Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[bg]

Citerar Mark Sims :

In the standards definitions that include "at sea level", the  
question these days is "which sea level?".  As ocean temperature  
changes sea level will change (except maybe in Washington DC).  Will  
the standards be amended to include something like "at sea level in  
1990" or will the value being defined drift around with the changing  
sea level?


From the current Swedish vertical datum.  
(http://www.lantmateriet.se/globalassets/kartor-och-geografisk-information/gps-och-matning/geodesi/rapporter_publikationer/rapporter/lmv-rapport_2007_4.pdf)


 "This realisation was made using the Normaal Amsterdams Peil (NAP)  
as zero level
in the traditional European way. [...] It has for instance been  
questioned whether NAP is the most suitable way to fix the
zero level. Is it not better to wait for a so-called World Height  
System (WHS), which is fixed using GPS and a global geoid model of cm  
accuracy?"


Has the World Height System been agreed/released?

  http://www.euref.eu/documentation/Tutorial2015/t-04-02-Ihde.pdf

Picture showing reference origin for vertical datums in Europe.

  https://en.wikipedia.org/wiki/File:Vertical_references_in_Europe.svg

--

 Björn


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Re: [time-nuts] Ships fooled in GPS spoofing attack suggest Russian cyberweapon

[bg]

Hi Martin,
No there was also a SDR hack to spoof.
http://www.rtl-sdr.com/cheating-at-pokemon-go-with-a-hackrf-and-gps-spoofing/
--
     Björn


Sent from my smartphone.
 Original message From: Martin Burnicki 
 Date: 14/08/2017  11:42  (GMT+01:00) To: 
Discussion of precise time and frequency measurement  
Subject: Re: [time-nuts] Ships fooled in GPS spoofing attack suggest Russian
  cyberweapon 
Clint Jay wrote:
> Absolutely, their use of it was for something trivial and my reason for
> using that example was to show how 'simple' and available the technology is
> if a couple of students could do it with lab equipment that anyone can buy
> (obviously you'd need deep pockets).

I just searched for "Pokémon GO GPS spoofing" on the 'net.

Looks like this was just a hack in Android where apps were provided with
a spoofed position from the hack instead of the true position determined
by the GPS/GNSS receiver.

So this is quite a different thing than spoofing the real GPS signals,
and it only affects the devices which have that hack installed.

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Re: [time-nuts] TU30 jump second

[bg]

Hi Bob & Bo,
This was discussed a long time ago on 
    http://www.gpskit.nl/forum/
which is defunced since many years. To measure the delay I suggest setting it 
up as a NMEA refclock to ntpd. But fudge it so that it is only collecting data 
to watch and log the offsets. IIRC delays for the receiver I had was 1013ms or 
2013ms in NMEA-mode.
1024 wk issues are not related to this. And as discussed many times in the 
archives. Rx firmware programmers often checked dates to see if they were older 
than say the firmware release date. If so they added 1024wk. Thus the magic 
rollover-dates are often not the actual problem dates.
--
     Björn

Sent from my smartphone.
 Original message From: Bob kb8tq  Date: 
04/04/2017  17:47  (GMT+01:00) To: timen...@rudius.net, Discussion of precise 
time and frequency measurement  Subject: Re: [time-nuts] 
TU30 jump second 
Hi


> On Apr 4, 2017, at 10:01 AM, Bo Hansen  wrote:
> 
> Hi all
> 
> The data can be a bit hard to read in an email. So I will give it another try.
> 
> PC-time | Diff. | GPS-time | Diff.
> ...
> 011606.005 | 0.992 | 011604 |1
> 011607.013 | 1.008 | 011605 |1
> 011608.005 | 0.992 | 011607 |2 <--- The issue
> 011609.013 | 1.008 | 011608 |1
> 011610.004 | 0.991 | 011609 |1
> ...
> 
> I used a terminal program to log the NMEA data to a file and do the PC 
> timestamp. Calculations were done in a spreadsheet by me. The PC-time is kept 
> under control by Meinberg and also OK vs.  during the 
> time of observation.
> 
> The PC-timestamp wobble is not the issue. It is a combination of the PC-time 
> itself and the NMEA wobble. Nobody should expect the NMEA data to come at the 
> same time every time relative to the 1 PPS. As Björn correctly points out it 
> is always late and wobbles with processor load.
> 
> Sometimes the 2-something lag can last for many hours - I have seen more than 
> 48 h.
> 
> The issue is the "seconds jump". The issue is not the relative difference 
> between the PC-time and the GPS-time but the jump, e.g. using Tac32 reveals 
> that the TU30 is always ~1200 ms late on in case of the "jump second" ~2300 
> ms late.
> 
> I wonder if it has anything to do with the Week 1024 Syndrome?

We are roughly 2 years away from the next week 1023 to week 0 GPS rollover 
point. If you see this multiple times in a 20 year period
it is not a 1024 week issue ….

Bob

> 
> Indeed the TU30 is a old device. I guess some 30 years if not more looking at 
> the components. F/W I have no idea.
> 
> The 10 kHz seems unaffected.
> 
> Bo
> 
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Re: [time-nuts] ADEV query Timelab and TICC

[bg]

Look at ICD-GPS-060.
10V into 50ohm, sub 50ns risetime and 20us pulse lenght is specified in figure 
3-2.
--     Björn


Sent from my smartphone.
 Original message From: Hal Murray  
Date: 21/03/2017  19:18  (GMT+01:00) To: Tom Van Baak , 
Discussion of precise time and frequency measurement  Cc: 
hmur...@megapathdsl.net Subject: Re: [time-nuts] ADEV query Timelab and TICC 

t...@leapsecond.com said:
> The TAPR dividers tend not to have "this problem" because they output at
> wimpy TTL/CMOS levels.

