Hi,
We have an FSUP8 which means it Works up to 8GHz. It's an impressive piece of
equipment, but the control interface has some bugs, it regularly crashes so
hard you have to turn it off so that is a bit of a bummer. However, it measures
quite good. The spectrum analyzer functionality starts
Now you can see the problem with designs that require both a PCB and a
programmed uP. Most people can't do either of these and those who can
typically are good at only one. Then you find someone and after he looses
interest the project is dead and un-suportable.
So I was thinking of how to
Yes. The idea was the simplest GPSDO that can be build with no PCB around
an Arduino. We already know how to build compllelx and expensive GPSDO.
That is too easy.
I think you can use the PWM DAC on the Aruino to drive the OCXO. The
bandwidth of this signal is way low so you can filter the
Don't need anything so complex. A GPSDO depend on an OCXO that is VERY
stable. It can be controlled with a very low bandwidth analog signal.
The output from a OCXO is divided down and then the phase of the divided
down 10MHz RF is compared to the PPS and you don't need to even know the
how far
Chris,
If you want to understand how to approach the issue, you need to study the Shera
controller system. It does exactly what you and others are discussing doing.
It
is relatively simple, straight forward and the HEX file is available to program
the CPU with. The circuit board is all ready
Hello Michael!
Michael Tharp g...@partiallystapled.com ha scritto:
On 12/05/2012 08:03 AM, Fabio Eboli wrote:
I'm seriously thinking to attempt a gpsdo.
...
The platform I will try to use is the STM32F103
microcontroller
Coincidentally, my previous time-nut project was built around the
On Wed, Dec 5, 2012 at 2:50 PM, saidj...@aol.com wrote:
If there is one thing I learned, it is that one is never finished improving
the software. That is why we are time-nuts I guess.
This is the reason I suggested using the Arduino. It is so easy to program
that MANY people will be able
Chris:
The question I have again is about a simple phase detector.
I did ask if the arduino interrupt ports could be used as a phase
detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
work? I'm simply
Hi
True, but you can do a fairly simple filter to separate the 250 KHz note you
don't want from the 8 KHz highest frequency that you do want. There are a lot
of ADC's that will do that for you with their built in filtering.
Bob
On Dec 5, 2012, at 9:23 PM, Rick Karlquist rich...@karlquist.com
Karen,
I still have maybe another half an hour of work to do.
If I can wake up to be on the call I will. I'd say there might be a 50%
chance I'll make it...
--
Harlan Stenn st...@ntp.org
http://networktimefoundation.org - be a member!
___
Hi
Simple answer - no, not in a precision part. They are neither high enough
resolution or deterministic enough to give you very high resolution.
More complex answer - you can do just about anything if you are willing to
limit the best possible outcome. With the normal integration times you
Hi
Note to self - coffee first , morning emails second….
Bob
On Dec 6, 2012, at 6:39 AM, Harlan Stenn st...@ntp.org wrote:
Karen,
I still have maybe another half an hour of work to do.
If I can wake up to be on the call I will. I'd say there might be a 50%
chance I'll make it...
--
Hi
There are many marvelous things you can do in software. In some cases you are
fundamentally limited by the hardware. Regardless of the hardware chosen, the
effort is 99.99% in other areas. Starting with a hardware platform that lets
you evolve (even if it's a few dollars more) is generally
Chris wrote:
I have the 10MHz output from David's divider feeding the counter. When
fed from this the Band 2 seems unreliable starting at 10MHz. If I feed
it 10Mhz at 50mV from my sig gen it starts reliably. Is it a mismatch
from the divider, or has it perhaps not got enough drive level?
On 12/05/2012 02:32 PM, M. Simon wrote:
Do you have a link for the nifty site?
This one is not just for the west coast, but has good reporting of grid
conditions:
http://fnetpublic.utk.edu/index.html
They have several real time graphic and table displays of grid frequency.
The Sample
On Mon, Dec 4, paul swed wrote:
Yes sir $139. But boy I have not seen cheap tbolts in bit. As I recall
$260 these days?
On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp lists at rtty.us wrote:
Hi
The gotcha is that you go from paying surplus prices to paying new prices.
