[time-nuts] Important parameters for a GPS/GNSS antenna

[Attila Kinali]

On Thu, 7 May 2015 08:18:05 -0700
"Tom Van Baak" <tvb at LeapSecond.com> wrote:

> Attila,
> 
> My thought was to put PHK's proposed experiment entirely on the rotating 
> table: antenna, receiver, local Cs standard, laptop, and battery.

Then you have to be carefull, that the rotation does not modulate
the reference. I am pretty sure rotation would at least shift the
Cs frequency (atoms fly in an arc) and thus any change in rotation
speed would be visible in the measurement. An vapor cell Rb might
be better for that case.

The periodic shift of the magnetic field would also need to be considered.

Maybe the best way would to put the GPS receiver onto the rotating table
as well, modulate some laser which points down the middle of the central
shaft, and extract that using a small aperture and a photodiode.
(The aperture to make sure that only light commming down the exactly
in the center is used). This way the reference would be at a stable
place, yet the transfer of the signal would be quite stable.

> You could
> also get interesting data if you slightly offset the antenna from the center. 
> It would make the ultimate GPS Spirograph. (for those of you under 40, 
> http://en.wikipedia.org/wiki/Spirograph will explain)

Hehe. That would be really cool!

			Attila Kinali

-- 
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