Modern CMOS drivers have fast rise times.  As long as the rise time is short 
relative to the cable length, it gets doubled if the end of the cable is an 
open circuit.

> Older equipment can have powerful outputs. 10V into 50R is, what, 1/5th of
> an amp? Logarithmically, that puts a 5061A 1PPS closer to an automobile
> starter motor or heart defibrillator compared to modern logic gates. 

There is a big difference across logic families.  Many can drive 50 ohms.

RS-232 drivers are explicitly limited to reduce EMI.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] time/sampling behavior of RTL-SDR

[bg]

Hi Jim,
Did you look at the below article?
http://www.rtl-sdr.com/a-multi-channel-coherent-rtl-sdr-product-for-passive-radardirection-finding-and-more/
--     Björn
Sent from my smartphone.
 Original message From: jimlux  Date: 
07/03/2017  22:08  (GMT+01:00) To: Discussion of precise time and frequency 
measurement  Subject: [time-nuts] time/sampling behavior of 
RTL-SDR 
Has anyone ever looked at the timing consistency/behavior of the cheap 
RTL-SDR dongles?

That is, if you feed a sine wave in and get the samples out via the USB 
interface, are there missing samples?  What's the ADC clock look like?

If you had two of them, and you determine the relative phase of them at 
some time t0, and you let it run for minutes, how far will it have moved?



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Re: [time-nuts] Temperature (environmental) sensors

[bg]

I like the Bosch BME280 conneced to a Raspberry PI.
https://learn.adafruit.com/adafruit-bme280-humidity-barometric-pressure-temperature-sensor-breakout/pinouts
https://github.com/adafruit/Adafruit_Python_BME280/blob/master/README.md
--   Björn
Sent from my smartphone.
 Original message From: Bob Camp  Date: 
03/01/2017  19:36  (GMT+01:00) To: Discussion of precise time and frequency 
measurement  Subject: Re: [time-nuts] Temperature 
(environmental) sensors 
Hi

There’s always the “cool factor” of higher resolution. Apparently it’s not 
enough
of a issue to make it a worthwhile market to serve.  

Based on what has been tossed around, it sounds like an Arduino with some 
bits plugged in is the low cost leader. 3D print up and enclosure and you have 
it all in a some large form factor.

Bob

> On Jan 3, 2017, at 12:54 PM, jimlux  wrote:
> 
> On 1/3/17 9:15 AM, Bob Camp wrote:
>> Hi
>> 
>> There is an ever increasing pool of good sensors to put into something like 
>> this.
>> (More so for temperature and pressure. Humidity still is a bit of an issue.)
>> There’s not a lot to interface between the sensor and a USB “chip”. It’s 
>> surprising
>> that there aren’t more cheap / high accuracy choices out there.
>> 
> 
> 
> the market probably isn't there for a cheap "pod" with an interface and high 
> accuracy..
> 
> The Lascar units (and similar $100-ish ones from others) meet most of the 
> existing need fairly well (e.g. monitoring the temperature of your freezer 
> for FDA regulatory compliance, monitoring the temp and humidity in your ESD 
> controlled space)..
> 
> The need for 0.1 degree C room temp measurement is, I think, fairly limited
> 
> 
> 
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Re: [time-nuts] TrueTime/Symmetricon XL-AK date reset failure

[bg]

Hi Joe!
The Gps receiver module inside the XL-AK could have been hit by the 1024 week 
problem.
Do the XL box have a display showing date/year? What does that show?
--    Björn

Sent from my smartphone.
 Original message From: Joe Pendergrass  
Date: 02/01/2017  23:29  (GMT+01:00) To: time-nuts@febo.com Subject: 
[time-nuts] TrueTime/Symmetricon XL-AK date reset failure 
Hello, all. I am a new member, having discovered this forum a few days ago,
whilst doing a Google search looking for current telephone contact
information for TrueTime/Symmetricon technical support.

 

For many years I've had a TrueTime/Symmetricon Model XL-AK GPS time &
frequency receiver in service here, which drives multiple serially slaved
9-digit LED IRIG-B remote readouts spread around my station. They display
the day-of-the-year [counted up from 1/1] and the satellite GMT time. At
midnight on each January 1st, the display always updated to reflect the
coming of a new calendar year, and the day-of-the-year on the remote
displays would reset to "0" [Zero]. On 1/1/2016, I noticed that the day
counter display did not automatically reset to zero, and start over. The day
counter display continued increasing incrementally, until 139 days ago, it
finally reset itself to zero and started incrementally increasing again from
[day] 1. Which means that the day-of-the-year counter function currently
reads "139," when it should read "2." The time display has always remained
accurate. I had hoped the day counter issue would resolve itself at midnight
on 1/1/2017; but nothing changed. 

 

I know that the TrueTime/Symmetricon XL-AK and XL-DC GPS receivers are
popular, and now that I have discovered this forum; I would like to solicit
feedback as to what the root of the problem is and how to remedy it, from
anyone on the forum having personal experience with this line of GPS
receivers. Ideas???

 

Thanks de Joe-W6VI

 

 

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Re: [time-nuts] GALILEO online: any changes seen?