New price to new price,
On 12/6/12 1:06 AM, Chris Albertson wrote:
Yes. The idea was the simplest GPSDO that can be build with no PCB around
an Arduino. We already know how to build compllelx and expensive GPSDO.
That is too easy.
I think you can use the PWM DAC on the Aruino to drive the OCXO. The
bandwidth of
On 12/6/12 4:42 AM, Bob Smither wrote:
On 12/05/2012 02:32 PM, M. Simon wrote:
Do you have a link for the nifty site?
This one is not just for the west coast, but has good reporting of grid
conditions:
http://fnetpublic.utk.edu/index.html
They have several real time graphic and table
If you want a low noise mixer use a varicap mixer. A varicap has no
ohmic characteristics thus
no Johnson noise.
Secondly, You can create low noise harmonics using a vaicap multiplier
or a nonlinear transmission
line using inductors and nonlinear capacitors (varicaps). NIST has been
Very interested as I have one of these and its troubled but differently.
Can't really dig in right now.
Paul
WB8TSL
On Thu, Dec 6, 2012 at 7:33 AM, Chris Wilson ch...@chriswilson.tv wrote:
Chris wrote:
I have the 10MHz output from David's divider feeding the counter. When
fed from this
Still, there are always a number of talks of more general interest to us time
nuts.
In the next few postings I'll give more details on a couple of topics:
And here's the third part of my PTTI report...
- Vendor presentations/Symmetricom/Miles
Besides 3 days of presentations, PTTI also hosts
On 12/06/2012 08:04 AM, Jim Lux wrote:
On 12/6/12 4:42 AM, Bob Smither wrote:
On 12/05/2012 02:32 PM, M. Simon wrote:
Do you have a link for the nifty site?
This one is not just for the west coast, but has good reporting of grid
conditions:
http://fnetpublic.utk.edu/index.html
They
As a lurker, I just want to chime in and say that I for one would love
to see an open-source GPSDO implementation. There are quite a few open
hardware designs out there, but as Bob suggests, all the interesting
bits are tied up in the closed-source software they run. And most of
them are no longer
Interesting Arthur. I don't think I had a clue you were selling them and
would have paid the difference of what I actually picked one up for. Though
mine was clean and I have not a complaint in the world. Like you I watched
things go up and they were very controlled day by day. At the time it
Great comments and a good read. OK so what does the drop in replacement
cost???
Thanks lots to read here.
Later
Paul
WB8TSL
On Thu, Dec 6, 2012 at 10:24 AM, Tom Van Baak t...@leapsecond.com wrote:
Still, there are always a number of talks of more general interest to us
time nuts.
In the
Hi
There are at least 500 different processors out there that could / might
work in a GPSDO. I can think of 40 or more families of parts one could look
at from more than a dozen companies. That's just counting the majors, and
not getting into any of the smaller outfits. It's also not including
Arduino is Dirt Cheap!
At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor
with the arduino bootloader programmed into it. Easily obtainable from
several sources for 5 bucks or so. All the code, toolchain etc. (the
ecosystem as it were) is free. it's real easy to put one
Hi
It's a rare microcontroller these days that does *not* come with a free tool
chain. Same goes for the debugger. Most MCU lines have family members with
similarly low (or lower) prices and good availability. They pretty much all
either work with a crystal two caps and a resistor. Most will run
Hello All - Just a quick comment from an olde RF engineer.
Bob Camp wrote:
Hi
You might be surprised by the noise floor of an XOR run at 125 KHz. They
are quite good at that low a frequency.
Bob
An XOR, unlike a mixer, does not have a null when the
phases are in quadrature. This is the
On Tuesday, 4 December 2012, Tom Van Baak wrote:
We are using the SR620 to measure the interval between 1PPS signals from
two clocks. One is the Septentrio PolaRx4 GPS receiver and the other is a
Rubidium clock.
Many Thanks,
Paul
1) If you are making frequency measurements, the warm-up of the
Boy do I have to agree. uProcs by the dozens and with all kinds of counters
onboard.
I think it was Bob who said none of thats the challenge.
