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

[Magnus Danielson]

On 04/16/2013 05:23 AM, Tom Van Baak wrote:

I too would be interested. The topic of common view GPS comes up every now and 
then. The incentive to use common view time transfer (CVTT) is reduced when 
plain old time transfer (TT) is so good already. Still, it's worth a try.

I'd be curious what level of improvement is possible. It will depend on the 
receiver and the antenna. I believe the NIST project uses fancy antennas but 
normal M12 receivers.


They use the Novatel 700 pin-wheel antenna.


So there's hope for the amateur. I don't think the TIC is that important: the 
sawtooth granularity is 1 ns so precision greater than that is wasted. One 
averages over many minutes anyway.

Simulations would be a great idea. If you need raw data let me know.

Google for CGGTTS and RINEX. Not all GPS receivers provide the level of 
per-satellite information required for common view. I know the M12 does, as 
well as high-end specialty timing receivers. I don't know if the Trimble TBolt 
or Res-t give out enough information to generate RINEX. But you can get the 
individual SV contribution to the solution using TBolt packet 0x8F-A7.


Setting up my M12M-T for this would be fun. That should be attainable 
for most folks around here.


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
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Re: [time-nuts] Brooks Shera ASM release

[Robert Atkinson]

Me too,
Didn't say anything before to keep the noise down.
 
Robert G8RPI.



From: Alan Melia 
To: time-nuts measurement  
Sent: Tuesday, 16 April 2013, 0:40
Subject: Re: [time-nuts] Brooks Shera ASM release


Bert  I am grateful for the work you and friends have done.

Is there any way we can add our names to some expression of thanks from
members of the Group to his  widow Karen and her helpers for their work in
making the checked source code for the GPSDO available to us and maybe leave
a  token of remembrance of his worldwide friends, for his family?

Even if it is just a "me too" replying to this message.

Alan Melia (G3NYK)  Ipswich, UK

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

[Jim Lux]

On 4/15/13 10:40 PM, bg wrote:

Chris,

Chokering is not needed.  Measured quality antennas are listed at

  http://www.ngs.noaa.gov/ANTCAL/

  Or at

   
http://www.geopp.de/index.php?sprachauswahl=en&bereich=0&kategorie=34&artikel=62

/Björn





A lot of the antennas on that list are choke ring type.  If you are 
doing geodetic work, millimeter scale changes in phase center are 
important.  For time transfer, maybe not.. 1mm is 3 ps, after all.


A ratty old patch antenna has a phase center variation of a few cm at 
most, and that's 30-50 ps.


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





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

[Jim Lux]

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.






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

[bg]

Chris,

Chokering is not needed.  Measured quality antennas are listed at

     http://www.ngs.noaa.gov/ANTCAL/

 Or at 

      
http://www.geopp.de/index.php?sprachauswahl=en&bereich=0&kategorie=34&artikel=62

/Björn



 Originalmeddelande 
Från: Chris Albertson  
Datum: 2013-04-16  5:36  (GMT+01:00) 
Till: Tom Van Baak ,Discussion of precise time and 
frequency measurement  
Rubrik: Re: [time-nuts] Common-View GPS Network 
 
On Mon, Apr 15, 2013 at 8:23 PM, Tom Van Baak  wrote:

I'd be curious what level of improvement is possible. It will depend on the
> receiver and the antenna. I believe the NIST project uses fancy antennas
> but normal M12 receivers. So there's hope for the amateur.
>

The M12 is certainly affordable, something like $60. but what is a "fancy
antenna"?  How are they different from a normal timing antena?

-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Common-View GPS Network

[Jim Lux]

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.

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

[Tom Van Baak]

> but what is a "fancy antenna"?  How are they different from a normal timing 
> antena?

Google for: NIST SIM GPS common view pinwheel

/tvb

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

[Jim Lux]

On 4/15/13 8:36 PM, Chris Albertson wrote:

On Mon, Apr 15, 2013 at 8:23 PM, Tom Van Baak  wrote:

I'd be curious what level of improvement is possible. It will depend on the

receiver and the antenna. I believe the NIST project uses fancy antennas
but normal M12 receivers. So there's hope for the amateur.



The M12 is certainly affordable, something like $60. but what is a "fancy
antenna"?  How are they different from a normal timing antena?




Probably a choke ring? With small variation in phase center over viewing 
angles.  The "secret sauce" is in the design of the crossed dipole 
elements which are not flat, nor are they constant width.


http://facility.unavco.org/kb/questions/311/Choke+Ring+Antenna+Calibrations 
has dimensions


fins are 50-63 mm tall, 25 mm apart, etc.

