[time-nuts] Bls: time-nuts Digest, Vol 130, Issue 38

Anton Moehammad moehanton at yahoo.com
Tue May 26 12:58:00 EDT 2015


Dear All
This is the first time I posted in this forum so please forgive me if its already discuss before
I like to ask You who has more experience about my plan for "USD75 GPSDO" before I explain my plan let me tell You some "real world" limitation 
1. The parts I choose must be available in local store (custom bussiness cost a lot of time)
2. I do not aim for something special a magnitude better than my MTI milliren OCXO is welcome.

Now What in my mind 
I will use Ublox 7m GPS board that can program from 0,25Mhz to 10Mhz
(https://sites.google.com/site/g4zfqradio/u-blox_neo-6-7)

But the problem are I found someone (http://www.ra3apw.ru/proekty/ublox-neo-7m/) already do the spectrum analysis for this board and the result is like this :
and the last picture is far better, correct ? so what I need to do I have 2 plan :
1. use the board 10Mhz output than use very narrow (100Hz bandwith) Crystal filter
2. Use the 4Mhz output than again filter it use Crystal filter to clean it than use it as reference for PLL for controling 10Mhz OCXO 
Which one you think a better way.
last I also like to know because MTI only spec the OCXO model 240 harmonics to down to -30dB (http://www.mti-milliren.com/pdfs/240.pdf) is there any benefit to use a crystal filter in the output to clearer it more.

any opinion is very welcome 
Thank You
Anton
 



     Pada Selasa, 26 Mei 2015 23:00, "time-nuts-request at febo.com" <time-nuts-request at febo.com> menulis:
   

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Today's Topics:

  1. Re: Terrestrial Tides and Land Movement (Bob Camp)
  2. Re: Terrestrial Tides and Land Movement (Bob Stewart)
  3. pp2s? No, 1pps from a Nortel GPSTM! (Nathaniel Bezanson)
  4. Re: FTS 8400 (Gregory Beat)
  5. Re: 3048A software question (davidh)
  6. Re: LTC6957 internal architecture (David C. Partridge)
  7. Re: pp2s? No, 1pps from a Nortel GPSTM! (Tom Van Baak)
  8. Re: 3048A software question (Chuck Harris)
  9. Re: Terrestrial Tides and Land Movement (Chuck Harris)
  10. Re: TymServe 2100 1995 Issue - A Kludgy Fix (Esa Heikkinen)


----------------------------------------------------------------------

Message: 1
Date: Mon, 25 May 2015 19:01:02 -0400
From: Bob Camp <kb8tq at n1k.org>
To: Bob Stewart <bob at evoria.net>, Discussion of precise time and
    frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Terrestrial Tides and Land Movement
Message-ID: <C83D4DA8-3E3D-462F-ABFF-3DAE1F645A69 at n1k.org>
Content-Type: text/plain; charset=utf-8

Hi

Let’s step back a bit:

Your module is accurate to maybe 2 ns over a short period of time and something in the 10 to 20 ns range
over 24 hours. The 2 ns comes from a variety of issues. The 20 ns comes mainly from the ionosphere.

One example of a part of the 2 ns - the satellite positions in orbit are only known to some level of accuracy. The
data your module gets is a broadcast data set that represents a “best guess” made yesterday to fit the fight 
path today. 

A GPS that does an on the fly position solution to 3M is not that exceptional these days. You certainly see
claims of performance at the 1M or even 0.5M level. Yes people do fudge the numbers. Yes they do use WAAS
and the like to improve things. 

A 3M error is at most a 10 ns timing error. It’s more likely to be a 3-4 ns timing error. That’s not all that big compared to the numbers above. 

Am I fudging the numbers a bit? Of course I am. There is an implicit assumption that the mobile platform has
a good view of the sky. Dropping below 4 sats would not happen in this case. I’d also upgrade the LEA-6T to 
an LEA-8T (or similar). More sats is going to give you a better position solution. 

The bottom line is that an L1 GPSDO that wanders 10 to 20 ns per 24 hours compared to a Cesium or maser is 
doing pretty well. Taking that to 8 to 18 ns  vs 12 to 22 is a worthy thing to do. *Proving* that a specific  implementation better … maybe not so easy. I’ve seen a lot of plots of well respected eBay GPSDO’s that wander
30 ns or more (peak to peak) per day one day and 20 ns p-p the next….