[bg]

The key change is that now there is a "Service definition document" for each 
service entering Initial Services. Thus there is a Quality (or lack) of service 
defined for each signal.
--
     Björn


Sent from my smartphone.
 Original message From: Tim Shoppa  Date: 
15/12/2016  19:54  (GMT+01:00) To: Discussion of precise time and frequency 
measurement  Subject: Re: [time-nuts] GALILEO online: any 
changes seen? 
David, several of your satellite count graphs show a slow upward trend
throughout this calendar year, with a bump up for the month of October,
falling back down for part of November, then another step up at the
beginning of December.

http://www.satsignal.eu/mrtg/performance_gps.php?period=year

This is particularly clear on the graph labeled "u-blox MAX-M8Q" on
"RasPi-10", showing a sharp uptick since December 1.

Could this be Galileo or hard to say?

Or maybe just leaves falling off of the trees? :-)

Tim N3QE

On Thu, Dec 15, 2016 at 10:43 AM, David J Taylor <
david-tay...@blueyonder.co.uk> wrote:

> Dear all,
> the GALILEO system is supposed to go online today (at least for initial
> operational capability). Does anybody of you has a GALILEO compatible
> receiver and sees already a difference?
>
> Best regards,
> Achim
> 
>
> Achim,
>
> I'm not sure whether the signals were turned on today, or whether they
> have been there for some time but just in a pre-operational status.
>
> I think all my receivers which /might/ be able to get Galileo need an
> update, and I've not seen any change in the number of satellites
> potentially visible according to gpsd, at least:
>
>  http://www.satsignal.eu/mrtg/performance_gps.php
>  http://www.satsignal.eu/mrtg/performance_gps.php?period=month
>  http://www.satsignal.eu/mrtg/performance_gps.php?period=year
>
> I heard that for some receivers, it was a choice of Galileo or
> GPS/GLONASS. I would be helpful if a list of Galileo receivers were
> available.  I did one mobile phone which offered Galileo - but "in a future
> update"...
>
> Cheers,
> David
> --
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-tay...@blueyonder.co.uk
> Twitter: @gm8arv
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Re: [time-nuts] How can I measure GPS Antenna quality?

[bg]

Hi Atilla,
Read the document below
https://www.ngs.noaa.gov/ANTCAL/docs/NGSantcalprocedures.pdf
And the reference within
        antenna_README.pdf
Antennas are generally not calibrated individually by the user. You make sure 
the antenna you buy are in the ANTCAL or Geo++ lists. Any use of a snow cone 
should be with one the antenna was measured with.
Browse around for your favorite antenna vendor at
https://www.ngs.noaa.gov/ANTCAL/
MfG
     Björn
Sent from my smartphone.
 Original message From: Attila Kinali 
Now I wonder how the calibration data for mass produced geodetic antenna
are collected. I very much doubt they put them outside for a couple
of days to measure them exactly.

Attila Kinali
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Re: [time-nuts] L1 L2 choke Ring Question

[bg]

Hi,
There is(was) a 26dB lna in that antenna.
--
   Björn

Sent from my smartphone.
 Original message From: Magnus Danielson 
 Date: 20/11/2016  21:42  (GMT+01:00) To: 
time-nuts@febo.com Cc: mag...@rubidium.se Subject: Re: [time-nuts] L1 L2 choke 
Ring Question 
Tom,

If I recall correctly, that antenna element is passive and I expect 
there to be an amplifier there. The antenna element you can find 
separately on ebay.

Cheers,
Magnus

On 11/20/2016 08:48 PM, Tom Knox wrote:
> I recently purchased a used L1 L2 Choke ring antenna AeroAntenna 
> AT2775-20W-000-05-26-NM, it has an AT2775 aircraft antenna with a 3.3" x 1.8" 
> bolt pattern at it's heart.
>
> Sadly the antenna is dead. I have been looking into the possibility of 
> replacing the aircraft antenna portion and was wondering what the critical 
> specs were and the approximate tolerances. I found an antenna from another 
> manufacturer with the exact bolt pattern, but it appears the phase center is 
> 1-2mm lower.
>
> Any thoughts would be greatly appreciated.
>
> Or if anyone has a AeroAntenna AT2775 aircraft antenna with a 3.3" x 1.8" 
> bolt pattern they would be willing to sell or trade contact me off list.
>
> Thanks!
>
>
> Thomas Knox
>
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Re: [time-nuts] Ashtech Z-12 firmware?

[bg]

Hi Gregory,
For a long time ftp://ftp.ashtech.com was useful.
--
     Björn


Sent from my smartphone.
 Original message From: Gregory Maxwell  
Date: 27/08/2016  01:34  (GMT+01:00) To: Discussion of precise time and 
frequency measurement  Subject: [time-nuts] Ashtech Z-12 
firmware? 
I recently picked up a couple non-functional Ashtech Z-12 receivers
with the external frequency input (these appear to PLL an internal
TCXO; I understand there are other models where they replace the TCXO
completely).

I was hoping to use them both better data sources for common view time
transfer with better performance than the GPS L1/CA  that I've been
using; as well as using them for ground truth data for a SDR
semi-codeless CRPA receiver I'm slowly building.

These units were hanging at startup at "Downloading channel". I
determined that they would work a single time if the memory were
cleared (by holding an arrow, right for external up for internal,
during start). Because the internal 3.6v primary cell batteries were
reading about 40mv I took a guess that the low battery was causing
memory corruption across restarts.

New batteries and a bit of soldering later, and they are working
reliably across restarts, locking sats on L1/L2, talking on RS232,
etc. (hurrah).  Hopefully this message in the archives is useful if
someone else encounters similar symptoms.

