Re: [time-nuts] Raspberry Pi 4 oscillator replacement (Avamander)

[Tim S]

I've been working on something similar with a CM4 (finally got a few this
week).  The reason to me for having the GNSS discipline is to not need a
local rubidium - but the oscillator can be improved still.

Using this 54MHz VCTCXO for the CPU:
https://www.digikey.com/product-detail/en/connor-winfield/TB514-054.0M/CW808-1-ND/4311758

...and this 25MHz VCTCXO for the IEEE-1588 NIC:
https://www.digikey.com/en/products/detail/connor-winfield/T604-025.0M/3757210

...a couple of these 3mm tall mezzanine headers:
https://www.mouser.com/ProductDetail/798-DF40HC30100DS451/

...and some 3mm working envelope pogo-pins to take the clocks from the
baseboard to the module without soldering:
https://www.digikey.com/en/products/detail/mill-max-manufacturing-corp/0900-0-15-20-76-14-11-0/663496

This gets around the package size limits for the oscillator, gives a very
stable temperature compensated clock, and some control to discipline the
long term frequency.  The extra z-height of the connectors allows the
oscillators to sit between the two boards, protecting them more from
circulating air - also allows for cleaner power supply for the clocks.

A Spartan-3 runs the 20-second phase counters, takes the GPS out of standby
about 5 seconds before the GPS needs to have a valid 1PPS, and runs the
PDM-dither DAC.  This cuts the GPS power about in a third (application is
vehicle-borne) when navigation is not needed. Some low jitter clock
distribution amps allow a free-running GPS 1PPS to keep the clocks aligned
even if the CM4 is powered down.  2x Ublox F9T GNSS modules in RTK mode,
dual antennas measured antenna distance, same cable length (calibrated).

This module was my inspiration: https://www.teradak.com/products/115.html

Board design is about done, I'll probably put up a webpage for it around
summer.  The general baseboard layout is going to become my core design for
a few different devices, including a CCTV IP-camera (self time/date setup,
GPS location watermarking, global shutter video frames and audio samples
aligned to time).

-T

On Thu, Feb 4, 2021 at 9:42 AM  wrote:

> Date: Thu, 4 Feb 2021 12:20:23 +0200
> From: Avamander 
> To: time-nuts@lists.febo.com
> Subject: [time-nuts] Raspberry Pi 4 oscillator replacement
> Message-ID:
>  o...@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Hi,
>
> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?
>
> Here's where I got my inspiration from, someone replacing the oscillator on
> a Pi 3 with a TXCO:
>
> https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3
>
>
> Yours sincerely,
> Avamander
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Bob kb8tq]

Hi

A lot depends on the intended application of the chip. For
a general purpose MCU that could go into a wide range 
of things and that has very few peripherals,  1 to 40 MHz
might be just fine.  There are chips out there with much
wider clock input ranges.

Toss in USB and that locks in a clock tree output. Pile on
various Video formats and they need this or that specific
output frequency. Various speeds of Ethernet need this or
that. Fancy audio may adds in its needs. These are outputs 
from the clock system rather than inputs, but they do impact 
what inputs will work.

A general purpose device may still allow a range of inputs
and then play games to get the needed outputs. An on chip
VCO and a variety of dividers feeding a PLL are one common
setup. There may be multiple sets of this and that onboard. 

The issue becomes that only very specific individual frequencies 
in the specified range will work. Many of those specific frequencies 
may be quite strange looking …. 

On a purpose built device ( = one intended use) it is not 
uncommon to see them saving die space on the clock tree. 
You have one target input that it will accept. If you are lucky, 
it might accept 2X  and 4X that frequency. I suspect that this 
approach also makes the part a bit easier to test / validate. 

None of this is to say that the RPi will not work at (say)
50 MHz in. It is very likely that it will.  It is a pretty good bet 
that a whole bunch of peripherals will have issues if you do. 

Bob

> On Feb 5, 2021, at 2:44 AM, Poul-Henning Kamp  wrote:
> 
> 
> Trent Piepho writes:
>> On Thu, Feb 4, 2021 at 4:09 PM Hal Murray  wrote:
> 
>> I've not seen one where the input clock frequency had much of a range.
>> It might be 24-26 MHz, but never 10 - 52 MHz.
> 
> Usually if you read very closely, you will find a wide range is OK
> but a footnote to the effect that they only warrant USB will work at
> the following specific frequencies.
> 
> -- 
> 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.
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Poul-Henning Kamp]

Trent Piepho writes:
> On Thu, Feb 4, 2021 at 4:09 PM Hal Murray  wrote:

> I've not seen one where the input clock frequency had much of a range.
> It might be 24-26 MHz, but never 10 - 52 MHz.

