Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

[Bruce Griffiths]

However the value of the second time constant in the active PI filter required 
to achieve reasonable damping will be around 1600 seconds. This corresponds to 
an active PI filter proportional gain of 16.

Bruce
 

On Wednesday, 25 May 2016 3:20 PM, Bruce Griffiths 
 wrote:
 

 When comparing a 10MHz OCXO divided down to 1Hz with a GPS PPS signal, the 
effective VCO gain (Ko/N) is likely to be around 6E-7 rad/s/V (eg HP10811A) and 
the phase detector gain around 1V/rad. Consequently a PLL loop bandwidth of 
100uHz only requires an Integrator time constant of around  100 sec or so for a 
second order PLL with an active PI filter. The required integrator time 
constant can be reduced further by using an attenuator between the filter 
output and the OCXO EFC input.

Bruce
 

On Wednesday, 25 May 2016 9:00 AM, Wes  wrote:
 

 A cleaver design, but the OP wanted 1pps.  I have the Leo Bodnar GPSDO.  It 
too 
is a nice frequency standard, but it doesn't know what time it is.

On 5/24/2016 9:53 AM, Graham / KE9H wrote:
> If you want an "existence proof" for a simple, mostly analog, a few digital
> counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO..
> He designed it for his own use, then put it into production because of
> demand for a simple, cheap GPSDO.  It has been characterized, and works
> well for the simple circuit.
>
> The schematics are published, since it started as a hobby project.
>
> http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm
>
> http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm
>
> You can buy his, or build your own with his design as a starting point.
>
> He does use a GPS with 10 kHz output to simplify some of the timing and
> integration issues Bob referred to.
>
> --- Graham
>
> ==
>

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Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

[Bruce Griffiths]

When comparing a 10MHz OCXO divided down to 1Hz with a GPS PPS signal, the 
effective VCO gain (Ko/N) is likely to be around 6E-7 rad/s/V (eg HP10811A) and 
the phase detector gain around 1V/rad. Consequently a PLL loop bandwidth of 
100uHz only requires an Integrator time constant of around  100 sec or so for a 
second order PLL with an active PI filter. The required integrator time 
constant can be reduced further by using an attenuator between the filter 
output and the OCXO EFC input.

Bruce
 

On Wednesday, 25 May 2016 9:00 AM, Wes  wrote:
 

 A cleaver design, but the OP wanted 1pps.  I have the Leo Bodnar GPSDO.  It 
too 
is a nice frequency standard, but it doesn't know what time it is.

On 5/24/2016 9:53 AM, Graham / KE9H wrote:
> If you want an "existence proof" for a simple, mostly analog, a few digital
> counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO..
> He designed it for his own use, then put it into production because of
> demand for a simple, cheap GPSDO.  It has been characterized, and works
> well for the simple circuit.
>
> The schematics are published, since it started as a hobby project.
>
> http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm
>
> http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm
>
> You can buy his, or build your own with his design as a starting point.
>
> He does use a GPS with 10 kHz output to simplify some of the timing and
> integration issues Bob referred to.
>
> --- Graham
>
> ==
>

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Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)

[David]

On Tue, 24 May 2016 16:15:15 -0700, you wrote:

>
>kb...@n1k.org said:
>> The glitches are to narrow (short duration) and far to regular for the
>> ionosphere to be the issue.  
>
>Is multipath from a large airliner in a landing pattern likely to cause that 
>sort of problems?
>
>I'm 20+ miles off the end of SFO, but it's common to see large planes going 
>over and turning to line up for a landing.  On my one-of-these-days list is 
>to grab the airline location data and see if it correlates with GPS glitches.

Back when I did a lot of transmitter hunting, I listened to multipath
from airliners from 2 meters to 23 centimeters.  The 2 meter
directional antenna I ultimately designed was good enough to not only
track airlines by their reflected RF, but it could see reflections and
shadows from nearby objects like street lights and trees which
ultimately limited outside performance testing.