I suspect that this is not a high precision sort of thing.. (that is, if 
your fin spacing isn't exactly 25.1 mm it doesn't make much difference)


L1 is 1575 MHz (approx) or a wavelength of 19 cm.  So the fins are 0.315 
to 0.26 lambda high and 0.13 lambda apart.  If you were making a fancy 
corrugated horn, you make the fins range from 1/2 lambda to 1/4 lambda 
so you get a nice transition from shorted to open, but that's not what 
they're doing here.



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

[Chris Albertson]

On Mon, Apr 15, 2013 at 8:23 PM, Tom Van Baak  wrote:

I'd be curious what level of improvement is possible. It will depend on the
> receiver and the antenna. I believe the NIST project uses fancy antennas
> but normal M12 receivers. So there's hope for the amateur.
>

The M12 is certainly affordable, something like $60. but what is a "fancy
antenna"?  How are they different from a normal timing antena?

-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Common-View GPS Network

[Tom Van Baak]

I too would be interested. The topic of common view GPS comes up every now and 
then. The incentive to use common view time transfer (CVTT) is reduced when 
plain old time transfer (TT) is so good already. Still, it's worth a try.

I'd be curious what level of improvement is possible. It will depend on the 
receiver and the antenna. I believe the NIST project uses fancy antennas but 
normal M12 receivers. So there's hope for the amateur. I don't think the TIC is 
that important: the sawtooth granularity is 1 ns so precision greater than that 
is wasted. One averages over many minutes anyway.

Simulations would be a great idea. If you need raw data let me know.

Google for CGGTTS and RINEX. Not all GPS receivers provide the level of 
per-satellite information required for common view. I know the M12 does, as 
well as high-end specialty timing receivers. I don't know if the Trimble TBolt 
or Res-t give out enough information to generate RINEX. But you can get the 
individual SV contribution to the solution using TBolt packet 0x8F-A7.

/tvb

- Original Message - 
From: "Lachlan Gunn" 
To: 
Sent: Monday, April 15, 2013 5:27 PM
Subject: Re: [time-nuts] Common-View GPS Network


> My inclination is that one would need three things to participate in such a 
> system---
> 
> 1. A GPS receiver. 
> 2. A local reference oscillator. 
> 3. A way to measure their relative phase.
> 
> I understand that the Thunderbolt can perform all of these functions, so 
> expect that this would be the favoured option for those without an Rb 
> oscillator. I do not have one, so will move on to the next setup. For 
> development the ResT could work the same way, but it's oscillator isn't as 
> good. So, we consider the next option. 
> 
> For those without a receiver that has itself a high-quality oscillator, the 
> next option would be to use a local reference and build a separate 
> phase-measurement circuit. I have already written a time-tagging system with 
> an FPGA, which could be reworked into what we need. This is probably 
> overboard, though, and might be achieved with a micro, possibly paired with a 
> PICTIC for the final interpolation.
> 
> The next step would be to either transfer directly or to upload the phase 
> data to a central location where it could be processed together to estimate 
> everyone's offset to the average at once.
> 
> A DMTD will be needed somewhere to evaluate performance, but this needs only 
> to be done somewhere rather than everywhere. 
> 
> Since there has been some interest I'll start whacking some simulations 
> together in the near future.
> 
> Thanks, 
> Lachlan Gunn
> 
>  Original message 
> From: Mark Spencer  
> Date:  
> To: time-nuts@febo.com 
> Subject: Re: [time-nuts] Common-View GPS Network 
> 
> 
> 
> I'd be interested in understanding what it would take to participate in this 
> type of experiment. I'm unlikely to have any free time for this over the next 
> several months but if for example there was a particular GPS receiver that 
> was well suited for this type of work that would be useful info for me. 
> (Recently at work I've started to become involved with precision GPS location 
> systems and the claimed 3D accuracies that can be achieved using post 
> processing seem very impressive.)
> Thanks in advance for any comments.
> 
> 
> Regards
> Mark Spencer
> --
> 
> Message: 6
> Date: Mon, 15 Apr 2013 22:49:38 +0200
> From: Magnus Danielson 
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Common-View GPS Network
> Message-ID: <516c67e2.80...@rubidium.dyndns.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Lachlan,
> 
> This would be fun to try with a few sites involved. It requires a fairly 
> decent GPS and antenna at each location, and loging and then 
> post-processing. Would be fun to see how well it can be made to perform.
> 
> Cheers,
> Magnus
> 
> On 04/15/2013 02:55 PM, Lachlan Gunn wrote:
>> 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 j

Re: [time-nuts] Signal Hound

[Jim Lux]

On 4/15/13 1:48 PM, Dr. David Kirkby wrote:

On 04/15/13 04:39 AM, Jim Lux wrote:

Inexpensive USB spectrum analyzer.. http://www.signalhound.com/


It's not that inexpensive. I assembled a 22 GHz spectrum analyzer based
on the HP 7 modular measurement system for about the same money.


