Re: [time-nuts] Mitsubishi GPS antenna data

[Ray Hudson]

Nigel, I bet there is more than a few companies re-badging these things. 
That photo of the HP base and two screw clamp is exactly the same as the 
VIC100, The PCB in the VIC100 is flat and you could have a puck cover like the 
HP, the VIC100 pointy shape cover is designed as a snow retardant dome.

I'll take a photo of the internals of a VIC100 for you as a conparison.

Ray VK4TFT.

--- On Tue, 23/2/10, gandal...@aol.com  wrote:

> From: gandal...@aol.com 
> Subject: Re: [time-nuts] Mitsubishi GPS antenna data
> To: time-nuts@febo.com
> Received: Tuesday, 23 February, 2010, 10:03 PM
>  
> In a message dated 21/02/2010 23:52:15 GMT Standard
> Time,  
> hudson...@yahoo.com.au
> writes:
> 
> Nigel,  that part number looks very much like a MEW /
> Panasonic VIC100 
> antenna.  CCAH32ST02  with a H instead of a 5 .
> does it look anything like the  
> VIC100 see link  below.
> http://denko.panasonic.biz/Ebox/gps_en/spec.html
> 
> 
> -
> Hi Ray
>  
> Many thanks for the information, that very close match on
> part numbers  
> would certainly imply some similarity but externally at
> least the units are  
> different.
>  
> What I have is a puck antenna that looks identical to the
> HP  58504A and 
> was supplied to me already mounted inside an HP 58510A
> external  housing.
> I'm now told the assembly was supplied complete by HP,
> although I have no  
> way of verifying that, so it's possible the Mitsubishi is a
> rebadged HP.
> However, all photos I've seen of the HP antenna are
> labelled as  such and I 
> wouldn't normally have expected HP to supply their own
> parts  with someone 
> else's label, which is why I was hoping to find some
> information  specific 
> to the Mitsubishi.
>  
> Some good photos of a "proper" 58504A can be seen here by
> using the "View  
> more images" link.
>  
> _http://www.finchremarketing.zoovy.com/product/HP-58504A-1/HP-58504A-GPS-L1-
> Carrier-Antenna---NEW.html_ 
> (http://www.finchremarketing.zoovy.com/product/HP-58504A-1/HP-58504A-GPS-L1-Carrier-Antenna---NEW.html)
> 
>  
> regards
>  
> Nigel
> GM8PZR
>  
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> 


  
__
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Re: [time-nuts] Low noise voltage regulators

[WB6BNQ]

Bruce,

Why not just use a diode in place of the 2M3904 circuit ?  Seems like it would 
do the same
thing with less parts.

Also, would not the Texas Instruments TL-431 be a better choice as it has a 
lower noise spec
them the LM329 part.  In addition, with its adjustable nature, the TL-431 would 
be adjusted
to make sure the single diode (in place of the 2N3904 circuit) is shut off when 
the TL-431
comes up to speed.

Obviously, this would be best with intended output voltages above the reference 
level.

BillWB6BNQ


Bruce Griffiths wrote:

> I meant something like the attached circuit schematic for an LM723 based
> 15V regulator.
> The circuit can be easily extended to use an external pass transistor
> where more current is needed.
>
> The LM329 is biased from the regulator output which improves the
> reference line rejection.
> The 723's internal reference is used only during startup.
> The 2N3904 disconnects the internal reference when the LM329 terminal
> voltage exceeds about 5.4V.
> Some optimisation of the circuit may be required.
>
> Bruce
>
> Arnold Tibus wrote:
> > Hi,
> >
> > NS gives some informations about improvements in their AN-173.pdf
> > http://www.national.com/ds.cgi/LM/LM117.pdf
> > Audio freaks are discussing it in
> > http://www.diyaudio.com/forums/solid-state/28978-improving-lm3x7-regulator-circuit.html
> > Is that what you are looking for?
> >
> > 73
> > Arnold
> >
> >
> > On Thu, 25 Feb 2010 11:22:02 +1300, Bruce Griffiths wrote:
> >
> >
> >> You can improve the performance of the LM723 if one substitutes an LM329
> >> for the internal reference biased from the regulator output.
> >> The trick is to use the internal reference for startup and decouple it
> >> with a diode or similar once the LM329 achieves its nominal output.
> >>
> >
> >> Currently, there appear to be 2 variants of the LM723 one (made by
> >> National) that uses a noisy bandgap reference and another variant that
> >> actually uses a quieter zener reference.
> >>
> >
> >> Bruce
> >>
> >
> >> Brooke Clarke wrote:
> >>
> >>> Hi neville:
> >>>
> >>> My old Gibbs rack mount 5 MHz standard used the LM723 linear
> >>> regulator.  I believe it's one of the lowest noise regulators you can
> >>> use.
> >>> http://www.national.com/mpf/LM/LM723.html#Overview
> >>>
> >>> Have Fun,
> >>>
> >>> Brooke Clarke
> >>> http://www.PRC68.com
> >>>
> >>>
> >>> Neville Michie wrote:
> >>>
>  Hi,
>  I remember a reference, probably by Bruce, that LEDS provide a low
>  noise voltage reference.
>  I am proposing to build a voltage regulator for a thermally
>  controlled LPRO rubidium oscillator,
>  with the voltage regulator being mounted on the 0.5 inch thick
>  aluminium heat sink plate.
>  The LEDS would also be mounted on the plate, which has controlled
>  temperature.
>  The LPRO has internal voltage regulation, and by running it at ~40C
>  and 18Volts, the thermal
>  flux within the unit is minimised as is the power demand.
>  What I want to know is if a LM317 running on a stack of LEDs driven
>  by the LM317 output
>  would provide a low noise power source? What would be better?
> 
>  cheers, Neville Michie
> 
> 
> >
> >
> >
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> > and follow the instructions there.
> >
> >
>
>   
>  Name: LowNoiseLM723Regulator.pdf
>LowNoiseLM723Regulator.pdfType: Portable Document Format 
> (application/pdf)
>  Encoding: base64
>
>   
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Re: [time-nuts] Wrist Watch for Time Nuts

[Matt Osborn]

On Wed, 24 Feb 2010 12:03:32 -0500, "Bob Camp"  wrote:

>Hi
>
>A square foot of solar cells fashioned into "geek stylish" hat would keep it
>running for quite a while.
>
>-
>
>Has anybody actually poked at one of these yet?
>
>Bob

The MSP430F5438 combined with a Zarlink ZL70250 RF transceiver



is an unbeatable combination for low power consumption. The 'A'
version of the MSP430 offers even better performance when released.

