Chris
All the details are in the article:
http://www.edn.com/contents/images/6607197.pdf
However it would be best to read the article posted by Bob Camp first:
Bruce
Chris Stake wrote:
Hi Bruce,
This sounds like a promising idea, please could you expand on the
synchronous filter technique?
Here's a link to a pdf version of the synchronously filtered low ripple
pwm dac:
http://www.edn.com/contents/images/6553625.pdf
Bruce
Bruce Griffiths wrote:
Chris
All the details are in the article:
http://www.edn.com/contents/images/6607197.pdf
However it would be best to read the article
and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
Here's a link to a pdf version of the synchronously filtered low ripple
pwm dac:
http://www.edn.com/contents/images/6553625.pdf
Bruce
Bruce Griffiths wrote:
Chris
All the details are in the article:
http
Moin,
On Sun, 27 Jun 2010 02:24:31 -0700
Said Jackson saidj...@aol.com wrote:
The 4002 expects a tight phase lock on the two inputs to properly stay
locked,
Why does the ADF4002 need that? Or do you mean by locked that the
locked output of the ADF4002 does reflect the actual locked state?
If
Hi,
What would be easier to try is to replace the gps internal Tcxo with
an external ocxo, but you have to generate the frequency the gps is
using, such as 26 MHZ and do some soldering on the gps itself.
Yes, that would be an idea. But it's not that easy. I dont know
how the control loop in
Moin,
On Sat, 26 Jun 2010 21:14:02 EDT
ewkeh...@aol.com wrote:
What you want is basically a Shera Board. That design has been around for
quite some time and has served me very well.
Yes. The Shera Board and similar designs serve as an example for me.
I have a total of six running
Attila Kinali wrote:
Moin,
On Sat, 26 Jun 2010 21:14:02 EDT
ewkeh...@aol.com wrote:
What you want is basically a Shera Board. That design has been around for
quite some time and has served me very well.
Yes. The Shera Board and similar designs serve as an example for me.
I
Hi,
just a clarification, I did write 4066 it is a 4046 that I replaced. Take
a look at the MCP 4822 dual 12 bit D/A In the data sheet they have an
example using one for coarse, the other for fine steps, I realize that the
transition is not perfect but maybe code can compensate for the
The problem is that the gain and offset of the 2 DACs changes with time
and temperature so that the required corrections also change.
Ideally an autocalibration technique would be used to dynamically track
such changes.
Since changes in the coarse DAC are only required infrequently and the
Not being able to write code and not understanding what is required it is
easy for me to suggest a fix. In the case of a good Rub. the annual aging
rate is 1 E-10 which would mean the lower 12 bits would cover one month.
During transition the PIC could modify the time constant and at the
Bruce Griffiths wrote:
Attila Kinali wrote:
Moin,
On Sat, 26 Jun 2010 21:14:02 EDT
ewkeh...@aol.com wrote:
What you want is basically a Shera Board. That design has been around
for
quite some time and has served me very well.
Yes. The Shera Board and similar designs serve as an
On Tue, 29 Jun 2010 21:32:10 +1200
Bruce Griffiths bruce.griffi...@xtra.co.nz wrote:
Its possible to build a 24 bit resolution D/A using a synchronously
filtered PWM circuit.
A pair of PWM outputs and a few relatively low precision resistors and
capacitors together with a low noise low
adjustment,
because the aging rate of the old well run in units can be orders of
magnitude better than their worse case spec after the first month or so of
continuous operation.
ws
**
[time-nuts] yet another GPSDO design, or so
Attila Kinali attila at kinali.ch
Tue Jun 29 13:31:34
of precise time and frequency measurement time-nuts@febo.com
Sent: Tue, June 29, 2010 5:31:50 AM
Subject: Re: [time-nuts] yet another GPSDO design, or so
The problem is that the gain and offset of the 2 DACs changes with time
and temperature so that the required corrections also change.
Ideally
...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Bruce Griffiths
Sent: Tuesday, June 29, 2010 5:32 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
Attila Kinali wrote:
Moin,
On Sat, 26 Jun 2010 21:14:02 EDT
ewkeh
On Tue, 29 Jun 2010 09:17:39 -0700 (PDT)
Stanley Reynolds stanley_reyno...@yahoo.com wrote:
If we lower the size of each step to over lap more would this
lower the error ? Software would adjust both converters at the
cross over point so neither would change it's full range at this point.
