Author Topic: Eevblog #235 - Rubidium Frequency Standard  (Read 47601 times)

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Offline BlueTopic starter

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Eevblog #235 - Rubidium Frequency Standard
« on: January 12, 2012, 02:31:35 pm »
Nice  :)

 

Offline BlueTopic starter

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #1 on: January 12, 2012, 02:32:50 pm »
Sinus output looks a bit wierd.

Dave, Is there a calibration screw cap inside?
 

Offline Neganur

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #2 on: January 12, 2012, 04:20:44 pm »
There was something about those 5V, I can't remember properly but I think they were not needed and actually harmed internal circuitry.

I may be able to dig up the info somewhere again.

Edit: never mind, that was regarding 5V on pin 3 (the lock indication). The 5 V are for the internal DDS.
« Last Edit: January 12, 2012, 04:59:23 pm by Neganur »
 

Offline benemorius

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #3 on: January 12, 2012, 05:06:06 pm »
http://www.vk3um.com/Rubidium%20Standard.html

There was apparently some bad pinout information at some point directing people to apply +5v to pin 3, which is actually the active low lock output. This went unnoticed by some since the 5v rail would be powered by the clamping diode in the IC connected to pin 3 and the device would function, but then someone opened one up and caught the error. Pin 4 is apparently the correct pin for +5v.
 

Offline tnt

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #4 on: January 12, 2012, 06:19:56 pm »
There is a _lot_ of variations of those Rb standard ... all with the same reference number and all different inside.
The one Dave has is one of the more recent one. It has a different architecture than the previous ones. It's not programmable but it is trimmable via the RS232.

The "sinus" is the output of a Xilinx CPLD filtered through a LC filter inside and then again though that special "filtered" DB9 connector (it's _not_ a simple DB9, each pin is actually a small filter !)

If you probe the sinus at it's source (you'll see a small miniature rf connector inside), you'll see it looks awful there ...
 

Offline EEVblog

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #5 on: January 12, 2012, 08:39:26 pm »
Is anyone seeing any/video sync problems on this video?
I can't see it, but I've had two people report it.
I hope it's not my new video editor VideoPad causing problems.
But I thought Youtube re-encodes all uploaded videos, so I'd expect everyone to see any problems.

Thanks
Dave.
 

Offline benemorius

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #6 on: January 12, 2012, 08:44:53 pm »
Is anyone seeing any/video sync problems on this video?
I can't see it, but I've had two people report it.
I hope it's not my new video editor VideoPad causing problems.
But I thought Youtube re-encodes all uploaded videos, so I'd expect everyone to see any problems.

Thanks
Dave.

I didn't notice any such problems. I don't suppose anyone mentioned any specifics?
 

Offline EEVblog

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #7 on: January 12, 2012, 08:46:44 pm »
Is anyone seeing any/video sync problems on this video?
I can't see it, but I've had two people report it.
I hope it's not my new video editor VideoPad causing problems.
But I thought Youtube re-encodes all uploaded videos, so I'd expect everyone to see any problems.

Thanks
Dave.

I didn't notice any such problems. I don't suppose anyone mentioned any specifics?

Nope, just "outa sync"  ::)

Dave.
 

Offline rf-loop

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #8 on: January 12, 2012, 08:56:14 pm »
Sinus output looks a bit wierd.

Dave, Is there a calibration screw cap inside?

Sinewave is distorted but looks normal for this Rb, this do not affect frequency accuracy.

C-Field adjustment is behind small hole on left long side.
If adjust it need good reference and enough accuracy counter. Not this philips.
Or it can do also with oscilloscope with enough good frequency reference. Example GPS disciplined OCXO or Rb.
(without oscilloscope it need least frequency counter what resolution is minimum 1mHz @ 10MHz or better and enough accurate reference. With oscilloscope it need only enough accurate reference and waiting long time for look phase drift.
If not enough good test posibility better to keep fingers out from C-Field adjustment. Becouse normally these have still "good" accuracy (oh well... what is "good" accuracy... of course they are not inside +- 5x10exp-11 error window (mostly) but maybe inside +-10x10exp-10 after long time use without calibrating. )

This Rb model serie have really lot of variations as someone tell.
I have some of these models. Some of these can "program" to different frequency using inside RS232. But only some models.
Also difficult to find good documents.  10MHz output need 50ohm load afaik. (but also this may have variations)
« Last Edit: January 12, 2012, 09:20:25 pm by rf-loop »
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Offline IanB

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #9 on: January 12, 2012, 09:02:06 pm »
Nope, just "outa sync"  ::)

Dave.

It might be the player. Just lately I've noticed a few videos with the audio badly out of sync (2-3 seconds), from many different uploaders. I can't imagine every case is a problem with the original content, so my bet is the trouble lies at YouTube's end.
 

Offline Zad

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #10 on: January 12, 2012, 09:18:16 pm »
Aaah that explains it. I have just posted a comment on YouTube about that. The "sine" wave is absolutely awful! It must generate an amount of jitter when you try to sync it. Simple enough to amplify and clip to a square wave though I guess.