It is the phase comparison method and a stable D/A converter and reference.
From what I have seen and I could be dead wrong here the on board uprocs
have
Volker,
That's a great question and I'm afraid I don't have a good answer
for you. If pressed, I would estimate less than 100ps.
The error of this measurement contributes to the error in our
final measurement which has many components. I haven't worked out an
error budget for each
Keenan,
You can see my GPSDO source code for a mere $50. It comes with manual and
executables. The executables alone are $20.
See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm
While this design does not use a Kalmann filter, it has pretty good
holdover, and you can see how the phase
Hi
This is a project that is a multi year endeavor in a commercial setting.
That's where you have multiple people on the payroll who can put 40+ hours a
week into it. You are set up with groups of people who do this or that. They
all aren't on this job full time, but there's a lot of resources
On 12/6/12 9:45 AM, Dale J. Robertson wrote:
Arduino is Dirt Cheap!
And available over the counter retail at hundreds of Radio Shacks..
You get an idea during the day, and you can run out and buy one right
then.. (yes, you can mail order, but the fastest turnaround is a few
days, unless you
I would use a digital pot for coarse setting. Or a manual trimpot. That way
your control signal holds even if your comparison goes away or if for some
reason your loop comes out of lock. Something like that also reduces the noise
contribution of the DAC.
Simon
=
Date: Thu, 6
Most of the free tool chains are not truly free I.e. open source including
all libraries and coupled with an open source compiler and debugger. In
addition few of them are currently offered in hobbyist friendly DIP packages.
Once you resign yourself to having to build hardware glue for some of
Hi
That is where most of these tools were many years ago. Competition has
forced them to open things up quite a bit. You can code a very nice GPSDO
and not use anything but freely available tools. You can do it on several
processors, none of which come from AVR (and thus use the Arduino chain).
In past designs I just included an EEPROM so in the event of a cold
start, the last settings would be known.
On Thu, 6 Dec 2012 10:45:48 -0800 (PST), M. Simon
msimon6...@yahoo.com wrote:
I would use a digital pot for coarse setting. Or a manual trimpot. That way
your control signal holds even
Bob,
Did Atmel (AVR) kill your dog or something?
They have some pretty powerful MCU's. Are you flatly stating that none of
them could be used for a very nice GPSDO?
Dale
Just fooling around, no offence intended.
-Original Message-
From: Bob Camp
Sent: Thursday, December 06, 2012
Hi
By no means am I saying that they *can't* be used. My point is that there
are a multitude of alternatives that are at least equally as cheap and
attractive. There is no clear you must use this one to pick.
Bob
-Original Message-
From: time-nuts-boun...@febo.com
How about quit talking and build something and show us some results!
Bert Kehren
In a message dated 12/6/2012 2:09:38 P.M. Eastern Standard Time,
d...@nap-us.com writes:
Bob,
Did Atmel (AVR) kill your dog or something?
They have some pretty powerful MCU's. Are you flatly stating that none
Paul
I agree. That is my main frustration, lot of talk no results. The good part
of time nuts is that I have made some very good contacts that share my
interest of actually building some things and results are great.
Remember the Loran simulator?
Bert Kehren
In a message dated 12/6/2012
On 6 December 2012 18:28, Murray Greenman denw...@orcon.net.nz wrote:
Keenan,
You can see my GPSDO source code for a mere $50. It comes with manual and
executables. The executables alone are $20.
See http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm
Murray ,
There's a huge difference
I'm excited, for sure.
I've got a whole box of goodies over here I bought full of the Arduino uP
and a ton of its 'shields'. Been collecting, so-to-speak.
I just new I could use it for a, down-and-dirty GPSDO. The Trimble Lassen
looks good down to 20ns UTC (I got two for $10); then add a
If by OpenSource he means that he used the OpenSource
tool chain, and libraries, and then is keeping his source
and executables closed, he may be in violation of
the GNU licenses.