Before I go further I was wondering if anyone knew of a source for
firmware for these old units?  One of mine is marked "Z-12 700751-6
(b)", unfortunately it seems ashtech has been sold many times, and the
old web/ftp sites have been scattered to the wind.

The nearest I was able to find was this page
http://kb.unavco.org/kb/article/astech-micro-z---firmware,-firmware-release-notes,-firmware-upload-programs-and-how-to-use-them-368.html
 with micro-Z firmware.

[If there is a relevant GNSS nuts list, I'd be glad to hear about it--
my interest is in CVTT but perhaps somewhere else there is a den of
people obsessed with old survey hardware that would prefer these
questions.]
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Re: [time-nuts] Q/noise of Earth as an oscillator

[bg]

A bit short on the phone...
Both the ECI and ECEF frames are rotating at sidreal rate. The earth rate is (a 
small) part of the navigation equations. Thus its needed in inertial nav.
Glenn, look at the performance of the big land RLGs - NZ and German that were 
linked last week. How much better are those compared to your (also extremely 
good) sub gyros.--     Björn




Sent from my smartphone. Original message From: Tom Van Baak 
 Date: 01/08/2016  20:01  (GMT+01:00) To: Discussion of 
precise time and frequency measurement  Subject: Re: 
[time-nuts] Q/noise of Earth as an oscillator 
Hi Glenn,

Your 15.04 number rings a bell [1]. The conventional solar day is simply 86400 
seconds (24 hours). So each hour is 15 degrees, exactly.

But the actual (sidereal) earth rotation rate is about 86164 SI seconds (23h 
56m 4.091s). So each hour is 15.0411 degrees.

Someone who understands celestial mechanics or an ex-Navy person with sextant 
skills could explain better, but I bet that's where your 15.04 number comes 
from.

/tvb

[1] http://www.navy.mil/navydata/questions/bells.html ;-)

- Original Message - 
From: "Glenn Little WB4UIV" 
To: "Tom Van Baak" ; "Discussion of precise time and 
frequency measurement" 
Sent: Monday, August 01, 2016 10:38 AM
Subject: Re: [time-nuts] Q/noise of Earth as an oscillator


In navigation we used the earth rate of 15.04 degrees per hour.
This was treated as a 'constant' even though it varied with wind, waves 
on the ocean and other things affecting the instantaneous rotational 
speed of the earth.

How does this factor into leap seconds, or, does it?

We accept that the day is 24 hours long, this would be for a earth 
rotational speed of 15.0 degrees per hour.

I am not a mathematician, but, I dis do electronic navigation on submarines.

73
Glenn
WB4UIV


On 8/1/2016 10:54 AM, Tom Van Baak wrote:
> Hi Jim.
>
>> You said: "you need energy; you need energy loss; you need cycles over which 
>> that loss repeatedly occurs."
>> With regard to the earth, where is the first one?
>
> By first one, do you mean where does the initial energy come from?
>
> For a pendulum clock, you supply energy with a lift or a push. For a lift to 
> the side, E = mgh, where h is the height above the base. For a push from 
> center, E = 1/2 mv^2. Either way, it takes all the potential or kinetic E you 
> provide and starts making time from there.
>
> For a rotating clock, you just give it a twist. In this case, E = 1/2 Iw^2, 
> where I is the moment of inertia and w (omega) is angular velocity. For earth 
> the total E is 2.1e29 J. That's the energy number you want, yes?
>
>> Sure it was there at the start when the solar system formed, but where is it 
>> now?
>
> I don't have data on where the initial swirl of solar system mass came from, 
> or how much of that rotational energy went into our planet and its pesky 
> moon, or Who or what gave that initial twist. The Q is pretty high so I 
> assume you could work backwards, but I leave that to astronomers and 
> cosmologists. I believe the 2 ms/day / century estimate we use is one such 
> measurement.
>
> For more on earth rotation rate, UTC and leap seconds see 
> https://www.ucolick.org/~sla/leapsecs/dutc.html
>
> Surely in the literature there is a pile of information or speculation 
> regarding all the rotational energy in the universe. It seems a common theme 
> everywhere you look; maybe it was as much Big Twist as Big Bang? Perhaps in 
> your Pulsar research you've run across some papers you could share. Off-list 
> is ok, unless you think it has general time-nuts appeal. We're running the 
> risk of spinning off-topic already.
>
> Thanks,
> /tvb
>
> - Original Message -
> From: "Jim Palfreyman" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Sunday, July 31, 2016 7:34 PM
> Subject: Re: [time-nuts] Q/noise of Earth as an oscillator
>
>
> Hi Tom,
>
> You said: "you need energy; you need energy loss; you need cycles over
> which that loss repeatedly occurs."
>
> With regard to the earth, where is the first one? Sure it was there at the
> start when the solar system formed, but where is it now?
>
> Jim
>
>
> On 1 August 2016 at 12:16, Tom Van Baak  wrote:
>
>> Hal:
>>> Is there a term other than Q that is used to describe the rate of energy
>> loss
>>> for things that aren't oscillators?
>>
>> Jim:
>>> cooling (as in hot things)
>>> discharge (as in capacitors and batteries)
>>> leakage (as in pressure vessels)
>>> loss
>>
>> Scott:
>>> An irreversible process would be a better description versus energy loss.
>>> Like joule heating (resistance, friction).
>>
>> Notice that these are all energy losses over time; gradual processes with
>> perhaps an exponential time constant, but without cycles or periods. We
>> know not to apply Q in these scenarios.
>>
>> But when you have an oscillator, or a resonator, or (as I suggest) a
>> "rotator", it seems to make sense to use Q to describe the normalized 

