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

["Björn Gabrielsson"]

Also consider phase wind up.

   http://www.navipedia.net/index.php/Carrier_Phase_Wind-up_Effect

Sure there are also some papers on rotating antennas.

http://www.researchgate.net/profile/Simon_Banville/publication/257945217_Antenna_Rotation_and_Its_Effects_on_Kinematic_Precise_Point_Positioning/links/0deec5266c9c6ac718000000.pdf

"Due to the polarization of GPS signals, carrier-phase
measurements made by GPS receivers are affected by the
orientation of the antenna. "

"On the other hand, code measurements are not affected by
this effect. "

--

    Björn


> I'm curious whether it would need 360 degree rotation? Would simply
> cycling about 120 degrees on the end of a short arm be just as good and
> could be done without a rotary joint? I understand that now the RX is
> moving but within a small radius would it be unbearable? Or would 300
> degrees around the axis be sufficient?
>
> From Tom Holmes, N8ZM
>
>
>> On May 7, 2015, at 11:49 AM, John Ackermann N8UR <jra at febo.com> wrote:
>>
>> Just put the GPS antenna, receiver, battery, and a low power RF
>> transmitter modulated by the PPS (wide bandwidth = fast edge time) on
>> the turntable, then use an appropriate receiver to demodulate the PPS
>> and feed it to the rest of the system.  Put the RX antenna directly
>> above (or below) the turntable so the path length remains close to
>> constant.  Using FM might also remove Doppler effects from the received
>> pulse.
>>
>> On 5/7/2015 11:18 AM, Tom Van Baak wrote:
>>>>> I wonder if anybody ever made a rotating GPS antenna to average out
>>>>> the
>>>>> X-Y phase-center offset ?
>>>
>>>> Of course, this does not really work with a gps antenna, unless you
>>>> put the whole receiver onto the rotary table. But then you shift
>>>> the problem onto the PPS output (note: amplitude noise translates
>>>> into phase noise).
>>>
>>> Attila,
>>>
>>> My thought was to put PHK's proposed experiment entirely on the
>>> rotating table: antenna, receiver, local Cs standard, laptop, and
>>> battery. 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)
>>>
>>> /tvb
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