[time-nuts] time-nuts Digest, Vol 48, Issue 76

Richard Dabney ddabney01 at yahoo.com
Mon Jul 28 23:09:02 EDT 2008


Reply to message 6:.............               .7300 de Dick W5UFZ
How are leap seconds declared?

The International Earth Rotation and Reference System Service (IERS)
observes the Earth's rotation and nearly 6 months in advance (January
and July) a "Bulletin C" message is sent out, which reports whether or
not to add a leap second in the end of June and December.
--- On Mon, 7/28/08, time-nuts-request at febo.com <time-nuts-request at febo.com> wrote:
From: time-nuts-request at febo.com <time-nuts-request at febo.com>
Subject: time-nuts Digest, Vol 48, Issue 76
To: time-nuts at febo.com
Date: Monday, July 28, 2008, 5:09 PM

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Today's Topics:

   1. Re: A fan for the Z3801A (Greg Burnett)
   2. Low power GPSDO (SAIDJACK at aol.com)
   3. Re: time-nuts Digest, Vol 48, Issue 75 (Kit Scally)
   4. Re: How to get 32.768KHz from 10MHz. (Neon John)
   5. Re: How to get 32.768KHz from 10MHz. (Jim Lux)
   6. Leap Second Pending (Mark Sims)
   7. Re: How to get 32.768KHz from 10MHz. (Neville Michie)
   8. Re: Leap Second Pending (Ken Winterling)
   9. Re: How to get 32.768KHz from 10MHz. (Neon John)


----------------------------------------------------------------------

Message: 1
Date: Mon, 28 Jul 2008 11:11:01 -0600
From: "Greg Burnett" <gbusg at comcast.net>
Subject: Re: [time-nuts] A fan for the Z3801A
To: "Discussion of precise time and frequency measurement"
	<time-nuts at febo.com>
Message-ID: <003101c8f0d4$e93f4570$6501a8c0 at gb02>
Content-Type: text/plain;	charset="iso-8859-1"

Another thing to consider: Depending on how well you shock-mount the fan, 
what if its vibration translates to sideband spurs or noise?

-Greg

----------------------
Alberto wrote:
Talking of the Z3801A, has anybody added a small fan to it ? Mine is very 
hot inside, especially the large VLSI chips on
the upper board. I contemplated adding a couple of small DC fans, to push 
out the hot air, but first would like to know
your opinions and your experiences, if any, about that.   Thanks

Alberto  I2PHD




------------------------------

Message: 2
Date: Mon, 28 Jul 2008 17:04:03 EDT
From: SAIDJACK at aol.com
Subject: [time-nuts] Low power GPSDO
To: Murray.Greenman at rakon.com, time-nuts at febo.com
Message-ID: <cd5.35992e17.35bf8e43 at aol.com>
Content-Type: text/plain; charset="US-ASCII"

Hello Murray,
 
no problem :) just wanted to make sure folks know that there are  options 
below 5W out there.
 
I am impressed with your 50mW TCXO unit. We've been thinking about offering
 
DIP14 TCXO's as well on the FireFly. That would allow for true battery  
operation.
 
We are also testing extremely low power (~120mW) OCXO's, with the  heating 
elements integrated into the Crystal Blank itself, but I am not happy  with the

stability of these just yet.
 
We also have a Fury GPSDO wired up to the Agilent E1938A - while it's  the 
best Fury I have it's a real power hog. In fact I am having a hard time 
finding 
a power supply capable of delivering sufficient warmup current to that  box..
 
bye,
Said
 
 
In a message dated 7/28/2008 11:33:44 Pacific Daylight Time,  
Murray.Greenman at rakon.com writes:

Jack,

I didn't claim that the Trimble NTGS50AA was the "lowest  power
GPSDO".
Those are your words. I simply said it was "at the other  extreme",
meaning (although not said) at the other extreme of my  limited
experience of about 10 different models. I own only five  commercial
GPSDOs (HP Z3801A; Symmetricom Z3815A with MTI 260 OCXO; CIC  GPSR-A and
Samsung GCRU-D with Rakon CFPO-2 OCXO; and the Trimble  NTGS50AA), plus a
working relationship with the Datum and Symmetricom units  at work and a
previously owned HP Z3815A with E1938A OCXO.

I've also  built a few, but not in the class of the commercial units. My
lowest power  one is battery operated (uses a V-TCXO) and has a power
consumption of 50mW  (with display backlight off!), but is more affected
by sun load than is  desirable. Another uses the HP 10811A OCXO, and can
hardly be classed as  low power.