As you can calculate from the geometry, the flutter started out fast
and decreased in frequency until there was a slow null/peak and then
it reversed.  If the same happened with GPS, then maybe the receiver
could briefly lock onto the reflection from the plane producing a
different solution for a short time.
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Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)

[Bob Camp]

HI

The gotcha with anything local is the sidereal day repeat pattern The local 
stuff would have to 
be very solar oriented to be slipping at exactly that rate over a few months of 
data.  My guess 
is that when *this combo* gets into *that position* and *this multi path* 
happens … you get a 
glitch. It’s not there for long, but it is there. 

Credit where credit is due … some guy named Tom (who also drives around with 6 
5071’s on 
a regular basis … handing them out to strangers) spotted the sidereal day time 
slip. I had been 
chasing it as if it was 24 hours and some weird local “train goes by an 
midnight” sort of thing. 

Bob


> On May 24, 2016, at 7:15 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> The glitches are to narrow (short duration) and far to regular for the
>> ionosphere to be the issue.  
> 
> Is multipath from a large airliner in a landing pattern likely to cause that 
> sort of problems?
> 
> I'm 20+ miles off the end of SFO, but it's common to see large planes going 
> over and turning to line up for a landing.  On my one-of-these-days list is 
> to grab the airline location data and see if it correlates with GPS glitches.
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)

[Hal Murray]

kb...@n1k.org said:
> The glitches are to narrow (short duration) and far to regular for the
> ionosphere to be the issue.  

Is multipath from a large airliner in a landing pattern likely to cause that 
sort of problems?

I'm 20+ miles off the end of SFO, but it's common to see large planes going 
over and turning to line up for a landing.  On my one-of-these-days list is 
to grab the airline location data and see if it correlates with GPS glitches.

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)

[Bob Camp]

HI

If you have a good antenna location and always have more sat’s in view than the 
receiver can use, 
the constellation shift may not be a big deal at some level. No matter how good 
the antenna, day / night
ionosphere compared to the estimated numbers they broadcast will be an issue. 

Is the level that the local multi path and the constellation "gets you" higher 
than the level that the ionosphere 
correction falls apart? Without a lot of data, you will have a hard time 
sorting that out. 

All of that said, I have seen “glitches” in long term plots that space out at 
the expected “just short of 24 hours” 
period. In my location and with the gear I’m running … it’s more likely the 
constellation than the ionosphere. 
The glitches are to narrow (short duration) and far to regular for the 
ionosphere to be the issue. 

Bob



> On May 23, 2016, at 11:52 PM, Skip Withrow  wrote:
> 
> Hello Bob,
> 
> Good point.  Ionosphere between day and night could very well explain it.
> 
> Thanks,
> Skip Withrow
> 
> On Mon, May 23, 2016 at 5:37 PM, Bob Camp  wrote:
> Hi
> 
> Well, *maybe* there is a 24 hour component in the GPS constellation :)
> 
> Indeed a lot of stuff repeats at the 24 hour point. The ionosphere is a bit 
> different at midnight than at noon.
> 
> Bob
> 
> > On May 23, 2016, at 6:43 PM, Skip Withrow  wrote:
> >
> > Hello Nuts,
> >
> > I am attaching a capture from Lady Heather of a 3-day run.  You can see the
> > temperature vary by 7C over each day.  The TB is being run open loop and
> > another GPSDO 10MHz input to the unit instead of the unit's oscillator.
> >
> > I expected the purple line to repeat every 12 hours based on the GPS
> > constellation being the same (which maybe it kind of does), but there is
> > definitely a 24 hour repeat.  What is really weird is that the number of
> > satellites that LH sees also repeats on a 24 hour cycle, not 12 (bottom
> > trace).
> >
> > Any help in understanding this behavior?  Thanks in advance.
> >
> > Skip Withrow
> >
> > 
> > Virus-free.
> > www.avast.com
> > 
> > <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> > ___
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> > To unsubscribe, go to 
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> > and follow the instructions there.
> 
> 

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Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

[Wes]

A cleaver design, but the OP wanted 1pps.  I have the Leo Bodnar GPSDO.  It too 
is a nice frequency standard, but it doesn't know what time it is.