The MSP430 controls and samples up to 1500 12 samples per second from
multiple analog inputs while sleeping 750 msec out of each second.

The Zarlink offers two way communications (keeps the device synced
with the PC). The data transfers are managed by the MSP430 DMA through
an SPI port to the Zarlink.

We  should end up with 1 milliamp current draw at maximum throughput
of 3000 bytes per second.

-- kc0ukk at msosborn dot com

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Re: [time-nuts] Low noise voltage regulators

[Bruce Griffiths]

I meant something like the attached circuit schematic for an LM723 based 
15V regulator.
The circuit can be easily extended to use an external pass transistor 
where more current is needed.


The LM329 is biased from the regulator output which improves the 
reference line rejection.

The 723's internal reference is used only during startup.
The 2N3904 disconnects the internal reference when the LM329 terminal 
voltage exceeds about 5.4V.

Some optimisation of the circuit may be required.

Bruce

Arnold Tibus wrote:

Hi,

NS gives some informations about improvements in their AN-173.pdf
http://www.national.com/ds.cgi/LM/LM117.pdf
Audio freaks are discussing it in
http://www.diyaudio.com/forums/solid-state/28978-improving-lm3x7-regulator-circuit.html
Is that what you are looking for?

73
Arnold


On Thu, 25 Feb 2010 11:22:02 +1300, Bruce Griffiths wrote:

   

You can improve the performance of the LM723 if one substitutes an LM329
for the internal reference biased from the regulator output.
The trick is to use the internal reference for startup and decouple it
with a diode or similar once the LM329 achieves its nominal output.
 
   

Currently, there appear to be 2 variants of the LM723 one (made by
National) that uses a noisy bandgap reference and another variant that
actually uses a quieter zener reference.
 
   

Bruce
 
   

Brooke Clarke wrote:
 

Hi neville:

My old Gibbs rack mount 5 MHz standard used the LM723 linear
regulator.  I believe it's one of the lowest noise regulators you can
use.
http://www.national.com/mpf/LM/LM723.html#Overview

Have Fun,

Brooke Clarke
http://www.PRC68.com


Neville Michie wrote:
   

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low
noise voltage reference.
I am proposing to build a voltage regulator for a thermally
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C
and 18Volts, the thermal
flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven
by the LM317 output
would provide a low noise power source? What would be better?

cheers, Neville Michie

 




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LowNoiseLM723Regulator.pdf
Description: Adobe PDF document
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Re: [time-nuts] Wrist Watch for Time Nuts

[MOSEL, Sam]

CR2032, expensive at the store but cheap online:

http://www.dealextreme.com/details.dx/sku.751

Good value even if 75% of them are poor (which is unlikely).

> -Original Message-
> From: time-nuts-boun...@febo.com 
> [mailto:time-nuts-boun...@febo.com] On Behalf Of Robert Darlington
> Sent: Thursday, 25 February 2010 2:34 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Wrist Watch for Time Nuts
> 
> Which means a battery every month for somebody actively 
> developing projects that talk to wireless sensor networks.  
> Still not a bad deal.
> 
> -Bob
> 
> On Wed, Feb 24, 2010 at 8:08 AM, paul swed 
>  wrote:
> 
> > That is indeed neat.
> > Just no time for another project to tinker with.
> > $49 quite the deal
> > Whats funny is it eats a battery at least every 6 months 
> for average use.
> >
"Warning:
The information contained in this email and any attached files is
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recipient, any use, disclosure or copying of this email or any
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[time-nuts] Tbolt OCXO

[Pete Rawson]

I'm trying to identify the OCXO in my Tbolt; hoping that it's one
of the newer parts, as in the TAPR units.

Is there a P/N, or other obvious means of identifying the newer,
low noise OCXOs?

Pete Rawson

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Re: [time-nuts] Low noise voltage regulators

[Bruce Griffiths]

The LM723 from STMicroelectronics still uses a buried zener and its 
typical noise specs about 4x less noisy than the National part.

With an LM329 4reference it should be about 2x quieter than the ST version.

Bruce

Didier Juges wrote:

The original 723 (I remember the uA723 made by Fairchild, I still have a couple 
of 30 year old parts here) had a buried Zener and was considered pretty quiet 
at the time.

I am not sure how it would compare with today's low noise references, but the 
last time I checked, it was pretty good, even more so when considering the 
voltage is 6 or 7 volts, compared to typically much less for a modern reference.

Didier

 Sent from my BlackBerry Wireless thingy while I do 
other things...

-Original Message-
From: Bruce Griffiths
Date: Thu, 25 Feb 2010 11:22:02
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Low noise voltage regulators

You can improve the performance of the LM723 if one substitutes an LM329
for the internal reference biased from the regulator output.
The trick is to use the internal reference for startup and decouple it
with a diode or similar once the LM329 achieves its nominal output.

Currently, there appear to be 2 variants of the LM723 one (made by
National) that uses a noisy bandgap reference and another variant that
actually uses a quieter zener reference.

Bruce

Brooke Clarke wrote:
   

Hi neville:

My old Gibbs rack mount 5 MHz standard used the LM723 linear
regulator.  I believe it's one of the lowest noise regulators you can
use.
http://www.national.com/mpf/LM/LM723.html#Overview

Have Fun,

Brooke Clarke
http://www.PRC68.com


Neville Michie wrote:
 

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low
noise voltage reference.
I am proposing to build a voltage regulator for a thermally
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C
and 18Volts, the thermal
flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven
by the LM317 output
would provide a low noise power source? What would be better?

cheers, Neville Michie

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Re: [time-nuts] Low noise voltage regulators

[Didier Juges]

The original 723 (I remember the uA723 made by Fairchild, I still have a couple 
of 30 year old parts here) had a buried Zener and was considered pretty quiet 
at the time. 

I am not sure how it would compare with today's low noise references, but the 
last time I checked, it was pretty good, even more so when considering the 
voltage is 6 or 7 volts, compared to typically much less for a modern reference.

Didier

 Sent from my BlackBerry Wireless thingy while I do 
other things... 