New vs used.



 The

22 Ghz tracking generator module is very expensive, but I don't have
that. Since I have a 20 GHz VNA, owning a tracking generator on a
spectrum analyzer is not that important. The 2.9 GHz tracking generator
for the HP 7 series is not that expensive.


The used HP or similar kit has done most of its depreciating.

Of course, I can see advantages in small, compact units with a warranty,
but I'd certainly want to consider buying used professional equipment.



I was thinking about it for use at work, where calibration and repair is 
an issue.  We've got plenty of old HP gear at JPL, and while it works 
great, it's also often got clunky interfaces for computer control, it's 
difficult to get repaired, etc.   (HP 8663Bs for instance..) and 
sometimes, it's just plain obsolete.


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Re: [time-nuts] Brooks Shera ASM release

[EB4APL]

Bert,

As one of Brooks "customers" I would like to express my thanks to him 
for his generous work (fortunately I did it when we contacted in early 
2009), and also now to thank you and the others who made possible to 
finally have his code, including the efforts to fix and test it.

And of course thank his widow for letting this to happen.
I was traveling abroad when you posted the code and intermediately 
downloaded and secured it while at the airport.  Back home now it is the 
time to say thank you all.


Best regards,
Ignacio EB4APL

On 15/04/2013 21:17, ewkeh...@aol.com wrote:

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

[Hal Murray]

lach...@twopif.net said:
> I'm starting with a Resolution T, which claims to offer a single-satellite
> mode.  I gather that it's not an amazing receiver, but I'm hoping it will be
> good enough for a first foray at least.  I'm rather hoping that it will do
> well, though, since it would mean a cheapish way of making a self-contained
> device with 10MHz/ANT on one end and Ethernet on the other. 

Why are you interested in Common-View if your target is Ethernet?

As I understand it, Common-View is a way of very accurately comparing two 
clocks.  Typical GPS receivers with a good antenna will get you to 10s of ns. 
 Can you measure Ethernet packet timing to better than that?


-- 
These are my opinions.  I hate spam.



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

[Lachlan Gunn]

Hello.

I'm starting with a Resolution T, which claims to offer a single-satellite
mode.  I gather that it's not an amazing receiver, but I'm hoping it will be
good enough for a first foray at least.  I'm rather hoping that it will do
well, though, since it would mean a cheapish way of making a self-contained
device with 10MHz/ANT on one end and Ethernet on the other.

Thanks,
Lachlan
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Bob Camp
Sent: Tuesday, 16 April 2013 7:10 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Common-View GPS Network

Hi

One common requirement is a receiver that will give you "per satellite"
information that you can turn into time. About the only way around that is
to pre-determine a set of sats and flag the rest as "do not use". With the
second approach, various geometric issues can get a bit exciting.  Either
way good antenna locations and local clocks are needed. 

Do you have a specific receiver in mind?

Bob

On Apr 15, 2013, at 8:55 AM, Lachlan Gunn  wrote:

> 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
> 
> 
> 
> 
> 
> [1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf
> 
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Re: [time-nuts] time-nuts Digest, Vol 105, Issue 47

[M. Simon]

Near the bottom of this is a bit on the UC lab school.


 



Engineering is the art of making what you want from what you can get at a 
profit.



