Re: [time-nuts] FA-2 questions

[Bob kb8tq]

Hi

Taking the “questions” topic in a bit different direction …..

If the FA-2 is like the other projects from the same people, there is active 
work being done
on the project. That is likely to create updated code for the device as issues 
are spotted. Is
anybody on the list linked into that side of things? 

Given the number of people who seem to have them, it probably would be a good 
idea to 
come up with a way to monitor what’s going on with the original project. As 
time goes by, 
it might not hurt to watch for firmware / rev number changes on newer 
purchases. 

So another question: what firmware / rev’s do people have now? 

Bob

> On Oct 12, 2019, at 7:45 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Yo Bubba Dudes!,
> First, does the internal OCXO run when the power is turned off?
> Wrote:
> We are presently experimenting using a ISC570B  multiplier at 100 MHz and get 
> 13 digits seeattached but the data out of the back is only 12 digits reliable.
> Looking it up I found out that the ISC570B is a teeny - tiny IC which for me 
> would pose a problem to implement. 
> 
> So looking at alternatives that I already had I came up with two possible 
> alternative multiplier ideas.
> The first was to put the 10 MHz DUT into the external reference of my (boat 
> anchor) HP signal generator set the output frequency to 200 MHz and put the 
> output into the channel 1 input to get extra resolution digits.
> Expanding upon that, I came with more complex but what may be a better error 
> multiplier reading since I have both signal generators on hand.
> First I feed the 10 MHz DUT signal into my Fluke 6080 setting the output to 1 
> GHz.  I'd then feed the reference 10 MHz signal into the external reference 
> of my HP 8656 and set the output to 990 MHz.
> Next I'd feed both outputs into a  
> AD8342 LF to 3.8GHZ Active Mixer Down conversion Output withBalun Transformer
> 
> board from ebay ($23) and then feed the multiplied signal into channel 1. (I 
> may need a simple low pass filter.)
> 
> 
> This should give me a 100X error multiplication. 
> 
> 
> Am I on the right track or am I missing something?
> 
> 
> Regards,
> Perrier
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
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Re: [time-nuts] Cold Rubidium?

[Poul-Henning Kamp]

In message 
, Dana Whitlow writes:

>I can only answer one of your questions with any confidence, but I'd
>suspect that the chamber walls are cooled a fair bit in addition to
>being highly reflective.

Why would you need to cool them any more than you need to cool them
in a cesium standard ?

I wonder if you can replenish the Rb supply ?

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
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Re: [time-nuts] Cold Rubidium?

[Michael Wouters]

The atoms are laser cooled and held in a magneto-optical trap. It’s
basically a short, one-way fountain.

Cooling the microwave cavity would be useful for reducing the black body
radiation shift, but without checking the numbers, this would not be so
useful at the relatively low accuracy claimed for the clock. Otherwise,
it’s pretty much irrelevant to the atom temperature. It’s all UHV, so
there’s no time to come to thermal equilibrium with whatever residual gas
is in the vacuum enclosure.

NIST used to operate a mercury ion microwave clock at cryogenic
temperatures.

Cheers
Michael

On Sun, 27 Oct 2019 at 8:01 am, Dana Whitlow  wrote:

> I can only answer one of your questions with any confidence, but I'd
> suspect that the
> chamber walls are cooled a fair bit in addition to being highly
> reflective.  Your other
> questions age very good ones, too, and I'm looking forward to *somebody*
> answering
> them.  I'd also love to hear the details of how they go about interrogating
> that cloud of
> cold Rb atoms in such a short time (< 100 msec).
>
> Dana
>
>
> On Sat, Oct 26, 2019 at 3:01 PM Richard (Rick) Karlquist <
> rich...@karlquist.com> wrote:
>
> > The proverbial "dumb questions":
> >
> > Is there an actual refrigerator somewhere
> > in this gadget, or are the Rb atoms in a
> > room temperature vacuum and the laser cools
> > just the atoms.  It appears to be the latter.
> >
> > So the enclosure has low emissivity so it
> > doesn't transfer too much heat to the atoms
> > by radiation?
> >
> > And is it correct that the atoms are not ionized
> > to trap them because the laser does that?
> >
> > Rick N6RK
> >
> > On 10/26/2019 1:39 AM, Anders Wallin wrote:
> > > ptti2018:
> > >
> >
> https://www.researchgate.net/publication/322920519_Long_term_frequency_instability_of_a_portable_cold_87Rb_atomic_clock
> > > ifcs2018:
> > >
> >
> https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range
> > >
> > > this one is apparently a darpa/spectradynamics/nist effort, and
> there's a
> > > similar story with muquans and syrte in france, see:
> > > https://www.muquans.com/product/muclock/
> > >
> > >
> > > On Fri, Oct 25, 2019 at 11:09 PM AC0XU (Jim) <
> james.schatz...@ac0xu.com>
> > > wrote:
> > >
> > >> Does anyone have any experience/first hand knowledge of this Cold
> > Rubidium
> > >> standard?
> > >>
> > >> 
> > >> https://spectradynamics.com/products/crb-clock/
> > >>
> > >> The specs look very good. The mfr claims that, unlike traditional
> > rubidium
> > >> oscillators, it has no long-term drift.
> > >> Thanks!
> > >> Jim
> > >> ___
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> > >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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> > >>
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> > > and follow the instructions there.
> > >
> > >
> >
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Re: [time-nuts] Rubidium cell or lamp rejuvenation. WAS-HP 5065A owners, a question!