Usually if you read very closely, you will find a wide range is OK
but a footnote to the effect that they only warrant USB will work at
the following specific frequencies.

-- 
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.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Trent Piepho]

On Thu, Feb 4, 2021 at 4:09 PM Hal Murray  wrote:
> In case anybody isn't familiar with ARM SOC chips, they typically have a layer
> of muxes between the external pins and the internal I/O devices.  I don't know
> if the chip used in the Pi-4 works this way.  Quite likely.
>
>
> The system designer has to find a combination of mux settings that works for
> the application.  Leftover pins can be used as GPIO.  And the clocking is
> tangled up in there.

While true for many pins, usually quite a few are not muxed.  Those
deemed necessary for all designs or with specialized drivers.  So
typically there will be no mux for power pins, dram interface, xtal
inputs, and high speed differential data, like USB3, PCIe, SGMII, MIPI
CSI or DSI.  Or perhaps muxing between different high speed serial
interfaces.

It seems to be very common for ARM SoC chips to be designed to be
clocked by either an XTAL and a built in oscillator, or via an
external clock generator connected to the same pin.  But, I've never
seen a SoC where this pin could be muxed.

I've not seen one where the input clock frequency had much of a range.
It might be 24-26 MHz, but never 10 - 52 MHz.  At least documented.
But the clock is invariably an input to a programmable PLL or PLLs,
and those PLLs are likely programmable with a rather wider range of
multipliers and dividers than required for the limited documented
input frequency range.

One might have better luck with a chip from Ti or NXP, since, unlike
Broadcom, they have documentation on how their clocks and PLLs work.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Poul-Henning Kamp]

Hal Murray writes:
> 
> p...@phk.freebsd.dk said:
> > I dont know if the datasheet for the Rpi4 is available to check what the
> > requirements are, but you should probably expect to need some kind of PLL
> > chip to deliver a clean 54 MHz on the RPi4, locked to your external
> > frequency. 
>
> Plan B would be to avoid the 10=>54 PLL chip by reprogramming the software 
> that sets up the internal PLLs to run off 10 MHz rather than 54MHz.  That may 
> not be possible.  It depends on how the clocking inside the ARM chip is setup.

One of the big problems with the RPi family is that only a skeleton
datasheet has been made available - because: Qualcom magic sauce
recipe or similar verbiage..

I've heard a lot of gripes about precisely the clock circuits being
underdocumented, but I have deliberately stayed well clear of the
details.

-- 
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.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Hal Murray]

p...@phk.freebsd.dk said:
> I dont know if the datasheet for the Rpi4 is available to check what the
> requirements are, but you should probably expect to need some kind of PLL
> chip to deliver a clean 54 MHz on the RPi4, locked to your external
> frequency. 

Plan B would be to avoid the 10=>54 PLL chip by reprogramming the software 
that sets up the internal PLLs to run off 10 MHz rather than 54MHz.  That may 
not be possible.  It depends on how the clocking inside the ARM chip is setup.

If you are lucky, you won't need to change the kernel.  If you are half-lucky, 
you have to make a few tweaks to the kernel software and rebuild.

-

In case anybody isn't familiar with ARM SOC chips, they typically have a layer 
of muxes between the external pins and the internal I/O devices.  I don't know 
if the chip used in the Pi-4 works this way.  Quite likely.

It's a chinese menu sort of deal, only more complicated.  If you get the beef 
from column A, you can't get the chicken from column B.

The basic idea is that there are more I/O devices on the chip than there are 
pins.  After reset, all the pins are setup as GPIO input so they don't 
accidentally drive an input pin.  There is a mux in front of each input signal 
to an I/O device that picks the signal from one of several pins.  There is a 
mux on the output side of each pin that selects from an output of several I/O 
devices.

The system designer has to find a combination of mux settings that works for 
the application.  Leftover pins can be used as GPIO.  And the clocking is 
tangled up in there.


-- 
These are my opinions.  I hate spam.