I have a professional interest in achieving low power in the  GPSDO, as
the company I work for are part of the Femtocell working group. I  am
certainly impressed that the Firefly is down at 1.35W.  

Regards,
Murray  Greenman




**************Get fantasy football with free live scoring. Sign up for 
FanHouse Fantasy Football today.      
(http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)


------------------------------

Message: 3
Date: Tue, 29 Jul 2008 08:56:24 +1000
From: "Kit Scally" <kScally at BYTECAN.com.au>
Subject: Re: [time-nuts] time-nuts Digest, Vol 48, Issue 75
To: <time-nuts at febo.com>
Message-ID:
	<281090D5003763419A5AC496FF087B2A3B81D8 at msg01nsw.BYTECAN.com.au>
Content-Type: text/plain;	charset="us-ascii"

Alberto,

In the commercial world that the Z3815A's (and quite possibly the Z3801
etc) were used in, they were installed "vertically" at the bottom of
a
large equipment cabinet that had convection air channels running within
it.  A bank of 12-16 fans towards the top of the cabinet sucked up
ambient air and forced it past the PA heatsinks.  The hot air was vented
out the PA modules & cabinet top.  Ambient air temp was controlled at
20-25 deg C.
The GPSDO pcb (and associated electronics) was cooled with incoming
ambient air with the pcb and IC temperatures settling at some value.
The critical point here is that the whole cabinet was operating 24x365
and for years on end.

While semiconductor life is inversely proportional (?) to Tamb and
cooling the electronics may seem a logical approach to prolonging life,
I would suggest that <in this application>, this is a second-order
effect.  The killer is thermal cycling which can induce premature
failure in any electronic assembly - passive or active - with everything
else being equal.

Most (if not all) of these commerciall modules were designed with very
high MTBF's in mind when used "au natural".  I would leave well
alone
and look into providing "standby power" to your Z3801.  

Regards,

Kit
VK2LL


*************

Message: 3
Date: Mon, 28 Jul 2008 15:40:40 +0200
From: Alberto di Bene <dibene at usa.net>
Subject: Re: [time-nuts] A fan for the Z3801A
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <488DCC58.6000802 at usa.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Murray,

   thanks for the advice.

Well, my intention was, as suggested by a private message, to use a 12V
fan powered at 5V, so that it runs slowly and silently, not blowing
external air into the unit, but just extracting the hot air from the
inside.

  And given that the unit is placed in the basement of the house, with a
change in temperature between the day and the night of no more than 1
Celsius, may be the use of the fan should not disturb the thermal
regulation of the OCXO and the other temperature-sensitive devices,
while at the same time lowering the working temperature of those hot
ICs, thus prolonging (maybe) their life.

  Anyway I am open to comments and suggestions.    Thanks

73  Alberto  I2PHD
--



------------------------------

Message: 4
Date: Mon, 28 Jul 2008 19:22:37 -0400
From: Neon John <jgd at johngsbbq.com>
Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz.
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <chks84prns9f7rgs02f871erg2b1m2jub5 at 4ax.com>
Content-Type: text/plain; charset=us-ascii

On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux <James.P.Lux at jpl.nasa.gov>
wrote:

>At 03:01 PM 7/23/2008, Mike S wrote:

>>You're missing the point. The application is to drive a common,
readily
>>available consumer clock. Simple and cheap. It can be done with a
>>single $1 PIC. You could spend $20 or $100 and not get better results
>>for the application. If you can describe a way of doing it for $0.50,
>>please do.
>
>
>But this is time-nuts... Any approach that doesn't have the 
>performance of a hydrogen maser or cryogenic sapphire resonator just 
>isn't good enough.  Why, we haven't even started on how to build a 
>radial ruling engine to make sure the clock face is precisely divided 
>into 60 segments to ppb accuracy.

Yep.  There's turd polishing and then there is time nuts turd polishing.
Going
for the angstrom finish on the turd.  The latter sometimes makes me grit my
teeth....

>
>Based on the clocks I've taken apart, dividing the 10MHz down to 1 Hz 
>is probably your best bet, rather than trying to hit 32768. However, 
>I don't know of a non-programmable single chip solution that will do 
>a divide by 1E7. If you want programmable chips, there's countless 
>ways, some more elegant than others.

Seems to me that all the solutions proposed so far are a bit complex, trying
to go for the 32khz frequency when that's not necessary.  The quartz analog
clockworks has a one or two winding stepper motor.  The SIMPLEST solution is
to drive those coils directly with the PIC output and scrap the rest of the
circuitry.