>
> From: "time-nuts-requ...@febo.com" 
>To: time-nuts@febo.com 
>Sent: Tuesday, April 16, 2013 12:13 AM
>Subject: time-nuts Digest, Vol 105, Issue 47
> 
>
>Send time-nuts mailing list submissions to
>    time-nuts@febo.com
>
>To subscribe or unsubscribe via the World Wide Web, visit
>    https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>or, via email, send a message with subject or body 'help' to
>    time-nuts-requ...@febo.com
>
>You can reach the person managing the list at
>    time-nuts-ow...@febo.com
>
>When replying, please edit your Subject line so it is more specific
>than "Re: Contents of time-nuts digest..."
>
>
>Today's Topics:
>
>   1. Re: Signal Hound (Dr. David Kirkby)
>   2. Re: Common-View GPS Network (Bob Camp)
>   3. Re: Common-View GPS Network (Mark Spencer)
>   4. Re: Brooks Shera ASM release (Alan Melia)
>   5. Re: Brooks Shera ASM release (Alan Melia)
>   6. Re: Brooks Shera thanks options (Chris Howard)
>
>
>--
>
>Message: 1
>Date: Mon, 15 Apr 2013 21:48:45 +0100
>From: "Dr. David Kirkby" 
>To: Discussion of precise time and frequency measurement
>    
>Subject: Re: [time-nuts] Signal Hound
>Message-ID: <516c67ad.4040...@onetel.net>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>On 04/15/13 04:39 AM, Jim Lux wrote:
>> Inexpensive USB spectrum analyzer.. http://www.signalhound.com/
>
>It's not that inexpensive. I assembled a 22 GHz spectrum analyzer based on the 
>HP 7 modular measurement system for about the same money. The 22 Ghz 
>tracking generator module is very expensive, but I don't have that. Since I 
>have 
>a 20 GHz VNA, owning a tracking generator on a spectrum analyzer is not that 
>important. The 2.9 GHz tracking generator for the HP 7 series is not that 
>expensive.
>
>
>The used HP or similar kit has done most of its depreciating.
>
>Of course, I can see advantages in small, compact units with a warranty, but 
>I'd 
>certainly want to consider buying used professional equipment.
>
>
>-- 
>Dr. David Kirkby Ph.D C.Eng MIET
>
>
>--
>
>Message: 2
>Date: Mon, 15 Apr 2013 17:40:20 -0400
>From: Bob Camp 
>To: Discussion of precise time and frequency measurement
>    
>Subject: Re: [time-nuts] Common-View GPS Network
>Message-ID: 
>Content-Type: text/plain; charset=us-ascii
>
>Hi
>
>One common requirement is a receiver that will give you "per satellite" 
>information that you can turn into time. About the only way around that is to 
>pre-determine a set of sats and flag the rest as "do not use". With the second 
>approach, various geometric issues can get a bit exciting.  Either way good 
>antenna locations and local clocks are needed. 
>
>Do you have a specific receiver in mind?
>
>Bob
>
>On Apr 15, 2013, at 8:55 AM, Lachlan Gunn  wrote:
>
>> 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
>> 
>> 
>> 
>> 
>> 
>> [1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf
>> 
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>> and follow the instructions there.
>
>
>
>--
>
>Message: 3
>Date: Mon, 15 Apr 2013 15:45:47 -0700 (PDT)
>From: Mark Spencer 
>To: time-nuts@febo.com
>Subject: Re: [time-nuts] Common-View GPS Network
>Message-ID:
>    <1366065947.80876.yahoomailclas...@web121006.mail.ne1.yahoo.com>
>Content-Type: text/plain; charset=iso-8859-1
>
>
>
>I'd be interested in understanding what it would take to participate in this 
>type of experiment.?? I'm unlikely to have any free time for this over the 
>next several months but if for example th

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

[Bob Camp]

Hi

Unfortunately there's more to it than that. Unless both TBolts are looking at 
the same sats, they will get very different answers. Ideally you want to 
compare single sats, and have very precise station locations. That lets you 
eliminate a lot of geometric stuff and individual sat errors. Fancy sat orbit 
data also helps this.

The measurement stuff is pretty easy. Anything that will measure 100 to 200 ps 
is likely to be plenty good enough. There are a number of counters and boards 
that will do that. 

Then you get down to ionosphere stuff, and fiddly crustal tide shifts. There 
are lots of layers to this onion.

Bob

On Apr 15, 2013, at 8:27 PM, Lachlan Gunn  wrote:

> My inclination is that one would need three things to participate in such a 
> system---
> 
>   1. A GPS receiver. 
>   2. A local reference oscillator. 
>   3. A way to measure their relative phase.
> 
> I understand that the Thunderbolt can perform all of these functions, so 
> expect that this would be the favoured option for those without an Rb 
> oscillator.   I do not have one, so will move on to the next setup.  For 
> development the ResT could work the same way, but it's oscillator isn't as 
> good. So, we consider the next option.  
> 
> For those without a receiver that has itself a high-quality oscillator, the 
> next option would be to use a local reference and build a separate 
> phase-measurement circuit. I have already written a time-tagging system with 
> an FPGA, which could be reworked into what we need. This is probably 
> overboard, though, and might be achieved with a micro, possibly paired with a 
> PICTIC for the final interpolation.
> 
> The next step would be to either transfer directly or to upload the phase 
> data to a central location where it could be processed together to estimate  
> everyone's offset to the average at once.
> 
> A DMTD will be needed somewhere to evaluate performance, but this needs only 
> to be done somewhere rather than everywhere. 
> 
> Since there has been some interest I'll start whacking some simulations 
> together in the near future.
> 
> Thanks, 
> Lachlan Gunn
> 
>  Original message 
> From: Mark Spencer  
> Date:  
> To: time-nuts@febo.com 
> Subject: Re: [time-nuts] Common-View GPS Network 
> 
> 
> 
> I'd be interested in understanding what it would take to participate in this 
> type of experiment.   I'm unlikely to have any free time for this over the 
> next several months but if for example there was a particular GPS receiver 
> that was well suited for this type of work that would be useful info for me.  
>  
> (Recently at work I've started to become involved with precision GPS location 
> systems and the claimed 3D accuracies that can be achieved using post 
> processing seem very impressive.)
> Thanks in advance for any comments.
>  
>  
> Regards
> Mark Spencer
> --
> 
> Message: 6
> Date: Mon, 15 Apr 2013 22:49:38 +0200
> From: Magnus Danielson 
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Common-View GPS Network
> Message-ID: <516c67e2.80...@rubidium.dyndns.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Lachlan,
> 
> This would be fun to try with a few sites involved. It requires a fairly 
> decent GPS and antenna at each location, and loging and then 
> post-processing. Would be fun to see how well it can be made to perform.
> 
> Cheers,
> Magnus
> 
> On 04/15/2013 02:55 PM, Lachlan Gunn wrote:
>> 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
>> 
>> 
>> 
>> 
>> 
>> [1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf
>> 
>> ___
>> 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.
> 
> 
> 
> --
> 
> 

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

[Lachlan Gunn]

My inclination is that one would need three things to participate in such a 
system---

  1. A GPS receiver. 
  2. A local reference oscillator. 
  3. A way to measure their relative phase.

I understand that the Thunderbolt can perform all of these functions, so expect 
that this would be the favoured option for those without an Rb oscillator.   I 
do not have one, so will move on to the next setup.  For development the ResT 
could work the same way, but it's oscillator isn't as good. So, we consider the 
next option.  

For those without a receiver that has itself a high-quality oscillator, the 
next option would be to use a local reference and build a separate 
phase-measurement circuit. I have already written a time-tagging system with an 
FPGA, which could be reworked into what we need. This is probably overboard, 
though, and might be achieved with a micro, possibly paired with a PICTIC for 
the final interpolation.

The next step would be to either transfer directly or to upload the phase data 
to a central location where it could be processed together to estimate  
everyone's offset to the average at once.

A DMTD will be needed somewhere to evaluate performance, but this needs only to 
be done somewhere rather than everywhere. 

Since there has been some interest I'll start whacking some simulations 
together in the near future.

Thanks, 
Lachlan Gunn

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


I'd be interested in understanding what it would take to participate in this 
type of experiment.   I'm unlikely to have any free time for this over the next 
several months but if for example there was a particular GPS receiver that was 
well suited for this type of work that would be useful info for me.   
(Recently at work I've started to become involved with precision GPS location 
systems and the claimed 3D accuracies that can be achieved using post 
processing seem very impressive.)
Thanks in advance for any comments.
 
 
Regards
Mark Spencer
--

Message: 6
Date: Mon, 15 Apr 2013 22:49:38 +0200
From: Magnus Danielson 
To: time-nuts@febo.com
Subject: Re: [time-nuts] Common-View GPS Network
Message-ID: <516c67e2.80...@rubidium.dyndns.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Lachlan,

This would be fun to try with a few sites involved. It requires a fairly 
decent GPS and antenna at each location, and loging and then 
post-processing. Would be fun to see how well it can be made to perform.

Cheers,
Magnus

On 04/15/2013 02:55 PM, Lachlan Gunn wrote:
> 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
>
>
>
>
>
> [1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
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> and follow the instructions there.



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Re: [time-nuts] Brooks Shera thanks options

[Chris Howard]

The online obit at 
http://www.santafefuneraloption.com/sitemaker/sites/santaf0/obit.cgi?user=949646Shera
says,

"Memorials may be made to the University of Chicago Laboratory Schools,
the Sierra Club, or any organization of the Donor’s choice."