-Original Message-
From: Bruce Griffiths 
Date: Thu, 25 Feb 2010 11:22:02 
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Low noise voltage regulators

You can improve the performance of the LM723 if one substitutes an LM329 
for the internal reference biased from the regulator output.
The trick is to use the internal reference for startup and decouple it 
with a diode or similar once the LM329 achieves its nominal output.

Currently, there appear to be 2 variants of the LM723 one (made by 
National) that uses a noisy bandgap reference and another variant that 
actually uses a quieter zener reference.

Bruce

Brooke Clarke wrote:
> Hi neville:
>
> My old Gibbs rack mount 5 MHz standard used the LM723 linear 
> regulator.  I believe it's one of the lowest noise regulators you can 
> use.
> http://www.national.com/mpf/LM/LM723.html#Overview
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
>
>
> Neville Michie wrote:
>> Hi,
>> I remember a reference, probably by Bruce, that LEDS provide a low 
>> noise voltage reference.
>> I am proposing to build a voltage regulator for a thermally 
>> controlled LPRO rubidium oscillator,
>> with the voltage regulator being mounted on the 0.5 inch thick 
>> aluminium heat sink plate.
>> The LEDS would also be mounted on the plate, which has controlled 
>> temperature.
>> The LPRO has internal voltage regulation, and by running it at ~40C 
>> and 18Volts, the thermal
>> flux within the unit is minimised as is the power demand.
>> What I want to know is if a LM317 running on a stack of LEDs driven 
>> by the LM317 output
>> would provide a low noise power source? What would be better?
>>
>> cheers, Neville Michie
>>
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>>
>
>
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Re: [time-nuts] Low noise voltage regulators

[Bruce Griffiths]

Bob Camp wrote:

Hi

Since the LPRO has a "noisy" 3 terminal regulator inside it, making the
outside voltage quiet (as in noise density) probably will not help much.
   
I've seen people insist on a low noise regulator ahead of a fluxgate 
magnetometer that used an LM7805 regulator.
The plastic enclosure was sealed with acetoxy grade silicon and buried 
in the ground at the end of 50m of cable with the predictable result.

Keeping the voltage *stable* will indeed help things. I think you need a
high stability linear regulator rather than a low noise one.

One other thing to think about is line isolation at both audio and RF. Most
regulators have poor isolation above a few 10's of KHz.
   
At least the line isolation can be improved substantially at audio 
frequencies by adding active filtering (eg Wenzel style albeit with a 
few extra parts to prevent zenering transistor junctions or excessive 
base current on startup) at the regulator input. Cascade 2 or more if 
you need higher rejection.

RF rejection requires passive filtering.

Bruce

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Neville Michie
Sent: Wednesday, February 24, 2010 4:57 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Low noise voltage regulators

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low
noise voltage reference.
I am proposing to build a voltage regulator for a thermally
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C
and 18Volts, the thermal
flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven
by the LM317 output
would provide a low noise power source? What would be better?

cheers, Neville Michie

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Re: [time-nuts] Low noise voltage regulators

[Arnold Tibus]

Hi,

NS gives some informations about improvements in their AN-173.pdf
http://www.national.com/ds.cgi/LM/LM117.pdf
Audio freaks are discussing it in
http://www.diyaudio.com/forums/solid-state/28978-improving-lm3x7-regulator-circuit.html
Is that what you are looking for?

73
Arnold


On Thu, 25 Feb 2010 11:22:02 +1300, Bruce Griffiths wrote:

>You can improve the performance of the LM723 if one substitutes an LM329 
>for the internal reference biased from the regulator output.
>The trick is to use the internal reference for startup and decouple it 
>with a diode or similar once the LM329 achieves its nominal output.

>Currently, there appear to be 2 variants of the LM723 one (made by 
>National) that uses a noisy bandgap reference and another variant that 
>actually uses a quieter zener reference.

>Bruce

>Brooke Clarke wrote:
>> Hi neville:
>>
>> My old Gibbs rack mount 5 MHz standard used the LM723 linear 
>> regulator.  I believe it's one of the lowest noise regulators you can 
>> use.
>> http://www.national.com/mpf/LM/LM723.html#Overview
>>
>> Have Fun,
>>
>> Brooke Clarke
>> http://www.PRC68.com
>>
>>
>> Neville Michie wrote:
>>> Hi,
>>> I remember a reference, probably by Bruce, that LEDS provide a low 
>>> noise voltage reference.
>>> I am proposing to build a voltage regulator for a thermally 
>>> controlled LPRO rubidium oscillator,
>>> with the voltage regulator being mounted on the 0.5 inch thick 
>>> aluminium heat sink plate.
>>> The LEDS would also be mounted on the plate, which has controlled 
>>> temperature.
>>> The LPRO has internal voltage regulation, and by running it at ~40C 
>>> and 18Volts, the thermal
>>> flux within the unit is minimised as is the power demand.
>>> What I want to know is if a LM317 running on a stack of LEDs driven 
>>> by the LM317 output
>>> would provide a low noise power source? What would be better?
>>>
>>> cheers, Neville Michie
>>>




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Re: [time-nuts] Low noise voltage regulators

[Bruce Griffiths]

Poul-Henning Kamp wrote:

In message<4b85a2eb.4000...@pacific.net>, Brooke Clarke writes:

   

My old Gibbs rack mount 5 MHz standard used the LM723 linear regulator.
I believe it's one of the lowest noise regulators you can use.
http://www.national.com/mpf/LM/LM723.html#Overview
 

If you really want to get low noise, you do the "amplify noise by -1"
trick.

Vicor has a special "afterburner" module you can hook after their
switchers, which does this.

The trick is that you don't really need much power in the amplifier,
it just have to be able to cancel out the noise, a trivial transistor
or op-amp will do.

If you really want to go radical, take a peek at Nationals AN1651,
study the two opamps at the top of the schematics...

Poul-Henning


   
The 30uV/rtHz and greater noise (produced by U4 and U5) below 1Hz due to 
the 1M series resistor plus the amplified power supply noise for 
frequencies below 1Hz or so are a little high for some applications.


Bruce


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Re: [time-nuts] Low noise voltage regulators

[Bruce Griffiths]

You can improve the performance of the LM723 if one substitutes an LM329 
for the internal reference biased from the regulator output.
The trick is to use the internal reference for startup and decouple it 
with a diode or similar once the LM329 achieves its nominal output.


Currently, there appear to be 2 variants of the LM723 one (made by 
National) that uses a noisy bandgap reference and another variant that 
actually uses a quieter zener reference.