On 5/24/2016 9:53 AM, Graham / KE9H wrote:

If you want an "existence proof" for a simple, mostly analog, a few digital
counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO.
He designed it for his own use, then put it into production because of
demand for a simple, cheap GPSDO.  It has been characterized, and works
well for the simple circuit.

The schematics are published, since it started as a hobby project.

http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm

http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm

You can buy his, or build your own with his design as a starting point.

He does use a GPS with 10 kHz output to simplify some of the timing and
integration issues Bob referred to.

--- Graham

==



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Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

[Graham / KE9H]

If you want an "existence proof" for a simple, mostly analog, a few digital
counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO.
He designed it for his own use, then put it into production because of
demand for a simple, cheap GPSDO.  It has been characterized, and works
well for the simple circuit.

The schematics are published, since it started as a hobby project.

http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm

http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm

You can buy his, or build your own with his design as a starting point.

He does use a GPS with 10 kHz output to simplify some of the timing and
integration issues Bob referred to.

--- Graham

==



On Mon, May 23, 2016 at 8:21 PM, Bob Camp  wrote:

> Hi
>
> Ok, so how would you do a pure analog GPSDO?
>
> The GPS receiver and that side of it are what they are. I’ll assume that
> you have a 1 pps out of a module.
>
> Your OCXO needs to get to 1 Hz via dividers. You can do that with digital
> dividers or with a chain of regenerative
> dividers. One is a bit more analog, the other may be “ok” under the “don’t
> go to crazy” ground rule.
>
> You now have a PPS that is off somewhere relative to the GPS. A push
> button will get them into rough alignment.
> Your OCXO is quite likely a bit high or low. A multi turn pot on the EFC
> will let you get it within 1x10^-9 without a
> lot of crazy work. A reasonable counter tied to a reference will let you
> do this.
>
> Net result: The pps signals are roughly aligned and drifting < 1 ns / s.
> Considering the delta between them is
> bopping around by 10 ns, that’s quite good.
>
> Run a very normal bipolar charge pump off of the delta between the two pps
> signals. Fire a sample and hold when
> the transition is over. You now have a (maybe) +/- 60V signal that
> corresponds to the phase error. Since you are using
> film capacitors, the 60V comes along for free. Taking it to the maximum is
> just a way to save money on caps.
>
> Next up, do a fairly simple 20 second time constant R/C filter. That will
> take out a lot of the hopping around and make
> the rest of the system a bit easier to quiet down. You now have a somewhat
> linear +/- 60V signal that tells you how
> far off phase the setup is. After the RC you have a high input impedance /
> low drift buffer amplifier. Yes that’s a little
> tricky.
>
> Next you need a P and an I term. Both need to be variable as the system
> calms down. A rotary switch will do fine for
> this. Relays might also do the job. The P is a bank of resistors, each one
> to scale the buffered R/C to your control amp.
> The I goes off to a similar set of resistors driving an integrator. Net
> time constant there will be in the 200 to 2,000 second range.
> That’s were the ovenized caps come in. You also need a really good amp as
> part of the integrator to buffer out the signal.
>
> The nice thing about doing it this way is that you can *see* it all
> happening. There is a nice *clunk* noise as the filter
> steps off. Each number in the filter has a (likely large value) resistor
> that sets it up. To change the filter characteristics,
> you swap out resistors or twiddle pots.
>
> If you do the math, even with 60 V on the system, you probably don’t want
> anything over 1 meg ohm involved. At 2K seconds
> that gets you to a pretty big film capacitor bank. Even the 20 second
> lowpass isn’t exactly small by the standards of fancy
> capacitors.
>
> There are a few interesting tidbits like wire wound / high value / low
> temp co resistors that would help things a bit. Swapping
> those in and out as you change filter settings experimentally could get a
> bit crazy.
>
> The net result should be a good starting point for a GPSDO. You still
> would need to spend all of the time working out values
> and matching it up to your OCXO. The need for a good local reference and
> good measurement gear while doing this still is
> a limit, just like the pure digital approach.
>
> Bob
>
>
>
> > On May 23, 2016, at 12:46 PM, Nick Sayer via time-nuts <
> time-nuts@febo.com> wrote:
> >
> >
> >>
> >>> If that sounds too weird, I am open to receive advises for a
> microcontroller based solution.
> >>
> >> If you want to go that way, probably the simplest solution would be to
> >> take one of Nick Sayers boards, pull out the GPS receiver and feed the
> >> PPS input from your GPS receiver.
> >
> > It’d be kind of an awkward fit. For the OCXO/TCXO, you’d need to pull
> the oscillator as well as the GPS (I believe you said you had an oscillator
> already), and your EFC would be 1.65 volts wide centered on 1.65 volts.
> That’s unlikely to be absolutely correct for your oscillator. You could
> change around the Vref for the DAC, but at that point I’d consider
> redesigning the board for your purposes instead.
> >
> > That said, I think it’d be easy to adapt the circuit and code for a more
> arbitrary setup. And I believe my system is good down to the ADEV 10E-11
> leve