University of Chicago Laboratory Schools
http://www.ucls.uchicago.edu/  (look under 'Support Lab' for contribution links)

Sierra Club
http://www.sierraclub.org/   (big orange "DONATE" button)


I don't see a PayPal option on either one.



Chris
W0EP





On 4/15/2013 6:29 PM, Alan Melia wrote:
> Ok Bert I will stick my head above the parapet and repeat that 
> query.Sometimes it is frustarting the get no response, but later get personal 
> appreciation as you meet individuals. I didn't know the guy. I was trying 
> with a friend to contact him long after the original article. We were 
> disapointed but not unhappy. I certainly appreciate the help and expertise 
> the Group provides..and it is nice to be able to say so, and salute the 
> work Brooks did.
> 
> Thanks and Best Wishes
> Alan Melia
> (G3NYK)
> - Original Message - From: 
> To: 
> Sent: Monday, April 15, 2013 8:17 PM
> 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.
>>>  ___
>>> 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.
>>
>> ___
>> 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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>> and follow the instructions there. 
> 
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> 
> 

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Re: [time-nuts] Brooks Shera ASM release

[Alan Melia]

Bert  I am grateful for the work you and friends have done.

Is there any way we can add our names to some expression of thanks from
members of the Group to his  widow Karen and her helpers for their work in
making the checked source code for the GPSDO available to us and maybe leave
a  token of remembrance of his worldwide friends, for his family?

Even if it is just a "me too" replying to this message.

Alan Melia (G3NYK)  Ipswich, UK

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Re: [time-nuts] Brooks Shera ASM release

[Alan Melia]

Ok Bert I will stick my head above the parapet and repeat that 
query.Sometimes it is frustarting the get no response, but later get 
personal appreciation as you meet individuals. I didn't know the guy. I was 
trying with a friend to contact him long after the original article. We were 
disapointed but not unhappy. I certainly appreciate the help and expertise 
the Group provides..and it is nice to be able to say so, and salute the 
work Brooks did.


Thanks and Best Wishes
Alan Melia
(G3NYK)
- Original Message - 
From: 

To: 
Sent: Monday, April 15, 2013 8:17 PM
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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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the  instructions there.


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

[Mark Spencer]

I'd be interested in understanding what it would take to participate in this 
type of experiment.   I'm unlikely to have any free time for this over the next 
several months but if for example there was a particular GPS receiver that was 
well suited for this type of work that would be useful info for me.   
(Recently at work I've started to become involved with precision GPS location 
systems and the claimed 3D accuracies that can be achieved using post 
processing seem very impressive.)
Thanks in advance for any comments.
 
 
Regards
Mark Spencer
--

Message: 6
Date: Mon, 15 Apr 2013 22:49:38 +0200
From: Magnus Danielson 
To: time-nuts@febo.com
Subject: Re: [time-nuts] Common-View GPS Network
Message-ID: <516c67e2.80...@rubidium.dyndns.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Lachlan,

This would be fun to try with a few sites involved. It requires a fairly 
decent GPS and antenna at each location, and loging and then 
post-processing. Would be fun to see how well it can be made to perform.

Cheers,
Magnus

On 04/15/2013 02:55 PM, Lachlan Gunn wrote:
> 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
>
>
>
>
>
> [1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf
>
> ___
> 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] Common-View GPS Network

[Bob Camp]

Hi

One common requirement is a receiver that will give you "per satellite" 
information that you can turn into time. About the only way around that is to 
pre-determine a set of sats and flag the rest as "do not use". With the second 
approach, various geometric issues can get a bit exciting.  Either way good 
antenna locations and local clocks are needed. 

Do you have a specific receiver in mind?

Bob

On Apr 15, 2013, at 8:55 AM, Lachlan Gunn  wrote:

> 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
> 
> 
> 
> 
> 
> [1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf
> 
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Re: [time-nuts] Signal Hound

[Dr. David Kirkby]

On 04/15/13 04:39 AM, Jim Lux wrote:

Inexpensive USB spectrum analyzer.. http://www.signalhound.com/


It's not that inexpensive. I assembled a 22 GHz spectrum analyzer based on the 
HP 7 modular measurement system for about the same money. The 22 Ghz 
tracking generator module is very expensive, but I don't have that. Since I have 
a 20 GHz VNA, owning a tracking generator on a spectrum analyzer is not that 
important. The 2.9 GHz tracking generator for the HP 7 series is not that 
expensive.



The used HP or similar kit has done most of its depreciating.

Of course, I can see advantages in small, compact units with a warranty, but I'd 
certainly want to consider buying used professional equipment.



