Re: [time-nuts] Z3805A high value PU

[Charles P. Steinmetz]

Mark wrote:

For the first 6 hours PU stayed at 432us, then it dropped sharply to 
5.6us and then slowly climbed to 18us.

Doesn't seem right to me.


Nothing it does in the first 6 hours has anything to do with 
anything.  (1) The oscillator will be swinging around wildly 
(comparatively speaking, relative to its stability after it has been 
running unmolested for months).  (2) Further, 6 hours is almost 
certainly a shorter period than it normally uses to forecast PU, so a 
forecast after ANY six-hour period of data collection (even when 
fully warm and stable) will not be its best estimate.


I do not know HP's algorithm, but it sounds like it didn't seriously 
try to compute PU until after 6 hours, then it started trying with 
(1) too little data and (2) data from an unstable oscillator, so it's 
no surprise it is wandering around.  I'll be very surprised if it 
settles down near its long-term stability in less than a month of 
continuous, undisturbed running (continuous meaning don't turn it 
off, undisturbed meaning don't move it or bump it very hard -- if you 
do either of these, start counting from zero again).


Be patient.  OCXOs need time to reach stability when re-started in a 
new environment (particularly if they have been off for more than a 
few days and/or bumped around, both of which are probably true of 
yours).  Some are better about this than others, but what I've said 
is pretty typical of the 10811-and-better class of OCXOs, IME.


Best regards,

Charles






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Re: [time-nuts] antennas was Re: Common-View GPS Network

[David J Taylor]

From: Sarah White 


I just have to ask though... cake pans? really? I can't imagine it would
even be possible to modify a cake pan with enough accuracy to get a
usable antenna.

-- Sarah


Well, my GPS antenna farm uses an inverted baking tray

 http://www.satsignal.eu/ntp/2013-03-31-1226-32-GPS-antenna-farm.jpg

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] Windows serial port error reporting question

[Tom Van Baak]

See ClearCommError() and CE_RXPARITY, CE_FRAME, CE_OVERRUN

/tvb

- Original Message - 
From: "Mark Sims" 
To: 
Sent: Tuesday, April 16, 2013 10:19 PM
Subject: [time-nuts] Windows serial port error reporting question


>I have been working a version 4.0 of Lady Heather.  One thing that I would 
>like to implement is better error checking on the serial data port...  
>parity/framing/overrun errors.   I haven't been able to find much valid info 
>on how to coax this info out of Windows...  Does anybody know how?  


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Re: [time-nuts] Common-View GPS Network

[Tom Van Baak]

> Tom, you scare me some times, this is one of them... or the time actually.

Magnus,

I remember why I didn't measure the M12 oscillators directly -- it's a real 
challenge to get at the signal on the back side of the PCB and to measure it 
without loading the crystal. It's not like just connecting a wire to a 50R 
Timepod input. Here are photos of the oscillator on three different versions of 
the M12 board:

http://leapsecond.com/pages/m12/m12-osc.htm

Perhaps with some 'scope tracing you can find a buffered clock output on one of 
the ASIC pins. That way the same probing technique could be used on all 3 
boards.

/tvb


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[time-nuts] Windows serial port error reporting question

[Mark Sims]

I have been working a version 4.0 of Lady Heather.  One thing that I would like 
to implement is better error checking on the serial data port...  
parity/framing/overrun errors.   I haven't been able to find much valid info on 
how to coax this info out of Windows...  Does anybody know how? 

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[time-nuts] Common-View GPS Network

[Mark Sims]

Nope,  been there,  tried that.  Supposedly Trimble had a firmware option for 
doing/reporting proper carrier phase stuff,  but I have never seen a Tbolt with 
it.
---
I don't know if the Trimble TBolt or Res-t give out enough information to 
generate RINEX  
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Re: [time-nuts] Common-View GPS Network

[Lachlan Gunn]

A few reasons:

    - I am interested to see what can be done with the statistics of an 
ensemble of oscillators---in particular, whether the additional measurements 
can be used to get a timescale that is more stable than just GPS and OCXO or Rb.

    - To produce some data that could be used for modelling other systems. 

  - If the first point plays out, then to allow access to a more accurate 
timescale by amateurs who cannot justify 15k/yr for NIST's.

It might be interesting to see if one could extract ionospheric data from the 
ensemble too.

I've just started a Ph.D, so my free time is such that it will probably be a 
while before I can get anything running, but I'd like to see what can be done 
regardless, if only so that three years of statistics doesn't drain away what 
little timing knowledge I've managed to accumulate. 

Thanks, 
Lachlan Gunn

 Original message 
From: Mark Spencer  
Date:  
To: time-nuts@febo.com 
Subject: Re: [time-nuts] Common-View GPS Network 
 

Just curious what would a typical use case for this network be ?  My limited 
understanding of common view GPS in this context is that it can be used for 
time (and frequency) transfer between labs.
 
Thanks in advance for any replies.
 