An alternative method is to get a crystal oscillator (preferably TCXO or OCXO) and constrain it to a GPS 1pps pulse. This actually gives a better signal than rubidium sources. GPS has a phenomenal long term accuracy, but even on a good receiver the pulse jitter is +/-50nS. Conversely, the crystal oscillator has a relatively poor long term drift stability by a very clean and regular short term Tau. Combining the two with a locking loop gives an extremely good frequency source.

This is a good place to start when looking for into on time and frequency geekery: http://www.leapsecond.com/

Offline EEVblog

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #11 on: January 12, 2012, 09:21:47 pm »
It might be the player. Just lately I've noticed a few videos with the audio badly out of sync (2-3 seconds), from many different uploaders. I can't imagine every case is a problem with the original content, so my bet is the trouble lies at YouTube's end.

Good to know, thanks.

Dave.
 

Offline wkb

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #12 on: January 12, 2012, 09:46:36 pm »
It might be the player. Just lately I've noticed a few videos with the audio badly out of sync (2-3 seconds), from many different uploaders. I can't imagine every case is a problem with the original content, so my bet is the trouble lies at YouTube's end.

Good to know, thanks.

Dave.

Just watched the video (on a Mac), no problems that I noticed. YMMV ?
 

Offline Chet T16

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #13 on: January 12, 2012, 09:55:59 pm »
Definite sync issue my end, only very slight and i can only notice if i look at your mouth moving.

Why does this come with an OCXO?
Chet
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Offline firewalker

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #14 on: January 12, 2012, 10:08:04 pm »
With the Agilet LCR meter it was bad. 1~3 seconds. Only on 720,1080p. This episode was ok. It must be Google's issue.

Alexander.
 

Is anyone seeing any/video sync problems on this video?
I can't see it, but I've had two people report it.
I hope it's not my new video editor VideoPad causing problems.
But I thought Youtube re-encodes all uploaded videos, so I'd expect everyone to see any problems.

Thanks
Dave.
Become a realist, stay a dreamer.

 

Offline EEVblog

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #15 on: January 12, 2012, 10:12:12 pm »
With the Agilet LCR meter it was bad. 1~3 seconds. Only on 720,1080p. This episode was ok. It must be Google's issue.

That might say something, because I started using VideoPad instead of Sony Vegas with the Agilent LCR episode.

Dave.
 

Offline firewalker

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #16 on: January 12, 2012, 10:58:43 pm »
I will try the LCR episode again (when in front of a PC capable for HD res). I will also download the episode directy from youtube for off line playing to test it.

Alexander.
Become a realist, stay a dreamer.

 

Offline PeteInTexas

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #17 on: January 12, 2012, 11:14:04 pm »
Is anyone seeing any/video sync problems on this video?
I can't see it, but I've had two people report it.
I hope it's not my new video editor VideoPad causing problems.
But I thought Youtube re-encodes all uploaded videos, so I'd expect everyone to see any problems.

Thanks
Dave.

How many hours upon hours have you wasted wrestling with video editors and editing and YouTube and servers and such?  Don't you think your fans would rather see you wrestling with electronic curiosities?  It may be time to start thinking about bringing in an intern who wants to build their experience with these things.  I'm sure the local community college has students eager to work on something.  They might even have access to better editing equipment and software at their lab.

I understand you are having a great time and all but if you want your blog to "scale", letting go of some of these routine task is inevitable.  Not trying to be rude or anything, just rather see you doing electronics instead.   ;D :-[ (can't find a fitting smiley to convey my deference to you in making such a suggestion)
 

Offline Zyvek

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #18 on: January 12, 2012, 11:28:40 pm »
Dave, I think (meaning I'm probably wrong) all of the 5680A's have serial communication, but the base model can only be adjusted via RS232 to make minor adjustments to the output. vs the option that allows full frequency adjustment.   I picked up one of these last month, and I remember reading that somewhere...

For my some of test equipment the output voltage was low to use a a reference, and some also need a square vs a sine wave, so that's that next part to make a multiplexer with both square and sine wave outputs...maybe something else to do to yours as well?
« Last Edit: January 12, 2012, 11:30:25 pm by Zyvek »
-Z
 

Offline EEVblog

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #19 on: January 12, 2012, 11:30:16 pm »
How many hours upon hours have you wasted wrestling with video editors and editing and YouTube and servers and such?  Don't you think your fans would rather see you wrestling with electronic curiosities?  It may be time to start thinking about bringing in an intern who wants to build their experience with these things.  I'm sure the local community college has students eager to work on something.  They might even have access to better editing equipment and software at their lab.

