[time-nuts] Neutrinos not so fast? (defective connector)

Joseph M Gwinn gwinn at raytheon.com
Thu Feb 23 22:16:06 UTC 2012


time-nuts-bounces at febo.com wrote on 02/23/2012 04:53:06 PM:

> From: bg at lysator.liu.se
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Date: 02/23/2012 04:53 PM
> Subject: Re: [time-nuts] Neutrinos not so fast? (defectove connector)
> Sent by: time-nuts-bounces at febo.com
> >
> > A possible mechanism occurs to me.  High-precision GPS is
> very vulnerable
> > to multipath errors.  A loos connector will have a
> significant reflection.
> > The reflected energy will propagate backwards, and be reflected off the
> > transmitter output discontinuity, the twice-reflected energy
> propagating
> > back to the receiver.  The original and the triple-transit
> echo will add
> > coherently (for the modulation, not the photons)  in the
> receiver.  This
> > is
> > a perfect multipath scenario.  How long must the cable be?
> Depends on the
> > relative strength of main signal and triple-transit echo.
> > Joe Gwinn
> Joe,
> High precision GPS receivers use various correlator schemes that try to
> minimize multipath. "Normal" GPS receivers are more vulnerable than
> geodetic quality receivers.
> http://webone.novatel.ca/assets/Documents/Papers/PAC.pdf

You are of course correct, but timing receivers may not go to such lengths
are are needed for geodetic receivers.  A lot of the magic of geodetic
receivers is in the choke-ring antenna, which ignores signals arriving from
too low an angle above the horizon.

In the Neutrino case, the multipath is built into the cable between antenna
and receiver, so the antenna cannot help.  But I will read the article,
which looks interesting.  Wonder if it would solve such a triple-transit
echo problem.


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