Bruce

Brooke Clarke wrote:

Hi neville:

My old Gibbs rack mount 5 MHz standard used the LM723 linear 
regulator.  I believe it's one of the lowest noise regulators you can 
use.

http://www.national.com/mpf/LM/LM723.html#Overview

Have Fun,

Brooke Clarke
http://www.PRC68.com


Neville Michie wrote:

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low 
noise voltage reference.
I am proposing to build a voltage regulator for a thermally 
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick 
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled 
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C 
and 18Volts, the thermal

flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven 
by the LM317 output

would provide a low noise power source? What would be better?

cheers, Neville Michie

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Re: [time-nuts] Low noise voltage regulators

[Bob Camp]

Hi

Since the LPRO has a "noisy" 3 terminal regulator inside it, making the
outside voltage quiet (as in noise density) probably will not help much.

Keeping the voltage *stable* will indeed help things. I think you need a
high stability linear regulator rather than a low noise one.

One other thing to think about is line isolation at both audio and RF. Most
regulators have poor isolation above a few 10's of KHz. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Neville Michie
Sent: Wednesday, February 24, 2010 4:57 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Low noise voltage regulators

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low  
noise voltage reference.
I am proposing to build a voltage regulator for a thermally  
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick  
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled  
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C  
and 18Volts, the thermal
flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven  
by the LM317 output
would provide a low noise power source? What would be better?

cheers, Neville Michie

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Re: [time-nuts] Low noise voltage regulators

[Poul-Henning Kamp]

In message <4b85a2eb.4000...@pacific.net>, Brooke Clarke writes:

>My old Gibbs rack mount 5 MHz standard used the LM723 linear regulator.  
>I believe it's one of the lowest noise regulators you can use.
>http://www.national.com/mpf/LM/LM723.html#Overview

If you really want to get low noise, you do the "amplify noise by -1"
trick.

Vicor has a special "afterburner" module you can hook after their
switchers, which does this.

The trick is that you don't really need much power in the amplifier,
it just have to be able to cancel out the noise, a trivial transistor
or op-amp will do.

If you really want to go radical, take a peek at Nationals AN1651,
study the two opamps at the top of the schematics...

Poul-Henning


-- 
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] Low noise voltage regulators

[Brooke Clarke]

Hi neville:

My old Gibbs rack mount 5 MHz standard used the LM723 linear regulator.  
I believe it's one of the lowest noise regulators you can use.

http://www.national.com/mpf/LM/LM723.html#Overview

Have Fun,

Brooke Clarke
http://www.PRC68.com


Neville Michie wrote:

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low 
noise voltage reference.
I am proposing to build a voltage regulator for a thermally controlled 
LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick 
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled 
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C 
and 18Volts, the thermal

flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven by 
the LM317 output

would provide a low noise power source? What would be better?

cheers, Neville Michie

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Re: [time-nuts] Low noise voltage regulators

[Matthew Smith]

Quoth Neville Michie at 2010-02-25 08:27...
> ...the LM317 output
> would provide a low noise power source? What would be better?

Can't give you a proper answer, but the last time I saw this type of
question raised, someone pointed me to a linear regulator made from
discrete components, designed for high-end (rabidly obsessive
audiophile) hi-fi stuff.


-- 
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business:  http://www.smiffytech.com/
Blog/personal: http://www.smiffysplace.com/
LinkedIn:  http://www.linkedin.com/in/smiffy
Skype: msmiffy
Twitter:   @smiffy

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[time-nuts] Low noise voltage regulators

[Neville Michie]

Hi,
I remember a reference, probably by Bruce, that LEDS provide a low  
noise voltage reference.
I am proposing to build a voltage regulator for a thermally  
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick  
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled  
temperature.
The LPRO has internal voltage regulation, and by running it at ~40C  
and 18Volts, the thermal

flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven  
by the LM317 output

would provide a low noise power source? What would be better?

cheers, Neville Michie

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Re: [time-nuts] Primary Standards...

[Magnus Danielson]

Poul-Henning Kamp wrote:

In message <20100223214204.eae71117...@hamburg.alientech.net>, Mike S writes:

renamed, since the discussion has shifted.


"In the time and frequency field, the term primary standard is 
sometimes used to refer to any cesium oscillator, [...]


That rhymes with and Karls and my perception of the term:

A Cs clock is primary because when you turn it on, it latches onto
the physical phenomenon of a known and invariant frequency subject
to no systematic errors.


No, that's not quite accurate. The key is that the systematic errors is 
predictable and that you can compensate for them such that residue 
systematic errors becomes very small. The C-field frequency shift is one 
such systematic factor.


The phase-error of the Ramsey interregation cavities is another, which 
is first-degree compensated for in some laboratory standards, but which 
can be reduced by carefull design and compensated for if it can be 
controlled to be repeateable and stable.


Even for Caesiums there exists numerous shifts. Caesium fountains is one 
approach to address some of these issues, alongside that of thermal noise.



The reason the small Rb's do not qualify as primary is that each
unit has a slightly different frequency, due to vapour pressure,
isotopemix and other physical details, and thus you cannot know the
frequency of a particular unit, until you have measured it relative
a primary clock.


There are many factors for gas standards which makes them have 
unpredictable systematic errors. They also show long term drift factors.
The motivation for them is much lower price, volume and power 
consumption. Rubidium has proven a good choice for a gas standard.



In other words, Primary and Secondary has nothing to do with which
atoms, but depends a lot on the interogations mechanism used.


Agreed.

The reason Caesium is chosen is that when they where choosing, they 
higher frequency of Thallium was considered problematic as it would 
become harder to achieve the wanted repeatability from a technological 
point of view at that time. Thallium showed however a lower sensitivity 
to magnetic field than Caesium, so technically it is a better standard 
and it was known at the time. Thus, the aspect of gentlemens agreement.


By todays knowledge, Rubidium fointain outperforms Caesium, so with that 
technology scope Rubidium would be chosen and Caesium beams would be 
handy secondary standards



So the tiny 1cm^3 Cs standards are secondary, because they are also
subject to all sorts of pulls and offsets.


Agreed.


The "experimental" clocks based on lonely ions and quantum embraces
are very likely primary, once somebody has measured their intrinsic
frequency relative to Cs once.


Various clocks have been made for this purpose. The field is being 
investigated. The Aluminium-ion clock that was reported on recently is 
one among many different projects.



