[time-nuts] PIN define of VECTRON OCXO 217-8422

[Hui Zhang]

Dear Group:
I just got a VECTRON 5Mhz OCXO the model is 217-8422, does anyone have its 
datasheet or  PIN define? Thanks a lot.


Hui
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Re: [time-nuts] Speaking of Costas loops

[Jim Lux]

On 7/3/13 2:21 PM, Dennis Ferguson wrote:


On 3 Jul, 2013, at 11:47 , Bob Camp  wrote:

The pipe in this case is up on one frequency and down on another. The 
conversion oscillator on satellite that's the weak link, no matter how good the 
signal from the ground happens to be.


That's certainly true but it doesn't seem like a problem that the
presence of a high stability free-running oscillator, like a rubidium,
would help.  The oscillator on a geostationary satellite has a
continuous frequency reference to lock to (the uplink carrier) and
hence only needs short term stability sufficient to track this and
transfer it accurately to the downlink.  It seems like this is the
kind of problem that quartz excels at.



Kind of depends on what the transponder on the satellite looks like.

For deep space, we use a very narrow band loop filter to recover the 
received carrier.  The synthesis approach for the downlink is designed 
to cancel any variations in the local crystal oscillator (e.g. it's 
typically a ratio.. for X band, 880/749)



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Re: [time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

On Jul 3, 2013, at 3:51 PM, jmfra...@cox.net wrote:

> http://www.navipedia.net/index.php/WAAS_Signal_Structure
> 
> Doppler Shift: The Doppler shift, as perceived by a stationary user, on the 
> signal broadcast by WAAS GEOs is less than 40 meters per second (≈210 Hz at 
> L1)

So unless you can measure and correct for the doppler, you are at a few hundred 
Hz at 1.5 GHz. 150 Hz would be 0.1 ppm. That's not very accurate. 

> in the worst case (at the end of life of the GEOs). The Doppler shift is due 
> to the relative motion of the GEO. 
> Carrier Frequency Stability: The short term stability of the carrier 
> frequency (square root of the Allan Variance) at the input of the user´s 
> receiver antenna will be better than 5x10-11 over 1 to 10 seconds, excluding 
> the effects of the ionosphere and Doppler. 
> Polarization: The broadcast signal is right-handed circularly polarized. The 
> ellipticity will be no worse than 2 dB for the angular range of ±9.1o from 
> boresight. 
> Code/Carrier Frequency Coherence: The lack of coherence between the broadcast 
> carrier phase and the code phase shall be limited. The short term (<10sec) 
> fractional frequency difference between the code phase rate and the carrier 
> frequency shall be less than 5x10-11 (one sigma). Over the long term (<100 
> sec), the difference between the change in the broadcast code phase (convert 
> to carrier cycles) and the change in the broadcast carrier phase shall be 
> within one carrier cycle (one sigma). 

Once you are past 100 seconds, there's essentially no spec. One cycle per 100 
sec is a lot, even at 1.5 GHz

> Correlation Loss: Correlation loss is defined as the ratio of output powers 
> from a perfect correlator for two cases: 1) the actual receiver WAAS signal 
> correlated against a perfect unfiltered PN reference, or 2) a perfect 
> unfiltered PN signal normalized to the same total power as the WAAS signal in 
> case 1. The correlation loss resulting from modulation imperfections and 
> filtering inside the WAAS satellite payload is less than 1 dB. 

If you are only after the carrier, the code stuff pretty much does not matter.

Bob

> 
> John WA4WDL
> 
>  Bob Camp  wrote: 
>> Hi
>> 
>> The pipe in this case is up on one frequency and down on another. The 
>> conversion oscillator on satellite that's the weak link, no matter how good 
>> the signal from the ground happens to be. 
>> 
>> Bob
>> 
>> On Jul 3, 2013, at 1:48 PM, Attila Kinali  wrote:
>> 
>>> On Wed, 3 Jul 2013 08:29:02 -0400
>>> Bob Camp  wrote:
>>> 
 There are two batches of GPS / WAAS sats up there:
 
 1) The ones with numbers above 100 that are geosync and that only do WAAS
 
 2) The ones with numbers <= 32 that do nav. These are not geosync. 
 
 I believe the only ones with corrected / high stab clocks on board are
 those in the second group. The stuff in the first group aren't dedicated
 sats, just leased transponders on conventional multipurpose geosync birds. 
>>> 
>>> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
>>> ground using Cs references and retransmitted by the satelites using
>>> a "bend pipe". Ie. the signals should be of time-nut quality even without
>>> high accuracy frequency standards in the birds themselves.
>>> 
>>> (Sorry, i'm not able to find where i read about that, so no references 
>>> today)
>>> 
>>> Attila Kinali
>>> 
>>> -- 
>>> The people on 4chan are like brilliant psychologists
>>> who also happen to be insane and gross.
>>> -- unknown
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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Re: [time-nuts] Speaking of Costas loops

[Jim Lux]

On 7/3/13 12:42 PM, Azelio Boriani wrote:

Sure about the "bent pipe"? If so it seems that much power is required
at the transmitting ground station...


Much "equivalent" power is required.  If you have a 20 meter or so 
antenna, it doesn't take much to get a pretty  high EIRP.


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Re: [time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

If the WAAS sats were purpose designed to provide a high accuracy carrier, then 
yes there are ways to do it. The fundamental design concept of a "bent pipe" is 
that you don't do any of that. You do not care what's going through the bird, 
it just maps the input frequencies to the output and amplifies them (a lot). 
Again, the WAAS signal is simply piggybacking on existing hardware. The 
conversion oscillator is not locked to the GPS carrier (or to any other 
carrier). It's simply a free running quartz based oscillator, running into a 
synthesizer to get the appropriate microwave frequency. 

Bob

On Jul 3, 2013, at 5:21 PM, Dennis Ferguson  wrote:

> 
> On 3 Jul, 2013, at 11:47 , Bob Camp  wrote:
>> The pipe in this case is up on one frequency and down on another. The 
>> conversion oscillator on satellite that's the weak link, no matter how good 
>> the signal from the ground happens to be. 
> 
> That's certainly true but it doesn't seem like a problem that the
> presence of a high stability free-running oscillator, like a rubidium,
> would help.  The oscillator on a geostationary satellite has a
> continuous frequency reference to lock to (the uplink carrier) and
> hence only needs short term stability sufficient to track this and
> transfer it accurately to the downlink.  It seems like this is the
> kind of problem that quartz excels at.
> 
> Dennis Ferguson
> 
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[Mark C. Stephens]

You could also try questi...@lists.ntp.org.

The developers etc hang out on that list.
There are a lot of helpful experts on NTP there.