Re: [time-nuts] Maser 0.7 nsec jumps solved

[Poul-Henning Kamp]

In message <57441aca.8070...@arcor.de>, Gerhard Hoffmann writes:
>Am 23.05.2016 um 05:15 schrieb Jim Palfreyman:
>> As far as a remedy goes we are going to try a solid state relay that only
>> switches on at 0V in the AC waveform. This should slow the inrush current,
>> and hopefully the magnetic impulse.
>>
>>
>In the context of transformers and motors, switching on at 0V is 
>actually the worst point in time.

Well...

The motor is almost certainly an "Squirrel-cage" induction motor and
that means it is three phase, although one of the phases is probably
created with a "starting capacitor".

So which of the three phases is going to be the lucky one that
switches at maximum voltage, or are you going to switch the phases
on sequentially ?

A 4kW Variable Frequency Drive costs less than $1k and allows you
to control *both* the voltage/time and the frequency/time *both*
during startup and during rundown.

I wouldn't bother fuzzing around with hacks - I'd just go for the
known-to-work solution.

-- 
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] Maser 0.7 nsec jumps solved

[Gerhard Hoffmann]

Am 23.05.2016 um 05:15 schrieb Jim Palfreyman:

As far as a remedy goes we are going to try a solid state relay that only
switches on at 0V in the AC waveform. This should slow the inrush current,
and hopefully the magnetic impulse.


In the context of transformers and motors, switching on at 0V is 
actually the worst point in time.



< https://de.wikipedia.org/wiki/Einschalten_des_Transformators > (German)

< 
http://electrical-engineering-portal.com/practical-considerations-of-transformer-inrush-current 
>


regards, Gerhard
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Re: [time-nuts] Looking for a Linux user with a Z3816/Z3815/HP5xxxx

[jimlux]

On 5/23/16 4:22 PM, Mark Sims wrote:

Alas,  it has become very hard to email an EXE file.  The ISPs are on to all 
the tricks... zipping them,  renaming them, etc no longer work.  The net has 
become a real nanny about protecting people from potential malware, etc.   
Things like EXE files disguised as PDF file were/are a real threat and email 
servers have gotten rather draconian about what they let through.



zip file with a password will often get through.

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Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)

[Tom Van Baak]

Hi Magnus,

> Hi Skip and Tom,
> Yes... almost. The thing is that the GPS orbits is a few minutes shy of 12 
> hours

Right. I think that's why he picked the subject line: "12 hours (-2 minutes)".

