[time-nuts] Improving performance of a GPS antenna...?

[bg at lysator.liu.se]

Jim,

> There's a new "choke ring" style antenna (patented, of course, and they
> deserve it) which uses spikes instead of solid rings. And, they wrap the
> choke over a hemispherical surface as opposed to on a plane.
>
> Much tougher to design and fabricate  (no buying sets of cake pans any
> more), but if you want to differentiate yourself from the horde of
> Ashtech/D&M style chokes, you need something.

There are actually two new designs one coming from Novatel where the
"rings" are put in a pyramide/cone. The "rings" are also shopped of into
small ring segments.

     http://webone.novatel.ca/assets/Documents/Papers/GNSS-750.pdf

The other, coming as a response to the Novatel antenna, is from Topcon
which uses spikes.

   http://www.topconpositioning.com/products/gps/antennas/pn-a5
   http://www.topconpositioning.com/sites/default/files/PN-A5_white_paper.pdf


> At JPL, we also use what's called a "helibowl" for ground testing.  It's
> a quad helix or other element inside a bowl.  Doesn't have much pattern
> close to the horizon.  I suspect you can google and find more details,
> or if people are interested, I can ask around about design information.

I am interested in more information. Will look for whats later in the
thread. I have a situation where there is interference coming from a
specific direction (close to the horizon). Is it feasible to
block/attenuate/absorb L-band signals from one direction?

--

   Björn