Bob 



> On May 25, 2015, at 5:28 PM, Bob Stewart <bob at evoria.net> wrote:
> 
> Hi Tom,
> I'm not sure what you mean by this 0D vs 3D.  I'm using an LEA-6T.  There are three time transfer modes 0=disabled, 1=survey-in, 2=fixed mode.  Are you suggesting that I set it to disabled to run a test?  I've never tried that.  I know that if I monitor the output while doing a survey, the phase is all over the place.
> I'm in the middle of a therm correction test at the moment, but the plots at the link below are essentially where I am in development.  The PRS-45A is driving the reference and start inputs of the 5370A.  I'm using a somewhat modified PID system.
> 
> http://evoria.net/AE6RV/Status/
> 
> Development is essentially over, at this point except for details, like adding code for the M12+ receiver.  I can post a link to the schematic, if there's interest, but I've decided that the code will remain proprietary.  This has turned into something a lot bigger than a $25 GPSDO engine.
> 
> Bob
>      From: Tom Van Baak <tvb at LeapSecond.com>
> To: Discussion of Precise Time and Frequency Measurement <time-nuts at febo.com> 
> Sent: Monday, May 25, 2015 3:09 PM
> Subject: Re: [time-nuts] Terrestrial Tides and Land Movement
> 
> Hi Bob,
> 
> You only need a survey if your timing receiver is running in zero-D mode. If you move the antenna more than some practical threshold you should adjust the fixed position or maybe just do another survey.
> 
> If you plan to move a lot, or if your application is mobile, or are on a slippery slope, or you just don't want to bother with a time-consuming survey, then run the timing receiver in 3D mode. As I said it will perform "almost as well". If you normally get, say 9 SV, I predict the timing accuracy difference is maybe only 10 or 20%.
> 
> You're still building a homebrew GPSDO, right? Collect a day of performance data in 0-D and then a day in 3-D and see what difference there is in RMS timing residuals (or in ADEV). I wonder if your GPSDO can even measure the difference.
> 
> /tvb
> 
> ----- Original Message ----- 
> From: "Bob Stewart" <bob at evoria.net>
> To: "Discussion of Precise Time and Frequency Measurement" <time-nuts at febo.com>
> Sent: Monday, May 25, 2015 11:09 AM
> Subject: Re: [time-nuts] Terrestrial Tides and Land Movement
> 
> 
> Tom said: "The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house."
> I don't get that. What's the purpose of doing a survey when you move your antenna if this the case?
> Bob
> 
> _______________________________________________
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------------------------------

Message: 2
Date: Tue, 26 May 2015 00:40:20 +0000 (UTC)
From: Bob Stewart <bob at evoria.net>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] Terrestrial Tides and Land Movement
Message-ID:
    <1737488028.1532538.1432600820263.JavaMail.yahoo at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

Hi Bob,
Thanks for taking the time to explain the 4ns and 20ns wanders.  I have just been calling them "constellation errors" without being able to explain it better than that.  I've also wondered how much of the 20ns, if any, is attributable to the PRS-45A.

I still don't have the antenna located in a position suitable for precision timing.  The power of the HOA is not to be trifled with.  That, and the sky is full of power lines and other junk around here.

Bob

      From: Bob Camp <kb8tq at n1k.org>
 To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Monday, May 25, 2015 6:01 PM
 Subject: Re: [time-nuts] Terrestrial Tides and Land Movement
  
Hi

Let’s step back a bit:

Your module is accurate to maybe 2 ns over a short period of time and something in the 10 to 20 ns range
over 24 hours. The 2 ns comes from a variety of issues. The 20 ns comes mainly from the ionosphere.

One example of a part of the 2 ns - the satellite positions in orbit are only known to some level of accuracy. The
data your module gets is a broadcast data set that represents a “best guess” made yesterday to fit the fight 
path today. 

A GPS that does an on the fly position solution to 3M is not that exceptional these days. You certainly see
claims of performance at the 1M or even 0.5M level. Yes people do fudge the numbers. Yes they do use WAAS
and the like to improve things. 

