[time-nuts] ocxo

Bob Camp kb8tq at n1k.org
Mon Nov 24 17:59:36 EST 2014


Hi


> On Nov 24, 2014, at 1:47 PM, Don Latham <djl at montana.com> wrote:
> 
> 
> 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.

That’s pretty much the way everybody does it. 

>  So the “zero point” of the oxco has no setting voltage?

I’d bet the PLL output goes to “zero contribution” voltage wise with no ref in. The DAC is then the bias on the OCXO EFC. 

Just a guess - I’ve been wrong PLENTY of times before.

Bob

> 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
>>>>>>>>>>>>> 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
>>>>>>>>>>>> To unsubscribe, go to
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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
>>>>>>>>>> To unsubscribe, go to
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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
>>>>>>>> To unsubscribe, go to
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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
>>>>>> To unsubscribe, go to
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>>> 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.
>>>> 
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> 
> 
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