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

Rob Kimberley rk at timing-consultants.com
Mon Jan 3 21:16:51 UTC 2011

Would depend on the antennae gain maybe. 

Simple patch antennae shouldn't have a problem working close together. We
were installing Matsushita ones with about 35db gain.

Most certainly a problem with some of the older types with down-converters
built in.

Rob K

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bill Hawkins
Sent: 03 January 2011 9:04 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] GPS Antenna -Receiver Mutual Interference...

Well, I have two HP conical antennas 4 feet apart and just below the roof
level, with an elevation cutoff of 30 degrees for the large and growing oak
trees on 3 sides. Fifty feet of RG-8 each connects to two Z3801A receivers.

I've had no trouble in a dozen years, here in Minneapolis.
T1 to GPS runs at about +4E-008 for both from GPSCon.

My son runs a 50' deep sea fishing boat out of Ocean City, MD.
It has two GPS navigation antennas less than 4 feet apart up on the signal
mast. It also has portable GPS receivers used by fishermen who want to learn
his fishing spots, but these are about 10' away. He has had no trouble with

What would be the symptoms of interference? A disturbance in PPS signals at
the 10E-12 level?

Bill Hawkins

-----Original Message-----
From: shalimr9 at gmail.com
Sent: Monday, January 03, 2011 1:50 PM

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

But it now creates an issue which is how do you know who is right when both
receivers don't agree...

Didier KO4BB

-----Original Message-----
From: "Rob Kimberley" <rk at timing-consultants.com>
Sender: time-nuts-bounces at febo.com

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: Mark J. Blair
Sent: 03 January 2011 2:19 AM

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.

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