Two GPS Antennas?

myrv · #1 04-19-2006, 02:40 PM

If I want to install a second GPS antenna to connect my handheld GPSMAP 396 to is it going to interfere with the primary antenna? I assume the two devices can't share an antenna.

ged380 · #2 04-20-2006, 07:18 AM

If you have a second GPS using a second antenna you'll be fine.

Kahuna · #3 04-20-2006, 08:43 PM

performance will degrade with 2 antennaes right next to each other. I had 3 small trimbles on my glare shield and had to move my primary(430) under the cowl to get acceptable reception.

B Cunningham · #4 04-21-2006, 07:47 PM

Ok, so I have a Grand Rapids EFIS GPS antenna, an XM weather antenna, a Garmin 296 GPS antenna and a Sony XM radio antenna. How can I not put these near each other?

Ben

pbesing · #5 04-21-2006, 07:51 PM

There is a combination antenna from Comant that has XM, GPS, etc all in one. Pretty pricy at $700 I think.

Paul Eastham · #6 04-21-2006, 10:26 PM

I don't understand the physics behind what is being described here. How exactly does a passive (i.e. non-transmitting) GPS antenna interfere with another GPS antenna, as long as they're not physically overlapping or blocking one anothers' view of the satellites?

B Cunningham · #7 04-22-2006, 10:10 AM

Im with you Paul. I plan to line up all four in a row across my glareshield. As long as they have a clear view of the sky, they cannot interfere with each other -- that I know of.

Ben

mgomez · #8 04-22-2006, 08:04 PM

Quote:

Originally Posted by Paul Eastham

I don't understand the physics behind what is being described here. How exactly does a passive (i.e. non-transmitting) GPS antenna interfere with another GPS antenna, as long as they're not physically overlapping or blocking one anothers' view of the satellites?

I was curious about that, too. Perhaps it's the local oscillator leaking out of one antenna and being picked up by another? No receiver is truly passive if it has a local oscillator.

It's just fractions of a mW, but the GPS sats don't put out much power, either...doesn't take much to saturate the "neighbour" receiver's front end.

Another (half-baked) theory is that many GPS receivers use active antennas...there's an amplifier at the antenna. So the potential for interferences is -- at least theoretically -- present.

Any RF gurus here?

sf3543 · #9 04-22-2006, 08:26 PM

I have 2 BMA EFIS, each with a GPS. The BMA guys said I can mount them right next to each other without any problems. They look like the little Garmin antennas.

Kahuna · #10 04-24-2006, 03:07 PM

Quote:

Originally Posted by Paul Eastham

I don't understand the physics behind what is being described here. How exactly does a passive (i.e. non-transmitting) GPS antenna interfere with another GPS antenna, as long as they're not physically overlapping or blocking one anothers' view of the satellites?

I can tell you it is a fact. With each unit I turn on, I can watch the signal level degrate on the sat strength page. Dont know why, buy it does. To the point that with 3 right next to each other, and in IMC, I have lost the 430. Thats why I moved it.

Best,