Since you're interested in this level of detail, there are papers about GPS 
orbits, repeat times, sidereal time, and orbital maneuvers:

http://www.kristinelarson.net/wp-content/uploads/2015/10/ig0806_gnss-solutions.pdf
http://www.kristinelarson.net/wp-content/uploads/2015/10/gpsrep.pdf

These details turn out to be more important in the geodetic community than the 
T&F community. We tend to average a lot, but they have embraced high-rate 
kinematic GPS receivers as zero-drift seismometers. Some more papers:

http://xenon.colorado.edu/igs5_revised.pdf
ftp://ftp.ngs.noaa.gov/pub/abilich/papers/Bilich2008_Denali.pdf

This issue of "just a bit less than 12 hours" caught my eye because I ran 
across it in ADEV plots. See:

http://leapsecond.com/pages/sidereal/index.htm
http://leapsecond.com/pages/sidereal/sv.htm
http://leapsecond.com/pages/sidereal/14years.htm

The 14years.htm page nicely shows the occasional "station keeping" orbital 
maneuvers of each GPS SV.

/tvb


- Original Message - 
From: "Magnus Danielson" 
To: 
Cc: 
Sent: Monday, May 23, 2016 11:57 PM
Subject: Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)


> Hi Skip and Tom,
> 
> Yes... almost. The thing is that the GPS orbits is a few minutes shy of 
> 12 hours, since they is aligned to sidereal time, so the pattern shift 
> on the sky and it takes half a year to repeat exactly... if it where not 
> for orbital changes.
> 
> Cheers,
> Magnus
> 
> On 05/24/2016 02:01 AM, Tom Van Baak wrote:
>> Hi Skip,
>>
>>> Any help in understanding this behavior?  Thanks in advance.
>>
>> Yes, GPS satellites do repeat every ~12 hours in orbit around the mass of 
>> the earth -- but -- you and the earth turns 180 degrees during those 12 
>> hours. So you're no longer where you should be when the 1st repeat occurs. 
>> Instead you have to wait yet another 12 hours for the earth to get back to 
>> the place where you were, in time to see the 2nd repeat. Now when you hear 
>> "get back, get back, get back to where you once belonged", you'll think of 
>> GPS satellites instead of the Beatles.
>>
>> So the LH plots are correct. Here's another take:
>>
>> 1) Say it's 6 PM MDT in Denver at lat/lon +39/-104 and you see a pattern of 
>> N satellites in the sky.
>> 2) Tomorrow morning at 6 AM MDT that same pattern will be in the sky -- not 
>> for you -- but for some guy at 6 PM lost in Inner Mongolia at lat/lon 
>> +39/+104.
>> 3) Tomorrow evening at 6 PM MDT that same pattern will again be in the sky, 
>> this time for you in Denver.
>>
>> /tvb
>>
>> - Original Message -
>> From: "Skip Withrow" 
>> To: "time-nuts" 
>> Sent: Monday, May 23, 2016 3:43 PM
>> Subject: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)
>>
>>
>>> Hello Nuts,
>>>
>>> I am attaching a capture from Lady Heather of a 3-day run.  You can see the
>>> temperature vary by 7C over each day.  The TB is being run open loop and
>>> another GPSDO 10MHz input to the unit instead of the unit's oscillator.
>>>
>>> I expected the purple line to repeat every 12 hours based on the GPS
>>> constellation being the same (which maybe it kind of does), but there is
>>> definitely a 24 hour repeat.  What is really weird is that the number of
>>> satellites that LH sees also repeats on a 24 hour cycle, not 12 (bottom
>>> trace).
>>>
>>> Any help in understanding this behavior?  Thanks in advance.
>>>
>>> Skip Withrow
>>>
>>
>

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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Bert Kehren via time-nuts]

I like to disagree. In the late 90's I started to work on high efficiency  
boat air conditioners for my boat, written up in Power and Motor Yacht 
"COOL"  January 2003. To reduce inverter load and eliminate the power of the 
relays I  went to zero crossing opto couplers and triacs. Used it also on home 
AC systems  in some places eliminating lamp flicker on poorly supplied homes.
 