-Chuck Harris
David Kirkby wrote:
On 6 December 2012 18:28, Murray Greenman denw...@orcon.net.nz wrote:
Keenan,
On 6 December 2012 20:33, Chuck Harris cfhar...@erols.com wrote:
If by OpenSource he means that he used the OpenSource
tool chain, and libraries, and then is keeping his source
and executables closed, he may be in violation of
the GNU licenses.
-Chuck Harris
According to the web page
GPL violations are a good thing. That is how the FSF makes money. ;-)
http://www.linuxfordevices.com/c/a/News/Cisco-settles-with-FSF-on-GPL-violations/
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Don wrote:
you guys are reinforcing that just because its' cheap won't mean it
won't work.
Of course it doesn't. But keep in mind that working spans several
orders of magnitude in this area, and what one needs to design and
build depends on what degree of working one needs to support the
Hi
The single best thing about a TBolt is Lady Heather.
Consider how many years it's taken to get it to where it is today. Consider
how many people have worked extensively on it. It's a wonderful thing to
have available.
Could you make a homebrew gizmo look just like a TBolt? Sure you could.
Hi
Many of the vendor tool chains are now (or soon will be) gcc and Eclipse
based. It's very common to do closed source code on open source based
platforms.
Bob
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of David Kirkby
Sent:
The Open Source tool chain is generally GCC, its libraries,
and debuggers.
Closed source use of the GCC tool chain is done all the time,
but there are numerous gotchas that catch the unwary. Some of
the libraries are covered by the Lesser GPL license, and as
such are available for that kind of
On 12/6/2012 4:35 PM, Charles P. Steinmetz wrote:
From my perspective, the most interesting development would be an offer
by someone with a very well equipped lab to test any DIY GPSDO with a
consistent protocol and publish the results. That way, we could all see
how the various approaches
You'd have to seriously divide down the output from the 10MHz OCXO if you
were going to use it as an interrupt. Maybe to divide by 10,000? and even
at the higher clock rate you'd still have poor resolution.
I image each interrupt handler would sample some internal counter and the
background task
Hi
The math is pretty straightforward.
Let's say the clock is 10 MHz, that's 100 ns.
Say a handful is 5 +/- 3 (2 to 8)
Your measure will bounce up and down by 6x100 ns = 600 ns.
Over a 100 second period that's going to be 6.0 x10^-9 bounce in the data.
If you run a 100 second loop as well,
albertson.ch...@gmail.com said:
You'd have to seriously divide down the output from the 10MHz OCXO if you
were going to use it as an interrupt. Maybe to divide by 10,000? and even
at the higher clock rate you'd still have poor resolution.
I image each interrupt handler would sample some
Hi
That would be an input capture rather than an interrupt.
Bob
On Dec 6, 2012, at 6:16 PM, Hal Murray hmur...@megapathdsl.net wrote:
albertson.ch...@gmail.com said:
You'd have to seriously divide down the output from the 10MHz OCXO if you
were going to use it as an interrupt. Maybe to
Bob et al:
Have been following this thread with interest.
Re the input capture versus interrupt, I do believe (at least the 2560
does this) that you can do both. It's been a while since I looked. a
look at the hardware manual. Was interested in this feature to do
hardware timing.
Norm
On Thu, Dec
Hi
To be useful, you need an input capture that:
1) Runs at a fast enough clock (1 GHz would be nice)
2) Has enough bits to get to 1 pps (say 32 bits)
3) Has a built in period set, so the hardware works without a lot of silly stuff
Often you find parts that will do some of the above, but not
You can use the ATmega328 16 bit timer/counter in input capture mode
to count the number of 10 MHz OCXO cycles per pulse per second period
to a resolution of 100ns but there are some problems:
The ATmega328 16 bit timer/counter external clock is limited to 1/4 of
the CPU frequency with an
could you not add just a little 'glue' outside the uP to relieve it a tad.
Let the GPS' 1pps gate some ttl counters and then read for overflow or
underflow after xxx seconds. Have the uP determine dac correction setting
back to the TXCO.
-Don
My mistake was inferring that my GPSDO software was open source. It's
absolutely not. It is proprietary to me and written in AVR assembler. There
is no reference anywhere in it to any libraries from any other source.
