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

Don Latham djl at montana.com
Thu Nov 27 21:05:42 EST 2014


I’ve just replaced the SR620 oxco option 01 with a Morion, by simply adding a 7812 to the 15 v heater feed. Locks well with either gpsdo or cesium external source. Don’t forget to turn on the external option and set the frequency for 5 or 10 MHz. It took about 5 days for the Morion to reasonably settle down.
  I agree about the Rb, has to be set with Gpsdo anyway, and I’ve already had 2 of them go South.

Prescalers from RFBay.

Don

> On Nov 27, 2014, at 4:25 PM, Brooke Clarke <brooke at pacific.net> wrote:
> 
> 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:
> http://www.prc68.com/I/PRS10.shtml#Accel
> http://www.prc68.com/I/Images/FC_ROT.jpg
> 
> Mail_Attachment --
> Have Fun,
> 
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> http://www.prc68.com/I/DietNutrition.html
> 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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> 
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