The way to find out if your new invention has a chance to become a
primary clock, is to build N of them, turn them on, and see if they
all find the same frequency once they are locked, if they do,
you're on your way to become famous.



That helps. However, unless someone is able to independently build 
clocks and get equivalent levels of accuracy and stability, you still 
have a problem to show the actual performance.


It is challenging not to remake the same systematic design mistake. For 
hydrogen clocks use of different sized glas bulbs to investigate the 
wall-shifts and be able to cancel the effect, which has been important 
when measuring the unperturbed hydrogen frequency.


It is not an easy science, but it is a science which excels in 
increasingly improved methods.


Cheers,
Magnus

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Re: [time-nuts] Primary standard again

[Magnus Danielson]

Rick Karlquist wrote:

If you want to get technical, the frequency of a cesium standard
also depends on the gravitational acceleration, but for relativistic
reasons, not newtonian physics.  Any decent cesium is accurate
enough that it will noticably speed up at NIST in Boulder.  NIST's
best clocks speed up noticibly if you move them from the ground
floor to upstairs.

The pendulum is also not primary because it's length has to be
calibrated.  A cesium kit does not require any calibrated parts,
including the microwave cavity, which only has to be symmetrical.


One important aspect of a primary standard is that you want to achieve 
repeatability of realization. This involves avoiding calibrating to some 
arbitrary point. Caesium clocks have been realized in many very 
different forms, but achieves this to various degrees.


Another aspect is the accuracy. For a clock to be meaningfull in a 
calibration chain, it needs to realize an accuracy such that it is 
meaningfull to calibrate other clocks to it.


A further important aspect is the stability, as it will affect the 
calibration measures taken and usefullness for the purpose.


Then, on top of that, it is a gentlemens agreement on what is wise to 
use for common reference for such a realization. Many primary standards 
definitions would be possible, but in the end having a common one that 
everyone agrees upon is also important.


I think it would be challanging to define it more precisely than that. 
We know what it is when we see it. :)


Cheers,
Magnus

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Re: [time-nuts] Primary Standards...

[Ian Sheffield]

In my checkered past, I once legally owned, for about two minutes between 
signatures, the British Standard Pound weight. It was a bar of platinum.
I confess I did wonder how easy it would be to sell a pound of platinum, as 
it would have been a bit difficult to cut it up...



- Original Message - 
From: "Tom Holmes, N8ZM" 
To: "'Discussion of precise time and frequency measurement'" 


Sent: Wednesday, February 24, 2010 3:00 PM
Subject: Re: [time-nuts] Primary Standards...



Dave...

I went back and checked in my college Physics textbook, Halliday & 
Resnick,

Vol. II, circa 1960, and you are correct about the Ampere being defined
based on the force between two parallel wires. However, H&R does not 
specify

a vacuum nor negligible wire cross section. The latter seems reasonable to
minimize the effects of geometry. They also say that at the time, NBS was
using a balance beam technique with a moving coil between two fixed coils 
as

the primary measurement standard.

Where Avogadro's number comes in is that 1 coulomb is defined as "the 
amount
of charge that flows through a given cross section of wire in one second 
IF

there is a steady current of one Ampere". In other words, if I moved a
coulomb of charge in one second, then the current must have been one 
Ampere.
Kind of a strange way to state it given that one of the equations given 
for
charge is Q= the integral of I*d(t), implying that current and time are 
the

are the measurables.

So I think in a way we are both correct: you have the definition of the
standard, and I cited an equivalence that is based on the fundamental 
units

of the mks system.

In a table in the appendix called "Symbols, Dimensions, and Units for
Physical Quantities" there are listed about 60 quantities and their 
primary

units (Length, Mass, Time, and Charge). For example, capacitance has
dimensions of T^2 * Q^2 / M^2 * L^2, with the derived unit Farad.  Force 
has

dimensions of M*L/T^2, with derived units of newtons. This fits with F=MA,
that is, force is derived from mass, length, and time, all of which have
fundamental standards. The Kg is a slug of something carefully stashed in 
a

cave in France ( a little license here, please), the meter is a bunch of
wavelengths of a Krypton dance, and the second is based on...oh, wait, 
this

is the time-nuts forum.

So what is bugging me is that the Newton, a derived unit, is being used to
define the Ampere, which appears to be a fundamental part of the 
definition

of the Coulomb, a primary unit. This strikes me as backwards. However, it
does make sense that the method used to determine a 'standard' value for 
the

Ampere might not be possible using such a strict dependency on direct ties
to primary units.

OK, I think I have meandered far enough OT once again as to put this to 
rest

for now.


Regards,

Tom Holmes, N8ZM
Tipp City, OH
EM79xx

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dr. David Kirkby
Sent: Tuesday, February 23, 2010 8:12 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Standards...

Tom Holmes, N8ZM wrote:

My recollection of the definition of an Ampere is 6.02 x 10^23 electrons
per second (Avogadro's Number, I believe) passing a point in a conductor. 
To

this day, I wonder how they managed to count all those electrons. But it
does suggest that the silver deposit approach might be a better method of
building a standard. Seems, though, like you'd have to make a darned high
resolution weight measurement.

That certainly was not the definition I learned during my EE degree, and
neither
is it the one given on Wikipedia - not that I'd call Wikipedia a standard.

My recollection is the same as Wikipedia's - though I could not remember 
the

bit
about it needing to be a vacuum. But if you stuffed mu-metal between the
wires,
it would tend to reduce the force, so I can well believe its defined in a
vacuum.

I think as someone else said, this depends on one's definition of a
"standard".
There's no one standard definition of a standard (pun intended).

Dave

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No virus found in this incoming message.
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19:34:00



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Re: [time-nuts] Primary Standards...

[Bob Camp]

Hi

One significant point there about BIPM - "earth rotation measurements". UTC
is not a straight count of "standard" seconds. Somebody has to decide when
to slip it to match our wobbly planet. Not because of an error in the
second, it's the planet that's not stable enough...

--

Stuff that's more exotic than a Cesium tube does exist. The problem - you
can't afford to run one for very long. Even with a government paying the
bills that's true of a lot of this stuff. A clock that you can't run
continuously is not a real good thing to depend on. 

I'd bet at least a dollar that we'll be using Cesium for quite a while.

Bob




-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Rob Kimberley
Sent: Wednesday, February 24, 2010 7:38 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Primary Standards...

Yes, and no..

