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

[Bob Camp]

Hi

> On Nov 27, 2014, at 8:05 PM, Don Latham <djl at montana.com> wrote:
> 
> 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.

I’ve had much better luck with Rb’s once I started heat sinking them properly. I pretty much ignored that issue early on and would regularly loose them. So far I have not lost one with a decent heat sink (and sub 40C baseplate).  Without heat sinking, some of them are up around 60-70C on the baseplate. Internal temps are even higher. 

Bob

> 
> 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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> 
> 
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