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Hal Murray
Sent: Thursday, 4 July 2013 8:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] looking for low-power system for gps ntp timekeeping 
NANOSG20

> It is a garmin 18x lvc.

That's pretty vanilla.  It really should work.  I won't be surprised if the 
NMEA is off by hundreds of ms and/or has 100 ms of wander, but the PPS should 
work.

Would you please try ntpd's NMEA driver, preferably from the latest ntp-dev
  http://support.ntp.org/bin/view/Main/SoftwareDownloads
The PPS code used by ntpd is different from gpsd.

If that doesn't work we should try to fix it.


>> rather than ntpd's NMEA driver?
> Oh for convenience. I need to patch ntpd to use linux pps (afaik) and 
> on other systems I successfully run gpsd with ntpd (read: low jitter).

Were any of those systems ARM?

-

One possibility is that the CPU is getting turned off when idle to save power.  
If that includes the stuff normally used for timekeeping, things could get 
screwed up when it gets turned back on.  It has to reset the time, probably 
getting it from the RTC.


Can you measure the power when idle?  (kill off as much as possible, things 
like ntpd)  If that's suspiciously low that might be the problem.

Can you keep it busy?  If nothing else, "while true; do true; done"


--
These are my opinions.  I hate spam.



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Re: [time-nuts] BPSK decoder for WWVB

[Dennis Ferguson]

On 3 Jul, 2013, at 14:03 , Tim Shoppa  wrote:
> I have also heard YVTO on 5MHz underneath both WWV and WWVH, strangely
> off-kilter by half a second or so.

When BPM does that, like maybe at the beginning of this

http://www.youtube.com/watch?v=WRaRB-x84xg

I think it is because they are transmitting UT1 pips rather
than UTC pips.  I assume this might be convenient for celestial
navigation users, though I can't imagine that there are a whole
lot of those left.

Dennis Ferguson
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Re: [time-nuts] BPSK decoder for WWVB

[Majdi S. Abbas]

On Wed, Jul 03, 2013 at 05:03:40PM -0400, Tim Shoppa wrote:
> I have heard MSF on 60kHz in our early evening on some winter nights but
> never would describe it as jamming :-)

I have an MSF receiver, if only I could get rid of the
semi-local (1000 km) interference from WWVB.  :)

> I have also heard YVTO on 5MHz underneath both WWV and WWVH, strangely
> off-kilter by half a second or so.

Satellite bounce, maybe?

> All that said, BPSK sounds like it could be substantially more robust than
> on/mostly-off keying. I'm surprised given how enthusiastic WWVB was to drop
> continuous-phase transmissions, that nobody's bought into it yet.

Because we can't.  They converted to a new modulation for which,
the only legal (non-patent encumbered) receiver chipset...is not yet 
shipping.  Xtendwave is promising samples "real soon now," but
commercial quantities aren't supposed to be available until later this
year, and who knows when we'll see a product.

It's unclear to me why NIST was in such a hurry to go to full
time BPSK without a single receiver in an end-users hand.  Seems like
they could have alternated both modulations for a longer period of 
time without any harm.

--msa
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[Hal Murray]

> It is a garmin 18x lvc.

That's pretty vanilla.  It really should work.  I won't be surprised if the 
NMEA is off by hundreds of ms and/or has 100 ms of wander, but the PPS should 
work.

Would you please try ntpd's NMEA driver, preferably from the latest ntp-dev
  http://support.ntp.org/bin/view/Main/SoftwareDownloads
The PPS code used by ntpd is different from gpsd.

If that doesn't work we should try to fix it.


>> rather than ntpd's NMEA driver?
> Oh for convenience. I need to patch ntpd to use linux
> pps (afaik) and on other systems I successfully run gpsd
> with ntpd (read: low jitter).

Were any of those systems ARM?

-

One possibility is that the CPU is getting turned off when idle to save 
power.  If that includes the stuff normally used for timekeeping, things 
could get screwed up when it gets turned back on.  It has to reset the time, 
probably getting it from the RTC.

Can you measure the power when idle?  (kill off as much as possible, things 
like ntpd)  If that's suspiciously low that might be the problem.

Can you keep it busy?  If nothing else, "while true; do true; done"


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] BPSK decoder for WWVB

[Brian Alsop]

Yes, according to:
www.jks.com/wwvb.pdf‎
Brian
On 7/3/2013 20:48, Rob Kimberley wrote:

I assume you mean MSF...



Sent from Samsung Mobile

 Original message 
From: Brian Alsop 
Date:
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] BPSK decoder for WWVB

Apparently this modulation scheme is less prone to "jammers".
There is is British station which "jams" east coast WWVB.

Brian/K3KO

On 7/3/2013 18:00, Tim Shoppa wrote:


Potentially the BPSK encoding ought to offer much better decoding here on
the East Coast of US. Many of the commercially available, pre-BPSK WWVB
consumer clocks didn't sync so well in the summertime due to high noise
levels.

Tim N3QE




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Re: [time-nuts] BPSK decoder for WWVB

[Tim Shoppa]

I have heard MSF on 60kHz in our early evening on some winter nights but
never would describe it as jamming :-)

I have also heard YVTO on 5MHz underneath both WWV and WWVH, strangely
off-kilter by half a second or so.

Many evenings the Russian time stations are audible, offset by 4kHz from 5
and 10MHz.

All that said, BPSK sounds like it could be substantially more robust than
on/mostly-off keying. I'm surprised given how enthusiastic WWVB was to drop
continuous-phase transmissions, that nobody's bought into it yet.

Tim N3QE


On Wed, Jul 3, 2013 at 3:15 PM, Brian Alsop  wrote:

> Apparently this modulation scheme is less prone to "jammers".
> There is is British station which "jams" east coast WWVB.
>
> Brian/K3KO
>
>
> On 7/3/2013 18:00, Tim Shoppa wrote:
>
>  Potentially the BPSK encoding ought to offer much better decoding here on
>> the East Coast of US. Many of the commercially available, pre-BPSK WWVB
>> consumer clocks didn't sync so well in the summertime due to high noise
>> levels.
>>
>> Tim N3QE
>>
>
>
>
> -
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2242 / Virus Database: 3204/5961 - Release Date: 07/03/13
>
>
> __**_
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>
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[Doug Calvert]

On Wed, Jul 3, 2013 at 4:14 PM, folkert  wrote:
>
>
> Oh for convenience. I need to patch ntpd to use linux pps (afaik) and on
> other systems I successfully run gpsd with ntpd (read: low jitter).