___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Matthias Welwarsky]

On Donnerstag, 4. Februar 2021 11:20:23 CET Avamander wrote:
> Hi,
> 
> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?
> 
> Here's where I got my inspiration from, someone replacing the oscillator on
> a Pi 3 with a TXCO:
> https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-osci
> llator-on-a-rpi-2-3

Feeding a 10MHz (suitably conditioned) clock signal directly from a Rb into a 
Beaglebone Black's external clock input (available on the extension header) 
and adding a small driver module to use a timer driven by this external clock 
as system clocksource is _way_ easier.

Just my €0.02

BR,
Matthias



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[David Taylor via time-nuts]

On 04/02/2021 10:20, Avamander wrote:

Hi,

I was wondering if anyone here has replaced the 54 MHz oscillator on the
Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
upgrade, but is technically doable? What hardware would it take in addition
to a GNSS-disciplined rubidium standard and a Pi 4?

Here's where I got my inspiration from, someone replacing the oscillator on
a Pi 3 with a TXCO:
https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3


Yours sincerely,
Avamander


I would likely use one of these:


http://www.leobodnar.com/shop/index.php?main_page=product_info_id=301

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[ASSI]

Avamander wrote:
> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard?

The same things as replacing the XTAL on an RPi 1…3 I'd guess.  So, you need 
to remove the XTAL (hot air rework station), figure out which pin you need to 
feed the external clock into (the "return from XTAL" path), and actually 
create a rubidium stabilized 54MHz (using a clock synthesizer like the SiLabs 
SI53xx series, for which you can get breakout boards rather easily).

> An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?

Not much, see above.

However you'll probably find that it really is overkill and you can get much 
of the same end result more easily or much cheaper.  For instance a good OCXO 
or even TCXO would already get you the sort of stability that the other 
sources of timing uncertainty produced by the whole SoC / OS interaction start 
to dominate.  I haven't gotten myself a Pi4 yet, but I expect that self-
ovenization would still work more or less the same as with the earlier models, 
so you might not even need to touch the XTAL.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Factory and User Sound Singles for Waldorf rackAttack:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds




___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Poul-Henning Kamp]

Avamander writes:

> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?

This trick has gotten a lot harder over the decades.

Higher and higher PLL ratios in the chips means they demand more of their clock 
signal.

I dont know if the datasheet for the Rpi4 is available to check
what the requirements are, but you should probably expect to need
some kind of PLL chip to deliver a clean 54 MHz on the RPi4, locked
to your external frequency.

-- 
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.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Bob kb8tq]

Hi

> On Feb 4, 2021, at 11:37 AM, Avamander  wrote:
> 
> > 2) Grab any of the various conversion chips to take the 10 MHz to 54
> (= I don’t know of a standard that puts out 54 MHz). Wire the 10 into it
> and pull the 54 off of it. (Yes, the chip needs to be programmed and
> there will be various bits and pieces connected to it)
> 
> Do you have any recommendations as to which chip would let me achieve this?

Only because you can get it as a pre-assembled dev board:

https://www.silabs.com/timing/clock-generators/cmos/device.si5350c-gm1

at a semi-rational price. 

Most modern chips are a bit difficult to deal with. That makes finding a
dev board important. If you are set up to layout and assemble SMT PCB’s
then there are a lot of choices ( as in several hundred devices). 

Bob


> 
> In any case, thanks for the help. I will try and document the process when I 
> start it and share it here, might be interesting for some.
> 
> On Thu, Feb 4, 2021 at 5:15 PM Bob kb8tq  > wrote:
> Hi
> 
> Pretty basic approach:
> 
> 1) Get a Rb standard. 
> 
> 2) Grab any of the various conversion chips to take the 10 MHz to 54
> (= I don’t know of a standard that puts out 54 MHz). Wire the 10 into it
> and pull the 54 off of it. (Yes, the chip needs to be programmed and 
> there will be various bits and pieces connected to it)
> 
> 3) Rip the oscillator (or crystal) off the RPi board. 
> 
> 4) Figure out which pin is the drive to the crystal and which is the return.
> (or which is the output if it’s an oscillator)
> 
> 5) Wire the 54 MHz into the return / osc out pin. 
> 
> 6) Power it all up off of a common supply ( = power the conversion 
> chip off the RPi’s regulator.
> 
> Yes there is a lot of research needed to complete all of that. 
> 
> When done you would need to figure out how to ( … if you can ) disable
> the spread spectrum stuff on the clock. You still would be stuck with
> the normal issues related to clock frequency stepping ( turbo mode …).
> How much of that actually gets you on an RPi 4 … who knows. 
> 
> Bob
> 
> > On Feb 4, 2021, at 5:20 AM, Avamander  > > wrote:
> > 
> > Hi,
> > 
> > I was wondering if anyone here has replaced the 54 MHz oscillator on the
> > Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> > upgrade, but is technically doable? What hardware would it take in addition
> > to a GNSS-disciplined rubidium standard and a Pi 4?
> > 
> > Here's where I got my inspiration from, someone replacing the oscillator on
> > a Pi 3 with a TXCO:
> > https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3
> >  
> > 
> > 
> > 
> > Yours sincerely,
> > Avamander
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com 
> > 
> > To unsubscribe, go to 
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com 
> > 
> > and follow the instructions there.
> 
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com 
> 
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com 
> 
> and follow the instructions there.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Avamander]