So don't get too excited. You can still see what's inside it for $50, but
We need a real, Open Source GPSDO that uses an open source tool chain.
Cost is not the issue it is the ability to modify and redistribute the
modified copy that is what's needed.
On Thu, Dec 6, 2012 at 10:28 AM, Murray Greenman denw...@orcon.net.nzwrote:
Keenan,
You can see my GPSDO source
The key here is to step the time a few milliseconds at a time as ntpd has
various sanity checks.
Sent from my iPhone
On Dec 4, 2012, at 3:22 PM, Hal Murray hmur...@megapathdsl.net wrote:
server
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On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767 dlewis6...@austin.rr.com wrote:
could you not add just a little 'glue' outside the uP to relieve it a tad.
Let the GPS' 1pps gate some ttl counters and then read for overflow or
underflow after xxx seconds. Have the uP determine dac correction
Hi
Again, the math is pretty simple.
A 16 bit capture running at a 1/4 clock is not going to get you very near a
Shera. It's even further from the more modern enhanced Shera designs.
Bob
On Dec 6, 2012, at 6:59 PM, David davidwh...@gmail.com wrote:
You can use the ATmega328 16 bit
Hi
The simplest phase detector does indeed work. It just does not work very well.
Not correcting the oscillator at all works, you will have time and frequency to
some level of accuracy. Not correcting it at all is a whole lot cheaper and
simpler.
Bob
On Dec 6, 2012, at 7:30 PM, Chris
What if the OCXO had a sine wave output and then you used the PPS leading
edge to gate the sine wave to a sample and hold. then the sample is
measured by the Arduino's ADC? I think(?) you get a 10-bit ADC or is it
8-bits. The problem is the required speed of the sample and hold, maybe
not easy
Hi
The solution to the problem is well known in several forms. Cost is below $5
for pretty much all of them. No need to re-invent the wheel. The gotcha is that
you can't do it 100% with internal CPU peripherals. You will need *some* glue.
Bob
On Dec 6, 2012, at 7:43 PM, Chris Albertson
It is not a 16 bit capture and it does not run at 1/4 the clock rate.
The Shera uses a 12 bit counter to capture the phase difference
between the OCXO frequency divided by 16 and GPS pulse per second
output to a resolution of about 42ns.
What I suggested effectively captures the same phase
David,
The NXP LPC932 processor series are very cheap and small, and we got very
excited to see timers running at up to 32MHz internally if I remember
correctly.
Then setting up a test system we noted that the timer can capture with
32MHz resolution which is good enough for a low-cost
There are lots of sampling ADCs which will support that type of
operation directly or you can easily design and build a sampling phase
detector but that all involves significant extra circuitry outside of
the microcontroller.
Take a look at the Racal Dana 1992 reference frequency multiplier
The ATmega328 apparently has something similar going on since the
datasheet says that the maximum external asynchronous clock frequency
is 1/4 of the CPU frequency. That is why I suggested synchronously
clocking the CPU directly from the OCXO. Atmel's datasheet is
annoyingly vague about some
Sorry. The Shera counter is 16 bits and not 12 bits but that does not
change what I posted.
On Thu, 06 Dec 2012 19:17:48 -0600, David davidwh...@gmail.com
wrote:
It is not a 16 bit capture and it does not run at 1/4 the clock rate.
The Shera uses a 12 bit counter to capture the phase
Chris: yes, dividing would have to be done. Doesn't TVB have a simple
divider block?
You don't really have to close the difference, just maintain it?
Don L
Chris Albertson
You'd have to seriously divide down the output from the 10MHz OCXO if
you
were going to use it as an interrupt. Maybe to
Hi
The Shera counter is not running in the same fashion you would be running an
input capture pin.
Bob
On Dec 6, 2012, at 8:45 PM, David davidwh...@gmail.com wrote:
Sorry. The Shera counter is 16 bits and not 12 bits but that does not
change what I posted.
On Thu, 06 Dec 2012 19:17:48
Hi
Unless you really want to go crazy with measuring very long delays, you do
indeed want to align the pps from your OCXO with the pps from your GPS.
