[FOSS-GPS] Good antenna

[Christopher S.]

A friend and I did a bunch of research on this several years ago and our
conclusion was that the best single frequency antenna which we could build
ourselves was the "shorted annular patch" design. (SAP)

See
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.180.3985&rep=rep1&type=pdf

However, it needs a 90 degree hybrid which one needs to design for on the
PCB. One should also put an LNA and SAW filter there for out of band signal
rejection.

Anybody who knows their way around Eagle or Kicad should be able to make
one, but its not a good project for a beginner.  An alternative which can
work well for multi-constellation use is a two or four arm archimedian
spiral, logarithmic spiral or "pinwheel" style antenna. (as in Novatel
antennas)  The #1 consideration is keeping the phase center of the antenna
in the exact same place for different frequencies which means four arms are
better than two and the antenna should be perfectly flat. (it needs to be a
PCB) All of the four arm antennas need a 90 degree hybrid for phasing.

Building our own antennas at that stage seemed to be more trouble than it
was worth at that moment but its still something which I would like to
explore.

The SAP looks like a very good single frequency antenna.

Multiconstellation use - good performance on multiple frequencies with the
same phase center is much more of an engineering challenge. I just have a
GPS L1 only receiver so for now I've been using  and have had fairly good
results with a quadrifilar helix timing antenna made by PCTEL (also sold by
Lucent)

Its the sixth in Professor Takasu's list of antennas linked from his home
page.  http://gpspp.sakura.ne.jp/anteva/anteva.htm

These specific antennas are often available on ebay for around $30-40,
sometimes less (I got one for $22 plus $9 shipping).  They look like a
gnomes' hat, they are conical.

The article is in Japanese but its very much worth translating and reading.


On Tue, Mar 11, 2014 at 1:52 AM, mazahirp <mazahir.poonawalla at gmail.com>wrote:

> Hi All,
>
> Can anyone help me to buy a good antenna which can give me accurate
> results.
> I am using u-blox 6T as receiver and RTKLIB.
> Currently I am using GILSON GPS active antenna on both the receivers (base
> and rover). I am not an expert into antennas so I wanted to know if this
> antenna is good enough? If not, which one should I go for. My budget is
> around $100.
>
> Thanks for the help.
>
> Cheers,
> Max
>
>
>
> --
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