[time-nuts] ocxo

Don Latham djl at montana.com
Mon Nov 24 18:47:50 UTC 2014


sorry, Bob, I spaced this one.  The dac is indeed a trimpot, and if the external source is enabled, the 1:1 pll controls the ocxo through, as you thought, a fast loop, about 2 sec t/c and the trimpot dac is not connected. The pll is an ecl  phase detector and a pump, very simple.  So the “zero point” of the oxco has no setting voltage? more thought needed!

Don


> On Nov 23, 2014, at 7:34 PM, Bob Camp <kb8tq at n1k.org> wrote:
> 
> 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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>>>>>>>>>>> 
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> 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
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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
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>>>>>>> _______________________________________________
>>>>>>> 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
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>>>>> 
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>>>>> 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
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