Using gpsd with ntpd reduces the jitter versus just using ntpd by itself?
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Re: [time-nuts] Speaking of Costas loops

[Dennis Ferguson]

On 3 Jul, 2013, at 11:47 , Bob Camp  wrote:
> The pipe in this case is up on one frequency and down on another. The 
> conversion oscillator on satellite that's the weak link, no matter how good 
> the signal from the ground happens to be. 

That's certainly true but it doesn't seem like a problem that the
presence of a high stability free-running oscillator, like a rubidium,
would help.  The oscillator on a geostationary satellite has a
continuous frequency reference to lock to (the uplink carrier) and
hence only needs short term stability sufficient to track this and
transfer it accurately to the downlink.  It seems like this is the
kind of problem that quartz excels at.

Dennis Ferguson

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Re: [time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

The power at transmit is partially a function of making it tough for backyard 
"what ever nuts" to broadcast through the sats. Since there's no demodulation / 
decoding / encoding / remodulation, power is the only practical lockout 
mechanism. 

It's secondarily a function of the massive amount of random RF we generate all 
over the planet. They want signals that are "clean" to -60 dbc or better. They 
actually sell slots that are in the > -50 dbc range to people for specialized 
use. There is some modulation magic involved, so that's not quite the same as 
main transmit is 60 db >  sum of (everything else). 

http://en.wikipedia.org/wiki/Transponder_(satellite_communications)

Bob

On Jul 3, 2013, at 3:42 PM, Azelio Boriani  wrote:

> Sure about the "bent pipe"? If so it seems that much power is required
> at the transmitting ground station...
> 
> On Wed, Jul 3, 2013 at 7:48 PM, Attila Kinali  wrote:
>> On Wed, 3 Jul 2013 08:29:02 -0400
>> Bob Camp  wrote:
>> 
>>> There are two batches of GPS / WAAS sats up there:
>>> 
>>> 1) The ones with numbers above 100 that are geosync and that only do WAAS
>>> 
>>> 2) The ones with numbers <= 32 that do nav. These are not geosync.
>>> 
>>> I believe the only ones with corrected / high stab clocks on board are
>>> those in the second group. The stuff in the first group aren't dedicated
>>> sats, just leased transponders on conventional multipurpose geosync birds.
>> 
>> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
>> ground using Cs references and retransmitted by the satelites using
>> a "bend pipe". Ie. the signals should be of time-nut quality even without
>> high accuracy frequency standards in the birds themselves.
>> 
>> (Sorry, i'm not able to find where i read about that, so no references today)
>> 
>>Attila Kinali
>> 
>> --
>> The people on 4chan are like brilliant psychologists
>> who also happen to be insane and gross.
>>-- unknown
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[Chris Albertson]

The computer itself and the NTP installation are OK because we can see it
syncing to other NTP servers.  Likely you have a problem in the way the GPS
using is connected.
Some common errors is an inverted PPS, just flip it ad see if you gets
better, it is really hard to see a 1Hz signal on a scope.
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Re: [time-nuts] Speaking of Costas loops

[Dennis Ferguson]

On 3 Jul, 2013, at 10:48 , Attila Kinali  wrote:

> On Wed, 3 Jul 2013 08:29:02 -0400
> Bob Camp  wrote:
> 
>> There are two batches of GPS / WAAS sats up there:
>> 
>> 1) The ones with numbers above 100 that are geosync and that only do WAAS
>> 
>> 2) The ones with numbers <= 32 that do nav. These are not geosync. 
>> 
>> I believe the only ones with corrected / high stab clocks on board are
>> those in the second group. The stuff in the first group aren't dedicated
>> sats, just leased transponders on conventional multipurpose geosync birds. 
> 
> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> ground using Cs references and retransmitted by the satelites using
> a "bend pipe". Ie. the signals should be of time-nut quality even without
> high accuracy frequency standards in the birds themselves.
> 
> (Sorry, i'm not able to find where i read about that, so no references today)

I have also read that WAAS satellites can be usefully included in the GPS
solution, so they aren't necessarily inferior, but I also don't have
a reference.  There is this:

http://tf.boulder.nist.gov/general/pdf/2299.pdf

The clocks are indeed ground based and good quality.  The advantage of using
them as an alternative to GPS CV (which is what the paper is about) is that
they transmit unencrypted code on two frequencies to allow computing ionospheric
corrections and they don't move (much) so you can track them continuously with
a dish to get a big signal-to-noise improvement and multipath insensitivity.  
The
last bit seems like a mixed blessing, though, since the dish means you depend on
only the one satellite it is pointed at and hence suffer from whatever bad 
things
happen to it.  The paper notes events that it characterises as an "increasing 
problem
with the broadcast WAAS ephemeris", followed by an outage and clock jump, which 
I
interpret as maybe being an adjustment made to the satellite orbit which can't
be represented properly in the ephemeris.  I assume that could happen with 
regular GPS
satellites too, but if you are tracking a lot of them at once it is easy to 
detect
and toss out a solution outlier.

Dennis Ferguson
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[time-nuts] An upcoming anniversary of interest to Time-Nuts

[Tom Holmes]

http://www.wired.com/wiredscience/2013/07/wwvb-time-radio/

Tom Holmes, N8ZM
Tipp City, OH
EM79



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Re: [time-nuts] Quartz crystal aging and applied voltage

[Magnus Danielson]

Hi Bob,

On 07/02/2013 02:46 AM, Bob Camp wrote:

Hi

There's a gotcha with trying to anneal quartz. If you take it above the Curie 
temperature, it'll twin when it comes back down. You will have random right and left 
handed domains in the bar. Net result is that you can't get it hot enough to 
"heal" any imperfections.


Ah, now that is critical knowledge.

Cheers,
Magnus
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Re: [time-nuts] BPSK decoder for WWVB

[Rob Kimberley]

I assume you mean MSF...



Sent from Samsung Mobile

 Original message 
From: Brian Alsop  
Date:  
To: Discussion of precise time and frequency measurement  
Subject: Re: [time-nuts] BPSK decoder for WWVB 
 
Apparently this modulation scheme is less prone to "jammers".
There is is British station which "jams" east coast WWVB.

Brian/K3KO

On 7/3/2013 18:00, Tim Shoppa wrote:

> Potentially the BPSK encoding ought to offer much better decoding here on
> the East Coast of US. Many of the commercially available, pre-BPSK WWVB
> consumer clocks didn't sync so well in the summertime due to high noise
> levels.
>
> Tim N3QE



-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2242 / Virus Database: 3204/5961 - Release Date: 07/03/13

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Re: [time-nuts] Speaking of Costas loops

[Azelio Boriani]

Sure about the "bent pipe"? If so it seems that much power is required
at the transmitting ground station...