Re: [time-nuts] Q/noise of Earth as an oscillator

[bg]

http://www.prc68.com/I/Sensors.shtml#Gyroscopic
"A note on gyros.  When located in a dynamic platform, like an airplane, the 
gyro needs to be located at the center of mass of the vehicle.  This way when 
the plane banks, pitches or yaws the gyro will only respond to the angles.  But 
if it's located anywhere else it will be in error.  This applies to models as 
well as to full size vehicles."
This is not true. You can - and people do - mount gyros (interial systems) 
anywhere in the rigid part of the body - wingtip mount might be a bad idea...
If the gyro is away from the center of rotation it will experience the same 
rotation and also an acceleration. The chosen gyro should be good enough at 
separating rotation from acceleration. This has not been a problem for a very 
long time - 40+ years - for typical aviation nav systems.
For specialized applications - say spinning munitions - where your performance 
is really limited by acceleration - you should keep your sensors at the center. 
The same could be said for accelerometers, oscillators and many other sensors 
that might have errors amplified by the extra acc.
--      Björn




Sent from my smartphone. Original message From: Brooke Clarke 
 Date: 27/07/2016  01:00  (GMT+01:00) To: Discussion of 
precise time and frequency measurement  Subject: Re: 
[time-nuts] Q/noise of Earth as an oscillator 
Hi Hal:

I resemble that remark.

Momentum and drift.  It's interesting that the drift rate depends on the 
physical volume.  See table at: 
http://www.prc68.com/I/Sensors.shtml#Gyroscopic
http://www.prc68.com/I/Gyroscopes.html

-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 
> att...@kinali.ch said:
>> I am not sure you can apply this definition of Q onto earth. Q is defined
>> for harmonic oscillators (or oscillators that can be approximated by an
>> harmonic oscillator) but the earth isn't oscillating, it's rotating. While,
>> for time keeping purposes, similar in nature, the physical description of
>> both are different.
> What do gyroscope-nuts use to describe the quality of their toys?
>
>

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Re: [time-nuts] Warped back to 1993

[bg]

As has been discussed here before.

The GPS firmware programmer finalizing his stuff at GPS week X (approaching 
1024) will make sure his receiver will survive until X weeks into the next era. 
What X is is hard for the end user to know. 1024 weeks is long time beyond 
normal warranties. 

I have seen era predictions based on # of leap seconds. But that particular 
implementation did not fare well with long leapsecondless periods we had.

/Björn



Skickat från min Mobil 

 Originalmeddelande 
Från: "Mark C. Stephens"  
Datum: 2013-08-11  11:04  (GMT+01:00) 
Till: Discussion of precise time and frequency measurement  
Rubrik: Re: [time-nuts] Warped back to 1993 
 
Yep Sorry, I see what you mean, can't be the GPS week rollover bug then.
I am at a loss to explain this one then.


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Mark C. Stephens
Sent: Sunday, 11 August 2013 6:33 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

Please explain what happened today then?
Also, the 2 module that I cannot set to the correct date are both Furino 
GT-77's.
Over on the NTP list they are claiming it's the start of the new GPS 1024 week 
epoch.
If you have a look at the rest of the days here: http://adn.agi.com/GNSSWeb/ 
Today was special.



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Azelio Boriani
Sent: Sunday, 11 August 2013 6:17 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Warped back to 1993

Yes. This week is not the start of a new epoch.

On Sun, Aug 11, 2013 at 10:10 AM, Hal Murray  wrote:
> ma...@non-stop.com.au said:
>> Today is start of new epoch.
>> As per: http://adn.agi.com/GNSSWeb/
>> 1753:0  Full GPS week since 1st epoch : day of week number
>> 729:0 GPS Week since latest epoch : seconds of week at midnight for 
>> that day
>
> I don't think so.  If this was a new epoch, that 729 would be 0 and 
> the 1753 would be 2048.
>
> The 0s above are the day of week and seconds of week, nothing to do 
> with the epoch.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] Trimble Nortel GPSTM Boards

[bg]

Hi Nigel!

This has been discussed before in time-nuts. I have two of the big boards, but 
they are not running right now. If I remember correctly the big ones are more 
of a cost reduction model compared to the 2 board split solition. Giving lower 
SV snr than the split version. 

But my ran just fine compared to my standard Tbolts.

--
    Björn


Skickat från min Mobil 

 Originalmeddelande 
Från: gandal...@aol.com 
Datum: 2013-08-01  11:09  (GMT+01:00) 
Till: time-nuts@febo.com 
Rubrik: Re: [time-nuts] Trimble Nortel GPSTM Boards 
 
Hi Charles

Thanks for your comments, the surveyed position on this is looking pretty  
good but what I have now realised is that the severity of the jumps  seems 
very much related to the number of sattelites being tracked.

Switching from 8 to 7, or 7 to 8, sats seems to produce the biggest  step 
change whilst switching in either direction between 5 and 6, for  example, 
doesn't seem to show up at all on the monitored DAC voltage.
Ok, I take that back, it does still seem to depend on the number of sats  
being switched between but I've just seen a switch from 5 to 4 sats induce a  
very noticeable step change in DAC voltage, so the relationship  doesn't 
appear to be linear.

Unfortunately I need to power this down now for a few days but  will 
investigate more later.