Time as we know it (UTC) is coordinated at the BIPM in Paris between
observations from primary standards at contributing laboratories and also
earth rotation measurements. Each lab contributing will at any time (excuse
the pun) have a small time offset with regard to UTC. E.g. time from NPL in
UK would say be offset from UTC at any time by a few microseconds, and would
be designated UTC-NPL. Worth reading
http://www.npl.co.uk/science-technology/time-frequency/time/

Interestingly there is a lot of research into more stable clocks using
Mercury and Ytterbium. This then leads to discussion about a future possible
re-definition of the second (which IMHO will happen).

Rob Kimberley

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Mike S
Sent: 24 February 2010 12:14 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Standards...

At 07:46 PM 2/23/2010, Rick Karlquist wrote...

>The TAI is a weighted average to improve short term stability and
>to average out random frequency errors.

IOW, there is a variance from clock to clock. So, if there are 80 
different clocks, are there 80 different seconds, or 80 imperfect 
clocks? Is this a problem with the definition (i.e. Cs resonance is 
unstable), or with the clocks?


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Re: [time-nuts] Wrist Watch for Time Nuts

[Bob Camp]

Hi

A square foot of solar cells fashioned into "geek stylish" hat would keep it
running for quite a while.

-

Has anybody actually poked at one of these yet?

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of paul swed
Sent: Wednesday, February 24, 2010 11:59 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Wrist Watch for Time Nuts

2 big alligator clips to an external supply.
Limitless operation. Maybe a 6v car battery and regulator. Worn around the
waste
get the cardio up

On Wed, Feb 24, 2010 at 11:03 AM, Robert Darlington
wrote:

> Which means a battery every month for somebody actively developing
projects
> that talk to wireless sensor networks.  Still not a bad deal.
>
> -Bob
>
> On Wed, Feb 24, 2010 at 8:08 AM, paul swed  wrote:
>
> > That is indeed neat.
> > Just no time for another project to tinker with.
> > $49 quite the deal
> > Whats funny is it eats a battery at least every 6 months for average
use.
> >
> > On Wed, Feb 24, 2010 at 4:12 AM, Matthew Smith 
> > wrote:
> >
> > > Quoth David at 24/02/10 19:35...
> > >
> > >  Something for the more adventurous, link your wrist watch to your own
> > time
> > >> standards. TI have brought out a 'sports watch' based development
> > system,
> > >> the 'eZ430-Chronos' based on their 430 processor. It includes an RF
> data
> > >> link so you should be able to write code to automatically sync the
> watch
> > >> to
> > >> your GPS / Rubidium / Caesium / Maser standards and calibrate the
> watch
> > >> drift (including temp effects) etc. It might be a bit of a trick to
> get
> > >> Lady
> > >> Heather to run on it.
> > >>
> > >
> > > Last I heard, only the US frequency (whatever it is) version was
> > available.
> > >  For those of us in 433MHz-land (ie: rest of the world,) available
next
> > few
> > > weeks.
> > >
> > > And I WANT ONE!  Perfect wrist-top manager for wearable sensors.
> > >
> > > Cheers
> > >
> > > M
> > >
> > >
> > > --
> > > Matthew Smith
> > > Smiffytech - Technology Consulting & Web Application Development
> > > Business:  http://www.smiffytech.com/
> > > Blog/personal: http://www.smiffysplace.com/
> > > LinkedIn:  http://www.linkedin.com/in/smiffy
> > > Skype: msmiffy
> > > Twitter:   @smiffy
> > >
> > >
> > > ___
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Re: [time-nuts] Wrist Watch for Time Nuts

[paul swed]

2 big alligator clips to an external supply.
Limitless operation. Maybe a 6v car battery and regulator. Worn around the
waste
get the cardio up

On Wed, Feb 24, 2010 at 11:03 AM, Robert Darlington
wrote:

> Which means a battery every month for somebody actively developing projects
> that talk to wireless sensor networks.  Still not a bad deal.
>
> -Bob
>
> On Wed, Feb 24, 2010 at 8:08 AM, paul swed  wrote:
>
> > That is indeed neat.
> > Just no time for another project to tinker with.
> > $49 quite the deal
> > Whats funny is it eats a battery at least every 6 months for average use.
> >
> > On Wed, Feb 24, 2010 at 4:12 AM, Matthew Smith 
> > wrote:
> >
> > > Quoth David at 24/02/10 19:35...
> > >
> > >  Something for the more adventurous, link your wrist watch to your own
> > time
> > >> standards. TI have brought out a 'sports watch' based development
> > system,
> > >> the 'eZ430-Chronos' based on their 430 processor. It includes an RF
> data
> > >> link so you should be able to write code to automatically sync the
> watch
> > >> to
> > >> your GPS / Rubidium / Caesium / Maser standards and calibrate the
> watch
> > >> drift (including temp effects) etc. It might be a bit of a trick to
> get
> > >> Lady
> > >> Heather to run on it.
> > >>
> > >
> > > Last I heard, only the US frequency (whatever it is) version was
> > available.
> > >  For those of us in 433MHz-land (ie: rest of the world,) available next
> > few
> > > weeks.
> > >
> > > And I WANT ONE!  Perfect wrist-top manager for wearable sensors.
> > >
> > > Cheers
> > >
> > > M
> > >
> > >
> > > --
> > > Matthew Smith
> > > Smiffytech - Technology Consulting & Web Application Development
> > > Business:  http://www.smiffytech.com/
> > > Blog/personal: http://www.smiffysplace.com/
> > > LinkedIn:  http://www.linkedin.com/in/smiffy
> > > Skype: msmiffy
> > > Twitter:   @smiffy
> > >
> > >
> > > ___
> > > time-nuts mailing list -- time-nuts@febo.com
> > > To unsubscribe, go to
> > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
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> > and follow the instructions there.
> >
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Re: [time-nuts] Wrist Watch for Time Nuts

[Robert Darlington]

Which means a battery every month for somebody actively developing projects
that talk to wireless sensor networks.  Still not a bad deal.

