[time-nuts] ocxo

Bob Camp kb8tq at n1k.org
Mon Nov 24 02:34:05 UTC 2014


Hi

The main question is - is there a PLL between the external ref and the OCXO? If so does it go through the DAC? 

If there’s a PLL through the DAC, then bits do matter. If the DAC is simply a replacement for a trim pot, then it may not matter much at all. The OCXO will likely age more in a few days than the reported LSB resolution of the DAC. I’d bet DAC is not part of a PLL.

Bob


> On Nov 23, 2014, at 8:04 PM, Neil Schroeder <gigneil at gmail.com> wrote:
> 
> No but a little math based on your ocxo's range can help... but measuring
> it in person does give you the best numbers.
> 
> More precision and more bits WON'T hurt here and the application notes from
> the leading crystal makers suggest a DAC front ended by a precision op amp
> with and that the xo be followed by a buffer.  So I took the nuclear option:
> 
> http://www.analog.com/static/imported-files/circuit_notes/CN0257.pdf
> 
> My Wenzels don't have a reference out and neither do any of my VCXOs, but
> my $30 Vectron from Ebay does - so my circuit for it is modified to accept
> its reference voltage (its also plugged into an ADF4001 now)
> 
> NS
> 
> 
> On Sun, Nov 23, 2014 at 4:56 PM, Bob Camp <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> About the only other question would be the proper resolution for the DAC.
>> There’s not much of a way to to answer that one without playing with a
>> woking original OCXO.
>> 
>> Bob
>> 
>>> On Nov 23, 2014, at 7:22 PM, Don Latham <djl at montana.com> wrote:
>>> 
>>> No question about that. The morion does run a little warmer than the old
>> unit
>>> apparently did. Fan is temp-controlled, so I think OK. will monitor box
>> temp
>>> with a digital :-) thermometer, very poor resolution, but probably ok.
>>> When I get the last obs done. will do a little blurb to the group.
>>> Don
>>> 
>>> Bob Camp
>>>> 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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>>>>>>>>>> and follow the instructions there.
>>>>>>>>>> 
>>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> --
>>>>>>>>> "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
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>>>>>>>>> and follow the instructions there.
>>>>>>>> 
>>>>>>>> _______________________________________________
>>>>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>>>>> and follow the instructions there.
>>>>>>>> 
>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> --
>>>>>>> "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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>>>>>> and follow the instructions there.
>>>>>> 
>>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> "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.
>>>> 
>>>> _______________________________________________
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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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