[]
WAAS only works in North America. I don't know details elsewhere, but the
PMTK313 message says it turns searching for SBAS satellites on and off.
--Jim Harman
==
Thanks for the information on the messages, Jim.
For your information, in Europe we have EGNOS,
csteinm...@yandex.com said:
(Note that a 256 cycles per second error is 51 PPM at 5 MHz.)
You need a bit for the sign. That leaves only 25.6 PPM error from nominal,
51.2 peak-peak. Half that at 10 MHz.
In the real world, you should be able to trust that any oscillator that is
chosen
Hi Brooke,
HP had some way around SA that improved the timekeeping.
HP called it the Smartclock Algorithm and you can find some very basic
information about it here:
http://www.hpl.hp.com/hpjournal/96dec/dec96a9.pdf
I have been trying months to find a reference on how it REALLY works but it
Hi All,
I've used the STM32F4 for a few projects, and was considering it for a
time tagger for a DMTD system. I have a question about the clocking
though that someone may be able to help me with.
The 32F4 (like lots of similar ARMs) uses a PLL to generate the internal
clocks from much
I wonder if a CSAC used as a wristwatch would need constant C-field
adjustment?
On Thu, Apr 10, 2014 at 12:41 PM, Attila Kinali att...@kinali.ch wrote:
On Thu, 10 Apr 2014 10:43:13 -0400
Ronald Held ronaldh...@gmail.com wrote:
I am curious what people think of this watch at least from the
Brooke, Ulrich,
Keep in mind the hp SmartClock product line dated from the early-90's and it
was one of the first GPSDO on the market. So even simple things like using
timing receivers, partial ionospheric correction, sawtooth correction, sub-ns
TIC, 1PPS filtering, high-quality OCXO, PIID,
David we may be drifting from Hals thread. So don't want to do that.
I looked at the system and its governed by the xtal they use. Granted its
cheap and totally in an uncontrolled environment. Mine typically is +.79
ppm at 1 Mhz. Semi consistent. Its really easy to bypass that xtal and to
inject
Yea! I remember when they shut it down at the nadir of the sunspot
cycle, saying no one was using it. Duh!
David N1HAC
On 4/11/14 12:07 AM, Max Robinson wrote:
WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they
shut it down. That was years ago. I'm glad to know they
I worked for the HP Santa Clara Division during
the Smart Clock days and knew all the players.
In terms of holdover, the report cited mentions
temperature compensation and learning aging.
The temperature compensation was simply a crutch
for the 10811 to fix its tempco problems. The
E1938A had
I wrote:
(Note that a 256 cycles per second error is 51 PPM at 5 MHz.)
In the real world, you should be able to trust that any oscillator that is
chosen for a GPSDO will free-run within 1 PPM when it is warmed up, and
that your PPS will always be within 1 PPM, as well.
Hal wrote:
On Thu, Apr 10, 2014 at 2:48 PM, Bob Stewart b...@evoria.net wrote:
The only particular anomaly I can see is that it uses satellites
close to the horizon for position fixing.I'm getting a reported SNR of 39
at 5 degrees elevation and 37 at 3 degrees, though I notice the sat at 3
degrees
rich...@karlquist.com said:
Still, there was no way to guarantee that a crystal in the future would
never have a jump or sudden change in aging.
What was really needed was an ensemble of oscillators, but that was not
economically competitive with rubidium.
How many would you need? Is 3
dho...@gmail.com said:
The 32F4 (like lots of similar ARMs) uses a PLL to generate the internal
clocks from much lower frequency clock or crystal. Has anyone quantified
the stability of the synthesised clock?
I'm not familiar with the 32F4, but most of the SOC type ARM chips have ways
to
On 4/11/2014 11:04 AM, Hal Murray wrote:
How many would you need? Is 3 enough?
How well could you do with several low(er) cost oscillators relative to one
good but expensive one? It might be an interesting experiment in a nutty
sort of way.
My guess would be 3 would be a minimum, so you
On 10 Apr, 2014, at 22:06 , Chris Albertson albertson.ch...@gmail.com wrote:
You originally described a system that counts to 5M every second. Tom and
others pointed out that you do not need the complete 5M count, all you need
is the remainder of a modulo count. The question then is, how
Interesting idea. It might be an interesting experiment to couple a large
number of inexpensive xtals to see how it impacts effects such as sudden
changes in a single xtal.
With sufficient monitoring of each one, you could even tune the coupling to
amplify/attenuate the results of the 'good'
Ulrich
Thanks for posting the reference.
Very interesting and useful. The clues they give sounds like enough
information to do the Smartclock loop control things that they talk about.
ws
***
Hi Brooke,
HP had some way around SA that improved the timekeeping.
HP
flavors of seconds: Those with N overflows and those with N+1 overflows.
Just to beat this to death from a different angle...
In a simple case of N = 0 and an 8-bit counter you can see that
200 - 190 (= 10) has no (N) overflows and
004 - 250 (= 10) has one (N+1) overflow.