With some clever fiddling, one could use one of the 8 pin PICs and that WOULD
get the solution cost down to around 50 cents :-)

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Save the whales, collect the whole set!




------------------------------

Message: 5
Date: Mon, 28 Jul 2008 16:35:53 -0700
From: Jim Lux <James.P.Lux at jpl.nasa.gov>
Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz.
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <6.2.5.6.2.20080728163240.02dd5ed0 at jpl.nasa.gov>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 04:22 PM 7/28/2008, you wrote:
>On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux
<James.P.Lux at jpl.nasa.gov> wrote:
>
>
> >
> >Based on the clocks I've taken apart, dividing the 10MHz down to 1
Hz
> >is probably your best bet, rather than trying to hit 32768. However,
> >I don't know of a non-programmable single chip solution that will
do
> >a divide by 1E7. If you want programmable chips, there's countless
> >ways, some more elegant than others.
>
>Seems to me that all the solutions proposed so far are a bit complex,
trying
>to go for the 32khz frequency when that's not necessary.  The quartz
analog
>clockworks has a one or two winding stepper motor.  The SIMPLEST solution
is
>to drive those coils directly with the PIC output and scrap the rest of the
>circuitry.
Actually, it's not even that complex... it's often an 
electromagnet/solenoid driving a conventional escapement type clock 
mechanism. Why use 2 coils when you don't ever need to go backwards?

One advantage of generating 32kHz (averaged over 1 second) is that 
you don't have to build the power driver stage to actuate that 
electromagnet.. (since it's built into the single dirt-cheap chip in 
the clock in the first place)


>With some clever fiddling, one could use one of the 8 pin PICs and that
WOULD
>get the solution cost down to around 50 cents :-)


And, one could probably figure out a way to use the original 32kHz 
crystal AND run at different speeds..







------------------------------

Message: 6
Date: Tue, 29 Jul 2008 00:01:24 +0000
From: Mark Sims <holrum at hotmail.com>
Subject: [time-nuts] Leap Second Pending
To: <time-nuts at febo.com>
Message-ID: <BLU125-W34CCF75E2D27EC0953D359CE820 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"


My Thunderbolts have just raised the "Leapsecond Pending" minor
alarm...  six months seems a bit early for such a warning...
----------------------------------------

_________________________________________________________________
Stay in touch when you're away with Windows Live Messenger.
http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_messenger2_072008


------------------------------

Message: 7
Date: Tue, 29 Jul 2008 10:04:46 +1000
From: Neville Michie <namichie at gmail.com>
Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz.
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <C84E2EC1-C324-4E1A-8E66-BAA14266787A at gmail.com>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

FYI,
Quartz analogue clocks almost universally use a bipolar motor, a two  
pole
magnetic circuit with the minimum reluctance axis displaced from the  
direction
of the energised field.
When activated the 2 pole magnetic rotor aligns with the magnetic  
field, when the field collapses,
the magnetic rotor moves a little towards the position of greater  
self attraction, so that it is
set up for a move in the right direction when the reverse field is  
applied.
To drive these motors as clock displays you either replicate the  
alternate 1.5 volt 20mS pulses, or connect a capacitor,
about 10 - 100 mfd in series and drive them with a 0.5 hertz square  
wave of about 1.5 volt amplitude.
The drive voltage and pulse duration should be adjusted for each type  
of motor, or else
the voltage and capacitor size so that reliable stepping occurs.  
Overdrive can stop some types as the rotor "poles".
just in case you were interested,
cheers, Neville Michie


On 29/07/2008, at 9:35 AM, Jim Lux wrote:

> At 04:22 PM 7/28/2008, you wrote:
>> On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux  
>> <James.P.Lux at jpl.nasa.gov> wrote:
>>
>>
>>>
>>> Based on the clocks I've taken apart, dividing the 10MHz down
to  
>>> 1 Hz
>>> is probably your best bet, rather than trying to hit 32768.
However,
>>> I don't know of a non-programmable single chip solution that
will do
>>> a divide by 1E7. If you want programmable chips, there's
countless
>>> ways, some more elegant than others.
>>
>> Seems to me that all the solutions proposed so far are a bit  
>> complex, trying
>> to go for the 32khz frequency when that's not necessary.  The  
>> quartz analog
>> clockworks has a one or two winding stepper motor.  The SIMPLEST  
>> solution is
>> to drive those coils directly with the PIC output and scrap the  
>> rest of the
>> circuitry.
> Actually, it's not even that complex... it's often an
> electromagnet/solenoid driving a conventional escapement type clock
> mechanism. Why use 2 coils when you don't ever need to go backwards?
>
> One advantage of generating 32kHz (averaged over 1 second) is that
> you don't have to build the power driver stage to actuate that
> electromagnet.. (since it's built into the single dirt-cheap chip in
> the clock in the first place)
>
>
>> With some clever fiddling, one could use one of the 8 pin PICs and  
>> that WOULD
>> get the solution cost down to around 50 cents :-)
>
>
> And, one could probably figure out a way to use the original 32kHz
> crystal AND run at different speeds..
>
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ 
> time-nuts
> and follow the instructions there.




