[time-nuts] ocxo

[Bob Camp]

Hi

At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way.

Bob

> On Nov 22, 2014, at 3:55 PM, Don Latham <djl at montana.com> wrote:
> 
> Hi Bob: no. cobble, not double :-)  A little research has me thinking I can
> easily adapt a morion. I can try it at least by starting with the morion on an
> external power supply and patching the output and control voltages in to the
> sr.
> 
> The sr620 has a control circuit which apparently accomplishes your
> suggestions; they claim to use the internal oscillator for short term and
> "lock" it to a supplied external source for longer term. Probably has a long
> time constant on the built-in phase lock to do this.
> 
> Anyhow, autocal calibrates everything except, guess what, the 10 mhz source.
> Thats done separately.
> So a bootup self check shows OK even if the frequency standard is way off.
> 
> Onward and upward.
> Don
> 
> Bob Camp
>> Hi
>> 
>> I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a
>> 5 MHz doubled to 10 OCXO. The counter may or may not be happy with
>> sub-harmonic induced jitter.
>> 
>> Best bet at the specs:
>> 
>> +12V power
>> 0-5V EFC
>> Sine wave out +7dbm
>> 
>> +/- 5x10^-9 0 to 70C
>> 
>> Pinout - trace what you have.
>> 
>> Bob
>> 
>>> On Nov 21, 2014, at 6:59 PM, Don Latham <djl at montana.com> wrote:
>>> 
>>> 
>>> So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The ocxo is
>>> out of tolerance. All self tests pass with flying colors, autocal works as
>>> well. So the best parts are OK.
>>> Does anyone:
>>> 1) have a spare Isotemp OCXO36-53 10.000 MHz  p/n 6-00051?
>>> 2) know the specs, ie the input voltage/current and the control voltage span
>>> and direction? pinout?
>>> I have some Morion mv-89's  and could easily cobble one in if it will work.
>>> Apparently a correct oscillator must be in place to use an external source,
>>> if
>>> I read the manual right.
>>> 
>>> 3) do we have a source for the schematics for the SR 620?
>>> 
>>> The FTS 4060 is up, pumpin' and firmly locked. At least for now. That dealer
>>> was not lyin'
>>> 
>>> Much thanks to all of you.
>>> The adventure continues
>>> 
>>> 
>>> --
>>> "The power of accurate observation is commonly called cynicism by those who
>>> have not got it."
>>> -George Bernard Shaw
>>> 
>>> Dr. Don Latham AJ7LL
>>> Six Mile Systems LLC
>>> 17850 Six Mile Road
>>> Huson, MT, 59846
>>> mail:  POBox 404
>>> Frenchtown MT 59834-0404
>>> VOX 406-626-4304
>>> Skype: buffler2
>>> www.lightningforensics.com
>>> www.sixmilesystems.com
>>> 
>>> 
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>> 
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> 
> 
> -- 
> "The power of accurate observation is commonly called cynicism by those who
> have not got it."
> -George Bernard Shaw
> 
> Dr. Don Latham AJ7LL
> Six Mile Systems LLC
> 17850 Six Mile Road
> Huson, MT, 59846
> mail:  POBox 404
> Frenchtown MT 59834-0404
> VOX 406-626-4304
> Skype: buffler2
> www.lightningforensics.com
> www.sixmilesystems.com
> 
> 
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