[time-nuts] Galvanic decoupling of GPS antenna

Robert Benward rbenward at verizon.net
Thu Jun 17 11:09:11 EDT 2010


Yuri,
Another suggestion would be to look for a low power GPS; I can't image with 
all the GPSs out there in all those cell phones, that they all take 40mA or 
more.  If you find one that does have low power, then locate it at the 
antenna and then you won't need an active antenna.  (canabalize a cell 
phone?)

Another solution, is start looking for those fully integrated GPSs, e.g. the 
old Delorme self contained ones, then do an optical coupling on the RS-232. 
Again check the power consumption.

Depending on how long you need operation, you can try a Bluetooth device.  I 
have one, it's about the size of a Zippo lighter, and will run 16 hours on a 
battery charge.  If you can deal with the battery charging once a day, this 
might be a solution for you.  The range is short, you need to check it for 
your application, but another way around that is to run a RS-232 - bluetooth 
converter and get the controller side of the bluetooth closer to the antenna 
side.

Here is a link to a provider


www.usglobalsat.com

Bob




----- Original Message ----- 
From: "Yuri Ostry" <yuri at ostry.ru>
To: <time-nuts at febo.com>
Sent: Wednesday, June 16, 2010 8:34 PM
Subject: Re: [time-nuts] Galvanic decoupling of GPS antenna


> Hello,
>
> Thursday, June 17, 2010, 2:44:43, Didier Juges wrote:
>
> D> It is not clear to me why the antenna should be isolated from the
> D> receiver, I would prefer to keep the antenna and receiver on the
> D> same return, and isolate that assembly from the rest of the world.
>
> D> It is much easier to provide isolation on the supply, RS-232 and
> D> 10MHz (if you use it) than on the antenna, in my opinion, at least
> D> as much as it is less likely to have a negative performance impact,
> D> and you can do it with off-the-shelf parts.
>
> Too long story to explain it now. I have very limited power available
> on those what named "outside world" here. Just enough to "feed" some
> low-power active GPS antenna (I can allocate approx 15 ma @ 3.6V).
> In addition, whole design is battery powered, so it will be
> difficult to allow extra 30-40 ma for DC-DC converter module
> quiescent current. ;)
>
> From my first look it was a good idea to isolate antenna (and maybe
> even consider passive antenna if tests will show that there is enough
> gain) and make a full use of low-power features of that tiny uBlox
> NEO6Q.
>
> -- 
> Best regards,
> Yuri                          mailto:yuri at ostry.ru
>
>
>
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