Yet they
Look at what NTP does to select good clocks when it has many to choose
from. It does not simply average them.
It looks at the noise in each one and then sees which clocks have
overlapping error bars. It assumes that all good clocks have the same time
within limits of their precision. Then
On 10/04/14 23:48, Bob Stewart wrote:
My Adafruit has gone walkabout again. This is a different unit than the one I spoke
about some months ago. It's been about 150 ft from my actual location, which has, of
course, made a mess of my GPSDO. Well, at least it verified my unlock code.
I did
Fired up the R1051 on 25 Mhz and its great to hear wwv back on the air in
Boston.
Pretty good signal.
Regards
Paul
WB8TSL
On Fri, Apr 11, 2014 at 10:12 AM, David McGaw n1...@dartmouth.edu wrote:
Yea! I remember when they shut it down at the nadir of the sunspot cycle,
saying no one was using
I think the solution is easy.
1) count all the cycles using an overflow interrupt until you see the
result is stable to about 1ppm. We all know that even a simple $8
controller can do this.
2) then switch to a mode where we look only at the last few bits of the
counter. I think this will
Hi all,
I'm thinking about an upcoming project, if this is off topic please
disregard or contact me off list. :)
I have a large LC tank, with a very lossy inductor. Being driven by a
pulse width push pull driver, that is digitally controlled. The driver
circuit will couple through a N:1
At resonance, an LC looks pure resistive.
For a parallel LC, sample the voltage across the LC and the drive current,
and tweek the frequency until they are in-phase.
For a series LC, sample the voltage across the L or C and tweek as above.
If you want to do it analog, dither the frequency a
Hi Magnus,
Yeah, there's no getting over the fact that it's a cheap $30 (or whatever it
was) nav receiver. But I think the walkabout issue has been resolved. I
think this thing is going to be OK for me, but I certainly wouldn't even give
it a glance for professional use. Now that I've got
First order approximation of course would be to sweep the frequency and
look for a dip (peak for series resonant) in the DC current drawn by the
driver.
On Fri, Apr 11, 2014 at 4:15 PM, Dan Kemppainen d...@irtelemetrics.comwrote:
when actively driving a tank circuit, how do you
know you are
albertson.ch...@gmail.com said:
2) then switch to a mode where we look only at the last few bits of the
counter. I think this will actually perform better than mode #1 above
because there is zero chance of the two interrupts happening at the same
time causing your PPS sample to be delayed
I have a large LC tank, with a very lossy inductor. ...
So the question is, when actively driving a tank circuit, how do you know
you are driving it with the same frequency ad the same phase it naturally
oscillates at.
If it's lossy, the peak will be broad so tuning the driving frequency
I would have done exactly what Hal said. I do this all the time when trying
to figure out the LC tanks operating frequency. An example keeping this
time nuts friendly, the d-psk-r circuits at 60 Khz. I am lucky in that I
can add or subtract C on the stuff I work on.
Regards
Paul
WB8TSL
On Fri,
That's why you want to look for the phase of the tank impedance. The phase
goes through zero at resonance. It is far more precise. The steepness of
the phase v. frequency plot is steep w/ a high Q circuit... flatter w/ a
low Q tank. Either way, it does go through zero at resonance.
The phase v.
Tried three times today to get WWV on 25, heard nothing under the power
line noise.
I did have a nice QSO on 12 meters with a station in Rochester, NY so
the band is open.
WWV is currently weak on 20, strong on 15 and 10 MHz.
On 04/11/2014 12:09 PM, paul swed wrote:
Fired up the R1051 on 25
On Fri, Apr 11, 2014 at 2:51 PM, Hal Murray hmur...@megapathdsl.net wrote:
Unless the CPU is doing something complicated (like serving web pages), you
can do the whole thing without any interrupts. Just use a polling loop
that
checks the ready-now? status for all the things the CPU has to
On Thu, Apr 10, 2014 at 6:42 AM, Jim Harman j99har...@gmail.com wrote:
I have not tried the dual PWM-based DAC, but my concern is that depending
on the ratio of the resistors it might not be monotonic as the output goes
from say 0FF to 100 hex. You would see this problem in the output every
Easily heard on a 12 ft wire in NH this afternoon. Chuck - You may be
too close and it is skipping over.
David N1HAC
On 4/11/14 8:37 PM, paul swed wrote:
Chuck
The an/urr R1051 does not have a signal meter. It has level meters for
audio.
Those navy radios. I guess they figured the radio
albertson.ch...@gmail.com said:
My plan was to eventually fix this in software. Using ultra precision
resisters is not a good fix. I'm using normal 5% 1/4W resisters.
I don't think I will get stuck. if a step is to small it will simply move
up the next DAC value. The I term in the PID
Yes I agree. My long term plan with the software is to write a C++ class
called DAC where you send it a voltage. The class hides the way the DAC
works. I was also thinking like you to treat this as two DACs where you
use one for fine tuning and the other to make a course adjustment to place
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