[JF PICARD via time-nuts]

 Observed on 3 R XSR, on 10 5065A decommissioned together after 10...20 years 
of service (blue ones with Patek clock, green, black and green...with 10811A 
and digital clock...) --they were replaced by a GPS based synchronisation 
network--. plus some 5065A got here and there. The lamp assy I sold last year 
had the same problem. The HP specs were met in 50% of the units but there was 
Rb deposits (small irregular spots) in the lamps.
It is the main cause of the XSR failure and the lamp is field replacable (metal 
threaded base) On Saturday, October 26, 2019, 11:01:06 PM GMT+2, 
 wrote:  
 
 JF, Reference your statement:

"Sorry, but I don't agree with your first statement about the 5065A :
after long use, the rubidium plates on the inner envelope of the lamp
(like silver on a mirror) and years after years the Rb light and photo I
decreases."

After working on the 5065A for over 40 years and across the full range of
Serial numbers and ages of instruments (somewhere over 70 units) I have
only seen Rubidium plated on the inside of the bulb twice. All the other
lamps provided performance that met the HP specifications. The design of
the lamp assy causes the tip of the lamp to be cold compared to the bulb
causing the majority of the Rubidium to condense into the tip.

The two bulbs were in units where the lamp oven winding shorted and
"cooked" the lamp Assy.
Those two bulbs were recovered using a heat gun.
I suppose if the unit was stored for years in a very hot environment the
Rubidium could get out of the tip but as long as the lamps starts you can
just let it run for a week or so and it will condense back into the tip.

If a you have a bulb that exhibits the plating I would recommend that you
measure the lamp oven temperature to make sure it is not too hot. Also
the two nuts on the lamp assy. rod that protrudes out of the cover should
clamp the outer cover firmly between them. The outer cover is a heat sink
for the lamp assy. and maintains the Rubidium in the tip. Operating for
years without this clamping might cause what you saw.

Other units specifically the Efratom FRS were poorly designed and are
known for this problem.

Cheers,

Corby
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Re: [time-nuts] Cold Rubidium?

[Bob kb8tq]

Hi

If you look at the ADEV plot, there is some sort of bump out in the 1 to 2 days 
region.
That would suggest it’s not 100% immune to the local environment….

The box is big enough that you *might* fit a chiller in it. If so, heat would 
need to be vented.
I see no (obvious) vents or heatsinks. 

Bob

> On Oct 26, 2019, at 3:04 PM, Richard (Rick) Karlquist  
> wrote:
> 
> The proverbial "dumb questions":
> 
> Is there an actual refrigerator somewhere
> in this gadget, or are the Rb atoms in a
> room temperature vacuum and the laser cools
> just the atoms.  It appears to be the latter.
> 
> So the enclosure has low emissivity so it
> doesn't transfer too much heat to the atoms
> by radiation?
> 
> And is it correct that the atoms are not ionized
> to trap them because the laser does that?
> 
> Rick N6RK
> 
> On 10/26/2019 1:39 AM, Anders Wallin wrote:
>> ptti2018:
>> https://www.researchgate.net/publication/322920519_Long_term_frequency_instability_of_a_portable_cold_87Rb_atomic_clock
>> ifcs2018:
>> https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range
>> this one is apparently a darpa/spectradynamics/nist effort, and there's a
>> similar story with muquans and syrte in france, see:
>> https://www.muquans.com/product/muclock/
>> On Fri, Oct 25, 2019 at 11:09 PM AC0XU (Jim) 
>> wrote:
>>> Does anyone have any experience/first hand knowledge of this Cold Rubidium
>>> standard?
>>> 
>>> 
>>> https://spectradynamics.com/products/crb-clock/
>>> 
>>> The specs look very good. The mfr claims that, unlike traditional rubidium
>>> oscillators, it has no long-term drift.
>>> Thanks!
>>> Jim
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe, go to
>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>>> 
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> 
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Re: [time-nuts] Rubidium cell or lamp rejuvenation. WAS-HP 5065A owners, a question!