-Bob

On Wed, Feb 24, 2010 at 8:08 AM, paul swed  wrote:

> That is indeed neat.
> Just no time for another project to tinker with.
> $49 quite the deal
> Whats funny is it eats a battery at least every 6 months for average use.
>
> On Wed, Feb 24, 2010 at 4:12 AM, Matthew Smith 
> wrote:
>
> > Quoth David at 24/02/10 19:35...
> >
> >  Something for the more adventurous, link your wrist watch to your own
> time
> >> standards. TI have brought out a 'sports watch' based development
> system,
> >> the 'eZ430-Chronos' based on their 430 processor. It includes an RF data
> >> link so you should be able to write code to automatically sync the watch
> >> to
> >> your GPS / Rubidium / Caesium / Maser standards and calibrate the watch
> >> drift (including temp effects) etc. It might be a bit of a trick to get
> >> Lady
> >> Heather to run on it.
> >>
> >
> > Last I heard, only the US frequency (whatever it is) version was
> available.
> >  For those of us in 433MHz-land (ie: rest of the world,) available next
> few
> > weeks.
> >
> > And I WANT ONE!  Perfect wrist-top manager for wearable sensors.
> >
> > Cheers
> >
> > M
> >
> >
> > --
> > Matthew Smith
> > Smiffytech - Technology Consulting & Web Application Development
> > Business:  http://www.smiffytech.com/
> > Blog/personal: http://www.smiffysplace.com/
> > LinkedIn:  http://www.linkedin.com/in/smiffy
> > Skype: msmiffy
> > Twitter:   @smiffy
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
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Re: [time-nuts] 5071A question

[Richard (Rick) Karlquist]

When the 5071A product line was sold to Symmetricom ~4 years ago,
the production manager and his team of 15 moved with the product.
The manager left Symmetricom a few years ago, and recently most
of the rest of the team left Symmetricom.  The 5071A will now
be made on the east coast at the facility that made Symmetricom's
other cesium products.  A few ex-HP'ers may assist in some capacity.
These guys are top notch and there is at least some hope that
they won't lose the recipe.  Everyone is watching to see what
happens.  (Note:  I am not involved with Symmetricom).

Beyond any problems having to do with Symmetricom, the design is
getting very long in the tooth in terms of components.  The boards
I designed have, for example, 1206 passives and discrete transistors.
They were, at least, surface mount, which was still a novelty in
1990.  Eventually, something will have to be done along the
lines of redesign.  I hate to think what would happen in that case.

Rick Karlquist N6RK


Christopher Hoover wrote:
We time nuts, and time labs worldwide too, recognize the 5071A as an 
amazingly accurate and precise instrument as well as an extraordinary 
industrial product with these same qualities repeated many times over 
and over.


Most of us know the product was transferred from HP/Agilent to Symnetricom.

My question is as follows.  Is the 5071A (or at least its tube?) still 
in production at Symnetricom to HP/Agilent specifications and quality?


If not, we've really lost something.

-ch


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Re: [time-nuts] Wrist Watch for Time Nuts

[paul swed]

That is indeed neat.
Just no time for another project to tinker with.
$49 quite the deal
Whats funny is it eats a battery at least every 6 months for average use.

On Wed, Feb 24, 2010 at 4:12 AM, Matthew Smith  wrote:

> Quoth David at 24/02/10 19:35...
>
>  Something for the more adventurous, link your wrist watch to your own time
>> standards. TI have brought out a 'sports watch' based development system,
>> the 'eZ430-Chronos' based on their 430 processor. It includes an RF data
>> link so you should be able to write code to automatically sync the watch
>> to
>> your GPS / Rubidium / Caesium / Maser standards and calibrate the watch
>> drift (including temp effects) etc. It might be a bit of a trick to get
>> Lady
>> Heather to run on it.
>>
>
> Last I heard, only the US frequency (whatever it is) version was available.
>  For those of us in 433MHz-land (ie: rest of the world,) available next few
> weeks.
>
> And I WANT ONE!  Perfect wrist-top manager for wearable sensors.
>
> Cheers
>
> M
>
>
> --
> Matthew Smith
> Smiffytech - Technology Consulting & Web Application Development
> Business:  http://www.smiffytech.com/
> Blog/personal: http://www.smiffysplace.com/
> LinkedIn:  http://www.linkedin.com/in/smiffy
> Skype: msmiffy
> Twitter:   @smiffy
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Primary Standards...

[Tom Holmes, N8ZM]

Dave...

I went back and checked in my college Physics textbook, Halliday & Resnick,
Vol. II, circa 1960, and you are correct about the Ampere being defined
based on the force between two parallel wires. However, H&R does not specify
a vacuum nor negligible wire cross section. The latter seems reasonable to
minimize the effects of geometry. They also say that at the time, NBS was
using a balance beam technique with a moving coil between two fixed coils as
the primary measurement standard. 

Where Avogadro's number comes in is that 1 coulomb is defined as "the amount
of charge that flows through a given cross section of wire in one second IF
there is a steady current of one Ampere". In other words, if I moved a
coulomb of charge in one second, then the current must have been one Ampere.
Kind of a strange way to state it given that one of the equations given for
charge is Q= the integral of I*d(t), implying that current and time are the
are the measurables. 

 So I think in a way we are both correct: you have the definition of the
standard, and I cited an equivalence that is based on the fundamental units
of the mks system.  

In a table in the appendix called "Symbols, Dimensions, and Units for
Physical Quantities" there are listed about 60 quantities and their primary
units (Length, Mass, Time, and Charge). For example, capacitance has
dimensions of T^2 * Q^2 / M^2 * L^2, with the derived unit Farad.  Force has
dimensions of M*L/T^2, with derived units of newtons. This fits with F=MA,
that is, force is derived from mass, length, and time, all of which have
fundamental standards. The Kg is a slug of something carefully stashed in a
cave in France ( a little license here, please), the meter is a bunch of
wavelengths of a Krypton dance, and the second is based on...oh, wait, this
is the time-nuts forum.

So what is bugging me is that the Newton, a derived unit, is being used to
define the Ampere, which appears to be a fundamental part of the definition
of the Coulomb, a primary unit. This strikes me as backwards. However, it
does make sense that the method used to determine a 'standard' value for the
Ampere might not be possible using such a strict dependency on direct ties
to primary units. 

OK, I think I have meandered far enough OT once again as to put this to rest
for now.


Regards,

Tom Holmes, N8ZM
Tipp City, OH
EM79xx

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dr. David Kirkby
Sent: Tuesday, February 23, 2010 8:12 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Standards...

Tom Holmes, N8ZM wrote:
> My recollection of the definition of an Ampere is 6.02 x 10^23 electrons
per second (Avogadro's Number, I believe) passing a point in a conductor. To
this day, I wonder how they managed to count all those electrons. But it
does suggest that the silver deposit approach might be a better method of
building a standard. Seems, though, like you'd have to make a darned high
resolution weight measurement.