Regards

Nigel
GM8PZR


In a message dated 01/08/2013 09:45:24 GMT Daylight Time,  
charles_steinm...@lavabit.com writes:

Nigel  wrote:

>at times I'm seeing very noticeable step changes in the DAC  voltage 
>on this one as that happens.
>   *   *   *
>I am a bit surprised by the extent, a  Mark Sims online plot from 
>2012 shows some correlation on an NTGS50AA  but not as noticeable as 
>this, and I  don't recall seeing  anything quite so pronounced on a 
Thunderbolt.

IME (with TBolts), the  magnitude of the DAC steps with constellation 
changes varies with the  accuracy of the positional data used by the 
GPS.  To a point, the  more accurate the survey, the smaller the DAC 
jumps will be.  (Other  errors prevent reducing the 
constellation-change DAC steps to  zero.)

Mark has commented here on survey accuracy, and the methods he  used 
in Lady Heather to maximize it.

Best  regards,

Charles




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Re: [time-nuts] Story in the Economist about GPS jamming

[bg]

Satnav are not LEO but MEO. Which is good - less sv to cover the earth. Less 
good because distance is higher compared to LEO regarding signal power at earth.

 --

Björn


Skickat från min Mobil 

 Originalmeddelande 
Från: Scott McGrath  
Datum: 2013-07-30  14:50  (GMT+01:00) 
Till: j...@quikus.com,Discussion of precise time and frequency measurement 
 
Kopia: Discussion of precise time and frequency measurement 
 
Rubrik: Re: [time-nuts] Story in the Economist about GPS jamming 
 
Any competent engineer could have told the powers that be that a satellite 
system based in LEO has a relatively high risk profile from the 
Universe/hostile activity/spoofing and jamming

Yes GPS is/was oversold.  

Trouble is Clarkes law applies here (any sufficiently advanced technology is 
indistinguishable from magic).  And this applies double to the technological 
illiterates in DC

See Sen 'Tubes' Stevens for the canonical example

Sent from my iPhone

On Jul 29, 2013, at 12:46 PM, "J. Forster"  wrote:

> It seems to me that GPS has been oversold as the be all, end all system
> that made all other systems obsolete and GPS has become all but an
> indespensible utility.
> 
> Reports like this, could well be used to promote a backup, like LORAN or
> eLORAN, just as public buildings have backup generators.
> 
> YMMV,
> 
> -John
> 
> ==
> 
> 
>> 
>> http://www.economist.com/news/international/21582288-satellite-positioning-data-are-vitalbut-signal-surprisingly-easy-disrupt-out?fsrc=scn/tw/te/pe/outofsight
>> 
>>    -Bill
>> 
>> 
>> 
>> 
>> 
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Re: [time-nuts] Lecia L1 GPS chokering antenna voltage,

[bg]

Good!

"N"  is supposed to go to north, yes! But for this antenna it does not 
matter... longer story below. 

This is used when you do phase differential stuff. Which usually means L1/L2 
stuff and specifically antenna calibration data for az/el.

I cannot find any calibration data. 

http://www.ngs.noaa.gov/ANTCAL/Antennas.jsp?manu=AeroAntenna

http://www.geopp.de/index.php?bereich=5&kategorie=34&artikel=62

However if you look at the AT antennas at NOAA with a spike radome - I think 
the base chokering is the same as ours. Just a different antenna element in say 
the AT2775-43. For that antenna it matters!

I think the application for the AT575-90 was code differential dgps (marine 
DGPS) base stations. This service gives the users 1m:ish accuracy. Phase 
calibration is clearly <<10cm and not needed for basic code DGPS.

--
   Björn



 Originalmeddelande 
Från: "Mark C. Stephens"  
Datum: 2013-07-15  12:13  (GMT+01:00) 
Till: Discussion of precise time and frequency measurement  
Rubrik: Re: [time-nuts] Lecia L1 GPS chokering antenna voltage, 
 
Thank you, It is a AT575-90_G!

Now, On the bottom, there is an arrow labelled N.
I presume that is supposed to face north?

I can't tell you how ideal this antenna is for my application, outstanding!


Thank you again.
-marki

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of b...@lysator.liu.se
Sent: Monday, 15 July 2013 7:02 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lecia L1 GPS chokering antenna voltage,

Hi,

Is the antenna identical to this?

 http://www.aeroantenna.com/PDF/AT575-90_G.pdf

 http://ebookbrowse.com/at575-90-g-pdf-d359926216   (alternate link)

Do you have some pictures of the antenna? In particular the antenna element?

Aeroantennas of this vintage is usually "RG" which according to the spec above 
5-18VDC. I recall having seen 4.5V as lower level to.

Modern antennas are usually good to 3.3 or lower. With vintage antennas this is 
much more uncertain.

--

 Björn

> I have been trying to find a datasheet for my Leica Antenna.
>
> All that is marked on the antenna is part number 10147.
>
> I want to find out what voltage range the preamp works off.
>
> Anybody have any idea?
>
>
> -marki
>
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Re: [time-nuts] Lecia L1 GPS chokering antenna voltage,

[bg]

Hi,

Is the antenna identical to this?

 http://www.aeroantenna.com/PDF/AT575-90_G.pdf

 http://ebookbrowse.com/at575-90-g-pdf-d359926216   (alternate link)

Do you have some pictures of the antenna? In particular the antenna element?

Aeroantennas of this vintage is usually "RG" which according to the spec
above 5-18VDC. I recall having seen 4.5V as lower level to.