A 3M error is at most a 10 ns timing error. It’s more likely to be a 3-4 ns timing error. That’s not all that big compared to the numbers above. 

Am I fudging the numbers a bit? Of course I am. There is an implicit assumption that the mobile platform has
a good view of the sky. Dropping below 4 sats would not happen in this case. I’d also upgrade the LEA-6T to 
an LEA-8T (or similar). More sats is going to give you a better position solution. 

The bottom line is that an L1 GPSDO that wanders 10 to 20 ns per 24 hours compared to a Cesium or maser is 
doing pretty well. Taking that to 8 to 18 ns  vs 12 to 22 is a worthy thing to do. *Proving* that a specific  implementation better … maybe not so easy. I’ve seen a lot of plots of well respected eBay GPSDO’s that wander
30 ns or more (peak to peak) per day one day and 20 ns p-p the next….

Bob 

  

------------------------------

Message: 3
Date: Mon, 25 May 2015 22:08:21 -0400
From: Nathaniel Bezanson <myself at telcodata.us>
To: time-nuts at febo.com
Subject: [time-nuts] pp2s? No, 1pps from a Nortel GPSTM!
Message-ID: <1432606101373908991 at telcodata.us>
Content-Type: text/plain

As anyone with a Nortel GPSTM knows, it's a close cousin to the Thunderbolt but not exactly identical. Notably, coming from a CDMA environment, the unit has an "even second" output, aka PP2S, aka 0.5pps, aka 0.5Hz, etc. (Hoping to make this searchable...) There are software commands to configure this on the Thunderbolt too, but the GPSTM appears to have this function hard-coded into the PAL, and it can't be set back to PPS in software.
However, there exists a PPS signal on the PCB, at TP13 between the Trimble chip and the PAL, discovered by some folks at the hackerspace here, during some noodling-around with an oscilloscope this afternoon. It's all documented here:
https://www.i3detroit.org/wiki/Nortel_GPSTM
This is for a NTBW50AA-11 module (single long board), other parts may have the signal in different places but I bet it's in there. 
Enjoy!-Nate B-


------------------------------

Message: 4
Date: Mon, 25 May 2015 20:31:03 -0500
From: Gregory Beat <w9gb at icloud.com>
To: "time-nuts at febo.com" <time-nuts at febo.com>
Subject: Re: [time-nuts] FTS 8400
Message-ID: <06B6BAB6-8866-4FCA-BBE7-AD68AA9E0458 at icloud.com>
Content-Type: text/plain; charset=us-ascii

> Ole -
> 
> These became obsolete in 1999.  Actually led to development of TAC-2 board (TAPR) in 1996.
> Tom Clark, K3IO could tell you about the FTS 8400 usage with the 
> VLBI large dish array in 1980s and 1990s.
> 
> Scroll down the TAC32Plus software notes for discussion on Trimble FTS 8400. 
> https://www.cnssys.com/cnsclock/Tac32PlusSoftware.php
> 
> Greg
> w9gb
> 


------------------------------

Message: 5
Date: Tue, 26 May 2015 12:19:06 +1000
From: davidh <dhooke at gmail.com>
To: Discussion of precise time and frequency measurement
    <public-time-nuts-JSkTLETqlTM at plane.gmane.org>
Subject: Re: [time-nuts] 3048A software question
Message-ID: <5563D81A.6040604 at gmail.com>
Content-Type: text/plain; charset=windows-1252; format=flowed



Folks,

I'm also working on getting the MSDOS version running. What is the most 
recent version of DOS that people have found to work with the A 01.01 
version.

Also, can anyone advise where the command drivers for the 82335 can be 
found?