 
In a message dated 5/23/2016 11:11:08 P.M. Eastern Daylight Time,  
ai.egrps...@gmail.com writes:

On Sun, May 22,  2016 at 11:15 PM, Jim Palfreyman  
wrote:

As  far as a remedy goes we are going to try a solid state relay that only
>  switches on at 0V in the AC waveform. This should slow the inrush  
current,
> and hopefully the magnetic impulse.
>

If the  load being switched on is inductive, it would be better to switch
the AC  waveform at the voltage peaks, not at 0V.  This might  seem
counter-intuitive, but it's real.  Switching on at the 0V  crossing may
maximize the current pulse through the magnetics.

OTOH,  if the origin of the impulse is mechanical in nature, neither remedy
may  help.

Regards,
Andy
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Re: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)

[Magnus Danielson]

Hi Skip and Tom,

Yes... almost. The thing is that the GPS orbits is a few minutes shy of 
12 hours, since they is aligned to sidereal time, so the pattern shift 
on the sky and it takes half a year to repeat exactly... if it where not 
for orbital changes.


Cheers,
Magnus

On 05/24/2016 02:01 AM, Tom Van Baak wrote:

Hi Skip,


Any help in understanding this behavior?  Thanks in advance.


Yes, GPS satellites do repeat every ~12 hours in orbit around the mass of the earth -- 
but -- you and the earth turns 180 degrees during those 12 hours. So you're no longer 
where you should be when the 1st repeat occurs. Instead you have to wait yet another 12 
hours for the earth to get back to the place where you were, in time to see the 2nd 
repeat. Now when you hear "get back, get back, get back to where you once 
belonged", you'll think of GPS satellites instead of the Beatles.

So the LH plots are correct. Here's another take:

1) Say it's 6 PM MDT in Denver at lat/lon +39/-104 and you see a pattern of N 
satellites in the sky.
2) Tomorrow morning at 6 AM MDT that same pattern will be in the sky -- not for 
you -- but for some guy at 6 PM lost in Inner Mongolia at lat/lon +39/+104.
3) Tomorrow evening at 6 PM MDT that same pattern will again be in the sky, 
this time for you in Denver.

/tvb

- Original Message -
From: "Skip Withrow" 
To: "time-nuts" 
Sent: Monday, May 23, 2016 3:43 PM
Subject: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes)



Hello Nuts,

I am attaching a capture from Lady Heather of a 3-day run.  You can see the
temperature vary by 7C over each day.  The TB is being run open loop and
another GPSDO 10MHz input to the unit instead of the unit's oscillator.

I expected the purple line to repeat every 12 hours based on the GPS
constellation being the same (which maybe it kind of does), but there is
definitely a 24 hour repeat.  What is really weird is that the number of
satellites that LH sees also repeats on a 24 hour cycle, not 12 (bottom
trace).

Any help in understanding this behavior?  Thanks in advance.

Skip Withrow



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Re: [time-nuts] 1937 Time Standard

[Dave Brown]

In the context of public time dissémination, the Shepherd master and gate 
clocks are worth noting as well-

http://collections.rmg.co.uk/collections/objects/79636.html
But somewhat earlier than 1937..
DaveB, NZ

- Original Message - 
From: "Tom Van Baak" 
To: "Discussion of precise time and frequency measurement" 


Sent: Tuesday, May 24, 2016 12:57 PM
Subject: Re: [time-nuts] 1937 Time Standard



Thanks Paul.

I accumulate a pile of PDF's over time and when the right question shows 
up in the list I dig them out. It turns out Thomas, the OP, is doing a 
report on public clocks, including synchronous motor clocks. He added 
another source:

https://clockhistory.com/telechron/company/documents/warren_1937/index.html

The idea of time standards and time transfer methods has not changed over 
the centuries. What these guys did way back with telegraph (Western Union) 
or with 60 Hz (Telechron) we now do with WWVB, NTP, GPS, etc. The decimal 
point moves.


