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

[Bob Camp]

Hi

Putting the GPS on a fiber is fine, except you need a very large battery to
keep it running. As soon as you have a power line up to it, you are right
back to a metal conductor going to the wrong place(s).

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Attila Kinali
Sent: Wednesday, April 11, 2012 4:37 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best location for a GPS antenna...?

On Wed, 11 Apr 2012 22:06:06 +0200
"Andrea Baldoni" <erm1eaae7 at ermione.com> wrote:

> On Wed, Apr 11, 2012 at 10:19:40AM -0400, Bob Bownes wrote:
> 
> > I do like the optical isolation suggestion. While less than optimal,
> > perhaps the easiest solution is not to put the isolation between the
t'bolt
> > and the antenna, but to put the isolation between the t'bolt and the
> > distribution amplifier.
> 
> By the way, would it be possible to retransmit the GPS signal to isolate
it?
> 
> I mean, rx external antenna -> preamp -> tx directional internal antenna
-> big
> air gap -> rx directional internal antenna -> receiver.
> The preamp would not be so power hungry as the full thunderbolt and maybe
> it could be powered via a magnetic link (or a little solar panel with a
> lamp illuminating it).

Yes it would be. What you basically would need is to have a LNA,
a bandpass filter and something that converts the voltage into
light with very little noise. I think it would be easiest to down
mix it first to 100MHz or so, then modulate a laser diode. In the
house you'd have to mix it up to 1.5GHz again, of course.

I have no clue whether that is feasible from the noise this whole
circuitry will add or whether it would add so much noise that the
receiver would have no chance...

				Attila Kinali
-- 
Why does it take years to find the answers to
the questions one should have asked long ago?

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