Cheers,

david

> Hi Adrian,
>
> Got the spec lines working now, thanks!
>
> Yes, the DOS version. I was hoping for an updated user manual for that version as the manual describes the other software version, and maybe a slightly later sw version. Oh well.
>
> Thanks for you help!
> Said
>
>
>
> On Feb 17, 2012, at 5:06, Adrian <rfnuts-KvP5wT2u2U0 at public.gmane.org> wrote:
>
>> Said,
>>
>> are you using the Opt. 311 (MS-DOS) software?
>> I don't know of any more recent versions.
>>
>> To answer your initial question:
>> You can not change anything on the diagram _after_ the measurement, not even the title.
>> The spec lines will be visible only when you have defined them prior to starting the measurement.
>>
>> Regards,
>> Adrian
>>
>>
>> SAIDJACK-YDxpq3io04c at public.gmane.org schrieb:
>>> Hello team,
>>>
>>> I am trying to get an HP 3048A system up and running, and I am having
>>> problems with enabling spec limit lines on the graph.
>>>
>>> I can enter the spec line data under the "manipulate results" then "spec
>>> lines" menu, but the lines I entered are not visible. There are the standard
>>> spec lines visible when I do the internal noise floor test, so I know this
>>> should work.
>>>
>>> Does anyone know how to enable these properly? The user manual doesn't talk
>>>  about this, and it is written for an older version of the software
>>> anyway's.
>>>
>>> Also, I have software version A 01.01 from 1994, does anyone have any more
>>> recent software version?
>>>
>>> Thanks in advance,
>>> Said
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts-JSkTLETqlTM at public.gmane.org
>>> 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-JSkTLETqlTM at public.gmane.org
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>




------------------------------

Message: 6
Date: Tue, 26 May 2015 09:51:26 +0100
From: "David C. Partridge" <david.partridge at perdrix.co.uk>
To: "'Discussion of precise time and frequency measurement'"
    <time-nuts at febo.com>
Subject: Re: [time-nuts] LTC6957 internal architecture
Message-ID: <81474EBE905B4522A24C6B8FFE76BB7D at APOLLO>
Content-Type: text/plain;    charset="utf-8"

With all this talk of the LT6957 I'm wondering if there's interest in a re-spin of my frequency divider with one of these at the front end instead.

Regards,
David Partridge 
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
Sent: 26 May 2015 00:40
To: time-nuts at febo.com
Subject: [time-nuts] LTC6957 internal architecture

The following patent hints that the LTC6957 front end probably consists of several cascaded long tailed pair differential amplifier stages each with a selectable bandwidth set by capacitors shunting the collector load resistors. : US8319551 The input limiter is in effect a Collins style limiter with selectable bandwidth for each stage to reduce the noise with respect to a comparator which typically has several high gain wide bandwidth cascaded differential amplifier stages.

Bruce


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time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.



------------------------------

Message: 7
Date: Tue, 26 May 2015 05:09:05 -0700
From: "Tom Van Baak" <tvb at LeapSecond.com>
To: "Discussion of precise time and frequency measurement"
    <time-nuts at febo.com>
Subject: Re: [time-nuts] pp2s? No, 1pps from a Nortel GPSTM!
Message-ID: <75D41F5911C04B70A87A2FB2EE8F993B at pc52>
Content-Type: text/plain;    charset="utf-8"

Hi Nate,

Nice page. Thanks for sharing your work.

The Nortel units are a reasonable and slightly cheaper alternative to a TBolt, if you don't mind the much larger size, mass, and non-standard connector issues.
The performance depends somewhat on which vendor's oscillator was used. I tested a bunch here:
http://www.leapsecond.com/pages/nortel/
For NTP none of these plots matter (most GPSDO are a thousand to a million times more stable than NTP or a PC can handle).

/tvb

----- Original Message ----- 
From: "Nathaniel Bezanson" <myself at telcodata.us>
To: <time-nuts at febo.com>
Sent: Monday, May 25, 2015 7:08 PM
Subject: [time-nuts] pp2s? No, 1pps from a Nortel GPSTM!