------------------------------

Message: 8
Date: Mon, 28 Jul 2008 20:05:25 -0400
From: "Ken Winterling" <wa2lbi at frontiernet.net>
Subject: Re: [time-nuts] Leap Second Pending
To: "Discussion of precise time and frequency measurement"
	<time-nuts at febo.com>
Message-ID:
	<608ed23c0807281705r2dc48576ob804dd9189b036a3 at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

So has mine.

Ken, WA2LBI

On Mon, Jul 28, 2008 at 8:01 PM, Mark Sims <holrum at hotmail.com> wrote:

>
> My Thunderbolts have just raised the "Leapsecond Pending" minor
alarm...
>  six months seems a bit early for such a warning...
> ----------------------------------------
>


------------------------------

Message: 9
Date: Mon, 28 Jul 2008 20:08:58 -0400
From: Neon John <jgd at johngsbbq.com>
Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz.
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <idms84199nj391d5bp4e8r97hni6ado5mt at 4ax.com>
Content-Type: text/plain; charset=us-ascii

On Mon, 28 Jul 2008 16:35:53 -0700, Jim Lux <James.P.Lux at jpl.nasa.gov>
wrote:


>>Seems to me that all the solutions proposed so far are a bit complex,
trying
>>to go for the 32khz frequency when that's not necessary.  The
quartz analog
>>clockworks has a one or two winding stepper motor.  The SIMPLEST
solution is
>>to drive those coils directly with the PIC output and scrap the rest of
the
>>circuitry.
>
>Actually, it's not even that complex... it's often an 
>electromagnet/solenoid driving a conventional escapement type clock 
>mechanism. Why use 2 coils when you don't ever need to go backwards?

The clockworks that I've taken apart almost all have 2 coils.  One brand
has
one. They all drive a permanent magnet rotor that turns 90 degrees on each
tick.  I'm not sure what the single coil design does to make sure the rotor
always turns the right direction.  Or maybe it doesn't matter if the rotor
turns a cam and ratchet mechanism.  I've never taken one apart far enough
to
know.

>
>One advantage of generating 32kHz (averaged over 1 second) is that 
>you don't have to build the power driver stage to actuate that 
>electromagnet.. (since it's built into the single dirt-cheap chip in 
>the clock in the first place)

No driver needed.  Each coil has about a bazillion (bazillion.000000 for time
nuts) turns of wire so fine I can't see it without my 7x OptiVisor. 
I've
never bothered to measure but the resistance has to be in the hundreds of ohms
or more.  It has to be that high to get over a year's operation from an AA
battery.  Duck soup for a PIC output pin driver.

Funny how this works.  I've been thinking about this same type problem for
a
few days independent of reading this list.  I'm old-fashioned and like
analog
clocks much better than digital.  I also like the precision of
radio-controlled clocks.  I've bought several different WWVB analog clocks,
all of which seem to use the same cheap ChiCom movement.  They uniformly suck
(to use a technical term) at receiving WWVB where I live.  The digital
versions have no problem receiving but I don't like the looks.

What I've been thinking about is a modern version of the Simplex
master/slave
clock system.  A GPS disciplined master clock sending out operating pulses to
slave clocks around my house and shop.

I thought about wireless, including synthesizing my own WWVB signal but I know
that I'll not get enough round tuits to do that.  What I'm working
toward is
just about what I described above, except that the master clock will drive 4
conductor telephone station wire and the slave clocks will contain no
electronics.  Only the clockwork and the coils.  All the clocks will be wired
in parallel.

This is an open-loop system that assumes all the clocks are in the same
mechanical position when the master is activated.  Perfectly acceptable, given
the relatively few number of clocks and the small area involved.

This architecture should give me what I want - REALLY simple, no electronics
in the individual clocks, "atomic" accuracy, automatic DST correction
and
perfect synchronism.

Comments?

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
No one can be right all of the time, but it helps to be right most of the time.
-Robert Half




------------------------------

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