Author Topic: Upgrading Counter 53220A to Option 010 Ultra High-stability OCXO Timebase?  (Read 8630 times)

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Offline TheSteve

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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.
VE7FM
 
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Offline swixo

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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
 
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Offline TheSteve

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In my case it is all just for fun, my entire lab is locked to the same reference source(GPSDO or Rb.)
VE7FM
 
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Offline swixo

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

Also want the built in oscillator to be good!
 
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Offline EE-digger

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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  ;D).
 
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Offline Andrew

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Re: Upgrading Counter 53220A to Option 010 Ultra High-stability OCXO Timebase?
« Reply #55 on: September 01, 2018, 06:37:03 pm »
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
 

Offline jpb

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Re: Upgrading Counter 53220A to Option 010 Ultra High-stability OCXO Timebase?
« Reply #56 on: September 02, 2018, 02:22:41 am »
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:
Quote
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. 
« Last Edit: September 02, 2018, 02:45:23 am by jpb »
 
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Offline Andrew

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Re: Upgrading Counter 53220A to Option 010 Ultra High-stability OCXO Timebase?
« Reply #57 on: September 06, 2018, 04:40:11 pm »
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.
 


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