Regards
Mark Spencer

--

Message: 6
Date: Tue, 16 Apr 2013 15:53:09 +0200
From: Achim Vollhardt 
To: time-nuts@febo.com
Subject: Re: [time-nuts] Common-View GPS Network
Message-ID: <516d57c5.9070...@physik.uzh.ch>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Count me in as well, if you need another participating station. I have 
my Thunderbolt running 24/7 with a solid stationary antenna..

Achim


--

Message: 7
Date: Tue, 16 Apr 2013 08:00:39 -0700
From: "WarrenS" 
To: "Discussion of precise time and frequency measurement"
    
Subject: Re: [time-nuts] Common-View GPS Network
Message-ID: 
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
    reply-type=original


"is one better off just taking the simple route and tracking GPS time 
directly?"
My response is Yes, as long as you use the GPS to discipline a good 
Oscillator.

GPS on its own is generally capable of about 10 ns of phase error, pretty 
much over any time period.
So the longer you average the closer you know the frequency.
I did some remote common view experiments a while back to see if I could 
find a way to improvement a GPSDO using low cost dual common view GPS.

I used Tbolt GPSs, because they are capable of more than a decade better 
performance than the 1 ns (with correction) GPS engines (*).
For monitoring I used Lady Heather so I could control and get real time data 
from the remote GPS.

After several unsuccessful test using various remote locations,
I got smarter and  moved the "Remote" GPS under the same roof to see what 
the limitations where.

I found the limitation was in my Antenna. (a  58532A type).
That is when I used two antennas, even with everything at the same location, 
taking common view differences added noise.
The only way I was able to improve the noise was to use the same GPS signal 
thru a splitter going to both GPS.
Not real useful for "remote" Common View, so my experiment turned into a 
dual Tbolt DMTD.

For some post I did, see Time Nuts back in Oct of 2011 from "WarrenS" and 
"ws at Yahoo"
"Common View Tbolt-Tic",  "DMTD using TBolts" and "Measuring ADEV using 
TBolt-Tic tester"

(*) The TBolt Engine is capable of 1e-11 at 3 seconds.
and 1e-12 ADEV at 300 seconds using the difference between two TBolts driven 
with a common GPS signal, see:


ws

*
Hello all.

Having spent some time working over the last year on GPS time stability
measurement, I'm keen to move onwards and upwards and have a go at
common-view time transfer.  While my receivers are in the post, I have
thinking about my next direction.  One thought that I have had is to try to
write some software that can be used for real-time common-view (public if
there is interest, but I am getting ahead of myself I think).

My question to those in the know is whether they have found common-view to
be useful over medium timescales (say, an hour or four).  My understanding
is that after a day or so the GPS signal itself becomes usable as a
standard, so building a network is probably not tremendously useful over
these sorts of time periods, but looking at such as figure 6 of [1],
common-view should still be useful between a few minutes and hours.  Has
anyone here tried using such a method to produce their own short-term time
scale, or is one better off just taking the simple route and tracking GPS
time directly?

Thanks,
Lachlan







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End of time-nuts Digest, Vol 105, I

Re: [time-nuts] Z3805A high value PU

[Jim Lux]

On 4/16/13 8:28 PM, Mark C. Stephens wrote:

Actually, before I plugged the GPS antenna into the second unit, I checked out 
where it last called home:
LAT N  36:01:05.225
LON E 128:41:48.761
HGT+1214.14 m  (MSL)



Mt Palgong, according to Google Earth
Lots of transmitter towers up there, and covered in ice and snow in 
January/Feb...


Seems to overlook Chilgok, Daegu, and Yeongcheong

http://en.wikipedia.org/wiki/Palgongsan

says it's 1193m ASL, which is awful close to the 1214.14...  That could 
be a datum difference, or a tower height issue.


Daegu is the 4th largest city in Korea and has 2.5 million residents

Fascinating stuff you learn.
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Re: [time-nuts] Z3805A high value PU

[Mark C. Stephens]

Actually, before I plugged the GPS antenna into the second unit, I checked out 
where it last called home:
LAT N  36:01:05.225
LON E 128:41:48.761
HGT+1214.14 m  (MSL)

So it was pretty high up somewhere in south Korea.

Regarding the second unit:
After I collected this information, I plugged the antenna in.
I then performed a
:SYSTEM:PRESET
:PTIM:TCOD:FORM F2
:GPS:REF:ADEL 59ns (~40ft lmr200)
:DIAG:GPS:UTC 1

It then went off and did its survey.
For the first 6 hours PU stayed at 432us, then it dropped sharply to 5.6us and 
then slowly climbed to 18us.
Doesn't seem right to me.

A further question, is there anything else I should reset, via the CLI to give 
it a new home?


Many thanks,
mark

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Charles P. Steinmetz
Sent: Wednesday, 17 April 2013 12:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Z3805A high value PU

Mark wrote:

>I recently purchased a pair of Z3805A
>
>The problem I am seeing on both is the predicted uncertainty is high 
>compared to other receivers I have seen.
>
>I am experiencing a PU of ~8us for the first and ~24us for the second.
>
>My questions are,
>What could be causing such bad figures?
>Is it an oven problem?
>Can I tweak it out?