That certainly was not the definition I learned during my EE degree, and
neither 
is it the one given on Wikipedia - not that I'd call Wikipedia a standard.

My recollection is the same as Wikipedia's - though I could not remember the
bit 
about it needing to be a vacuum. But if you stuffed mu-metal between the
wires, 
it would tend to reduce the force, so I can well believe its defined in a
vacuum.

I think as someone else said, this depends on one's definition of a
"standard". 
There's no one standard definition of a standard (pun intended).

Dave

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Re: [time-nuts] Primary Standards...

[Lux, Jim (337C)]

On 2/24/10 4:38 AM, "Rob Kimberley"  wrote:

> Yes, and no..
> 
> Time as we know it (UTC) is coordinated at the BIPM in Paris between
> observations from primary standards at contributing laboratories and also
> earth rotation measurements. Each lab contributing will at any time (excuse
> the pun) have a small time offset with regard to UTC. E.g. time from NPL in
> UK would say be offset from UTC at any time by a few microseconds, and would
> be designated UTC-NPL. Worth reading
> http://www.npl.co.uk/science-technology/time-frequency/time/
> 
> Interestingly there is a lot of research into more stable clocks using
> Mercury and Ytterbium. This then leads to discussion about a future possible
> re-definition of the second (which IMHO will happen).
>

Yes... At JPL there's work going on with a linear trapped Hg ion clock for
spacecraft. Stability is 1E-12/sqrt(tau), with temperature sensitivity on
the order of 1E-15/degree (at the basic sensor). Roughly a liter in volume
and 1 kg. When it's done, it will enable a lot of changes in things like
navigating spacecraft and making precise measurements over long distances.
(because you can do one-way measurements, as opposed to two way)


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Re: [time-nuts] Primary Standards...

[Rob Kimberley]

Yes, and no..

Time as we know it (UTC) is coordinated at the BIPM in Paris between
observations from primary standards at contributing laboratories and also
earth rotation measurements. Each lab contributing will at any time (excuse
the pun) have a small time offset with regard to UTC. E.g. time from NPL in
UK would say be offset from UTC at any time by a few microseconds, and would
be designated UTC-NPL. Worth reading
http://www.npl.co.uk/science-technology/time-frequency/time/

Interestingly there is a lot of research into more stable clocks using
Mercury and Ytterbium. This then leads to discussion about a future possible
re-definition of the second (which IMHO will happen).

Rob Kimberley

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Mike S
Sent: 24 February 2010 12:14 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Standards...

At 07:46 PM 2/23/2010, Rick Karlquist wrote...

>The TAI is a weighted average to improve short term stability and
>to average out random frequency errors.

IOW, there is a variance from clock to clock. So, if there are 80 
different clocks, are there 80 different seconds, or 80 imperfect 
clocks? Is this a problem with the definition (i.e. Cs resonance is 
unstable), or with the clocks?


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Re: [time-nuts] Primary Standards...

[Mike S]

At 07:46 PM 2/23/2010, Rick Karlquist wrote...


The TAI is a weighted average to improve short term stability and
to average out random frequency errors.


IOW, there is a variance from clock to clock. So, if there are 80 
different clocks, are there 80 different seconds, or 80 imperfect 
clocks? Is this a problem with the definition (i.e. Cs resonance is 
unstable), or with the clocks?



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Re: [time-nuts] Wrist Watch for Time Nuts

[Matthew Smith]

Quoth David at 24/02/10 19:35...

Something for the more adventurous, link your wrist watch to your own time
standards. TI have brought out a 'sports watch' based development system,
the 'eZ430-Chronos' based on their 430 processor. It includes an RF data
link so you should be able to write code to automatically sync the watch to
your GPS / Rubidium / Caesium / Maser standards and calibrate the watch
drift (including temp effects) etc. It might be a bit of a trick to get Lady
Heather to run on it.


Last I heard, only the US frequency (whatever it is) version was 
available.  For those of us in 433MHz-land (ie: rest of the world,) 
available next few weeks.


And I WANT ONE!  Perfect wrist-top manager for wearable sensors.

Cheers

M


--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business:  http://www.smiffytech.com/
Blog/personal: http://www.smiffysplace.com/
LinkedIn:  http://www.linkedin.com/in/smiffy
Skype: msmiffy
Twitter:   @smiffy

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[time-nuts] Wrist Watch for Time Nuts

[David]

Something for the more adventurous, link your wrist watch to your own time
standards. TI have brought out a 'sports watch' based development system,
the 'eZ430-Chronos' based on their 430 processor. It includes an RF data
link so you should be able to write code to automatically sync the watch to
your GPS / Rubidium / Caesium / Maser standards and calibrate the watch
drift (including temp effects) etc. It might be a bit of a trick to get Lady
Heather to run on it.

Links: 
www.ti.com/ez430
www.ti.com/chronoswiki


David



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Re: [time-nuts] Rb Oscillator - rather fundamental question

[Matthew Smith]

Quoth Kasper Pedersen at 24/02/10 17:44...

It will.
Set the fuses as you would have for a 10MHz crystal, and capacitively 
couple the source to XTAL1. Leave XTAL2 open.

Do not set the fuses for 'external clock mode'.

Do put something like 100pF+1k Ohm in series with the input. While they 
won't promise anything, I have deliberately run 1A into the protection 
diodes of an ATMega16 for many seconds and still had a functional part.


Many thanks.  I was wondering about doing this; Chris Keuthe quoted the 
figures from the datasheet but then I thought that this would be the 
ratings for an external oscillator, as surely an actual crystal would be 
putting out a much smaller voltage than those quoted.  A few days ago, 
on another list, David had suggested something similar with "faking" a 
crystal for an AT90S8535 RTC.


I also wondered how an AVR could not work when PICs are reported to.

I will certainly use the series R+C as you and David have suggested, but 
will not worry about further protection - the AVR is one of the cheapest 
components in the whole system - I am far more concerned about damaging 
the Rb module than the AVR!


Thanks to all who have answered on this.  I will post a link to details 
when I get this project up and running.


Cheers

M

--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business:  http://www.smiffytech.com/
Blog/personal: http://www.smiffysplace.com/
LinkedIn:  http://www.linkedin.com/in/smiffy
Skype: msmiffy
Twitter:   @smiffy

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