[time-nuts] GPS Antenna -Receiver Mutual Interference

k6rtm at comcast.net k6rtm at comcast.net
Mon Jan 3 19:31:13 UTC 2011

While you can try and run multiple GPS receivers off a single antenna using an off the shelf mini-circuits splitter, a bias tee, and a handful of dc blocks, you're likely to run into just this kind of problem. 

It's more than just the "normal" HP overdesign that has their GPS splitters like the 58535A comprising: 
an input narrowband (L1) filter feeding a low-noise gain block, 
the gain block feeding a splitter, and 
each output leg of the splitter having its own narrow band (L1) filter followed by a pad to improve isolation/return loss. 

73 bob k6rtm in not yet raining silicon valley 

Message: 6 
Date: Mon, 3 Jan 2011 15:59:24 -0000 
From: "Rob Kimberley" <rk at timing-consultants.com> 
Subject: Re: [time-nuts] GPS Antenna -Receiver Mutual Interference... 
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at febo.com> 
Message-ID: <000001cbab5f$319dd060$94d97120$@timing-consultants.com> 
Content-Type: text/plain; charset="us-ascii" 

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 
Sent: 03 January 2011 2:19 AM 
To: Discussion of precise time and frequency measurement 
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> 
Web page: http://www.nf6x.net/ 
GnuPG public key available from my web page. 

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