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Re: [Discuss-gnuradio] External clock source Info?

From: Gregory Maxwell
Subject: Re: [Discuss-gnuradio] External clock source Info?
Date: Tue, 17 Aug 2010 17:24:20 -0400

On Tue, Aug 17, 2010 at 3:10 PM, Mark J. Blair <address@hidden> wrote:
> On Aug 17, 2010, at 2:24 PM, William Pretty Security Inc wrote:
>> It seems that 52MHz /64MHz precision clock references are like hen’s teeth, 
>> so I’m working on a design.
>> What I need to know is what sort of level is the USRP1 looking for ? Is it 
>> 3.3V CMOS ?
>> Once I get the design working, I’ll make them available at a reasonable 
>> price J
> I think you will get bonus points if your design can accept an external 10MHz 
> reference provided by a GPS-disciplined oscillator. If there was some 
> convenient way to adjust out the crystal aging for use when the external 
> reference isn't available, that would be even better. I've been thinking of 
> designing something along these lines, but I won't complain if you do the 
> hard work and I can just buy one from you. ;)

A while back I decided I wanted a better clock in my USRP1s and went
hunting. I didn't have a lot of luck, and the few places I sent
inquiries to didn't get back to me.  My attention was eventually
pulled off onto other projects... but you can count me in as someone
who would like to partake in the results of this work.

I'd also like to echo the 10MHz comment.  GPSDOs Clocks with excellent
long term stability show up at fairly low prices on ebay all the time
(excess from cell site deployments, I assume).  I have a couple of
them.   What they don't usually have is the very low phase noise that
I'd want for a clock which is eventually going to multiplied up to GHz
levels.   So a USRP1 clock board which was primarily a 10->64MHz
up-converter with very low phase noise would be exactly what I would

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