[FOSS-GPS] Quadrifilar vs patch? Choke rings?

[Homan, Thomas]

The best antenna is the one that the receiver is designed to use in the environment it was designed to be used in. Any other answer requires testing of the various equipment combinations in a controlled environment to determine which is 'best'. Connecting an unknown/unrecognized GPS antenna to a receiver is a fantastic way to introduce an artificial source of positional noise. 

Every model of GPS antenna behaves slightly differently in the presence of a GPS signal, mainly in the reported Z axis but X and Y have minor components as well on occasion. Google 'GPs antenna phase center modeling' if you're interested. This error must be modeled out if high precision work is going to be accomplished. If the receiver recognizes the specific model of the patch antenna but has no setting for the quad antenna then the patch will work better or at least within published tolerances and vice versa. The same thing applies to the choke ring.

Hope this helps 

Tom
-----Original Message-----
From: foss-gps-bounces at lists.osgeo.org [mailto:foss-gps-bounces at lists.osgeo.org] On Behalf Of Danny Miller
Sent: Tuesday, June 21, 2011 11:02 AM
To: Open Source GPS-related discussion and support
Subject: Re: [FOSS-GPS] Quadrifilar vs patch? Choke rings?

I understand the purpose of the choke ring in snubbing multipath.

Protection of a choke ring and/or quad antenna in a rover is not a major 
problem.  I can contain and protect it.  The rover has room for a choke 
ring.

My primary question is, if a choke ring is not used, is the quad or 
patch antenna better for RTK?  If a choke ring IS used, it is better to 
use with a quad or patch antenna with RTK?

I'm still not sure what that relative difference is, and which one comes 
out ahead for RTK.

Danny

On 6/21/2011 9:49 AM, Homan, Thomas wrote:
> Choke Ring antennas are best utilized in areas of high multipath (signal reflections.) The fins are precision tuned RF elements that, if damaged, can cause significant antenna performance degradations.
>
> For our applications (cm level land surveying) we utilize a choke ring only on fixed locations like CORS stations that are not likely to hit the ground or other objects. Field work relies on patch antennas that can take more abuse. Typically our base has a large ground plane and the rover has a smaller one.
>
> As for your antenna WITH choke question, I don't have empirical evidence but would expect performance to be enhanced with both antennas but the relative difference to remain the same.
>
> Tom
>
> -----Original Message-----
> From: foss-gps-bounces at lists.osgeo.org [mailto:foss-gps-bounces at lists.osgeo.org] On Behalf Of Danny Miller
> Sent: Monday, June 20, 2011 10:59 PM
> To: Open Source GPS-related discussion and support
> Subject: [FOSS-GPS] Quadrifilar vs patch? Choke rings?
>
> I have a pair of quad antennas, and a patch.
>
> I don't have a choke ring for either one, although I'm considering
> building one, I don't have them now.  I have a CNC mill and it would be
> primarily an issue of getting aluminum billet stock.
>
> Which is better for RTK?  I was just told that the quad without a choke
> ring may not be as good as a patch without the choke ring- in which case
> I can use a pair of patches.
>
> WITH choke ring designs, are the patches or quad antennas better?
>
> The rover may climb a 30 deg or so slope at times.  There will be some
> tilting of the antenna.
>
> Thanks,
> Danny
> _______________________________________________
> This message is sent to you from FOSS-GPS at lists.osgeo.org mailing list.
> Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription
> For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
> _______________________________________________
> This message is sent to you from FOSS-GPS at lists.osgeo.org mailing list.
> Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription
> For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
>

_______________________________________________
This message is sent to you from FOSS-GPS at lists.osgeo.org mailing list.
Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription
For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS