On Jul 11, 11:44*am, jcarlyle wrote:
I'd be surprised if GPS antennas had oscillators, they're most likely
to be inside the unit itself and signal shouldn't leak out. Some GPS
antennas have preamps, for sure, and of course the only difference
between an amp and an oscillator is feedback. My own experience is
that active GPS antennas close enough to touch one another work
perfectly well. Naturally, keeping a transmitter (like FLARM or a VHF
radio antenna) at a distance from a GPS antenna is a wise idea to
prevent front end overload.

Perhaps a preamp experienced a thermal runaway once, and this led to
the legend of keeping GPS antennas separated? Are there any documented
instances to show that GPS antennas must be separated from one
another?

-John

On Jul 11, 1:31 pm, Darryl Ramm wrote:







Concerns about GPS antennas placed close to each other seem largely a
non-issue. e.g. there is really no local oscillator leakage from these
antennas. More common antenna problem are likely just good sky view/
obstruction issues.

Right, I should have been clear. They don't have local oscillators in
the active antennas, just pre-amps. And the good back-isolation means
the local oscillator in the GPS units themselves does not leak back to
the antenna.

Darryl