[time-nuts] GPS Antenna -Receiver Mutual Interference...

Burt I. Weiner biwa at att.net
Mon Jan 3 21:00:27 UTC 2011

The situation I was in at the time I experienced this was while 
making radio station signal strength measurements from an associate's 
vehicle.  We were using my laptop with Delorme's Topo USA 7.0 runign 
Quad maps and at the same time running a Garmin GPS128 system to 
confirm bearing and distance from the transmitter.

I had heard about mutual interference but had never actually had it 
happen.   In this case we were both having trouble staying 
locked.  Turning either one of the systems off allowed the other one 
to quickly lock and display in DGPS.  Turning the other system back 
on caused the other one to have severe drop-outs.  We were finally 
able to resolve the problem by placing the two antennas on opposite 
sides of the vehicle.

I'm not sure of the nature of the two receivers, but using 
conventional receiver design thinking, the only thing that comes to 
mind that might be radiating would be the oscillators or possibly the 
I.F. section taling to each other.  The antennas were originally 
about a foot or two apart so I can't imagine that any first RF tuned 
stages could be acting as "Suck-Out Filters" causing a notch to the 
other and I can imagine either one re-radiating enough of the bird's 
signal to be any problem.

Burt, K6OQK.

>From: shalimr9 at gmail.com
>Subject: Re: [time-nuts] GPS Antenna -Receiver Mutual Interference...
>Content-Type: text/plain
>The additional advantage is to give you diversity and some immunity 
>against multipath (at least it reduces the probability that both 
>receivers will be affected at the same time due to weird 
>constellation issues or local interference).
>But it now creates an issue which is how do you know who is right 
>when both receivers don't agree...
>Didier KO4BB
>Sent from my Verizon Wireless BlackBerry
>-----Original Message-----
>From: "Rob Kimberley" <rk at timing-consultants.com>
>Sender: time-nuts-bounces at febo.com
>Date: Mon, 3 Jan 2011 15:59:24
>To: 'Discussion of precise time and frequency measurement'<time-nuts at febo.com>
>Reply-To: Discussion of precise time and frequency measurement
>         <time-nuts at febo.com>
>Subject: Re: [time-nuts] GPS Antenna -Receiver Mutual Interference...
>Yes, I've seen this. On installations in the past, when we were putting up
>dual GPS systems, we always put them at least 10 metres apart. What is
>actually best practice, is to put one at one end of building and the other
>one at the other end.
>Rob Kimberley
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Mark J. Blair
>Subject: Re: [time-nuts] GPS Antenna -Receiver Mutual Interference...
>On Dec 30, 2010, at 6:53 PM, Burt I. Weiner wrote:
> > Has anyone run into a situation where two GPS Navigation type
>Antenna/Receivers interfere with each other?
>It's possible that LO leakage from one is jamming the other. When doing
>mobile GPS receiver testing at work with a single antenna feeding multiple
>receivers through a splitter, we sometimes had to insert attenuators in each
>receiver's antenna feed to keep them from jamming each other.
>Mark J. Blair, NF6X <nf6x at nf6x.net>

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net

More information about the time-nuts mailing list