--
Dr. David Kirkby Ph.D C.Eng MIET
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Re: [time-nuts] Common-View GPS Network

[Magnus Danielson]

Lachlan,

This would be fun to try with a few sites involved. It requires a fairly 
decent GPS and antenna at each location, and loging and then 
post-processing. Would be fun to see how well it can be made to perform.


Cheers,
Magnus

On 04/15/2013 02:55 PM, Lachlan Gunn wrote:

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





[1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf

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Re: [time-nuts] Brooks Shera ASM release

[Arnold Tibus]

Hi Bert,

I do fully support David's opinion, I appreciate very much all the past
and future work on this subject like all other developments in the group,
so please don't stop, it made me happy when I got the code list in your
past mail!

Thank you very much,

regards,

Arnold, DK2WT



am 15.04.2013 22:00, schrieb David McGaw:
> Hi Bert,
>
> Just because there was not much response to this inquiry does not mean
> that your efforts are not appreciated.  Considering how many requested
> the earlier code (many in person to myself) I expect your work is VERY
> MUCH appreciated.
>
> Thank you,
>
> David
>
>
> On 4/15/13 3:17 PM, ewkeh...@aol.com wrote:
>> 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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Re: [time-nuts] Brooks Shera ASM release

[Magnus Danielson]

On 04/15/2013 10:00 PM, David McGaw wrote:

Hi Bert,

Just because there was not much response to this inquiry does not mean
that your efforts are not appreciated. Considering how many requested
the earlier code (many in person to myself) I expect your work is VERY
MUCH appreciated.


I for one apprechiate the effort. Will look it through. See what he did 
and what there is to be learned.


Cheers,
Magnus
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Re: [time-nuts] Brooks Shera ASM release

[David McGaw]

Hi Bert,

Just because there was not much response to this inquiry does not mean 
that your efforts are not appreciated.  Considering how many requested 
the earlier code (many in person to myself) I expect your work is VERY 
MUCH appreciated.


Thank you,

David


On 4/15/13 3:17 PM, ewkeh...@aol.com wrote:

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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  https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Brooks Shera ASM release

[EWKehren]

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.
>  ___
> 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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[time-nuts] UPDATE: DATUM 9390-52054 Grief again...

[Burt I. Weiner]

Another update...  I wanted to post more in the hopes that it may 
help someone else with similar problems.


I told you about adding the simple voltage divider to reduce the 
drive to the circuits following the replacement of the original 
oscillator module.  When I thought all was well I put the DATUM 
9390-52054 back in the rack and it locked up quickly.  I soon 
discovered that I didn't have enough output to lock some of my 
externally referenced equipment.  A comparison between my two 9390's 
showed that the repaired one was about 15 dB low in output!  Just for 
fun I removed the voltage divider and ran the replacement 
oscillator's output directly to the following circuitry, just as the 
original oscillator did.  Testing, which I fully expected to give me 
the problem of driving the DAC and EFC voltage out of range, showed 
that all was well and the 9390's output levels were within a dB of 
DATUM's specs.  So, what happened earlier that caused me to think it 
was being over-driven.  I haven't any idea!  I've run it through 
several power cycles, some overnight, and it always comes back up 
with such happiness, and with the DAC around 28400 and the EFC at 
2.15 volts - right where it's supposed to be.  The only thing I can 
think of is that I did something foolish in my initial testing with 
the replacement oscillator.  The unit has been sitting in the rack 
for over 48 hours with no issues.  According to it's screen the 
frequency error is 1E-12 and the output level is where it should be.


Thanks to everyone for your input, you've given me a good 
understanding of how this particular GPS module works.  I hope my 
experience will be of some value down the road.  I'll keep you posted 
on any further 9390 adventures.


Thanks,

Burt, K6OQK

I had earlier written:
When I powered the 9390 up everything seemed to work and the 
oscillator was within 1-Hertz, except that the output was about 20 dB 
higher than with the original oscillator was when it was working 
properly.  Once the receiver locked up to 4 satellites and started 
"OSC Stabilizing", the oscillator suddenly jumped about 18 Hz low and 
shortly afterwards the DAC went to all zeros.  I let it sit all night 
figuring that it would eventually find itself.  Well, it didn't, it 
just sat at 18 Hz low and the DAC at all zeros, and the EFC 
(Electronic Frequency Control) voltage at 0.19 Volts.  (What a 
revolting development!)


