[time-nuts] ocxo

Don Latham djl at montana.com
Mon Nov 24 01:17:15 EST 2014


The 90 MHz is multiplied up from the 10 MHz, no pll.  Done with a 10 mhz rate
5 ns pulse and a filter chain, followed by a comparator and buffer.

from the manual:
The SR620 has a rear panel input that will accept either a 5 or 10Mhz external
timebase. The SR620 phaselocks its internal timebase to this reference. The
phase-locked loop has a bandwidth of about 20Hz and thus the characteristics
the the SR620's clock, for measurement times longer than 50ms, become that of
the external source. For shorter measurement times the clock characteristics
are unimportant compared to the internal jitter (25ps rms) of the SR620. Thus,
if the signal from a Cesium clock is input into a SR620 with a standard TCXO
oscillator the short-term and long-term stability of the SR620 will become
that of the Cesium clock.

Yes, all jitter is relative...

Don

Bob Camp
> Hi
>
> The ADEV of the reference source (OCXO / external reference) will most
> certainly impact the performance of the counter. The device is just comparing
> the input signal to the reference. Which ever one has the worse stability will
> limit the measurement. At some point (inside the 90 MHz VCXO’s PLL) jitter on
> the reference is no different than jitter on the signal you are trying to
> measure. If they do as many do, there’s a PLL that locks the OCXO up to the
> external reference through a narrowband loop. You then have two filter corners
> to worry about. One between the 90 MHz and the OCXO, the other between the
> external ref and the OCXO.
>
> Bob
>
>> On Nov 23, 2014, at 8:48 PM, Don Latham <djl at montana.com> wrote:
>>
>> From the manual, I infer the dac is 10 bit. ( 4096 max count) Span is 5
>> volts.
>> I've connected the gpsdo and the clock error light does not light; I'm
>> assuming the morion is locking to the gpsdo OK. I do have the original, was
>> going to open it up sometime. I suspect something wrong with the heater.
>> Should just start by measuring current into + and - 15 volts.
>> I think that Said's device could just be put inside the SR fb, and convert
>> the
>> external input bnc to the gps antenna. No sweat. Even the low end clock osc
>> would work quite well, no fancy ocxo needed. SR can also be used with
>> internal
>> clock if needed. The dac value is saved so the internal osc is automatically
>> calibrated by this technique.
>> I'm really impressed by this box! A lot of thought went into it.
>> Don
>>
>> Bob Camp
>>> 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
>>>>>>>>>>> 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.
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> 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.
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> 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.
>>>>>
>>>>> _______________________________________________
>>>>> 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.
>>>
>>> _______________________________________________
>>> 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.
>
> _______________________________________________
> 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




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