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We had a rubidium standard at our TV station. One day NASA called and asked if we had stopped using it. We hadn't, but the rubidium tube had gone bad and it was running on the ovenized crystal alone. It was still well within the gov't standards, but NASA had been using our TV signal to check the calibration of some of their field equipment. We weren't planning on replacing the rubidium so they sent us a cesium standard to use.

RU-vid is good... Got this recommendation straight after watching Curious Marc's latest video.

I have been with HP for 25 years. I worked on this kind of gear for the first 10. Love the old instruments!

LOL @ the handle. My employer is in the process of purchasing some portable gas calibration equipment. One vender sent us a pretty good looking ($) quote. We looked up the specs and the unit weighed almost 50 pounds. A site calibrator weighs about that much. We asked the vendor about that and they said "you required it to be portable, so we mounted a handle on it". That email is printed out and on the wall in the break room. :)

Some people think this is based on the frequency of the radiation from Caesium decay. It's not. It's the frequency of radio waves that resonate with the electron shell of Caesium atoms. All atoms have such frequencies, many in the frequency range known as light (that's what causes things to have different colors), while others are more manageable. The scientists chose one of the Caesium frequencies in the GHz range as the definition of how much a second is. That huge grey cylinder melts some Caesium, tosses the atoms into a vacuum (so they are not detuned by touching other atoms), uses a clever set of electromagnetic filters to sort out those that are the right kind, then bounces a radio signal from the electronics against the flying atoms giving an output signal that lets the electronics determine if it has hit the right frequency or not. The tube is also known as the "physics package".

I have to get some of those 'Museum Item - Do Not Dispose' stickers, could probably use them on half the kit in here!

Dave when I worked for Fordaerospace Satellite systems we has stations around the world. We had the cesium beam flying clock come to each site once a year to calibrate our satellite tracking system from Air Force Systems Command.

HP once was able to build devices that last longer than 25 months??

Manufacturing a commercial piece of equipment with that specification in 1961 was an extraordinary accomplishment when you consider the technologies available to the designers. I have huge respect for these guys, their vision and their knowledge of circuit design were amazing.

You are grossly confusing the use of the word "theory" in the scientific sense. This is a common misunderstanding. A Law simply allows you to calculate something, it does not explain why it is so. A scientific theory on the other hand is the highest form of tested and proven explanation of why something works.

the other clock used in this experiment is in the hands of curiousmarc he does a complete rundown and re-calibration to get it ticking again..

Dave I really like these type of videos, can't wait for our next field trip, we all liked it.

Not only my mouth, all my body. It's something that deserve respect! Keep working in this excellent videos! Regards from Venezuela

Full teardown!!! Hell yeah!

That's so neat - a Patek Phillippe clock there on the front

First Curious Marc and now EEVBLOG find a cesium clock.

More to come!

Good stuff, very interesting.

Being a prospective electrical engineer, slightly obsessed with precision, I must say I really enjoyed the last few videos about calibration, standards and just pure precision porn. Keep it up, Dave! :)

Wow, the dial on the front is made by Patek Phillipe. Wonderful.

Wow, cool stuff!

I used to calibrate my frequency counter using a tv station signal. I would take a analog color tv set and tune it into a high power OTA tv station (you don't wanna use a LP station or cable tv signal as they are resync via TBC). Then I would hook my FC to the chroma circuit and then set it for 3.579545MHz. Now that tv is digital. I use my own rubidium standard now.

I love these! MORE MORE MORE

Good stuff :)

Awesome!!!

How come this awesome video has way too few views..?

Wow. Thanks, Dave! I love that sixties tech. Makes you realize that those cheesy props in the early James Bond films weren't so unrealistic after all. Cheers!

Haha, you even manage to keep up teardown tuesday while you are away from the lab, double LIKE for this :)

So that's one of the marvels Harrison built! Hard to believe that it's all wood in there. This will make naval navigation much easier and safer!

Michelson's Speed of Light experiments done at between Mt. Wilson and Mt. San Antonio in 1924 provided the first modern and truly accurate measure of C.

I'm pretty sure qantas had an atomic clock fitted in the equipment bay on one of it's 747's in the late 70's. it was used to test one of the relativity theories. Trying to get more info on it.

02:57 But unfortunately the uncertainty of measurement was actually greater than what the trend was. So even though they had a linear progression the uncertainties associated with that measurement were greater than linear progression.