The predicted uncertainty is calculated from the character of the OCXO drift 
over some period in the past.  If you just hooked these up after they were off 
for who knows how long and were then shipped, the OCXO will not even have begun 
to settle in.  I never really begin to think seriously about how stable an OCXO 
might be until it has been running continuously and undisturbed for several 
months.

There is every reason to think your units will settle in after being run 
continuously and undisturbed, but there is always the chance that they won't.  
IMO, you won't be in a position to judge for several weeks, at the very least, 
more likely several months.

Best regards,

Charles








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Re: [time-nuts] antennas was Re: Common-View GPS Network

[Jim Lux]

On 4/16/13 5:19 PM, Sarah White wrote:


I just have to ask though... cake pans? really? I can't imagine it would
even be possible to modify a cake pan with enough accuracy to get a
usable antenna.



Sure.. cake pans, like other stamped goods, are actually pretty high 
precision, because they're all stamped out of the same die.  As long as 
the dimensions are right (and for choke rings that's not real critical), 
it works.




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Re: [time-nuts] Z3805A high value PU

[Charles P. Steinmetz]

Mark wrote:


I recently purchased a pair of Z3805A

The problem I am seeing on both is the predicted uncertainty is high 
compared to other receivers I have seen.


I am experiencing a PU of ~8us for the first and ~24us for the second.

My questions are,
What could be causing such bad figures?
Is it an oven problem?
Can I tweak it out?


The predicted uncertainty is calculated from the character of the 
OCXO drift over some period in the past.  If you just hooked these up 
after they were off for who knows how long and were then shipped, the 
OCXO will not even have begun to settle in.  I never really begin to 
think seriously about how stable an OCXO might be until it has been 
running continuously and undisturbed for several months.


There is every reason to think your units will settle in after being 
run continuously and undisturbed, but there is always the chance that 
they won't.  IMO, you won't be in a position to judge for several 
weeks, at the very least, more likely several months.


Best regards,

Charles








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Re: [time-nuts] Common-View GPS Network

[Jim Lux]

On 4/16/13 11:04 AM, Attila Kinali wrote:

On Mon, 15 Apr 2013 23:00:49 -0700
Jim Lux  wrote:


the effect of a strong multipath (which is what the choke ring
suppresses) would be a LOT bigger than that..


Uhmm.. to my understanding, this is not quite true.
The choke ring does not surpress general multipath, but
the waves from near and below the horizon, which are often
full multipath issues.

You can see the choke rings as forming of a specific wave impedance
(or wave resistance, if you want) in the region at the top.
At other places, this technique is known as electromagnetic bandgap.



Yes, I would agree..


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Re: [time-nuts] LTC6957 Low Phase Noise Buffer/Driver

[Richard (Rick) Karlquist]

On 4/14/2013 7:48 AM, Brian Davis wrote:

Not sure if it's already been mentioned, but Linear has introduced a new
part that looks interesting :

LTC6957 Low Phase Noise Buffer/Driver
http://www.linear.com/product/LTC6957-1


This is VERY interesting, especially the low noise PECL output.  I have
never seen any ECL device ever come close to that noise level.
It would be interesting to see how they did that.

Rick
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[time-nuts] Z3805A high value PU

[Mark C. Stephens]

Dear Fellows,


I recently purchased a pair of Z3805A off eBay seller tommy_chou.

I have fired them up with a MaxRad 26db timing antenna attached to each.
The antennae have a clear view of most of the sky.
The receivers are having no problems seeing enough satellites.

The problem I am seeing on both is the predicted uncertainty is high compared 
to other receivers I have seen.

I am experiencing a PU of ~8us for the first and ~24us for the second.

My questions are,
What could be causing such bad figures?
Is it an oven problem?
Can I tweak it out?


Many Thanks,
mark
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Re: [time-nuts] antennas was Re: Common-View GPS Network

[Sarah White]

