[time-nuts] ocxo

Bob Camp kb8tq at n1k.org
Sun Nov 23 18:58:01 EST 2014


Hi

That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. 

Bob

> On Nov 23, 2014, at 6:40 PM, Don Latham <djl at montana.com> wrote:
> 
> Running very nearly continuously for about 4 days now. The self-measured
> jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the
> Morion. I'm using my newly acquired cs source and a couple of z3801's for
> checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5
> parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the
> external freq port on the sr to see if the frequency change direction of the
> morion is OK.
> The scope display output from the SR620 is great!
> Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't
> do anything much new, but it's new to me. All this to drive moonbounce...
> Don
> 
> 
> Bob Camp
>> Hi
>> 
>> If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be
>> important at all. It’s just something to watch for. If you start seeing data
>> in two groups, each one 20 ps wide and separated by maybe 200 ps, you are
>> seeing a problem from the 5 MHz.
>> 
>> Running the box for a while before doing a full detailed cal is a very good
>> idea. It’s a bit warm inside and some of the stuff is temperature sensitive.
>> You want it to reach equilibrium.
>> 
>> Bob
>> 
>>> On Nov 23, 2014, at 1:06 AM, Don Latham <djl at montana.com> wrote:
>>> 
>>> Ah. Got it finally!  Doh. Just finished trying out the Morion this
>>> afternoon.
>>> Electrically works very well. Used a 7812 to drop the +15 volts from the
>>> option 1 ocxo, there is enough power headroom to bring the Morion up from
>>> cold
>>> and run it comfortably. As you said, the control voltage for the original is
>>> indeed 5 v, and can be set by the internal d/a. The output of the oscillator
>>> passes through an emitter follower voltage adjuster and through a low-q
>>> filter
>>> to three stages of ECL buffer and then out to the 10 MHz system bus clock.
>>> Another path proceeds to a relay-switched divide by 2 to the phase detector
>>> so
>>> an external 5/10 MHz source can lock the internal oscillator.
>>> The external 5/10 MHz source proceeds to the phase detector thru an
>>> identical
>>> buffer chain without the switched divider.  The remainder of the clock
>>> circuits is a multiplier to 90 MHz.
>>> 
>>> I'll run the autocal tomorrow and then get some jitter stats if possible.
>>> This
>>> is an early specimen, s/n about 700 or so. I can imagine seldom used, and
>>> sitting on standby for 20 years or so, pushing the ocxo out of tolerance.
>>> 
>>> The saga continues; I may have to look for a 10 MHz replacement on epay,
>>> there
>>> isn't room to put in an Hp, unfortunately.
>>> Don
>>> 
>>> 
>>> 
>>> 
>>> 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
>>>>>>> 
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>>>> and follow the instructions there.
>>>>>> 
>>>>>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts at febo.com
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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
>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to
>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>> 
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
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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
>>> 
>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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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
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



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