Modern antennas are usually good to 3.3 or lower. With vintage antennas
this is much more uncertain.

--

 Björn

> I have been trying to find a datasheet for my Leica Antenna.
>
> All that is marked on the antenna is part number 10147.
>
> I want to find out what voltage range the preamp works off.
>
> Anybody have any idea?
>
>
> -marki
>
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Re: [time-nuts] Leica L1 GPS Choke Ring Antenna

[bg]

I have two chokerings on my roof. Get something to mount a TV antenna or a 
small satellite dish. Use a threaded water pipe instead of the normal antenna 
mast.

If this is the oem version from Aeroantenna (AT575-90), there are also 3 bolt 
holes around the outer rim. Given a flat surface its pretty steady just resting 
on these bolts.

Good luck!

Björn

 Originalmeddelande 
Från: "Mark C. Stephens"  
Datum: 2013-07-10  22:09  (GMT+01:00) 
Till: time-nuts@febo.com 
Rubrik: [time-nuts] Leica L1 GPS Choke Ring Antenna 
 
I just scored a Leica L1 GPS choke ring antenna.

Of course I am anxious to get it up (pardon the pun) Sorry tom ;)

But its huge, I mean its 14" across the base and 12" high excluding the spike.

It came with a ½" and ¾" adaptor so I can choose mounting pole thread.

Obviously, the top of the roof is the place, but what can support such a 
massive object without getting blown over.

I have a tin roof.

Has anyone got experience with mounting such a large GPS antenna, please?


-marki
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Re: [time-nuts] Speaking of Costas loops (WAAS)

[bg]

Hi everyone,

Have not seen a reference to either the Fenton patent nor the Fruehof
paper, which discuss using WAAS for timing with a dish antenna.

http://www.freqelec.com/gps_gnss/waas_for_telecom_wp_5-06.pdf
https://www.google.com/patents/US6445340

kind regards,

Björn

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Re: [time-nuts] Speaking of Costas loops

[bg]

Attila,

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

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

Here are some references.

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

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

--

Björn

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Re: [time-nuts] GPS antenna splitter

[bg]

Both 'GPS Networking' and 'GPS Source' do good GPS splitters. Compared to Mini 
circuits type of splitters you will get the necessary dc-blocks and biasTs 
built in. Compared to HP/Agilent/Symmetricom splitters you will often get both 
L1&L2 through. On Epay they often cost less. 

Some example id's...
231007617041, 200937306966,300919014379

Good luck in finding something that suits your needs.
--
  Björn

Skickat från min Mobil 

 Originalmeddelande 
Från: Graham  
Datum: 2013-06-29  20:35  (GMT+01:00) 
Till: time-nuts@febo.com 
Rubrik: [time-nuts] GPS antenna splitter 
 
I find my self in need of either splitting a current GPS antenna feed or 
putting up yet another antenna, I would prefer splitting the current feed.

There are a few options one of which is a Mini Circuits ZAPD-2DC+ 
splitter/combiner whose data sheet specifically states DC pass through 
from one port to the combined port. Fair enough, this should work very well.

However, there is another model, the ZAPD-2-N (having type N connectors) 
whose data sheet states neither DC feed through or not, in other words, 
it is does not say explicitly that it does or doesn't.

I think the ZAPD-2-N splitter would work to split the antenna but I am 
sure about being able to feed the antenna through this splitter/combiner 
and was hoping someone could state yay or nay on that point.

However, if it would not pass DC to the antenna I suppose I could add a 
power feed to the splitter to do so and some sort of a load on the GPS 
side to trick the receiver into thinking there was an antenna attached.

I was about to order one of the ZAPD-2DC+ from the Mini Circuits web 
site but upon check out found they would only ship via UPS or some other 
courier rather than by USPS. This would double the price for this coming 
into Canada - I will only use UPS for domestic shipping if I have no 
choice but never for cross border purchases, their handling fees are 
just too much.

So, I was just looking for alternatives or perhaps someone knows a 
source for the ZAPD-2DC+ that would be willing to use USPS for shipping.

cheers, Graham ve3gtc

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Re: [time-nuts] 9390 GPS RX

[bg]

Hi Mark,

> Just a Follow up,
[..]
> Bah, I just noticed the GPS day is wrong, I think we are ~142 but its
> saying 278, Is that a GPS receiver bug?

If it gives the correct time, it is very likely it is 1024 weeks off.
Check what (today - 1024*weeks) gives you in day of year.

--

 Björn

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Re: [time-nuts] ת·¢£ºAbout timelab

[bg]

Hi,

1) Try google for 'timelab site:febo.com'. There is a list of supported
Counters besides the Timepod.

2) http://www.miles.io/TimePod_5330A_user_manual.pdf

3) Chech with your local Symmetricom dealer.

--

   Björn
>
>
>  hi all
>
> I recently downloaded your ‘ timelab’ software,
> http://www.ke5fx.com/timelab/readme.htm
> How to use it?
> can you provide the software manual？
>
> Btw,how much is timepod 5330A?
>
> Thanks.
> wei
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Re: [time-nuts] pin-wheel antenna

[bg]

> Hi Dave,
>
> On 04/21/2013 10:32 AM, David Kirkby wrote:
>> On 20 April 2013 20:52, Tom Van Baak  wrote:
>>
>>> For the rest of you:
>>>
>>> http://www.leapsecond.com/images/gps-pinwheel-1.jpg
>>> http://www.leapsecond.com/images/gps-pinwheel-2.jpg
>>>
>>> It's a thing of mysterious beauty. And the GPS World photo saves me
>>> from the temptation to break open my own pinwheel antenna just to see
>>> what's hidden inside.
>>>
>>> /tvb
>>
>> Does the antenna work better than other types?
>
> You should get close to choke-ring antenna performance at a much smaller
> size. For many purposes its good enough.