He forgot to show how to wind it up! Great, Great video...thank you for your efforts!

When the expert speaks do not interrupt.

There is an atomic clock more precise than the Cesium clock used as of now. A paper on it was published in Nature Communications. Nature Communications 6, Article number: 6896 doi:10.1038/ncomms7896 Received 14 January 2015 Accepted 11 March 2015 Published 21 April 2015 Here is a link to an evaluation of the work: www.nature.com/ncomms/2015/150421/ncomms7896/full/ncomms7896.html#affil-auth I've always been fascinated by anything 'atomic'. Including the NIST's use of the Cesium atomic clock as our standard for time measurements.

I have one. Got it at the MIT flea for $25. weighs a lot. neven turned it on. power cord soldered to power input plug (the jerk did not bother to try to find a real plug). and one neon indicating button is busted, I might have broken it when i transported this anchor to my car (I was recovering from several surgeries). no idea how much of the life if the tube is used up. plan on selling it to Raytheon as a replacement into one of their ancient but still used ATE automated test stations. hope to get a lot of cash for it.

I repaired one.... had a bad crystal oven (used as interim transfer standard). Oven heater was bad so crystal would never sync with cesium loop. Fixed.

How does a cesium clock compares to the rubidium frequency standard you reviewed a while back?

CuriousMarc just got one of these!

Almost got an internship at Agilent =( hope I'll make it one day

All that HP/Agilent gear makes my mouth water.

Cool :-) That must had been a strange call. The agents from man in black ringing at the door would be less strange then such a call.

Please buy something broken to fix. They're my favourite of your videos. I hope you don't mind me saying this.

I love the fact it has "Museum Item Do Not Dispose" on it! Also it's uncalibrated - so do not use... Not that it still works anyway...

Schmatic could be interresting to see.

I always wondered how they where able to frequency count or divide a 9GHz signal using circa 1962 technology.

That "Time elapsed" guage was neat. 0- 10k hours.

I have one of this clocks in the lab, and it doesn´t work anymore, I would like to put the analogic clock to work, There are 3 wires, maybe they are used like VCC , GND and signal pulse, ?? any idea? regards

Wow, I would not want one of them falling out of space and landing on my head!

9.192.631.770 Hertz !

Time dilation had not. And wasn't in fact full proven until 1971.

Oi, Dave, snap shot from this video in Vsauce video " what if the earth stopped spinning" knew I recognized it, get your royalties, that Michael is loaded :-)

Wait till you see the next video...

I see they went with the Patek instead of the Rolex for the front dial

"Don't turn it on" [CHECK!] "Take it apart!" [NOK]

Is this one for teardown Tuesday? :)

Strange that they wouldn't just use that cesium standard directly instead of giving it to your station to use the broadcast as a reference. What area does that TV signal covers?

I wonder if the Patek Philippe clock face on the front added $250k to the price :-)

PLL tutorial Dave ?

Cooooool! :D

Did he call Dave "Tom" at 0:20?

Why didnt yall turn it on?

You just couldn't wait to take it apart, right, Dave?

That mysterious cesium frequency is 9,192,631,770 cycles per second. An eastbound circumnavigation of the earth at the speed of sound lowers the clock frequency by about one part per trillion. It would be unlikely for a jet transport to be able to average more than 0.7 mach. That would give a frequency decrease of only 0.25x10^-12 The environmental drift of this clock approaches this so it was not an accurate test of special relativity. In the two days time to get the clock back to California, it would have lost roughly 43 nanoseconds. That is the time that it takes light to travel 42 feet.

No tear down?!?!?!!

when people are trying to explain stuff, just listen rather than talk over them please,its rude and annoying to watch

It is absurd to read "museum item do not dispose". Who would dispose of an atomic clock?

Museum item?!

funny when you ask a metrologist expert about weight :-)

Cmon just replace electrolytic capacitors and it will be as good as new!

Come on, the theory of relativity has been proven way before this.

"We stopped making Atomic clocks *about* 10 years ago" - Umm - could you be a bit more specific on that?

Do not eat the contents of the tube OK!

7.5g is a lot of Cs! I'd trade a testicle for one of these clocks.

4000 volts mmm juicy

dude like to interrupt eh?

Not a good video for Teardown Tuesday.

8:50 Panel porn.

Relativity is not proven, that is why it is still labeled as a theory. If the entire work was shown to be correct then it would be Einstein's Laws of Relativity.