On Wed, Jul 3, 2013 at 7:48 PM, Attila Kinali  wrote:
> On Wed, 3 Jul 2013 08:29:02 -0400
> Bob Camp  wrote:
>
>> There are two batches of GPS / WAAS sats up there:
>>
>> 1) The ones with numbers above 100 that are geosync and that only do WAAS
>>
>> 2) The ones with numbers <= 32 that do nav. These are not geosync.
>>
>> I believe the only ones with corrected / high stab clocks on board are
>> those in the second group. The stuff in the first group aren't dedicated
>> sats, just leased transponders on conventional multipurpose geosync birds.
>
> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> ground using Cs references and retransmitted by the satelites using
> a "bend pipe". Ie. the signals should be of time-nut quality even without
> high accuracy frequency standards in the birds themselves.
>
> (Sorry, i'm not able to find where i read about that, so no references today)
>
> Attila Kinali
>
> --
> The people on 4chan are like brilliant psychologists
> who also happen to be insane and gross.
> -- unknown
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[folkert]

> Thanks for your graphs, but what are the Y-axis units!

http://keetweej.vanheusden.com/~folkert/nanosg20.png is in ms and not
the delay, the offset instead.

> Inn your billboard above, the PPS looks to be on the wrong edge -
> perhaps the pulse is 250 ms wide and you are syncing to the trailing
> edge and not the leading.

well the offset is not constant. Now it is even 1 second:

 remote   refid  st t when poll reach   delay   offset  jitter
==
x127.127.28.0.NMEA.   0 l5   16  3770.000  -1002.1   0.096
*127.127.28.1.PPS.0 l9   16  3770.000  -1000.2 394.379
+192.168.64.18   .PPS.1 u   64   64  3770.548   -0.360   3.083
+192.168.64.2.PPS.1 u  108  128  3770.251   -1.128   0.918
-192.168.64.168  .PPS.1 u   34   64  3771.153   -0.755   3.958

> Can you check that out?  I recall that

I can but I think (open for telling me I'm wrong) the primary problem is with 
the offset jumping all over the place: see my mail a couple of minutes ago.

> it's the positive going transition on the DCD connection which needs
> to be on the exact second.   I think you are using the Garmin GPS
> 18x LVC.  There was a firmware update which ensured that the serial
> adta arrived /before/ the /next/ second edge rather than after it.
> Ensure your firmware is 3.70 or later.  See:
>  http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm
> I see that 3.80 is now out, but I think I am still on 3.70.

I'll have a look at it this weekend.


Folkert van Heusden

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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[folkert]

> folk...@vanheusden.com said:
>  remote   refid  st t when poll reach   delay   offset  jitter
> ==
> x127.127.28.0.NMEA.   0 l3   16  3770.000  -994.05   7.857
> x127.127.28.1.PPS.0 l7   16  3770.000  -250.13 572.812
> +192.168.64.18   .PPS.1 u   66  128  3770.553   -0.055   0.033
> *192.168.64.2.PPS.1 u   99  128  3770.237   -0.062   0.039
> +192.168.64.168  .PPS.1 u   44  128  3770.646   -0.013   0.321
> 
> Something is broken.  What NMEA device are you using?  Why are you using gpsd 

It is a garmin 18x lvc.

> rather than ntpd's NMEA driver?

Oh for convenience. I need to patch ntpd to use linux pps (afaik) and on
other systems I successfully run gpsd with ntpd (read: low jitter).

> It looks like the NMEA side it is off by a second.  Some devices do that.  
> You can fix that with some fudging.

Yes, I'm not so worried about the nmea part, I might even decide to
remove it from the configuration. What I mean is: if I set the clock to
the current time, than it is only a matter of keeping it at that with
the pps.

> The PPS stuff is off by 250 ms.  Are you using the wrong edge?  (Got a scope 
> handy?)

Well, the offset is not constant. If you look at
http://keetweej.vanheusden.com/~folkert/nanosg20.png you see it is
between 0 and -1ms. I now notice that it is not random-ish but consists
of a few specific values:

folkert@belle:~$ cat peerstats | grep 127.127.28.1 | awk '{ print $5; }' | cut 
-c 1-6 | sort | uniq -c | sort -rn
503 -0.874
497 -0.875
486 -0.999
467 -1.000
365 -0.249
332 -0.250
201 -0.857
188 -0.125
184 -0.142
140 -0.124
131 -0.000
113 0.
108 -0.166
 24 -0.833
  5 -0.200
  2 -0.856
  2 -0.799
  2 -0.199
  1 -0.167
  1 -0.143
  1 0.0002
  1 0.0001

This is with 3754 lines.

If I clean it a little:

1000x -0.8745
953x  -0.9995
697x  -0.2495
328x  -0.1245

and so on.


Folkert van Heusden

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Re: [time-nuts] Speaking of Costas loops

[jmfranke]

http://www.navipedia.net/index.php/WAAS_Signal_Structure

Doppler Shift: The Doppler shift, as perceived by a stationary user, on the 
signal broadcast by WAAS GEOs is less than 40 meters per second (≈210 Hz at L1) 
in the worst case (at the end of life of the GEOs). The Doppler shift is due to 
the relative motion of the GEO. 
Carrier Frequency Stability: The short term stability of the carrier frequency 
(square root of the Allan Variance) at the input of the user´s receiver antenna 
will be better than 5x10-11 over 1 to 10 seconds, excluding the effects of the 
ionosphere and Doppler. 
Polarization: The broadcast signal is right-handed circularly polarized. The 
ellipticity will be no worse than 2 dB for the angular range of ±9.1o from 
boresight. 
Code/Carrier Frequency Coherence: The lack of coherence between the broadcast 
carrier phase and the code phase shall be limited. The short term (<10sec) 
fractional frequency difference between the code phase rate and the carrier 
frequency shall be less than 5x10-11 (one sigma). Over the long term (<100 
sec), the difference between the change in the broadcast code phase (convert to 
carrier cycles) and the change in the broadcast carrier phase shall be within 
one carrier cycle (one sigma). 
Correlation Loss: Correlation loss is defined as the ratio of output powers 
from a perfect correlator for two cases: 1) the actual receiver WAAS signal 
correlated against a perfect unfiltered PN reference, or 2) a perfect 
unfiltered PN signal normalized to the same total power as the WAAS signal in 
case 1. The correlation loss resulting from modulation imperfections and 
filtering inside the WAAS satellite payload is less than 1 dB. 