On 4/16/2013 1:55 AM, Jim Lux wrote:
> On 4/15/13 10:22 PM, Jim Lux wrote:
>> On 4/15/13 9:27 PM, Tom Van Baak wrote:
>>> NIST SIM GPS common view pinwheel
>> described in one of the NIST reports as an aperture coupled slot fed
>> array that is better than a patch, but not as large and heavy as a choke
>> ring.
>>
>>   W. Kunysz, 2000, “High Performance GPS Pinwheel Antenna,” in
>> Proceedings of the 2000 International Technical Meeting of the Satellite
>> Division of the Institute of Navigation (ION GPS 2000), 19-22 September
>> 2000, Salt Lake City, Utah, USA (ION, Alexandria, Virginia), pp. 2506-251
>>
>> http://www.novatel.com/assets/Documents/Papers/GPS-704xWhitePaper.pdf
>> Patented by Novatel & Pinwheel is a trademark
>>
>>
>> Performance is almost as good as a choke ring but a heck of a lot
>> smaller and lighter.
>>
> 
> of course, cake pans with 2-2.5 inch high walls are readily available.
> 
> There's a Wilton cakepan set with 6",8" and 10" diameter pans with 3"
> walls.. hmm, an inch between fins..
> 
> Oddly, the package shipping size is 12x12x2"... I wonder how they fit a
> 3" high pan in a 2" thick box..
> 
> a real restaurant/pastry supply has a mindboggling variety of pans
> 
> http://www.fantes.com/cake-pans-round.html
> 
> every integer inch diameter from 4" to 18" and ditto for heights from 2"
> to 4"...
> 
> 
> People like those machined or cast choke rings because they're easier to
> fabricate: Slap a block of aluminum in the lathe or milling machine,
> push GO on the CNC, and stand back.
> 
> Or for those with a taste for hot metal.. you could cast it with scrap
> aluminum you've melted in the forge in your time nuts lab..  Turn those
> empty beer cans into something useful.
> 
> If you have a fancy multiaxis mill, you could probably do one of those
> porcupine looking things.
> 
> Or, if you have a swimming pool or pond, and some sheet aluminum, and
> some suitable high explosives.. hydroforming is your friend.
> 
> If you want true timenuts.. do the explosive hydroforming without a
> mold/buck, and instead use precision timing of shaped charges.  Finally,
> a use for those krytron switches you found at the surplus place.

Thanks for that. The last bit of your post was really cute. I needed a
good laugh :)

I haven't posted much in a while, partly because I've been kinda bummed
out by this list since I got the news about shera... There have been so
many constant reminders of his passing and whatnot (multiple thread
titles mentioning his legacy)

I just have to ask though... cake pans? really? I can't imagine it would
even be possible to modify a cake pan with enough accuracy to get a
usable antenna.

-- Sarah
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Re: [time-nuts] Common-View GPS Network

[Sarah White]

On 4/16/2013 9:53 AM, Achim Vollhardt wrote:
> Count me in as well, if you need another participating station. I have
> my Thunderbolt running 24/7 with a solid stationary antenna..

I'm not sure what all I'll need to participate, but I'd like to
volunteer my thunderbolt to this sort of network as well.

I'm wondering though, is there something inherently different about this
proposed network than a network of continually operating reference stations?

or are CORS stations for something else?

--Sarah

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Re: [time-nuts] Common-View GPS Network

[Magnus Danielson]

On 04/16/2013 08:04 PM, Attila Kinali wrote:

On Mon, 15 Apr 2013 23:00:49 -0700
Jim Lux  wrote:


the effect of a strong multipath (which is what the choke ring
suppresses) would be a LOT bigger than that..


Uhmm.. to my understanding, this is not quite true.
The choke ring does not surpress general multipath, but
the waves from near and below the horizon, which are often
full multipath issues.


Well, it's an approximation against the most likely sources, and has 
proven effective for exactly this form of mittigation. Arguing about the 
semantics fills no real purpose.



You can see the choke rings as forming of a specific wave impedance
(or wave resistance, if you want) in the region at the top.
At other places, this technique is known as electromagnetic bandgap.


You typically put three spatial zeros for the relevant frequencies at or 
sligthly below the horizon, with rotational symmetric around the axis of 
the antenna.


Cheers,
Magnus
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Re: [time-nuts] Common-View GPS Network

[Magnus Danielson]

On 04/16/2013 09:55 AM, Poul-Henning Kamp wrote:

In message, "Tom Van Baak" writes:


When you look at the actual clock solutions (which are in the @@Hn
message) you will be surprised at the variance.


A lot of that variance is because the position-hold coords are wrong.

I tried using the @@Hn data to "sneak" up on the right coords and got
some pretty good results, but the process too forever (as in: Months)

See:
http://phk.freebsd.dk/raga/sneak/

The improvement in the finished timing solution from the oncore is
quite marginel because on average you have satellites on all
sides of your antenna and the errors mostly cancel out.

The notable exception to that is where I live: at 56N.

56N is at the top of the GPS orbits, so satellites never venture
north of me, and I'm not sufficient north to have any benefits from
the satellites which rise above Canada/Alask on the other side of
the north pole.



Did you look at the pseudo-range correction data as an alternative approach?

Cheers,
Magnus
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Re: [time-nuts] Common-View GPS Network

[Magnus Danielson]

Hi Tom,

On 04/16/2013 09:42 AM, Tom Van Baak wrote:

I wonder if one should only measure the PPS thought. Looking directly at
the clock could help to separate the clock drift and the time, even if
you get sufficient clues from the PPS and sawtooth correction.

Cheers,
Magnus


I've never tried that.


Tom, you scare me some times, this is one of them... or the time actually.


Start with checking the ADEV of the LO. I always assumed the 1PPS was
pre-compensated for instantaneous LO offset and rate, as calculated
during the previous second(s).