[Dana Whitlow]

Corby, I have a question to add regarding the HP units:  is the tip
temperature hot
enough to melt Rb in addition to providing vapor?  If so, doesn't the
orientation of
the physics package in earth's gravity have to be about correct in order to
keep
the excess Rb in the tip?

Thanks,

Dana


On Sat, Oct 26, 2019 at 4:01 PM  wrote:

> JF, Reference your statement:
>
> "Sorry, but I don't agree with your first statement about the 5065A :
> after long use, the rubidium plates on the inner envelope of the lamp
> (like silver on a mirror) and years after years the Rb light and photo I
> decreases."
>
> After working on the 5065A for over 40 years and across the full range of
> Serial numbers and ages of instruments (somewhere over 70 units) I have
> only seen Rubidium plated on the inside of the bulb twice. All the other
> lamps provided performance that met the HP specifications. The design of
> the lamp assy causes the tip of the lamp to be cold compared to the bulb
> causing the majority of the Rubidium to condense into the tip.
>
> The two bulbs were in units where the lamp oven winding shorted and
> "cooked" the lamp Assy.
> Those two bulbs were recovered using a heat gun.
> I suppose if the unit was stored for years in a very hot environment the
> Rubidium could get out of the tip but as long as the lamps starts you can
> just let it run for a week or so and it will condense back into the tip.
>
> If a you have a bulb that exhibits the plating I would recommend that you
> measure the lamp oven temperature to make sure it is not too hot. Also
> the two nuts on the lamp assy. rod that protrudes out of the cover should
> clamp the outer cover firmly between them. The outer cover is a heat sink
> for the lamp assy. and maintains the Rubidium in the tip. Operating for
> years without this clamping might cause what you saw.
>
> Other units specifically the Efratom FRS were poorly designed and are
> known for this problem.
>
> Cheers,
>
> Corby
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> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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[time-nuts] Rubidium cell or lamp rejuvenation. WAS-HP 5065A owners, a question!

[cdelect]

JF, Reference your statement:

"Sorry, but I don't agree with your first statement about the 5065A :
after long use, the rubidium plates on the inner envelope of the lamp
(like silver on a mirror) and years after years the Rb light and photo I
decreases."

After working on the 5065A for over 40 years and across the full range of
Serial numbers and ages of instruments (somewhere over 70 units) I have
only seen Rubidium plated on the inside of the bulb twice. All the other
lamps provided performance that met the HP specifications. The design of
the lamp assy causes the tip of the lamp to be cold compared to the bulb
causing the majority of the Rubidium to condense into the tip.

The two bulbs were in units where the lamp oven winding shorted and
"cooked" the lamp Assy.
Those two bulbs were recovered using a heat gun.
I suppose if the unit was stored for years in a very hot environment the
Rubidium could get out of the tip but as long as the lamps starts you can
just let it run for a week or so and it will condense back into the tip.

If a you have a bulb that exhibits the plating I would recommend that you
measure the lamp oven temperature to make sure it is not too hot. Also
the two nuts on the lamp assy. rod that protrudes out of the cover should
clamp the outer cover firmly between them. The outer cover is a heat sink
for the lamp assy. and maintains the Rubidium in the tip. Operating for
years without this clamping might cause what you saw.

Other units specifically the Efratom FRS were poorly designed and are
known for this problem.

Cheers,

Corby
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Re: [time-nuts] Cold Rubidium?

[Richard (Rick) Karlquist]

The proverbial "dumb questions":

Is there an actual refrigerator somewhere
in this gadget, or are the Rb atoms in a
room temperature vacuum and the laser cools
just the atoms.  It appears to be the latter.

So the enclosure has low emissivity so it
doesn't transfer too much heat to the atoms
by radiation?

And is it correct that the atoms are not ionized
to trap them because the laser does that?

Rick N6RK

On 10/26/2019 1:39 AM, Anders Wallin wrote:

ptti2018:
https://www.researchgate.net/publication/322920519_Long_term_frequency_instability_of_a_portable_cold_87Rb_atomic_clock
ifcs2018:
https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range

this one is apparently a darpa/spectradynamics/nist effort, and there's a
similar story with muquans and syrte in france, see:
https://www.muquans.com/product/muclock/


On Fri, Oct 25, 2019 at 11:09 PM AC0XU (Jim) 
wrote:


Does anyone have any experience/first hand knowledge of this Cold Rubidium
standard?


https://spectradynamics.com/products/crb-clock/

The specs look very good. The mfr claims that, unlike traditional rubidium
oscillators, it has no long-term drift.
Thanks!
Jim
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Re: [time-nuts] Cold Rubidium?