John WA4WDL

 Bob Camp  wrote: 
> Hi
> 
> The pipe in this case is up on one frequency and down on another. The 
> conversion oscillator on satellite that's the weak link, no matter how good 
> the signal from the ground happens to be. 
> 
> Bob
> 
> On Jul 3, 2013, at 1:48 PM, Attila Kinali  wrote:
> 
> > On Wed, 3 Jul 2013 08:29:02 -0400
> > Bob Camp  wrote:
> > 
> >> There are two batches of GPS / WAAS sats up there:
> >> 
> >> 1) The ones with numbers above 100 that are geosync and that only do WAAS
> >> 
> >> 2) The ones with numbers <= 32 that do nav. These are not geosync. 
> >> 
> >> I believe the only ones with corrected / high stab clocks on board are
> >> those in the second group. The stuff in the first group aren't dedicated
> >> sats, just leased transponders on conventional multipurpose geosync birds. 
> > 
> > I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> > ground using Cs references and retransmitted by the satelites using
> > a "bend pipe". Ie. the signals should be of time-nut quality even without
> > high accuracy frequency standards in the birds themselves.
> > 
> > (Sorry, i'm not able to find where i read about that, so no references 
> > today)
> > 
> > Attila Kinali
> > 
> > -- 
> > The people on 4chan are like brilliant psychologists
> > who also happen to be insane and gross.
> > -- unknown
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to 
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> 
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Re: [time-nuts] BPSK decoder for WWVB

[Brian Alsop]

Apparently this modulation scheme is less prone to "jammers".
There is is British station which "jams" east coast WWVB.

Brian/K3KO

On 7/3/2013 18:00, Tim Shoppa wrote:


Potentially the BPSK encoding ought to offer much better decoding here on
the East Coast of US. Many of the commercially available, pre-BPSK WWVB
consumer clocks didn't sync so well in the summertime due to high noise
levels.

Tim N3QE




-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2242 / Virus Database: 3204/5961 - Release Date: 07/03/13

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Re: [time-nuts] Speaking of Costas loops

[bg]

Attila,

> On Wed, 3 Jul 2013 08:29:02 -0400
> Bob Camp  wrote:
>
>> There are two batches of GPS / WAAS sats up there:
>>
>> 1) The ones with numbers above 100 that are geosync and that only do
>> WAAS
>>
>> 2) The ones with numbers <= 32 that do nav. These are not geosync.
>>
>> I believe the only ones with corrected / high stab clocks on board are
>> those in the second group. The stuff in the first group aren't dedicated
>> sats, just leased transponders on conventional multipurpose geosync
>> birds.
>
> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> ground using Cs references and retransmitted by the satelites using
> a "bend pipe". Ie. the signals should be of time-nut quality even without
> high accuracy frequency standards in the birds themselves.
>
> (Sorry, i'm not able to find where i read about that, so no references
> today)
>
>   Attila Kinali

WAAS is the US implementation of SBAS, EGNOS the European, MSAS the
Japanese, GAGAN the Indian, etc...

Here are some references.

http://egnos-portal.gsa.europa.eu/library/technical-documents
http://egnos-portal.gsa.europa.eu/sites/default/files/content/documents/egnos-user-guide_en.pdf

You could also check the WAAS site at Stanford.edu.

--

Björn

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Re: [time-nuts] BPSK decoder for WWVB

[Bob Camp]

Hi

If there are any BPSK products out there, it's a *very* well kept secret. 

Bob

On Jul 3, 2013, at 2:00 PM, Tim Shoppa  wrote:

> Moving past the loss of 60kHz continuous phase reference.
> 
> Do any of the commercially available consumer clocks/watches use WWVB's new
> phase encoded time stamps instead of the backwards-compatible pulse-width
> keying?
> 
> Any homebrew projects of note?
> 
> Potentially the BPSK encoding ought to offer much better decoding here on
> the East Coast of US. Many of the commercially available, pre-BPSK WWVB
> consumer clocks didn't sync so well in the summertime due to high noise
> levels.
> 
> Tim N3QE
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[David J Taylor]

Hi,

I decided to buy a Nanos G20. Not too expensive, real serial port,
debian linux pre-installed.
I don't want to sound harsh as the people from Nanos probably did their
best to produce a good product, but for timekeeping it is totally crap
and also useless.
Well, unless I did something wrong.
I recompiled the kernel to enable PPS support, installed gpsd and ntpd,
configured at all and let it run for a while.

allan deviation: 
http://keetweej.vanheusden.com/~folkert/nanosg20/allandev.png


offset: http://keetweej.vanheusden.com/~folkert/nanosg20.png

remote   refid  st t when poll reach   delay   offset 
jitter

==
x127.127.28.0.NMEA.   0 l3   16  3770.000  -994.05 
7.857
x127.127.28.1.PPS.0 l7   16  3770.000  -250.13 
572.812
+192.168.64.18   .PPS.1 u   66  128  3770.553   -0.055 
0.033
*192.168.64.2.PPS.1 u   99  128  3770.237   -0.062 
0.039
+192.168.64.168  .PPS.1 u   44  128  3770.646   -0.013 
0.321



Folkert van Heusden
==

Folkert,

Thanks for your graphs, but what are the Y-axis units!

Inn your billboard above, the PPS looks to be on the wrong edge - perhaps 
the pulse is 250 ms wide and you are syncing to the trailing edge and not 
the leading.  Can you check that out?  I recall that it's the positive going 
transition on the DCD connection which needs to be on the exact second.   I 
think you are using the Garmin GPS 18x LVC.  There was a firmware update 
which ensured that the serial adta arrived /before/ the /next/ second edge 
rather than after it.  Ensure your firmware is 3.70 or later.  See:


 http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm

I see that 3.80 is now out, but I think I am still on 3.70.

Hope that helps

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk 


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Re: [time-nuts] looking for low-power system for gps ntp timekeeping

[folkert]

Here's a review of several small low power linux systems:
http://www.cooking-hacks.com/index.php/blog/new-linux-embedded-devices-comparison-arduino-beagleboard-rascal-raspberry-pi-cubieboard-and-pcduino


Folkert van Heusden

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Re: [time-nuts] Speaking of Costas loops

[J. Forster]

A 'bent pipe' or retroreflector doubles any Dopplar from range rate.