Well, it is... but it also solves the position-time each second and that 
takes over. If you loose signal, that's when the predicted PPSes will 
shine through.



If so and ADEV(1 s) is less than 1e-9 then the 1PPS + sawtooth will
have sufficient accuracy for your needs. Message @@Ha contains the
oscillator and clock parameters.


True. That get's you far. Just looking at that and bring it into your 
model is also something you can do. It's interesting to notice that the 
@@Ha message has a time (to nanosecond), and then clock bias and 
oscillator offset and on top of that a delta correction in the @@Hn 
message. Would be nice to know exactly how them all fitted together.


BTW. I hooked up my M12M-T to a Novatel 700 pinwheel just to check it 
out again.



As you know professional receivers bypass this issue because they take an 
external LO (e.g., Rb, Cs, HM).


Oh yes.

The TCXO sitting there looks like a RAKON thing, I haven't looked at the 
details, but maybe it can be steered? It's interesting that the TCXO 
temperature can be read out.



When you look at the actual clock solutions (which are in the @@Hn
message) you will be surprised at the variance. At the per-SV
per-second level it is not uncommon to see errors of many ns, even
tens of ns. But when you average up to 12 SV together every second
for 600 seconds then you start to see something trustable. You can
see first hand why GPSDO need long time-constants.

Here's a one second sample of a single Hn message:

@@Hn: sigma 36 sawtooth 10 0 0  mean frac 861564.000 (0.000)
ch  0 sv  6 frac 0.000861576 s = mean +   12 ns
ch  1 sv  5 frac 0.000861586 s = mean +   22 ns
ch  2 sv 10 frac 0.000861581 s = mean +   17 ns
ch  3 sv 19 frac 0.000861573 s = mean +9 ns
ch  5 sv 13 frac 0.000861571 s = mean +7 ns
ch  6 sv 26 frac 0.19831
ch  7 sv 28 frac 0.000861555 s = mean +   -8 ns
ch  8 sv  7 frac 0.000861548 s = mean +  -15 ns
ch  9 sv  3 frac 0.000861571 s = mean +7 ns
ch 10 sv  8 frac 0.000861546 s = mean +  -17 ns


The urge to get into the dirty details got higher by that. Curious at 
seeing a log of data.


Let's see if my M12M-T locks up in the current quick-hack setup.

Cheers,
Magnus
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Re: [time-nuts] Common-View GPS Network

[Bob Camp]

Hi

Most modern receivers give you corrections in ps rather than ns. That's not to 
say they are *good* to 1 ps. It's not uncommon to see adev (after doing the 
correction) running sub 1 ns at one second when compared to a 5071. 

Most people seem to do this in runs many minutes long. That's a bit away from 1 
second, so other things do come into the picture. 

Bob

On Apr 16, 2013, at 3:42 AM, "Tom Van Baak"  wrote:

>> I wonder if one should only measure the PPS thought. Looking directly at 
>> the clock could help to separate the clock drift and the time, even if 
>> you get sufficient clues from the PPS and sawtooth correction.
>> 
>> Cheers,
>> Magnus
> 
> I've never tried that. Start with checking the ADEV of the LO. I always 
> assumed the 1PPS was pre-compensated for instantaneous LO offset and rate, as 
> calculated during the previous second(s). If so and ADEV(1 s) is less than 
> 1e-9 then the 1PPS + sawtooth will have sufficient accuracy for your needs. 
> Message @@Ha contains the oscillator and clock parameters.
> 
> As you know professional receivers bypass this issue because they take an 
> external LO (e.g., Rb, Cs, HM).
> 
> When you look at the actual clock solutions (which are in the @@Hn message) 
> you will be surprised at the variance. At the per-SV per-second level it is 
> not uncommon to see errors of many ns, even tens of ns. But when you average 
> up to 12 SV together every second for 600 seconds then you start to see 
> something trustable. You can see first hand why GPSDO need long 
> time-constants.
> 
> Here's a one second sample of a single Hn message:
> 
> @@Hn: sigma 36 sawtooth 10 0 0  mean frac 861564.000 (0.000)
> ch  0 sv  6 frac 0.000861576 s = mean +   12 ns
> ch  1 sv  5 frac 0.000861586 s = mean +   22 ns
> ch  2 sv 10 frac 0.000861581 s = mean +   17 ns
> ch  3 sv 19 frac 0.000861573 s = mean +9 ns
> ch  5 sv 13 frac 0.000861571 s = mean +7 ns
> ch  6 sv 26 frac 0.19831
> ch  7 sv 28 frac 0.000861555 s = mean +   -8 ns
> ch  8 sv  7 frac 0.000861548 s = mean +  -15 ns
> ch  9 sv  3 frac 0.000861571 s = mean +7 ns
> ch 10 sv  8 frac 0.000861546 s = mean +  -17 ns
> 
> /tvb
> 
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Re: [time-nuts] Common-View GPS Network

[Attila Kinali]

On Mon, 15 Apr 2013 23:00:49 -0700
Jim Lux  wrote:

> the effect of a strong multipath (which is what the choke ring 
> suppresses) would be a LOT bigger than that..