[Poul-Henning Kamp]

In message 
, Anders Wallin writes:

So sort of a "one-way/drop" fountain really ?


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] HP5071A with bad tube.... can I get one used?

[Bob kb8tq]

Hi

In our case it was *Symmetricom* that was unaware of the exception. They
absolutely refused to accept the incoming shipment unless it was Hazmat. 
The stock shipping box they supplied each time had great big Hazmat labels
on it.

Bob

> On Oct 25, 2019, at 11:22 PM, Tom Knox  wrote:
> 
> 
> 
> That info was from Microsemi, perhaps an effort to standardize terminology?  
> My spell check likes Cesium..
> I am amazed that people were not aware of the shipping exemption, It 
> absolutely covers end users and I do not think there are specific packing 
> requirement. But I am not sure since I have always shipped using manufacturer 
> hard-cases. It was my understanding the exemption was related to the small 
> amount of Caesium/Cesium and more importantly the stainless tube enclosure. 
> If I am not mistaken this even allows shipment on commercial (Passenger) 
> airlines.
> Cheers;
> Tom Knox
> 
> 303-554-0307
> 
> act...@hotmail.com
> 
> "Peace is not the absence of violence, but the presence of Justice" Both MLK 
> and Albert Einstein
> 
> 
> From: time-nuts  on behalf of Richard 
> Solomon 
> Sent: Friday, October 25, 2019 2:52 PM
> To: Discussion of precise time and frequency measurement 
> 
> Subject: Re: [time-nuts] HP5071A with bad tube can I get one used?
> 
> When did the spelling of Cesium
> change ? As far back as I can
> remember (High School chemistry,
> easier then, we only had 52
> elements), it was spelled Cesium.
> 
> But then, they are still the San
> Diego Chargers to me.
> 
> 73, Dick, W1KSZ
> 
> On Thu, Oct 24, 2019 at 11:00 PM Tom Knox  wrote:
> 
>> The Latin form “caesium” is the internationally recognized legal spelling.
>> The common form “cesium” may still be found in older Symmetricom user’s
>> manuals and publications. The caesium inside any of the devices is
>> contained in a UN certified stainless steel cylinder. This cylinder meets
>> all of the
>> requirements for dangerous goods “containers” or “packages” for both
>> international and U.S. domestic shipments. The instructions in this document
>> refer to the labeling required on the outside of the carton or box that is
>> used to enclose the caesium device.
>> 1. All U.S. domestic (only) shipments must use and comply with all the
>> requirements of the DOT-SP11401 exemption. The document may be
>> downloaded from the DOT web site at
>> http://hazmat.dot.gov/sp_app/special_permits/docs/11000/E11401.pdf. All
>> Symmetricom customers who are
>> reshipping the Symmetricom device do not need to be listed as a grantee
>> and may use Symmetricom’s exemption (see Par. 8a of DOT-SP11401).
>> The prohibited “modifications or changes” to the “package” referenced in
>> Par. 8a refers to the stainless steel caesium beam tube cylinder, and not
>> any
>> other external packaging (see Par. 7a). Follow normal shipping and
>> handling practice and the following instructions.
>> 2. Attach a copy of DOT-SP11401 to the outer box or container. The
>> document may be legibly reduced, folded, placed in a clear plastic pouch and
>> attached outside the package (see Par. 10). The title page should be
>> readable through the pouch. Staple a copy of DOT-SP11401 to the shipping
>> invoice so that the copy attached to the package will not be disturbed. Do
>> not include this instruction sheet that you are now reading. Do not use
>> the preprinted, bar-coded dangerous goods label offered by the shipper,
>> which, if scanned, would incorrectly route the package to non-passenger
>> aircraft.
>> 3. Mark the outside of the package "DOT-SP11401 CAESIUM UN 1407". A
>> downloadable template is available from
>> http://www.symmttm.com/5071A/Shipping.
>> 4. Limit to five units the maximum number of caesium devices in each
>> shipment (par. 7b).
>> 5. Comply with the training requirement (Par. 11) for “Hazmat employee”
>> under 49CFR 172.704(a)(2) function-specific training (i). Explanation:
>> This requirement is fully met if the person handling the transportation of
>> the caesium device has read, understood and followed these
>> instructions and DOT-SP11401.
>> 6. Additional explanation: The following requirements of the IATA-DG
>> regulations are waived by DOT-SP11401., i.e. not required for U.S.
>> domestic only shipments. Paragraph numbers (Par. #) refer to the
>> paragraphs in DOT-SP11401:
>> LABELING “Dangerous When Wet” and “Danger – Do not load in passenger
>> aircraft” are waived (Par. 4).
>> PLACARDING “Dangerous When Wet” on the carrier’s vehicle is waived (Par.
>> 4).
>> AUTHORIZED PACKAGING or UN (United Nations) certified packaging is waived
>> (Par. 4). The stainless steel caesium beam tube cylinder
>> comprises the authorized or prescribed packaging. No other packaging over
>> the apparatus is required for compliance (Par. 4 and 7a).
>> PASSENGER AIRCRAFT is added as an authorized mode of shipment (Par. 9).
>> Note: FedEx recognizes DOT exemptions. Some carriers,
>> such as UPS and DHL may not recognize DOT 