-John





> On Wed, 3 Jul 2013 08:29:02 -0400
> Bob Camp  wrote:
>
>> There are two batches of GPS / WAAS sats up there:
>>
>> 1) The ones with numbers above 100 that are geosync and that only do
>> WAAS
>>
>> 2) The ones with numbers <= 32 that do nav. These are not geosync.
>>
>> I believe the only ones with corrected / high stab clocks on board are
>> those in the second group. The stuff in the first group aren't dedicated
>> sats, just leased transponders on conventional multipurpose geosync
>> birds.
>
> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> ground using Cs references and retransmitted by the satelites using
> a "bend pipe". Ie. the signals should be of time-nut quality even without
> high accuracy frequency standards in the birds themselves.
>
> (Sorry, i'm not able to find where i read about that, so no references
> today)
>
>   Attila Kinali
>
> --
> The people on 4chan are like brilliant psychologists
> who also happen to be insane and gross.
>   -- unknown
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>


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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[Hal Murray]

folk...@vanheusden.com said:
 remote   refid  st t when poll reach   delay   offset  jitter
==
x127.127.28.0.NMEA.   0 l3   16  3770.000  -994.05   7.857
x127.127.28.1.PPS.0 l7   16  3770.000  -250.13 572.812
+192.168.64.18   .PPS.1 u   66  128  3770.553   -0.055   0.033
*192.168.64.2.PPS.1 u   99  128  3770.237   -0.062   0.039
+192.168.64.168  .PPS.1 u   44  128  3770.646   -0.013   0.321

Something is broken.  What NMEA device are you using?  Why are you using gpsd 
rather than ntpd's NMEA driver?

It looks like the NMEA side it is off by a second.  Some devices do that.  
You can fix that with some fudging.

The PPS stuff is off by 250 ms.  Are you using the wrong edge?  (Got a scope 
handy?)




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Re: [time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

The pipe in this case is up on one frequency and down on another. The 
conversion oscillator on satellite that's the weak link, no matter how good the 
signal from the ground happens to be. 

Bob

On Jul 3, 2013, at 1:48 PM, Attila Kinali  wrote:

> On Wed, 3 Jul 2013 08:29:02 -0400
> Bob Camp  wrote:
> 
>> There are two batches of GPS / WAAS sats up there:
>> 
>> 1) The ones with numbers above 100 that are geosync and that only do WAAS
>> 
>> 2) The ones with numbers <= 32 that do nav. These are not geosync. 
>> 
>> I believe the only ones with corrected / high stab clocks on board are
>> those in the second group. The stuff in the first group aren't dedicated
>> sats, just leased transponders on conventional multipurpose geosync birds. 
> 
> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> ground using Cs references and retransmitted by the satelites using
> a "bend pipe". Ie. the signals should be of time-nut quality even without
> high accuracy frequency standards in the birds themselves.
> 
> (Sorry, i'm not able to find where i read about that, so no references today)
> 
>   Attila Kinali
> 
> -- 
> The people on 4chan are like brilliant psychologists
> who also happen to be insane and gross.
>   -- unknown
> ___
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[time-nuts] BPSK decoder for WWVB

[Tim Shoppa]

Moving past the loss of 60kHz continuous phase reference.

Do any of the commercially available consumer clocks/watches use WWVB's new
phase encoded time stamps instead of the backwards-compatible pulse-width
keying?

Any homebrew projects of note?

Potentially the BPSK encoding ought to offer much better decoding here on
the East Coast of US. Many of the commercially available, pre-BPSK WWVB
consumer clocks didn't sync so well in the summertime due to high noise
levels.

Tim N3QE
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Re: [time-nuts] Speaking of Costas loops

[Attila Kinali]

On Wed, 3 Jul 2013 08:29:02 -0400
Bob Camp  wrote:

> There are two batches of GPS / WAAS sats up there:
> 
> 1) The ones with numbers above 100 that are geosync and that only do WAAS
> 
> 2) The ones with numbers <= 32 that do nav. These are not geosync. 
> 
> I believe the only ones with corrected / high stab clocks on board are
> those in the second group. The stuff in the first group aren't dedicated
> sats, just leased transponders on conventional multipurpose geosync birds. 

I don't know about WAAS, but AFAIK the EGNOS signals are generated on
ground using Cs references and retransmitted by the satelites using
a "bend pipe". Ie. the signals should be of time-nut quality even without
high accuracy frequency standards in the birds themselves.

(Sorry, i'm not able to find where i read about that, so no references today)

Attila Kinali

-- 
The people on 4chan are like brilliant psychologists
who also happen to be insane and gross.
-- unknown
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping

[Chris Albertson]

There are many ways to solve the SD card problem.  One is to write the file
to a networked disk drive, or set up a disk image in RAM, but then you
loose the data if the power fails or you can use a small notebook disk in
place of the SD card.

You could write to the SD card in batches, say one batch per hour or per
day.  Set up a cron job to transfer files from the RAM based disk image to
the card.


On Tue, Jul 2, 2013 at 12:11 PM, Didier Juges  wrote:

> John,
>
> The SD Card issue is serious but not unique go the BBB. I believe there
> are ways to configure any Linux distro to make the SD card read only, at
> the cost of losing logging and data every time you power off. Alternately,
> one could partition the SD card with a second partition just for data you
> want to save.
>
>
-- 

Chris Albertson
Redondo Beach, California
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[time-nuts] Wanted: HP 117A

[Perry Sandeen]

List,

I'd like to buy or trade for a working  HP 117A.  I don;t need the HP antenna.

Please contact off line if interested.

Regards,

Perrier




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Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[folkert]

Hi,

I decided to buy a Nanos G20. Not too expensive, real serial port,
debian linux pre-installed.
I don't want to sound harsh as the people from Nanos probably did their
best to produce a good product, but for timekeeping it is totally crap
and also useless.
Well, unless I did something wrong.
I recompiled the kernel to enable PPS support, installed gpsd and ntpd,
configured at all and let it run for a while.

allan deviation: http://keetweej.vanheusden.com/~folkert/nanosg20/allandev.png

offset: http://keetweej.vanheusden.com/~folkert/nanosg20.png

 remote   refid  st t when poll reach   delay   offset  jitter
==
x127.127.28.0.NMEA.   0 l3   16  3770.000  -994.05   7.857
x127.127.28.1.PPS.0 l7   16  3770.000  -250.13 572.812
+192.168.64.18   .PPS.1 u   66  128  3770.553   -0.055   0.033
*192.168.64.2.PPS.1 u   99  128  3770.237   -0.062   0.039
+192.168.64.168  .PPS.1 u   44  128  3770.646   -0.013   0.321


Folkert van Heusden

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http://www.vanheusden.com/multitail/
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Re: [time-nuts] looking for low-power system for gps ntp timekeeping

[Mark C. Stephens]

At the risk of hijacking a thread, shooting of the subject and just generally 
bad etiquette for news group posting, I am running all my S1 NTP servers on HP 
thin clients!
They only draw ~14 watts of power.
I have managed to fit a 3.5 inch laptop drive in the T150's so they run a 
(minimal text based) full version of centos.

