[time-nuts] GPS: ADEV or MDEV?

Magnus Danielson cfmd at bredband.net
Sat Apr 14 07:32:14 EDT 2007


From: Peter Schmelcher <nebula at telus.net>
Subject: Re: [time-nuts] GPS: ADEV or MDEV?
Date: Sat, 14 Apr 2007 02:40:57 -0700
Message-ID: <5.2.1.1.2.20070414001036.02afa7d0 at pop.telus.net>

> 
> >Surely its better to detect the pseudorange instability in software (if
> >one has access)  rather than attenuating the signal from all SVs.
> >Another option is to use multiple GPS antennae operating as a phased array.
> >
> >Bruce
> 
> Of course but I think that approach is part of sub nanosecond time transfer 
> accuracy. Attenuation is simple and the results are descent. The signal is 
> less than 6dB above the receiver noise floor to acquire SV. Unfortunately 
> the SV do not have matched output power so they are acquired and weighted 
> unequally.

The difference in path-length and thus space attenuation is compensated by the
antenna pattern such that it emits stronger to the rimb of its earth view than
central. That evens out power-shifts due to space attenuation for the viewer.
Otherwise we would have yeat another problem to deal with.

Cheers,
Magnus




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