On Tue, 23 Apr 2013 14:36:45 -0500
David wrote:
> I always suspected something like this was at work.
>
> This would explain the ambiguous 1uS specification common in GPS
> receivers that are not intended for rigorous timing applications which
> I asked about a couple months ago. I did not ask
On Tue, 23 Apr 2013 19:05:53 +0200, Attila Kinali
wrote:
>On Tue, 23 Apr 2013 09:49:19 +0400
>Daniel Ginsburg wrote:
>
>> Not perfect, but should be reasonably good. It's an external magnetic
>> antenna on my windowsill.
>> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveye
On Tue, 23 Apr 2013 09:49:19 +0400
Daniel Ginsburg wrote:
> Not perfect, but should be reasonably good. It's an external magnetic antenna
> on my windowsill.
> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed
> location is better than this.
Windowsill? So you have only
Yes, the sawtooth correction is limited to tens of ns and is rapid: 10 to
30 seconds usually, the wander is larger and very slow.
If you want to build a simple GPSDO with a PPS output and disciplined by
the GPS PPS, take a look at my design:
http://www.c-c-i.com/exchange/
file: PiAutoTIC1.zip
On
On 23.04.2013, at 12:50, Azelio Boriani wrote:
> Daniel,
> a timing GPS receiver is not a GPSDO so its PPS is wandering about the
> nominal position. Using a digital oscilloscope, I can see how much the
> total wander is by activating the infinte persistence mode of the display.
> After 10 minute
Daniel,
a timing GPS receiver is not a GPSDO so its PPS is wandering about the
nominal position. Using a digital oscilloscope, I can see how much the
total wander is by activating the infinte persistence mode of the display.
After 10 minutes, 1 hour, 1 day or whatever you have an idea of the total
On 23.04.2013, at 6:15, Hal Murray wrote:
>
>> I wonder, what kind of timing GPS gives 112ns wander?
>
> How good is your antenna? 112 ns is roughly 112 feet. That's not at all
> surprising if your antenna is inside or under trees.
>
Not perfect, but should be reasonably good. It's an ext
I'd bet you could determine a lot about the cause by looking at the spectra
of the error.I'm guessing that if the cause is an inaccurate survey
location then the wondering will be periodic because at one point in the
satilite's orbit it will be "too close" and then the distance will be to
far.
> I wonder, what kind of timing GPS gives 112ns wander?
How good is your antenna? 112 ns is roughly 112 feet. That's not at all
surprising if your antenna is inside or under trees.
You might watch the number of satellites and/or watch the position while it
does a survey.
--
These are my o
On 23.04.2013, at 2:57, Azelio Boriani wrote:
> I agree with Hal and if you have a reference you can tell how much the
> crystal is off. My timing GPS receiver after 1 hour has a total uncorrected
> wander of 112ns. Never seen 400ns on a timing receiver (maybe I haven't
> waited long enough).
>
On 23.04.2013, at 3:02, Jim Lux wrote:
>
> Assuming the software is reading some hardware counter when it gets the
> pulse, there could be variable latency in the routine. 8000 ticks is a lot
> of instructions though..
The hw timer latches the counter value to a separate register when the le
Have you any reference? A TBolt, Z3801 or similar?
On Mon, Apr 22, 2013 at 9:53 PM, Daniel Ginsburg wrote:
> Hi all,
>
> I have bought a Resolution SMT GG for me to play with, and build a very
> simple breakout board.
>
> The receiver appears to be working (in a sense). That is, it powers up, it
On 4/22/13 3:15 PM, Hal Murray wrote:
dginsb...@gmail.com said:
First, the frequency offset of the microcontroller. I use a built-in
counting timer in the uC which runs at 84MHz to measure the duration between
2 PPS. What I get is ~84008000 timer ticks between two pulses, which
corresponds to a
I agree with Hal and if you have a reference you can tell how much the
crystal is off. My timing GPS receiver after 1 hour has a total uncorrected
wander of 112ns. Never seen 400ns on a timing receiver (maybe I haven't
waited long enough).
On Tue, Apr 23, 2013 at 12:49 AM, Azelio Boriani
wrote:
dginsb...@gmail.com said:
> First, the frequency offset of the microcontroller. I use a built-in
> counting timer in the uC which runs at 84MHz to measure the duration between
> 2 PPS. What I get is ~84008000 timer ticks between two pulses, which
> corresponds to about 95ppm offset. While the crys
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