> As anyone with a Nortel GPSTM knows, it's a close cousin to the Thunderbolt but not exactly identical. Notably, coming from a CDMA environment, the unit has an "even second" output, aka PP2S, aka 0.5pps, aka 0.5Hz, etc. (Hoping to make this searchable...) There are software commands to configure this on the Thunderbolt too, but the GPSTM appears to have this function hard-coded into the PAL, and it can't be set back to PPS in software.
> However, there exists a PPS signal on the PCB, at TP13 between the Trimble chip and the PAL, discovered by some folks at the hackerspace here, during some noodling-around with an oscilloscope this afternoon. It's all documented here:
> https://www.i3detroit.org/wiki/Nortel_GPSTM
> This is for a NTBW50AA-11 module (single long board), other parts may have the signal in different places but I bet it's in there. 
> Enjoy!-Nate B-



------------------------------

Message: 8
Date: Tue, 26 May 2015 08:41:52 -0400
From: Chuck Harris <cfharris at erols.com>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] 3048A software question
Message-ID: <55646A10.6020200 at erols.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

The easiest way of getting a new well supported version of
DOS, is to download FreeDOS.  Anything that worked on any
version of MSDOS will run under FreeDOS... and so much more!

-Chuck Harris

davidh wrote:
>
>
> Folks,
>
> I'm also working on getting the MSDOS version running. What is the most recent
> version of DOS that people have found to work with the A 01.01 version.
>
> Also, can anyone advise where the command drivers for the 82335 can be found?
>
> Cheers,
>
> david


------------------------------

Message: 9
Date: Tue, 26 May 2015 08:39:44 -0400
From: Chuck Harris <cfharris at erols.com>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] Terrestrial Tides and Land Movement
Message-ID: <55646990.3050502 at erols.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

Hi Bob S,

An HOA can be a daunting problem, but not one that cannot be
solved with a little guile.

Every house I have ever seen that has modern plumbing has a few
vent stacks on the roof.  Would the HOA even notice if yours
sprouted another one dark weekend evening?

All the kit you need to add one to your roof is available at
your local big box store.

The usual bullet style antenna, sitting on top of a PVC vent
pipe would be invisible on most houses, particularly if it were
to be placed in the same vicinity as the rest.

Also, GPS bullet antennas are pretty well sealed, save for the
connector on the bottom.  If you do a good job of sealing the
connector (eg. lots of wraps of electrical tape, followed by
a few of friction tape) there in no intrinsic reason you couldn't
safely mount yours on top of the main plumbing vent stack.  Drill
a hole in the side at some convenient spot inside of the house,
and snake the coax up through the vent stack, mount the antenna
over the top, leaving adequate vent space.  (OBTW, it isn't a
vent stack until it is above the highest fixture in the house.)

Although I don't have an HOA on my farm, I have my antenna mounted
that way on my radon mitigation pipe.  I bent up a couple of
pieces of aluminum to make an open plug and put the antenna up
without ever setting foot on my roof.  I simply snaked the cable
up and out the top of the radon pipe, and when I could reach it
from a window, installed the GPS antenna, and aluminum "plug",
and then pulled the antenna cable back through the pipe, causing
the plug and antenna to pop into the pipe mounting the antenna.

-Chuck Harris

Bob Stewart wrote:
> Hi Bob, Thanks for taking the time to explain the 4ns and 20ns wanders.  I have
> just been calling them "constellation errors" without being able to explain it
> better than that.  I've also wondered how much of the 20ns, if any, is
> attributable to the PRS-45A.
>
> I still don't have the antenna located in a position suitable for precision
> timing.  The power of the HOA is not to be trifled with.  That, and the sky is
> full of power lines and other junk around here.
>
> Bob


------------------------------

Message: 10
Date: Tue, 26 May 2015 17:18:47 +0300
From: Esa Heikkinen <tn1ajb at nic.fi>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] TymServe 2100 1995 Issue - A Kludgy Fix
Message-ID: <556480C7.2090106 at nic.fi>
Content-Type: text/plain; charset=UTF-8; format=flowed

descoubes kirjoitti:

> I am very pleased to inform you that the 1995 year bug on the TS2100 has 
> been solved. You will have to replace the existing Trimble ACE III
 > GPS receiver by our N024 with special firmware.

Does this also correct the 1 sec offset caused by upcoming leap second? 
To remind, TS2100 GPS mode failed already in February, having 1 sec 
offset right after the information about upcoming leap second was added.

How can we know that it doesn't fail again when actual GPS week rollover 
will happen? Now it seems to be week 1846 and 2047 will come less than 
four years. Did you test this with GPS simulator?

Best regards,

-- 
73s!
Esa
OH4KJU


------------------------------

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------------------------------

End of time-nuts Digest, Vol 130, Issue 38
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