And the serial port seems to be okay:
NTP 1 running of a HP 58534A integrated timing antenna:
State   Remote  Refid   Stratum TypeWhenPollReach   
Delay   Offset  Jitter
o   127.127.20.0GPS 0   Local clock 8   16  
377 0.000   -0.001  0.002   

NTP2 running off an Acutime (hmm, marketing) Gold:
State   Remote  Refid   Stratum TypeWhenPollReach   
Delay   Offset  Jitter
*   127.127.29.0GPS 0   Local clock 2   32  
377 0.000   0.166   0.005   

I Don't know about Load handling, I farm most of the NTP requests off to a 
Stratum 2 (well technically S3 as GPS PPS is not true stratum 1, please correct 
me if I am wrong?)

But works well for me, I'd love to find a ref driver for the Z3805A port 2 even 
second string...
Perhaps using the parse driver w/ PPS refclock (is possible?)

Anyway, there is my 0.02c :p

-marki


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Iain Young
Sent: Tuesday, 2 July 2013 4:14 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] looking for low-power system for gps ntp timekeeping

On 02/07/13 06:43, NeonJohn wrote:

> Before anyone wastes his money on a BeagleBone, I suggest you join the 
> mailing list and read the hundreds of messages each day that pass 
> through, most of them citing problems, mostly with the Linux implementation.
>
> Basically, the ancient implementation of Angstrom Linux is a POS.  
> Just barely enough code to be able to say, for example, that SPI 
> works.  It does - sorta - but not well enough for any application 
> where clock timing or jitter matters.

You are not restricted to just Angstrom. My fleet run Debian. FreeBSD is also 
available. First thing I do is blow away Angstrom from any SD card.

> I had intended to embed the BB white in my next revision induction 
> heater.  After several months of frustration and a considerable amount 
> of money to a kernel programmer to write drivers that actually worked, 
> I gave up.  I could easily had a man-year in the application that I 
> can do bare metal in a few months.

Hmm, is this a case of Angstrom being beind the kernel curve, or is it still an 
issue when running things like Debian ? I've not had the need to use SPI on the 
BB yet, only the Pi.

> The thing that finally canned the BB for me was the short SD card life.
>   Even though the implementation uses a virtualized root file system, 
> it still writes to the SD card about once a second.  The result is 
> that even industrial grade SD cards rarely live over a year.  With the 
> Black they tried to address the problem by putting some NAND memory on 
> board but that only prolongs the problem and with components that are 
> not easily changed.

I've only ever had one SD card go dead on me on my entire fleet, and I suspect 
that was actually my fault, not Debian's :)

  > A final negative is the support.  The team member, a guy named Gerald,
> who provides official support on the mailing lists is one of the most 
> hateful persons I've encountered on the net. No, I never personally 
> had an encounter with him but I daily shook my head in amazement that 
> TI would let such a person rep them.
>

I've heard he can be somewhat robust to deal with. That said, he is very 
knowledgeable from what I've seen/understand. Never actually had to mail the 
mailing list itself though - found all the answers I needed in the archive - 
often from him!

> PS: Before you go to buy the Black, take a careful look at what all 
> they left off in an effort to compete with the Pi.

Hmm. I checked a lot of the things I'd need on the black for this type of 
application, and found they were all still there (Serial Ports, PRUSS, Timers 
etc). Yes you may need to twiddle the pinmux as by default it goes to  he HDMI 
stuff etc, but they are still there

Is there something specific here you are thinking of ? Maybe I just don't need 
what they left off. I do remember looking and going "Meh, not important for 
what I'm doing"


Best Regards

Iain


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Re: [time-nuts] High Accuracy Averaging Was: Speaking of Costasloops

[Tom Van Baak]

Dan,

I agree with Bob. Google for words like u-blox LEA RINEX and you'll see how 
it's done. Google also for words like: teqc, RTKLIB, OPUS. I can send you the 
links and papers I found, or you can find them yourself. I use teqc and OPUS on 
my Ashtech's. Not sure if the LEA-6T I have is RINEX enabled, but I will check.

/tvb

- Original Message - 
From: "Bob Camp" 
To: "Discussion of precise time and frequency measurement" 
Sent: Wednesday, July 03, 2013 6:58 AM
Subject: Re: [time-nuts] High Accuracy Averaging Was: Speaking of Costasloops


> Hi
> 
> Since the LEA6-T will do conventional RINEX dumps, I suspect that all they 
> are doing is very long averaging on the data. I doubt the LEA6-T is the magic 
> part of the setup. 
> 
> Bob
> 
> On Jul 3, 2013, at 8:26 AM, Dan Kemppainen  wrote:
> 
>> 
>> 
>> On 7/2/2013 5:07 PM, time-nuts-requ...@febo.com wrote:
>>> On the other hand, i know a guy who does sub-cm positioning with unmodified
>>> LEA6-T, by logging their satelite phase data and heavy post processing over
>>> hours of data and comparing it to a neaby basline of two stations with
>>> known coordinates [3]. They are currently aiming at sub-mm resolution.
>> 
>> Is there by any chance additional information, or a web site I could
>> refer to for the above project/individual?
>> 
>> Thanks,
>> Dan


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Re: [time-nuts] High Accuracy Averaging Was: Speaking of Costas loops

[Jim Lux]

On 7/3/13 6:58 AM, Bob Camp wrote:

Hi

Since the LEA6-T will do conventional RINEX dumps, I suspect that all they are 
doing is very long averaging on the data. I doubt the LEA6-T is the magic part 
of the setup.



or sending the RINEX files to JPL for processing...If you don't need 
real time data, then it's pretty straightforward to get the processing done.

http://apps.gdgps.net/


On 7/2/2013 5:07 PM, time-nuts-requ...@febo.com wrote:

On the other hand, i know a guy who does sub-cm positioning with unmodified
LEA6-T, by logging their satelite phase data and heavy post processing over
hours of data and comparing it to a neaby basline of two stations with
known coordinates [3]. They are currently aiming at sub-mm resolution.




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[time-nuts] net4501 oscillator

[Eric Williams]

For those running a net4501 NTP server with the original clock, there are
some 33.333MHz TCXO modules on ebay for sale, item #181008085393.  I
haven't received mine yet so I can't guarantee they will work, but they're
3.3v parts, so I think they will. They are Chrystek CXOHV8-HF3-33.333MHz,
data sheet at http://www.crystek.com/crystal/spec-sheets/tcxo/CXOHV8.pdf
--
eric
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Re: [time-nuts] High Accuracy Averaging Was: Speaking of Costas loops

[Attila Kinali]

On Wed, 3 Jul 2013 09:58:51 -0400
Bob Camp  wrote:

> Since the LEA6-T will do conventional RINEX dumps, I suspect that all
> they are doing is very long averaging on the data. I doubt the LEA6-T
> is the magic part of the setup. 