Uhmm.. to my understanding, this is not quite true.
The choke ring does not surpress general multipath, but
the waves from near and below the horizon, which are often
full multipath issues.

You can see the choke rings as forming of a specific wave impedance 
(or wave resistance, if you want) in the region at the top.
At other places, this technique is known as electromagnetic bandgap.


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] Common-View GPS Network

[Mark Spencer]

Just curious what would a typical use case for this network be ?  My limited 
understanding of common view GPS in this context is that it can be used for 
time (and frequency) transfer between labs.
 
Thanks in advance for any replies.
 
Regards
Mark Spencer

--

Message: 6
Date: Tue, 16 Apr 2013 15:53:09 +0200
From: Achim Vollhardt 
To: time-nuts@febo.com
Subject: Re: [time-nuts] Common-View GPS Network
Message-ID: <516d57c5.9070...@physik.uzh.ch>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Count me in as well, if you need another participating station. I have 
my Thunderbolt running 24/7 with a solid stationary antenna..

Achim


--

Message: 7
Date: Tue, 16 Apr 2013 08:00:39 -0700
From: "WarrenS" 
To: "Discussion of precise time and frequency measurement"
    
Subject: Re: [time-nuts] Common-View GPS Network
Message-ID: 
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
    reply-type=original


"is one better off just taking the simple route and tracking GPS time 
directly?"
My response is Yes, as long as you use the GPS to discipline a good 
Oscillator.

GPS on its own is generally capable of about 10 ns of phase error, pretty 
much over any time period.
So the longer you average the closer you know the frequency.
I did some remote common view experiments a while back to see if I could 
find a way to improvement a GPSDO using low cost dual common view GPS.

I used Tbolt GPSs, because they are capable of more than a decade better 
performance than the 1 ns (with correction) GPS engines (*).
For monitoring I used Lady Heather so I could control and get real time data 
from the remote GPS.

After several unsuccessful test using various remote locations,
I got smarter and  moved the "Remote" GPS under the same roof to see what 
the limitations where.

I found the limitation was in my Antenna. (a  58532A type).
That is when I used two antennas, even with everything at the same location, 
taking common view differences added noise.
The only way I was able to improve the noise was to use the same GPS signal 
thru a splitter going to both GPS.
Not real useful for "remote" Common View, so my experiment turned into a 
dual Tbolt DMTD.

For some post I did, see Time Nuts back in Oct of 2011 from "WarrenS" and 
"ws at Yahoo"
"Common View Tbolt-Tic",  "DMTD using TBolts" and "Measuring ADEV using 
TBolt-Tic tester"

(*) The TBolt Engine is capable of 1e-11 at 3 seconds.
and 1e-12 ADEV at 300 seconds using the difference between two TBolts driven 
with a common GPS signal, see:


ws

*
Hello all.

Having spent some time working over the last year on GPS time stability
measurement, I'm keen to move onwards and upwards and have a go at
common-view time transfer.  While my receivers are in the post, I have
thinking about my next direction.  One thought that I have had is to try to
write some software that can be used for real-time common-view (public if
there is interest, but I am getting ahead of myself I think).

My question to those in the know is whether they have found common-view to
be useful over medium timescales (say, an hour or four).  My understanding
is that after a day or so the GPS signal itself becomes usable as a
standard, so building a network is probably not tremendously useful over
these sorts of time periods, but looking at such as figure 6 of [1],
common-view should still be useful between a few minutes and hours.  Has
anyone here tried using such a method to produce their own short-term time
scale, or is one better off just taking the simple route and tracking GPS
time directly?

Thanks,
Lachlan







--

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Re: [time-nuts] Common-View GPS Network

[Brooke Clarke]

Hi Poul:

Once you know the rise and set times (where the signal is stable) in sidereal time for each SV# you can simply 
enable/disable them based on time.

I think this may be a better approach than having a mask angle based on each 
degree of azimuth.
Keeping track of a rise and set time for each SV# is an order of magnitude less 
data than a 1 deg elevation mask.

Remember that each GPS satellite repeats it's ground track, that's to say that from a fixed antenna each satellite will 
always follow the same path in the sky.

This was how/why the GPS orbit altitude was chosen.
That's why I asked for a Sidereal time plot for the Thunderbolt. On a standard time position  plot the satellites appear 
to change paths.


Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

Poul-Henning Kamp wrote:

In message , "Tom Van Baak" writes:


When you look at the actual clock solutions (which are in the @@Hn
message) you will be surprised at the variance.

A lot of that variance is because the position-hold coords are wrong.

I tried using the @@Hn data to "sneak" up on the right coords and got
some pretty good results, but the process too forever (as in: Months)

See:
http://phk.freebsd.dk/raga/sneak/

The improvement in the finished timing solution from the oncore is
quite marginel because on average you have satellites on all
sides of your antenna and the errors mostly cancel out.

The notable exception to that is where I live: at 56N.