Bob
On Dec 6, 2012, at 8:48 PM, Don Latham d...@montana.com wrote:
Chris: yes, dividing would have to be done. Doesn't TVB have a simple
Hi
PSoC's are another attractive possibility that suffers from the same basic
re-clock everything flaw. Lots of time down the drain there….
Bob
On Dec 6, 2012, at 8:22 PM, saidj...@aol.com wrote:
David,
The NXP LPC932 processor series are very cheap and small, and we got very
excited
I think only TIMER2 on the AVR has the clk/4 limitation. The other timers can
count at full speed.I know that I have counted at 8-12 MHz before...
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Hi
If all you want is a something locked to a GPS:
Take the pps from the GPS and hook it to an AD9548. You probably will need a 50
cent CPU to set up the registers. No muss, no fuss, nothing to invent or
design.
Weather it does what you need to do is an entirely different question. Without
Hi
Here's another way to look at this:
An hourglass full of sand (with some attention) and a cesium standard are both
ways to answer the question what time is it?. Let's say you need a new
$40,000 tube replacement in your 5371 and management asks what else can we
do?. An hour glass is
The other timer on the ATmega328 lacks an input capture pin and
register. I did not check all of the different AVR microcontrollers
used in Arduinos.
On Fri, 7 Dec 2012 02:03:39 +, Mark Sims hol...@hotmail.com
wrote:
I think only TIMER2 on the AVR has the clk/4 limitation. The other
Perhaps this is all coming full circle. As more experience herein shows use of
the 1-pps from the gps module is valid, that opens the door to many more cheap
GPS modules available than just a few that have 10 KHz also.
Some of the low-cost GPS modules have the 1-pps associated with UTC
On 12/6/2012 4:26 AM, Fabio Eboli wrote:
Here are the design documents, if you're curious:
http://hg.partiallystapled.com/circuits/serafine/raw-file/d75ab09ca163/out/production.PDF
Thank you very much, I will study it with interest,
it will be very helpul to see what you have done.
Can I ask
If you had an Ikepod, I might be interested.
http://www.ablogtowatch.com/ikepod-hourglass-time-for-art/
http://www.hodinkee.com/blog/2011/3/29/the-ikepod-hourglass-by-marc-newson-q
uite-possibly-the-coole.html
http://www.ikepod.com/
Dave
-Original Message-
From:
saidj...@aol.com said:
Then setting up a test system we noted that the timer can capture with
32MHz resolution which is good enough for a low-cost GPSDO implementation,
but that they gated the input pin through a flip-flop running at CPU core
speed, which was around 6MHz if I remember
I'm doing some things of that order with the LPC1114. The board for the project
will be back from fab in a few days. If it works out well I have a
frequency/period counter designed around that chip. About $20 in parts. Not
counting the TCVCXO. Add in a case, I/O and power supply plus a display
li...@rtty.us said:
That would be an input capture rather than an interrupt.
Thanks. Yes, that's the term I was trying to remember.
li...@rtty.us said:
To be useful, you need an input capture that:
1) Runs at a fast enough clock (1 GHz would be nice)
2) Has enough bits to get to 1 pps
The output from a OCXO is divided down and then the phase of the divided
down 10MHz RF is compared to the PPS and you don't need to even know the how
far apart they are. All you need to know is led or lag just a one bit
answer. An XOR gate or a flip flop can tell you that.
Does a 1 bit
Hello,
metastability is not an issue in this type of application, nor can it be
avoided since we have two different clock domains.
It would only shift the capture point by one counter clock cycle back or
forth if the edge happens right on the transition point. At that point we
have 50%
Good thought, Bob. AD9548 $27, eval board a whopping $250, get a
thunderbolt :-). The eval board has a lot of SMA's on it...
Don L
Bob Camp
Hi
If all you want is a something locked to a GPS:
Take the pps from the GPS and hook it to an AD9548. You probably will
need a 50 cent CPU to set up
Folk,
I have received the following announcement:
+
Notice of Interruption
MSF 60 kHz Time and Frequency Signal
The MSF 60 kHz time and frequency signal broadcast from Anthorn Radio
Station will be shut down on Thursday 13 December 2012
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