[time-nuts] Question on GPS receiver selection for 1pps

[Magnus Danielson]

On 11/18/2010 02:16 AM, SAIDJACK at aol.com wrote:
> Hi Paul,
>
> "good enough" is in the eye of the beholder..
>
> The M12M receiver can achieve 2ns rms. So 300ns seems very bad.
>
> Some early units had up to 1000ns error, so 300ns is quite good in that
> context.

The 1 us number was never their actual performance, but the published 
number from the ICD-200 spec, and it was often given for the receivers. 
It was later reduced to about 340 ns with SA on... what the same old 
receivers give as performance in todays spec-manship needs to be 
measured. So the improvements may not have been that great actually.

We need to separate the development in GPS receiver spec-manship from 
their actual typical performance.

> Anything below 30ns from the GPS (with sawtooth correction) should be
> excellent by today's standards..

Sawtooth-correction is the single technological improvement over more 
channels. I have seen 1, 2, 5, 6, 8, 12 and 16 channel receivers...

Cheers,
Magnus