> 2) Grab any of the various conversion chips to take the 10 MHz to 54
(= I don’t know of a standard that puts out 54 MHz). Wire the 10 into it
and pull the 54 off of it. (Yes, the chip needs to be programmed and
there will be various bits and pieces connected to it)

Do you have any recommendations as to which chip would let me achieve this?

In any case, thanks for the help. I will try and document the process when
I start it and share it here, might be interesting for some.

On Thu, Feb 4, 2021 at 5:15 PM Bob kb8tq  wrote:

> Hi
>
> Pretty basic approach:
>
> 1) Get a Rb standard.
>
> 2) Grab any of the various conversion chips to take the 10 MHz to 54
> (= I don’t know of a standard that puts out 54 MHz). Wire the 10 into it
> and pull the 54 off of it. (Yes, the chip needs to be programmed and
> there will be various bits and pieces connected to it)
>
> 3) Rip the oscillator (or crystal) off the RPi board.
>
> 4) Figure out which pin is the drive to the crystal and which is the
> return.
> (or which is the output if it’s an oscillator)
>
> 5) Wire the 54 MHz into the return / osc out pin.
>
> 6) Power it all up off of a common supply ( = power the conversion
> chip off the RPi’s regulator.
>
> Yes there is a lot of research needed to complete all of that.
>
> When done you would need to figure out how to ( … if you can ) disable
> the spread spectrum stuff on the clock. You still would be stuck with
> the normal issues related to clock frequency stepping ( turbo mode …).
> How much of that actually gets you on an RPi 4 … who knows.
>
> Bob
>
> > On Feb 4, 2021, at 5:20 AM, Avamander  wrote:
> >
> > Hi,
> >
> > I was wondering if anyone here has replaced the 54 MHz oscillator on the
> > Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> > upgrade, but is technically doable? What hardware would it take in
> addition
> > to a GNSS-disciplined rubidium standard and a Pi 4?
> >
> > Here's where I got my inspiration from, someone replacing the oscillator
> on
> > a Pi 3 with a TXCO:
> >
> https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3
> >
> >
> > Yours sincerely,
> > Avamander
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Raspberry Pi 4 oscillator replacement

[Bob kb8tq]

Hi

Pretty basic approach:

1) Get a Rb standard. 

2) Grab any of the various conversion chips to take the 10 MHz to 54
(= I don’t know of a standard that puts out 54 MHz). Wire the 10 into it
and pull the 54 off of it. (Yes, the chip needs to be programmed and 
there will be various bits and pieces connected to it)

3) Rip the oscillator (or crystal) off the RPi board. 

4) Figure out which pin is the drive to the crystal and which is the return.
(or which is the output if it’s an oscillator)

5) Wire the 54 MHz into the return / osc out pin. 

6) Power it all up off of a common supply ( = power the conversion 
chip off the RPi’s regulator.

Yes there is a lot of research needed to complete all of that. 

When done you would need to figure out how to ( … if you can ) disable
the spread spectrum stuff on the clock. You still would be stuck with
the normal issues related to clock frequency stepping ( turbo mode …).
How much of that actually gets you on an RPi 4 … who knows. 

Bob

> On Feb 4, 2021, at 5:20 AM, Avamander  wrote:
> 
> Hi,
> 
> I was wondering if anyone here has replaced the 54 MHz oscillator on the
> Raspberry Pi 4 with a GNSS-disciplined rubidium standard? An overkill
> upgrade, but is technically doable? What hardware would it take in addition
> to a GNSS-disciplined rubidium standard and a Pi 4?
> 
> Here's where I got my inspiration from, someone replacing the oscillator on
> a Pi 3 with a TXCO:
> https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3
> 
> 
> Yours sincerely,
> Avamander
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.