Two
On 6/29/2010 11:10 AM, Attila Kinali wrote:
Yes, 16bit D/A seems to
be the maximum that is currently available. It crossed my mind
to build a 24bit R-2R D/A using discrete components, but this might
have actually a worse performance than a off the shelf 16bit D/A.
(temperature drifft, resistor
-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Attila Kinali
Sent: Tuesday, June 29, 2010 12:42 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
On Tue, 29 Jun 2010 09:17:39 -0700 (PDT)
Stanley Reynolds
Sent: Tuesday, June 29, 2010 12:42 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
On Tue, 29 Jun 2010 09:17:39 -0700 (PDT)
Stanley Reynolds stanley_reyno...@yahoo.com wrote:
If we lower the size of each step to over lap more
[mailto:time-nuts-boun...@febo.com] On
Behalf Of Bruce Griffiths
Sent: Tuesday, June 29, 2010 5:32 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
Attila Kinali wrote:
Moin,
On Sat, 26 Jun 2010 21:14:02 EDT
ewkeh...@aol.com wrote
On Tue, 29 Jun 2010 12:54:52 -0400
Bob Camp li...@rtty.us wrote:
Some of the TI (Burr Brown) 16 bit parts are 1/4 lsb DNL on 98% of the
transitions. Most of the time you have a coarse DAC that's at 18 bits.
Some of the errors are predictable and you can take them out with a simple
training
offers out there for
this device, because repair of the audio equipment is prohibitive
Bert
-Original Message-
From: ewkeh...@aol.com
To: time-nuts@febo.com
Sent: Tue, Jun 29, 2010 1:45 pm
Subject: Re: [time-nuts] yet another GPSDO design, or so
Hi
just bought four AD 1861 on ebay
and there will be more reasonable offers out there
for this device, because repair of the audio equipment is prohibitive
Bert
-Original Message-
From: ewkeh...@aol.com
To: time-nuts@febo.com
Sent: Tue, Jun 29, 2010 1:45 pm
Subject: Re: [time-nuts] yet another GPSDO design, or so
Hi
just
On Tue, 29 Jun 2010 14:07:17 EDT
ewkeh...@aol.com wrote:
just bought four AD 1861 on ebay with shipping was $11 each. Will see
hat I get, but they are out there and 18 bit will cover in my opinion
most
Any one interested should hold off for a day buying. I have contacted the
bruce.griffi...@xtra.co.nz said:
Its possible to build a 24 bit resolution D/A using a synchronously
filtered PWM circuit. A pair of PWM outputs and a few relatively low
precision resistors and capacitors together with a low noise low drift
reference are required. The technique takes
Another approach is to distribute the individual bits rather than clump them
together. If you want 1/2, send 10101010 rather than . You would
have to do something like build a bit pattern in memory and use a serial
port to send it out.
I can't determine if that's good enough.
or with a pair of current output DACs and a resistive divider/summer so you
have a high order and low order voltage.
If it were that simple, the manufacturers would package it up into a single
chip. :)
I think there are two areas of interest. One is the obvious one that steps
on the
Attila Kinali wrote:
On Tue, 29 Jun 2010 21:32:10 +1200
Bruce Griffithsbruce.griffi...@xtra.co.nz wrote:
Its possible to build a 24 bit resolution D/A using a synchronously
filtered PWM circuit.
A pair of PWM outputs and a few relatively low precision resistors and
capacitors together
...@febo.com] On
Behalf Of Bruce Griffiths
Sent: Tuesday, June 29, 2010 4:07 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
Attila Kinali wrote:
On Tue, 29 Jun 2010 21:32:10 +1200
Bruce Griffithsbruce.griffi...@xtra.co.nz wrote
...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Bruce Griffiths
Sent: Tuesday, June 29, 2010 4:07 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
Attila Kinali wrote:
On Tue, 29 Jun 2010 21:32:10 +1200
Bruce
Hal Murray wrote:
bruce.griffi...@xtra.co.nz said:
Its possible to build a 24 bit resolution D/A using a synchronously
filtered PWM circuit. A pair of PWM outputs and a few relatively low
precision resistors and capacitors together with a low noise low drift
reference are required. The
Hi Bruce,
This sounds like a promising idea, please could you expand on the
synchronous filter technique? I have seen some articles about how such
filters can be used to clean up the data from rotating machinery for
vibration analysis etc. but I don't follow how they can be used in a PWM
: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Bruce Griffiths
Sent: Tuesday, June 29, 2010 4:34 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] yet another GPSDO design, or so
Bob Camp wrote:
Hi
Are you referring to something like
Hal Murray wrote:
or with a pair of current output DACs and a resistive divider/summer so you
have a high order and low order voltage.
