[time-nuts] Convert Stanford Research SR620 time-interval counter to SR625 ???

Brooke Clarke brooke at pacific.net
Thu Nov 27 18:25:12 EST 2014

Hi David:

For me the key benefit of the SR620 is the 16 digit display.  That implies a lot of digits in the reference (although 
not all 16 of them) so I always use an external reference.

When I turn the PRS-10 upside down the crystal changes frequency and the Rb corrects the crystal, see:

Mail_Attachment --
Have Fun,

Brooke Clarke
Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> On 27 November 2014 at 22:15, Brooke Clarke <brooke at pacific.net> wrote:
>> Hi David:
> Hi Brooke
>> If you look just to the right of the SR620 you will see a separate box that
>> contains the PRS10.
> Ah, I missed that!!!
> I was thinking it fitted inside the SR620, but obviously not.
>> The PRS10 can work as either a Rb GPSDO or as a time stamping device.  For
>> the SR620 any GPSDO would make a good external reference.
> It would have been nice to have a better reference inside, as
> sometimes I move equipment around, and don't always want to take more
> than necessary, so having a better reference inside would have been a
> nice thing, but I see it is not what I thought.
> This unit I purchased has the option 01, the ovenized VCXO, but of
> course that is not going to have the long-term stability of a Rb
> source.
> I see one of the SR625 add-ons on eBay,
> http://www.ebay.com/itm/STANFORD-RESEARCH-SYSTEMS-SR625-2GHz-PRESCALER-/281486714451?pt=US_Marine_Aircraft_Radios&hash=item4189ea6653
> but it does not look in good condition, so I'm not paying $700 for it.
> Dave
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