Re: GPS frequency standard
- From: "David L. Jones" <altzone@xxxxxxxxx>
- Date: 14 Jan 2007 00:47:04 -0800
John Larkin wrote:
On 12 Jan 2007 15:48:35 -0800, maxfoo@xxxxxxxxxxx wrote:
David L. Jones wrote:
John Larkin wrote:
It would be nice to have a primary frequency standard around here. We
have a rubidium, but that's not technically primary, and we'd like to
check it anyhow. And we do have a huge ole HP cesium, but you damn
near need a PhD to operate it.
Has anybody used a GPS standard? Any comments or recommendations?
My Stanford Research FS725 Rubidium standard allows connection of any
1pps external GPS reference, that's a pretty cheap, simple, and
powerful combination.
http://www.thinksrs.com/products/FS725.htm
Get a load of that 60Hz spike in the phase noise plot.
http://www.thinksrs.com/assets/instr/FS725/FS725_diagLG.gif
It's a shame they don't use better line filtering in such a nice piece
of equipment.
We have an SRS ovenized SC-cut oscillator, clone of some old HP brick,
which we rack mounted with some buffers. It's pretty good, with jitter
of a few ps per second, and longterm stability in the 50 ppb/year sort
of range. There's no 60 Hz, because we did the power supplies
ourselves!
The temperature control loop is hilarious. It was made to work, but
obviously by someone who didn't understand the dynamics.
SRS is strange; they make one of everything, sort of all over the
place. The business model is to find some old, overpriced product and
kill it. Probably a fun place to work.
Yeah, would be a good place I recon. None of their gear is state of the
art, mostly using garden variety parts, but they are cheap and
functional. SRS gear makes a project budget stretch further which is a
nice thing, hence I have fair bit of their stuff. We use plenty of
their SR785 Dynamic Signal Analysers, a pretty good DSA and much
cheaper than the Agilent equivalent which has been the industry
standard for ever.
I like that they give you the full schematics and theory of operation
for almost every bit of gear. Came in handy when we blew up the SR560
preamp front end which is pretty easy to do BTW.
Dave :)
.
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