If it were that simple, the manufacturers would package it up into a single
chip. :)
And they do... hence delta sigma designs..
Back in the good old days
Hi
Ok, here's a BOM:
TI DAC8581 $1.85 each, two for 3.70
Linear LTC 2493 $2.95
TI LM4040C50$0.36
Freescale MCF52254AF80 $4.38
Quad Op-amp $1.00
Misc resistors and caps $3.00
Other semi's$2.00
Total $17.39 at moderate volume prices. Depending on your shopping approach
likely
Moin-Moin Atilla,
The 4002 expects a tight phase lock on the two inputs to properly stay locked,
and your adc/dac will likely introduce too much phase lag and cause
oscillation. In fact when using the Analog Devices PLL simulator one has to
closely follow the component values of the loop
- Original Message
From: ewkeh...@aol.com ewkeh...@aol.com
To: time-nuts@febo.com
Sent: Sat, June 26, 2010 8:14:02 PM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Attilia
What you want is basically a Shera Board. That design has been around for
quite some time and has served me very well
another GPSDO design, or so
Attilia
What you want is basically a Shera Board. That design has been around for
quite some time and has served me very well. I have a total of six running
including two controlling Rubidium. There are in my opinion a couple of
problems: not every 4066 works
another GPSDO design, or so
Stanley
the faster counter also has the jitter, no change, as long as it is not
tied to the input frequency. The 24 MHz is not unique, the 100 MHz is same
technology just four times faster and thus gives me smaller steps on the D/A
and since I use it on Rub. the full
is it also slight at 100 Mhz ? An average of 30 samples does
have a limit to what it will correct.
Stanley
- Original Message
From: ewkeh...@aol.com ewkeh...@aol.com
To: time-nuts@febo.com
Sent: Sun, June 27, 2010 8:58:55 AM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Interestingly, it is desirable to have the frequency of U7 drift slightly
rather than being synchronized with the VCXO. A slight random drift averages
out the count ambiguity that is inherent in any pulse-counting device. My
measurements indicate that the simple phase-measuring circuit I use
To: time-nuts@febo.com
Sent: Sun, June 27, 2010 1:17:51 PM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Going from 24 to 100 MHz only gives you smaller steps (resolution) every
thing else stays the same.
If the he saw 2 to 3 nsec should be more like 8, going to 100 MHz will
improve
equals better unless the faster counter no longer averages out the +-
count.
Stanley
- Original Message
From: ewkeh...@aol.com ewkeh...@aol.com
To: time-nuts@febo.com
Sent: Sun, June 27, 2010 1:17:51 PM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Going from 24 to 100 MHz
ewkeh...@aol.com
To: time-nuts@febo.com
Sent: Sun, June 27, 2010 4:27:39 PM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Stanley
I am not an expert but it is not only the jitter it is the fact that since
the two sources are not linked the independent drift of the 100 MHz causes
stanley_reyno...@yahoo.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Sun, June 27, 2010 5:23:13 PM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Jitter may not be the correct word. I also don't know how accurate or
repeatable the averaging effect
, 2010 8:58:55 AM
Subject: Re: [time-nuts] yet another GPSDO design, or so
Stanley
the faster counter also has the jitter, no change, as long as it is not
tied to the input frequency. The 24 MHz is not unique, the 100 MHz is
same
technology just four times faster and thus gives me
Moin,
I recently had a look at the data sheet of the LEA6-T GPS module
from ublox, which now features a second time pulse output that
is capable of delivering a 10MHz signal, synchronized to GPS.
After thinking quite some time quite some time about building
my own GPSDO and struggling with the
Hello Attila,
Another GPS board with a 10 MHz output is the Navsync CW-12 module
(price ~US$85-90). I measured the 1 PPS output and found a Standard
Deviation of 5 ns with a range of 30 ns. The 10 MHz output is kept
on frequency by occasionally adjusting the period of the 10 MHz output
Moin,
On Sat, 26 Jun 2010 12:38:29 -0600
Ed Palmer ed_pal...@sasktel.net wrote:
Another GPS board with a 10 MHz output is the Navsync CW-12 module
(price ~US$85-90).
Hmm.. i didn't know about this one. Both seem to be comparable
from the specs, the LEA6-T being slightly better (well, the
Attilia
What you want is basically a Shera Board. That design has been around for
quite some time and has served me very well. I have a total of six running
including two controlling Rubidium. There are in my opinion a couple of
problems: not every 4066 works on the design the 18 bit D/A is
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