Upgrading Counter 53220A to Option 010 Ultra High-stability OCXO Timebase?

[TheSteve]

Seems like a lot of drift, doesn't it?

Not at all from what I can tell. The specs of the factory unit gives +- 50 ppb per year and another +-50 ppb from cal. That would be +- 1 Hz. Now this is only half a year but the error is only 0.05 Hz - seems pretty darn good to me.

[swixo]

Fair.

But when your unit can show 15 digits, it seems like a lot.  I am looking at this OCXO:

http://www.morion-us.com/catalog_pdf/mv291.pdf

The ULN version is 8E-13 short term.  Imagine THAT in your counter.  This
unit appears to be able to fit in the spot for the OCXO, and will fit under the
cover.  I have another Morion OXCO, and it clocks in the E-12 all the time.

s

[TheSteve]

In my case it is all just for fun, my entire lab is locked to the same reference source(GPSDO or Rb.)

[swixo]

All of this is just for fun!  I lock to an SRS FS740, super stable. 

Also want the built in oscillator to be good!

[EE-digger]

Good thread.  I have a 53132A with a Ebay - Polish reference osc. and Rb lab reference for now.

I'm disturbed by Agilent / KS no clean flux residue.  I hope our scopes aren't full of that stuff.  I don't trust it.  Yes, it should be benign (low SIR, good ROSE numbers) but it also acts as a "gatherer" for dust, dirt, stray solder bits (ok, this can be good  ).

[Andrew]

I'm considering a similar upgrade to a 53220A using the Abracon AOCJY3 10ppb part.

A couple of questions in relation to ocxo's:

1) Abracon offer a 5ppb option in the AOCJY3 series however it's temperature range is restricted to 0 to 50C. The 10ppb part is -20 to 70C. What would be the maximum ambient temperature that the 50C part reliably operate?

2) The lock range to an external reference is narrower for the oem ocxo part, 0.2ppm, versus 2ppm for the tcxo part. Does this mean there is some performance gain using the ocxo even with an external reference? Perhaps this would be noticable on the faster 53230 model?

Thanks
Andrew

[jpb]

If you're using the counter indoors I'd think that the 0 to 50C part should be fine (temperature wise - I don't know about its suitability generally), it is very unlikely that the internals of a counter would get significantly hotter than the ambient - they are not high power devices and the main source of heat would probably be the ocxo but it would be in quite a lot of empty space. If you're planning on using the counter in on expeditions to the Sahara or the South Pole it might be better to use the wider temperature range or if you keep the counter in a rack with hot, high power gear on either side.

The narrow lock range is because ocxos generally have a much narrower tuning range (frequency versus voltage gain). They are better quality crystals (SC cut) but for the purposes of a counter there would be no advantage when it is locked to an external source as the external source will determine the timing over longer periods such as that of the counter gate. For RF generators the phase noise is more important but for a counter it is of less importance.

Here is a quote from the Stanford Research Systems SR620 counter manual:

EXTERNAL TIMEBASES
The SR620 has a rear panel input that will accept either a 5 or 10Mhz external timebase.  The SR620 phase-
locks 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. 

[Andrew]

Thanks jpb that answers many questions.

Interesting that measurement times shorter than the PLL bandwidth are not considered important compared to the internal clock jitter. I would have thought this would be an issue for counters like the SRS620 25ps and Keysight 35ps 53230A but apparently not.

[pamphonica]

I just put in a Vectron C4550A1-0213 from Ebay (from China) into my 53220A. It oscillates fine but the internal reference voltage output seems to be missing (looks like open-circuit), so the calibration routine failed.

My fix (for now) was to re-install R828 (0R) which re-connects the internal +5v reference to the adjustment circuitry. This strap was needed for the original smaller oscillator module as it has no reference voltage output.  Cal worked perfectly once this was done.

Has anyone put in one of these specific new/used devices from Ebay and tried the "Cal Step" routine? If this is a feature of this secondhand module, so be it, but if yours worked fine, than please let me know so I can get a replacement from the vendor.

The datasheet shows that ref voltage output can be removed as an option.

-Jeremy

[TheSteve]

I just put in a Vectron C4550A1-0213 from Ebay (from China) into my 53220A. It oscillates fine but the internal reference voltage output seems to be missing (looks like open-circuit), so the calibration routine failed.