The history of 60 Hz mains frequency, in particular, is extremely 
fascinating.
There's some basic intro here: 
https://en.wikipedia.org/wiki/Utility_frequency#History

Have a look at that table of frequencies used in 1897!

There's a great article (free, IEEE) on the use of 25 Hz at Niagara Falls:
http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4412948

And some wonderful information here:
http://ethw.org/Early_Electrification_of_Buffalo

Finally, this 3 part masterpiece:
http://ethw.org/Archives:Transformers_at_Pittsfield,_part_1
http://ethw.org/Archives:Transformers_at_Pittsfield,_part_2
http://ethw.org/Archives:Transformers_at_Pittsfield,_part_3

If nothing else, everyone should take a quick look at the photos in the 
above 3 URL's. Mini-Circuit transformers these are not.


/tvb
 - Original Message - 
 From: paul swed

 To: Tom Van Baak ; Discussion of precise time and frequency measurement
 Sent: Monday, May 23, 2016 4:23 PM
 Subject: Re: [time-nuts] 1937 Time Standard


 Some good articles I have read several that you sent Tom. Its funny such 
great information if you just search on the right terms.

 But then I appreciate the fact that you sent great links. No guessing.
 More to go and read.
 Regards
 Paul
 WB8TSL


 On Sat, May 21, 2016 at 4:50 PM, Tom Van Baak  wrote:

   Hi Thomas,

   > I was wondering if anyone knew what the "state of the art" time 
standard was in the 1937 ?


   The 1930's were an exciting time in this regard.

   The best time standards (in vacuum pendulum clocks) were those used by 
astronomers. Google: Shortt-Synchronome.


   Laboratory quartz clocks had just been developed. During this decade 
the best pendulum clocks were compared to the best quartz clocks. Google: 
Marrison Loomis Shortt


   And in the race between these two technologies, it was shown in 1936 by 
Scheibe and Adelsberger that irregularities seen by astronomers were due 
to the earth itself and not the pendulum or quartz clocks. This eventually 
led to the leap second. It was common to use a set of 3 clocks to do the 
comparison (sound familiar)


   To get a sense of the world of precise time in the 1930's I would 
recommend reading the following, each of which mentions something about 
the past century of timekeeping.


   The Evolution of the Quartz Crystal Clock
   http://www.ieee-uffc.org/main/history-marrison.asp
   https://ia902701.us.archive.org/25/items/bstj27-3-510/bstj27-3-510.pdf

   Time – the SI Base Unit “Second”, by Andreas Bauch

https://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/2012_Bauch_PTBM_125a_en.pdf

   The Evolution of Time Measurement, Part 2: Quartz Clocks
   http://tf.boulder.nist.gov/general/pdf/2533.pdf

   Atomichron: The Atomic Clock from Concept to Commercial Product
   http://www.ieee-uffc.org/main/history-atomichron.asp

   Precision time and the rotation of the Earth, by Dennis McCarthy

http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU2004_IAUC196%2FS1743921305001377a.pdf

   Some Aspects of Precision Time Measurement -- 1930's German quartz, 
Lothar Rohde, etc.

   http://pubs-newcomen.com/tfiles/75ap119.pdf
   http://www.cdvandt.org/PTR%20quartz-clock.pdf
   http://www.cdvandt.org/CFQ.pdf
   http://www.cdvandt.org/BIOS-1316.pdf

   I have more links and PDF's to share. But let's first find out how deep 
an answer you actually want.


   Thanks,
   /tvb


   - Original Message -
   From: "Thomas D. Erb" 
   To: 
   Sent: Saturday, May 21, 2016 11:40 AM
   Subject: [time-nuts] 1937 Time Standard


   >I was wondering if anyone knew what the "state of the art" time 
standard was in the 1937 ?

   >
   >
   >
   >
   >
   >
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