It's not conventional RINEX. The data is stored in a custom raw format
to save space. Afterall, the devices have only a 2GB SD Card and have to
be able to log data for at least 2 years :-)

Ie what the electronics around the LEA6-T does is to get the satelite
phase data from the appropriate LEA command, encode them and write it
all down to the SD Card.

But yes, there is nothing magic about the LEA. It got used because
u-blox is a spin-off of the same universty and working together with
them does not involve trans continental flights.

If anyone wants more info on the electronics, please contact me off list.

Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
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Re: [time-nuts] High Accuracy Averaging Was: Speaking of Costas loops

[Attila Kinali]

On Wed, 03 Jul 2013 08:26:14 -0400
Dan Kemppainen  wrote:

> On 7/2/2013 5:07 PM, time-nuts-requ...@febo.com wrote:
> > On the other hand, i know a guy who does sub-cm positioning with unmodified
> > LEA6-T, by logging their satelite phase data and heavy post processing over
> > hours of data and comparing it to a neaby basline of two stations with
> > known coordinates [3]. They are currently aiming at sub-mm resolution.
> 
> Is there by any chance additional information, or a web site I could
> refer to for the above project/individual?

It's part of the Permasense project (http://permasense.ch/).
The driving force behind the electronics and networking code is
Jan Beutel (http://www.tik.ee.ethz.ch/~beutel/) with Ben Buchli
doing a lot of the stuff recently (http://ben.buchli.net/)

If you want to know more about the GPS averaging, i guess Jan would
be the right person to contact.  

HTH

Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
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Re: [time-nuts] High Accuracy Averaging Was: Speaking of Costas loops

[Bob Camp]

Hi

Since the LEA6-T will do conventional RINEX dumps, I suspect that all they are 
doing is very long averaging on the data. I doubt the LEA6-T is the magic part 
of the setup. 

Bob

On Jul 3, 2013, at 8:26 AM, Dan Kemppainen  wrote:

> 
> 
> On 7/2/2013 5:07 PM, time-nuts-requ...@febo.com wrote:
>> On the other hand, i know a guy who does sub-cm positioning with unmodified
>> LEA6-T, by logging their satelite phase data and heavy post processing over
>> hours of data and comparing it to a neaby basline of two stations with
>> known coordinates [3]. They are currently aiming at sub-mm resolution.
> 
> Is there by any chance additional information, or a web site I could
> refer to for the above project/individual?
> 
> Thanks,
> Dan
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Re: [time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

There are two batches of GPS / WAAS sats up there:

1) The ones with numbers above 100 that are geosync and that only do WAAS

2) The ones with numbers <= 32 that do nav. These are not geosync. 

I believe the only ones with corrected / high stab clocks on board are those in 
the second group. The stuff in the first group aren't dedicated sats, just 
leased transponders on conventional multipurpose geosync birds. 

Bob


On Jul 2, 2013, at 5:06 PM, jmfra...@cox.net wrote:

> Valid concerns all. What I am building is a squaring circuit for recovering 
> the carrier from a WAAS GPS satellite. Granted there is still some Doppler 
> and other issues, but the accuracy would not be bad and it just looks like a 
> fun thing to do. Plus, I can use my four foot diameter dish antenna to reduce 
> the number of satellites seen, reduce thermal ground noise, and get some 
> signal gain.
> 
> John  WA4WDL
> 
>  "J. Forster"  wrote: 
>> More on your question:
>> 
>> I'm prettyt sure that just sticking up an antenna and hooking up a simple,
>> phase tracking receiver for GPS will yeild nothing useful, because there
>> are always several birds in view, so you will get a superposition of their
>> signals in the bandpass and each signal will be Dopplar shifted be a
>> different amount- a time-varying amount.
>> 
>> You have to use a complete GPS receiver that can unravel it all.
>> 
>> -John
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>> Here we go again - the first send didn't seem to get through. This is
>>> the second attempt.
>>> 
>>> This talk of Costas loops reminded me of something I wanted to
>>> investigate some day. I read somewhere a while back about
>>> carrier-phase measurements, and various methods for recovering the
>>> GPS carrier frequencies, including the Costas loop, and something
>>> with carrier-squaring. Nothing I found showed actual examples or
>>> detail of how this is done, only high-order mathematical descriptions.
>>> 
>>> For my needs, I'm more of a frequency-nut - I usually don't care
>>> about getting time info, but I'd like perfect 10 MHz for reference.
>>> Can using only the carriers lead to simple ways to get the same (or
>>> better) frequency stability as a conventional GPSDO, but without the
>>> time and location info, or is it pointless to worry about it, and
>>> just go with full GPS decoding of everything? Or, is carrier-phase
>>> just an enhancement only if you already have the full GPS info?
>>> 
>>> I know that the group could redesign the whole GPS system with tubes
>>> if necessary, considering recent philosophical discussions on that,
>>> so I think there's plenty of knowledge here about carrier-phase
>>> related stuff too.
>>> 
>>> Ed
>>> 
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>>> 
>> 
>> 
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[time-nuts] High Accuracy Averaging Was: Speaking of Costas loops

[Dan Kemppainen]

On 7/2/2013 5:07 PM, time-nuts-requ...@febo.com wrote:
> On the other hand, i know a guy who does sub-cm positioning with unmodified
> LEA6-T, by logging their satelite phase data and heavy post processing over
> hours of data and comparing it to a neaby basline of two stations with
> known coordinates [3]. They are currently aiming at sub-mm resolution.

Is there by any chance additional information, or a web site I could
refer to for the above project/individual?

Thanks,
Dan
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Re: [time-nuts] Speaking of Costas loops

[Attila Kinali]

On Tue, 2 Jul 2013 17:06:47 -0400
 wrote:

> Valid concerns all. What I am building is a squaring circuit for
> recovering the carrier from a WAAS GPS satellite. Granted there
> is still some Doppler and other issues, but the accuracy would not
> be bad and it just looks like a fun thing to do. Plus, I can use my
> four foot diameter dish antenna to reduce the number of satellites seen,
> reduce thermal ground noise, and get some signal gain.

Right.. i didnt think about the WAAS/EGNOS satelites.
If i'm not mistaken, then you dont have to correct for doppler, as
the satelites are stationary relative to you. The only thing you might
want to correct for are atmospheric changes, but if you are tracking
frequency only, and don't care about the phase relation, respektively
can live with some phase noise, then you dont even need to do that.

Correcting for atmospheric changes should be "fairly" simple. You just
need to decode the WAAS/EGNOS signal, read the atmosphere/TEC data out
and apply a phase shift according to that.

Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
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