My fix (for now) was to re-install R828 (0R) which re-connects the internal +5v reference to the adjustment circuitry. This strap was needed for the original smaller oscillator module as it has no reference voltage output.  Cal worked perfectly once this was done.

Has anyone put in one of these specific new/used devices from Ebay and tried the "Cal Step" routine? If this is a feature of this secondhand module, so be it, but if yours worked fine, than please let me know so I can get a replacement from the vendor.

The datasheet shows that ref voltage output can be removed as an option.

-Jeremy

I've used that exact OCXO - you should not need to install R827 or R828 for it to work perfectly.

[pamphonica]

Thanks Steve, I've asked the vendor for a replacement.  I know that these modules can be ordered with no reference voltage output.  It's re-assuring to know your identical one worked fine with the 0R resistors removed as indicated.
-Jeremy

Update: the vendor says that these modules have no connection to pin 4 (voltage ref out). There are a number of vendors on Ebay but all at higher prices.  Maybe I'll try another vendor and see if these ones are cheap because of faults.  Weird.

[rkeller]

Is there a consensus on the OCXO DIY upgrade.
Hesitant to take apart and start soldering in Chinese sourced Vectron C4550A1-0213's that have been removed from other equipment.
Tried to find these new but no Joy.
Has anyone got a concise DIY upgrade path.  I checked Keysight https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=2190178&nid=-33609.959902.02&id=2190178
It states the 010 upgrade is "not available" for those of us with non 010 units.
Seems simple enough, but for now the OCXO with the GPS timebase at 10 Mhz going in the back works but isn't the best solution especially if I need to carry the unit to another work station.
Thank you,
Russ

[tkamiya]

High-end counters often don't come with OCXO standard and built-in oscillators are usually awful.  This is because it is expected that customer will either use shop standard or pick an OCXO.  Shop standard being more common, later customers don't have to pay for extra.  This will be a significant amount of money when buying ten or more counters!  Standard oscillators are there just to check that the equipment works.  It was never meant to be used for measuring anything.

I typically don't like internal OCXO on counters.  It means separate calibrations and they will never be exactly the same.  This makes it impossible to check correlations.  Also, counters will keep OCXO turned on while equipment is turned off.  That means heat generation and power consumption.  Having few of these, it adds up. 

If this is for business, I would really NOT mess with it myself.  I would have certified hands do certified work and come back with certificate of the job performed and the result.  Can't imagine what would happen if unthinkable happens and thousands of miscalibrated products going out the door.  Compared to that, what HP charges is cheap.

[F64098]

I just put in a Vectron C4550A1-0213 from Ebay (from China) into my 53220A. It oscillates fine but the internal reference voltage output seems to be missing (looks like open-circuit), so the calibration routine failed.

My fix (for now) was to re-install R828 (0R) which re-connects the internal +5v reference to the adjustment circuitry. This strap was needed for the original smaller oscillator module as it has no reference voltage output.  Cal worked perfectly once this was done.

Has anyone put in one of these specific new/used devices from Ebay and tried the "Cal Step" routine? If this is a feature of this secondhand module, so be it, but if yours worked fine, than please let me know so I can get a replacement from the vendor.

I bought a bundle of 5 used OCXOs and 3 of them have the 4V Reference output enabled. Looking at the markings there are no differencies in type or mfg date.
Try your luck: https://de.aliexpress.com/item/4000760950500.html

Put one in my 53220A and i'm very happy 

Best regards

Frank

[SoundTech-LG]

No Luck...

Leider, ist dieser Artikel nicht mehr verfügbar!

[F64098]

Oh i'm very sorry,

got my items just a few days ago and c&p the link without
an actual click on it.
But there are other sellers with similar items.
From my view it is now shure, that the suffix -0213 don't say
anything about the optional reference voltage on pin 4.

Another user made the same experience: https://www.eevblog.com/forum/metrology/how-to-unsolderremove-ocxo-from-pcb/msg4030306/#msg4030306

HTH

Frank

[hartvige]

Just got a couple of C4550A1-0213 devices off Ebay, and both of these do not drive the reference voltage (4.0V nominally) out on pin 4.
It seems really odd that devices with the same marking and P/N (-0213) behave differently in this regard.

Someone mentioned that the pin 4 output was a selectable option in the P/N.
However, looking at:

https://www.vectron.com/products/ocxo/C4550.pdf

This does not seem to be the case. As I read the DS, all devices should drive this pin. Which begs the question: the -0213 devices that don't do this, are they simply broken?