I understand you are having a great time and all but if you want your blog to "scale", letting go of some of these routine task is inevitable.  Not trying to be rude or anything, just rather see you doing electronics instead.   ;D :-[ (can't find a fitting smiley to convey my deference to you in making such a suggestion)

I can't see that happening. Sounds great in theory, but it's just not that practical.
When I edit video I'm also making sure I haven't missed something I want to add, said something dumb, repeated myself, need to add something with a text overlay etc.
At the moment I do that at the same time as I'm editing, and I don't view back afterwards, I just upload when done hoping I've got it right (and I mostly do).
If someone else edited my content, then I'd still have to watch the entire video back and concentrate while doing so. Something wrong - another spin...
So I might as view it while editing the thing myself, it doesn't take that much longer, as I have my workflow pretty well down pat.
I'd likely spend more time interacting with the editor, sending files to them (unless they work on-site), downloading previews etc.

And beside, I like creating my own content, I get a sense of satisfaction even though it can be time consuming and a PITA sometimes.

Get someone else to edit it, and you end up like the Ben Heck show  ;D

It's just like going full time at this. Many people complain about why I'm not churning out a video or two every day now that I magically have another 40 hours a week to work on this full time. It doesn't quite work like that...  ::)

Dave.
« Last Edit: January 12, 2012, 11:37:25 pm by EEVblog »
 

Online mikeselectricstuff

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #20 on: January 12, 2012, 11:47:29 pm »
It might be the player. Just lately I've noticed a few videos with the audio badly out of sync (2-3 seconds), from many different uploaders. I can't imagine every case is a problem with the original content, so my bet is the trouble lies at YouTube's end.

Good to know, thanks.

Dave.
One of my recent vids had some de-syncing for a coupel of mins that wasn't showing in the editor so maybe YT have broken something again.
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Online mikeselectricstuff

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #21 on: January 13, 2012, 12:45:29 am »
Oh dear....
"NOW it is 2008 year .we need some coooooool super supply to enhance the sound quality of your CD Player

As you know most of CD or any other Audio Players Use the OCXO oscillator for  the Frequency Standard.

Ok,the OCXO oscillator just the short stable....why do you try some other Long stable  as your heart of your CD ?
"

http://www.ebay.co.uk/itm/11-2896Mhz-Rubidium-Master-clock-CD-/290273920268?pt=LH_DefaultDomain_0&hash=item4395ac850c


Oh FFS....

"Buy it and claim your atomic energy bragging rights. For those refusing to accept compromises with the audio quality there is the Isochrone 10M - a Rubidium Atomic Reference Generator based on real atomic technology. The 10M is designed specifically to appeal to the most discerning audiophiles and audio professionals. If your goal is to set up your studio for maximum performance, you will certainly appreciate a clocking reference that is a staggering 100,000 times more accurate than the quartz oscillators used in most equipment.
"
http://www.ebay.co.uk/itm/Antelope-Audio-Isochrone-10M-Rubidium-Atomic-Clock-/270809581736?pt=LH_DefaultDomain_0&hash=item3f0d8248a8

Question for the mathematically inclined - how fast would you need to move your head towards the speaker to induce a doppler shift of a similar order of magnitude to that of the error on a Rb standard?
« Last Edit: January 13, 2012, 12:52:14 am by mikeselectricstuff »
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Offline firewalker

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #22 on: January 13, 2012, 12:58:13 am »
He is an amateur. With the right promotion he could sell it more than a new one costs.

Alexander.

Oh dear....
"NOW it is 2008 year .we need some coooooool super supply to enhance the sound quality of your CD Player

As you know most of CD or any other Audio Players Use the OCXO oscillator for  the Frequency Standard.

Ok,the OCXO oscillator just the short stable....why do you try some other Long stable  as your heart of your CD ?
"

http://www.ebay.co.uk/itm/11-2896Mhz-Rubidium-Master-clock-CD-/290273920268?pt=LH_DefaultDomain_0&hash=item4395ac850c


Oh FFS....

"Buy it and claim your atomic energy bragging rights. For those refusing to accept compromises with the audio quality there is the Isochrone 10M - a Rubidium Atomic Reference Generator based on real atomic technology. The 10M is designed specifically to appeal to the most discerning audiophiles and audio professionals. If your goal is to set up your studio for maximum performance, you will certainly appreciate a clocking reference that is a staggering 100,000 times more accurate than the quartz oscillators used in most equipment.
"
http://www.ebay.co.uk/itm/Antelope-Audio-Isochrone-10M-Rubidium-Atomic-Clock-/270809581736?pt=LH_DefaultDomain_0&hash=item3f0d8248a8

Question for the mathematically inclined - how fast would you need to move your head towards the speaker to induce a doppler shift of a similar order of magnitude to that of the error on a Rb standard?
Become a realist, stay a dreamer.

 

Offline Rerouter

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #23 on: January 13, 2012, 01:14:52 am »
may be wrong but...

say a 1khz signal

the length of the waveform is 1mm, so a 10^-11 error means 10 picometers to exceed the error,
so by moving towards or away from the speaker at more than 10 pico-meters per second, you exeed the error.

not much eh.. :)
 

Offline robrenz

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Re: Eevblog #235 - Rubidium Frequency Standard
« Reply #24 on: January 13, 2012, 02:55:38 am »
1kHz = 2.9979e+5 meters wavelength


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