56N is at the top of the GPS orbits, so satellites never venture
north of me, and I'm not sufficient north to have any benefits from
the satellites which rise above Canada/Alask on the other side of
the north pole.



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Re: [time-nuts] Common-View GPS Network

[WarrenS]

"is one better off just taking the simple route and tracking GPS time 
directly?"
My response is Yes, as long as you use the GPS to discipline a good 
Oscillator.


GPS on its own is generally capable of about 10 ns of phase error, pretty 
much over any time period.

So the longer you average the closer you know the frequency.
I did some remote common view experiments a while back to see if I could 
find a way to improvement a GPSDO using low cost dual common view GPS.


I used Tbolt GPSs, because they are capable of more than a decade better 
performance than the 1 ns (with correction) GPS engines (*).
For monitoring I used Lady Heather so I could control and get real time data 
from the remote GPS.


After several unsuccessful test using various remote locations,
I got smarter and  moved the "Remote" GPS under the same roof to see what 
the limitations where.


I found the limitation was in my Antenna. (a  58532A type).
That is when I used two antennas, even with everything at the same location, 
taking common view differences added noise.
The only way I was able to improve the noise was to use the same GPS signal 
thru a splitter going to both GPS.
Not real useful for "remote" Common View, so my experiment turned into a 
dual Tbolt DMTD.


For some post I did, see Time Nuts back in Oct of 2011 from "WarrenS" and 
"ws at Yahoo"
"Common View Tbolt-Tic",  "DMTD using TBolts" and "Measuring ADEV using 
TBolt-Tic tester"


(*) The TBolt Engine is capable of 1e-11 at 3 seconds.
and 1e-12 ADEV at 300 seconds using the difference between two TBolts driven 
with a common GPS signal, see:



ws

*
Hello all.

Having spent some time working over the last year on GPS time stability
measurement, I'm keen to move onwards and upwards and have a go at
common-view time transfer.  While my receivers are in the post, I have
thinking about my next direction.  One thought that I have had is to try to
write some software that can be used for real-time common-view (public if
there is interest, but I am getting ahead of myself I think).

My question to those in the know is whether they have found common-view to
be useful over medium timescales (say, an hour or four).  My understanding
is that after a day or so the GPS signal itself becomes usable as a
standard, so building a network is probably not tremendously useful over
these sorts of time periods, but looking at such as figure 6 of [1],
common-view should still be useful between a few minutes and hours.  Has
anyone here tried using such a method to produce their own short-term time
scale, or is one better off just taking the simple route and tracking GPS
time directly?

Thanks,
Lachlan





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Re: [time-nuts] Common-View GPS Network

[Achim Vollhardt]

Count me in as well, if you need another participating station. I have 
my Thunderbolt running 24/7 with a solid stationary antenna..


Achim
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[time-nuts] Re Brooks Shera ASM release

[Merv Thomas]

Hi Bert,

Thanks for yours and Bob Leichner's time and others for this release.  I 
bought what was the latest version with AutoN from Brooks in 2010 but will 
program a PIC with what you have released to see if there are any 
significant differences.


Also a big thank you to Karen her permission to release the code.

Have signed the on line Condolences Book - a very good way to thank Karen as 
well and avoid the having to possibly use the normal postal services.


Merv  VK6BMT 


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Re: [time-nuts] Common-View GPS Network

[Poul-Henning Kamp]

In message , "Tom Van Baak" writes:

>When you look at the actual clock solutions (which are in the @@Hn
>message) you will be surprised at the variance. 

A lot of that variance is because the position-hold coords are wrong.

I tried using the @@Hn data to "sneak" up on the right coords and got
some pretty good results, but the process too forever (as in: Months)

See:
http://phk.freebsd.dk/raga/sneak/

The improvement in the finished timing solution from the oncore is
quite marginel because on average you have satellites on all
sides of your antenna and the errors mostly cancel out.

The notable exception to that is where I live: at 56N.

56N is at the top of the GPS orbits, so satellites never venture
north of me, and I'm not sufficient north to have any benefits from
the satellites which rise above Canada/Alask on the other side of
the north pole.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Brooks Shera ASM release

[REEVES Paul]

Hmmm,  apostrophe slip - apologies to any grammar-nuts amongst the 
time-nuts..

regards,
Paul R

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of REEVES Paul
Sent: 16 April 2013 08:07
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Brooks Shera ASM release

Bert,
I certainly appreciate all the work that has gone into the latest code. I 
learnt a lot from Brook's original (1.33) and modified it to suit my 'peculiar' 
hardware. I've only had time for a short look at the latest but I'm sure there 
is MUCH to learn here too. A very well written program with good commenting - 
not often seen nowadays.
Many thanks to all involved.

regards,
Paul Reeves   G8GJA


>-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of ewkeh...@aol.com
Sent: 15 April 2013 20:18
To: time-nuts@febo.com
Subject: Re: [time-nuts] Brooks Shera ASM release

>Alan
You may suggest something to time nuts, looking at the response I doubt it
and ask my self why did three of us spend three weeks to fully check it out
and  fix some of the code. Will reflect future projects.
Bert Kehren


>In a message dated 4/12/2013 8:39:40 P.M. Eastern Daylight Time,
alan.me...@btinternet.com writes:

>Bert is  there any way we can add our names to some expression of thanks to
his  widow Karen and her helpers for their work and maybe leave a
remembrance
of his worldwide friends for his family?

