Kevin Neave wrote:

Hi Folks,

Does anyone out there know if there are any adverse
effects of mounting two or more GPS antennae in close
proximity?


Yes, if the antennas are within (roughly) one wavelength,
there can be interference. That would be 20cm or so.

It depends very much on the antennas (patch/helix, active/passive)
and on the receiver itself.

In general, active antennas will be better neighbors.
However, I have once encountered a GPS antenna which
started to oscillate when it got cold and effectively
jammed 8 other antennas within a meter radius.

Unless you want more than one antenna for redundancy, the
classic way to handle this is to use a single high-gain
active antenna and a RF power splitter.

For example, the device at th bottom of this page:
http://www.procom-dk.com/component/d...ower-splitters

An active antenna needs power, which is normally fed
into the cable by the GPS receiver.

If you use a power splitter, make sure only one receiver
feeds power into the antenna. This is called "DC feedtrough".
Some power splitters have it on one port only, others
(like the one in the link) does it on all ports. In that case,
you need "DC blockers" on all but one port.

As you will notice, the splitters are not cheap.

I would advise to try placing the three antennas as far
apart as possible on top of your panel and see what
happens. As long as you are aware of the potential
problems, you can always switch some of the instruments
of when you get "bad reception".

Kind regards,

Iwo