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

[Bob Camp]

Hi

The “put the antenna up and rotate it to see what happens” experiment has indeed been done. The
objective was not correcting the antenna’s issues, but validating that their model of the antenna’s phase
center was correct. They were trying to see if anechoic chamber data really gave correct answers in
free space. 

Bob

> On May 7, 2015, at 5:02 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> In message <554BC3C3.7090305 at earthlink.net>, Jim Lux writes:
> 
>>>> I wonder if anybody ever made a rotating GPS antenna to average out the
>>>> X-Y phase-center offset ?
>>> 
>>> There is a severe mechanical problem with that. Moving contacts
>>> are very hard to keep electrically stable
> 
> You wouldn't need any of that because there is no need for continous
> one way rotation, a piece of coax would do just fine.
> 
> Simply rotate the antenna forth an back between 0 and 360 degree
> compas.
> 
> Let the coax drop from the antenna to a horizontal coil so
> that the stress is converted from torsion to longitudal tension
> and you'de don.
> 
> Doing continous rotation may not even be a good idea, rotating
> 90 degrees every hour is probably a better idea from a processing
> point of view, as that wouldn't need special software.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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