[time-nuts] Cesium shipping exemption. (was) HP5071A with bad tube.... can I get one used?

[cdelect]

Well I can't figure out how to attach the link but if you search for "hp
5071a shipping exemption" in google you will find :

"PDF] Shipping Instruction - Cesium & Rubidium ... - Microsemi how to" 

Click on it and it will open a PDF of the form.
You will see that it exempts most requirements, the training mentioned is
reading the instructions in the form.
Cheers,

Corby
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Re: [time-nuts] Rubidium cell or lamp rejuvenation. WAS-HP 5065A owners, a question!

[JF PICARD via time-nuts]

 Sorry, but I don't agree with your first statement about the 5065A : after 
long use, the rubidium plates on the inner enveloppe of the lamp (like silver 
on a mirror) and years after years the Rb light and photo I decreases. Finaly, 
adjustement becomes imossible. The solution (as described a long time ago by Mr 
Lazarus -- HP standards in Geneva--) was a little bit wild and tricky : put out 
the coild (which ignites the lamp) and heat the lamp with a blow torch to get 
the rubidium vaporised again into the lamp. On Friday, October 25, 2019, 
10:09:55 PM GMT+2,  wrote:  
 
 There are two separate Rubidium migration problems.

The first is Lamp flooding which occurs when too much Rubidium enters the
main bulb and plates onto the bulb envelope. (usually after long storage
or storage at high temperatures) This mainly in the small telecomm
Rubidiums due to design flaws. The 5065A is immune to this problem and I
believe the PRS10 is also.

The second is cell flooding where too much Rubidium enters the resonance
cell and blocks the light.
This is mainly a 5065A problem although older Varian V4700 and R20 units
also can be effected.
The procedure in the manual cools the tip of the stem and collects the
Rubidium back where it belongs!
This takes about a week and then after reconfiguring the TED back to
normal cooling levels another week to stabilize the Rubidium level in the
cell. Telecomm units have "starved" cells and don't exhibit this effect.

Cheers,

Corby


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[time-nuts] USRP B210 phase-meter

[Anders Wallin]

a short writeup of our phase-meter/digital-DMTD tests with an Ettus B210 is
now on researchgate:
https://www.researchgate.net/publication/336825605_Software_Defined_Radio_Based_Phase_Meter_for_Frequency_Metrology

an ADEV of 2e-14 at 1s in 0.5 Hz bandwidth is fairly straightforward to
achieve, for a 100MHz signal split into ch1 and ch2.
There are issues with cross-talk between the channels - looking to solve
that later.

The raw data comes in at 1MS/s and everything works as expected when
downsampling by three decades to about 1kS/s. Then ADC noise is something
else (1/f ?) than white at fourier frequencies below about 1 kHz - so there
isn't much 'process gain' achieved when downsampling further to 100S/s or
10 or 1 S/s.

Anders
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Re: [time-nuts] Cold Rubidium?

[Anders Wallin]

ptti2018:
https://www.researchgate.net/publication/322920519_Long_term_frequency_instability_of_a_portable_cold_87Rb_atomic_clock
ifcs2018:
https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range

this one is apparently a darpa/spectradynamics/nist effort, and there's a
similar story with muquans and syrte in france, see:
https://www.muquans.com/product/muclock/


On Fri, Oct 25, 2019 at 11:09 PM AC0XU (Jim) 
wrote:

> Does anyone have any experience/first hand knowledge of this Cold Rubidium
> standard?
>
> 
> https://spectradynamics.com/products/crb-clock/
>
> The specs look very good. The mfr claims that, unlike traditional rubidium
> oscillators, it has no long-term drift.
> Thanks!
> Jim
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