[time-nuts] ocxo

[Don Latham]

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
>>>>
>>>>
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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
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.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