[time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit

[Magnus Danielson]

From: Magnus Danielson <cfmd at bredband.net>
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Tue, 19 Dec 2006 23:00:55 +0100 (CET)
Message-ID: <20061219.230055.-706958800.cfmd at bredband.net>

> From: Brooke Clarke <brooke at pacific.net>
> Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
> Date: Tue, 19 Dec 2006 13:42:28 -0800
> Message-ID: <45885CC4.30007 at pacific.net>
> 
> > Hi Brendan:
> > 
> > It's interesting that the PRS10 can time stamp the 1 PPS input with a 
> > resolution of 10 ns.  I wonder how they do that.
> > http://www.thinksrs.com/downloads/PDFs/Catalog/PRS10c.pdf
> 
> It actually says it does it with 1 ns resolution. A x100 analog interpolator
> circuit for 1 ns to 100 ns (10 MHz) isn't rocket science. See the HP 5335A
> operations and service manual. Getting 10 ns accuracy isn't supprising.

Actually, if you look in the PRS10 manual you find the actual answer. I wasn't
that far off just by my educated guess. They do a x2000 time expansion against
a 2,5 MHz (400 ns). You can read-out and write in the calibration value for
the slope. The actual resolution is 200 ps but they do not use up more than
1 ns in the "public" interface. It actually uses the CPU builtin counter, which
will do for the purpose. They could have spent a little more and got better
single shot resolution out of it, but I suspect they didn't see the need.

http://www.thinksrs.com/downloads/PDFs/Manuals/PRS10m.pdf

Cheers,
Magnus