>Thanks for your  efforts
Best wishes
Alan Melia  (G3NYK)
UK


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Re: [time-nuts] Common-View GPS Network

[Tom Van Baak]

> I wonder if one should only measure the PPS thought. Looking directly at 
> the clock could help to separate the clock drift and the time, even if 
> you get sufficient clues from the PPS and sawtooth correction.
> 
> Cheers,
> Magnus

I've never tried that. Start with checking the ADEV of the LO. I always assumed 
the 1PPS was pre-compensated for instantaneous LO offset and rate, as 
calculated during the previous second(s). If so and ADEV(1 s) is less than 1e-9 
then the 1PPS + sawtooth will have sufficient accuracy for your needs. Message 
@@Ha contains the oscillator and clock parameters.

As you know professional receivers bypass this issue because they take an 
external LO (e.g., Rb, Cs, HM).

When you look at the actual clock solutions (which are in the @@Hn message) you 
will be surprised at the variance. At the per-SV per-second level it is not 
uncommon to see errors of many ns, even tens of ns. But when you average up to 
12 SV together every second for 600 seconds then you start to see something 
trustable. You can see first hand why GPSDO need long time-constants.

Here's a one second sample of a single Hn message:

@@Hn: sigma 36 sawtooth 10 0 0  mean frac 861564.000 (0.000)
ch  0 sv  6 frac 0.000861576 s = mean +   12 ns
ch  1 sv  5 frac 0.000861586 s = mean +   22 ns
ch  2 sv 10 frac 0.000861581 s = mean +   17 ns
ch  3 sv 19 frac 0.000861573 s = mean +9 ns
ch  5 sv 13 frac 0.000861571 s = mean +7 ns
ch  6 sv 26 frac 0.19831
ch  7 sv 28 frac 0.000861555 s = mean +   -8 ns
ch  8 sv  7 frac 0.000861548 s = mean +  -15 ns
ch  9 sv  3 frac 0.000861571 s = mean +7 ns
ch 10 sv  8 frac 0.000861546 s = mean +  -17 ns

/tvb

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[time-nuts] Brooks Shera another thank you

[Geoffrey Smith]

Thanks to all concerned it is a fitting memorial to him and his family.

 

Regards

Geoffrey Smith

Mobile: 0412 299 922

E-Mail  geoffsmit...@tpg.com.au

 

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Re: [time-nuts] Brooks Shera ASM release

[REEVES Paul]

Bert,
I certainly appreciate all the work that has gone into the latest code. I 
learnt a lot from Brook's original (1.33) and modified it to suit my 'peculiar' 
hardware. I've only had time for a short look at the latest but I'm sure there 
is MUCH to learn here too. A very well written program with good commenting - 
not often seen nowadays.
Many thanks to all involved.

regards,
Paul Reeves   G8GJA


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of ewkeh...@aol.com
Sent: 15 April 2013 20:18
To: time-nuts@febo.com
Subject: Re: [time-nuts] Brooks Shera ASM release

Alan
You may suggest something to time nuts, looking at the response I doubt it
and ask my self why did three of us spend three weeks to fully check it out
and  fix some of the code. Will reflect future projects.
Bert Kehren


In a message dated 4/12/2013 8:39:40 P.M. Eastern Daylight Time,
alan.me...@btinternet.com writes:

Bert is  there any way we can add our names to some expression of thanks to
his  widow Karen and her helpers for their work and maybe leave a
remembrance
of his worldwide friends for his family?

Thanks for your  efforts
Best wishes
Alan Melia  (G3NYK)
UK


-  Original Message -
From: 
To:  
Sent: Friday, April 12, 2013 8:52 PM
Subject:  [time-nuts] Brooks Shera ASM release


> The time-nuts server  takes out all spaces so allow me to  resend the
>  acknowledgementsBert Kehren
>  
>   
>
>
> At this time I like to thank  Brooks for all  the work he did, his wife
> Karen Stoll for  deciding to release HEX and ASM and  Bob Leichner who
> implemented  the software commands. Brooks did not have the  chance to
put
>  final
> touches in and complete his work, so Richard McCorkle   stepped in and
made
> the
> final changes. For almost a decade  Brooks and Richard  collaborated on
the
> GPSDO, which benefits all  of us. Also major recognition has  to go to
> Juerg
> Koegel  an other time nut that put our other projects on hold to  check
>  every
> iteration. Attached is part of a test that clearly shows  the
performance
> of
> the Alpha filter. Limited by  attachment size contact me off list  for
more
> data.
>  ___
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