[time-nuts] Best location for a GPS antenna...?

Bob Camp lists at rtty.us
Thu Apr 12 16:41:51 UTC 2012


Hi

GPS is pretty close to the noise "as received". A fully passive system with
significant cable loss and low / no gain antennas does not sound like it's
going to do a very good job.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Lux
Sent: Thursday, April 12, 2012 9:52 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Best location for a GPS antenna...?

On 4/12/12 2:09 AM, Rob Kimberley wrote:
> There are commercial "re-radiators" for GPS.  I found these on Google:
>
> <http://www.gps-repeating.com/?gclid=COTV88D6rq8CFcwTfAodhSKvmQ>
> <http://gpsnetworking.com/GPS-re-radiating-kits.asp>
>
>
> One of my old suppliers in the UK was marketing a range of these, but I
seem
> to remember some problem in getting approval in the UK, and they had to
drop
> them. Things may have changed as this was a few years ago.
>
Interestingly I've just been looking into this...  Why would you need 
anything special to reradiate.. It's not like you need a particular 
antenna pattern or constant gain or something. What about something like 
a fat monopole against a ground plane, with a attenuator at the feed to 
provide a good terminating impedance for the LNA/Line driver.

If it's L1 only, you don't even need particularly wide bandwidth (<1%)


Yes, I've seen setups at JPL where they reradiate with D&M or Ashtech 
chokering antennas (or even helibowls), but that might be because we've 
got a bunch of them sitting around, so why not use it.


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