinali.ch
Mon Nov 21 17:58:40 EST 2016

On Mon, 21 Nov 2016 08:22:50 -0800
jimlux <jimlux at earthlink.net> wrote:

> I'm not sure about whether an anechoic (which is really "hypoechoic") 
> chamber is going to get you the data you need.  Calibrating the chamber 
> to the needed level of accuracy might be harder than doing field 
> measurements.
>   sin(2 degrees) is 0.034, or -30dB.  So a spurious reflection that is 3 
> cm different path length (modulo wavelength) and 30 dB down will give 
> you a 1mm phase center error.  0.1 mm is -50dB.

Interesting. I haven't done the math, so I didn't think about that.
Yes, the reflections in the chamber would probably limit the resolution.

Now I wonder how the calibration data for mass produced geodetic antenna
are collected. I very much doubt they put them outside for a couple
of days to measure them exactly.

			Attila Kinali

Malek's Law:
        Any simple idea will be worded in the most complicated way.

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