Very early this AM I got up and put a simple 10:1 voltage divider 
using a series 680 Ohm and 68 Ohm resistor from the oscillator's RF 
out to ground This brought the levels pretty much back to the same as 
my good 9390.  I also substituted a pot for the EFC voltage.  I used 
a 1 K pot in series with a 300 Ohm resistor to the 5 Volt rail.  The 
resistor was on the high side, the bottom end to ground, and the 
wiper to the EFC terminal.  I was able to tune the oscillator to 
precisely 10 MHz long enough to measure the substitute EFC at +2.15 
Volts.  Leaving it hooked up this way I let the receiver do it's 
thing just to see what would happen.  It went through it's normal 
routine and finally the green lock light came on.  Although the 
oscillator wasn't being controlled by the 9390, the 9390 thought it 
was happy and the DAC went to about 28,000 - very close to ideal.  I 
tweaked the pot hither and yon to move the frequency and to see which 
way the EFC voltage went.  It went the right direction to properly 
steer the oscillator and should have worked.


Pondering the situation, I powered the 9390 down and reconnected the 
9390's EFC voltage back up to see what would happen this time.  This 
time it locked up quickly and the oscillator homed in on 10 MHz.  The 
EFC voltage is 2.15 Volts and the DAC settled in nicely at 28302 - 
very close to the recommended DAC numbers.  It's been cooking for 
about an hour now and is presently at 112E-12 and moving closer all 
the time.  When comparing the two GPS receivers I am not seeing the 
random drifts that I had seen in the past.


I suspect that the problem with the frequency jumping to -18 Hz and 
the DAC going to all zeros was the result of the new oscillator 
over-driving the following circuitry.  In hindsight, maybe I should 
have probed a bit with the scope to see if that is a correct 
assumption, but I didn't do that.


By the way, Stu sells the oscillators fully tested and with a note 
giving the EFC voltage for each unit to tune it to 10 MHz.  If this 
turns out to be as good a modification as it now appears, I'm going 
to get more of the oscillators from him.  I may replace the one in my 
other 9390 and for sure will replace internal reference oscillator in 
my IFR-1500 Service Monitor.


Burt, K6OQK


Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
b...@att.net
www.biwa.cc
K6OQK  


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[time-nuts] Common-View GPS Network

[Lachlan Gunn]

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

 

 

[1] http://www.pttimeeting.org/archivemeetings/2008papers/paper45.pdf

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Re: [time-nuts] spectracom PicoTime

[Bob Camp]

Hi

We have one and I've used it. You have to be a bit careful reading the specs. 
It does one set of things with an attached counter and another running as a 
self contained box. The specs are correct, but you have to be careful about 
which set the number on this or that page comes from. 

Bob

On Apr 14, 2013, at 10:43 PM, Robert Darby  wrote:

> Does anyone have any experience using the spectracom PicoTime test set?  Just 
> curious.
> 
> Datasheet:
> http://www.spectracomcorp.com/Desktopmodules/Bring2Mind/DMX/Download.aspx?EntryId=379&PortalId=0
> 
> Using with a CNT-91:
> http://www.spectracomcorp.com/Desktopmodules/Bring2Mind/DMX/Download.aspx?EntryId=435&PortalId=0
> 
> Regards,
> bob darby
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Re: [time-nuts] Signal Hound

[Orin Eman]

There is a yahoo group for the Signal Hound.  For one user, the original
Signal Hound showed really poor phase noise performance with an external
reference with the internal reference always being better... see the
"External ref vs internal ref.pdf" document on the yahoo group for
details.  The plot presented in that document looks really bad.

Orin.


On Sun, Apr 14, 2013 at 8:39 PM, Jim Lux  wrote:

> Inexpensive USB spectrum analyzer.. http://www.signalhound.com/
>
> I think it has the ability to capture raw samples, too. (the BB60
> definitely does.)  They have a 10MHz ref input.
>
> The spectrum analyzer has a phase noise feature
> Phase Noise Plot
> : Displays the phase noise amplitude, in dBc/Hz, vs. offset from carrier
> when checked. You must have a span of 10 KHz or less, and the signal should
> be within 1 division of the reference level (e.g. within 10 dB). This
> utility takes about 1 minute to run. It will sweep several times, then
> combine the sweeps into a phase noise plot. The data is approximate and is
> limited by the phase noise of the SignalHound itself. For best close in
> phase noise, use an external 10 MHz reference with > 10 dBm power level. To
> resume normal operation,click "Phase Noise Plot" a second time to un check.
>
>
> Anyone fooled with one?  Think it might work as a low cost part of a phase
> noise test set.
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