Note that the traditional JPL type choke-ring is beeing replaced by more
advanced designs in the money-is-no-problem market.

http://www.topconpositioning.com/sites/default/files/PN-A5_white_paper.pdf

http://www.novatel.com/assets/Documents/Papers/3D_choke_ring.pdf

--

Björn

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

[bg]

Magnus, Jim,

> On 04/18/2013 04:00 PM, Jim Lux wrote:
>> On 4/18/13 12:01 AM, Chris Albertson wrote:
>>> If I read the paper correctly you can skip the choke ring if you mount
>>> the
>>> antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot
>>> lengths. The choke ring is for portable survey antenna that can't be
>>> placed on tall rooftop masts. I think a 2 meter pole on a roof pretty
>>> much meets their criteria of multi path difference being over 10
>>> meters.
>>
>>
>>
>> yes.. multipath that is more than a chip away is generally filtered out
>> by the PN tracking loop, so all you really worry about is multipath
>> signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300
>> meters long. If you're doing P/Y code, it's a tenth of that.
>>
>> In reality, if the multipath signal is lower, and it's "far" away (a
>> good fraction of a chip) it doesn't contribute much to the output of the
>> correlator. So their 10 meter thing is probably a good number for a
>> "typical" receiver they make.
>
> It's an interesting mix of sample-rate/bandwidth, code you track and
> distance between early-late detectors (normal distance is one chip)
> comes in when analyzing and combat the multi-path. I recall there is
> some subtle points with some of the C/A codes.

All of the "high quality" GNSS receiver manufacturers have their own
version  of correlator that try to mitigate multipath. See for example
this Ashtech-document (for a ca 10 year old L1 only receiver (DG14/16)).

 
ftp://ftp.ashtech.com/OEM,%20Sensor%20&%20ADU/DG16%20&%20DG14/Reference%20Material/Correlator.doc


/Björn

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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] GPS antenna??

[bg]

There are even purpose built"glass mount" antennas-arrangements for sale.

   
http://www.antcom.com/documents/catalogs/Page/2G1215A-GMS-X_L1L2GPSAntennas_78.pdf

--

Björn

> Alan,
>
> I used to do a lot of my Datum demos with customers with antennae up
> against
> a window as outside access wasn't available.
>
> Usually worked OK, unless as you say, the glass is metalised.
> Rob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Alan Melia
> Sent: 08 April 2013 18:00
> To: time-nuts measurement
> Subject: [time-nuts] GPS antenna??
>
> Hi all an interesting problem you may have encountered, I want to use a
> GPS
> frequency standard inside a building with no opening windows (opening
> windows are known as air conditioning in the UK :-))  ) This is part of a
> two day amateur microwave conference so we should have the expertise.
>
> I intend to try and pass the signal through a a double glazed glass window
> unit (hopefully not metalised) using a couple of patch antennas. The outer
> GPS antenna is active so will need  a 5v supply via an inserter. Inner
> patch
> active, outer patch passive to avoid problems of feedback. Main antenna
> can
> be shielded from the "coupling" either physically or with a slab of
> absorber.
>
> Has anyone tried this? does it work?.any gotchas?
>
> Thanks
> Alan
> G3NYK
>
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Re: [time-nuts] OT - DC-10 gyros

[bg]

Hi Bill,

> Well, I can come up with something topical, read on. :)

[snip]

> Topical in a more abstract way, strapdown systems really are very
> interesting. They require precise integration of the rate output over
> time to derive velocity and position, and really weren't practical until
> the 70's when small enough computers existed to do the requisite
> calculations.  (I worked on the nav system for the Trident missile back
> in my Draper Labs days).

Well, for the analysis of your gyro performance, time-nuts are already
equiped with one of the tools used - the Allan Variance.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4404126&tag=1

There is also the relation

  GPS & oscillator -> GPSDO

where in the navigation field

  GPS & 3x gyro + 3x accel   ->  GPS stabilised inertial navigation
system


--

 Björn


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Re: [time-nuts] One Kg Quartz Resonator

[bg]

>
>> Isn't it defined for zero sea-level, that is standard acceleration?
>
> How do you define sea level?

http://en.wikipedia.org/wiki/EGM96
http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/egm08_wgs84.html

>
> Daniel Kleppner's Time Too Good to Be True in
> Physics Today, March 2006
> pointed out that the time-geeks will soon own the definition of sea level.

You need to use a lot of time-geek-tools to have a working GPS or VLBI
system.

/Björn

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Re: [time-nuts] Strange GPS behaviour

[bg]

Hi Magnus,

>> 2) Timing versions might get an upgraded oscillator. Maybe a TCXO
>> instead
>> of a standard XO.
>
> Don't think so. The noise and systematic stability is as important for
> positional as for timing versions, the timing version can benefit of the
> fixed position.

Look at the uBlox6 lineup. Position receivers are available with XO or
TCXO - timing only with TCXO.

http://www.u-blox.com/images/stories/linecards_u-blox_gps_modules_2012.pdf

--

Björn


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Re: [time-nuts] Strange GPS behaviour

[bg]

Hi Bob,

I am curious about the sacrifice time and get better position. I have not
seen any discussions about that in manuals, books or papers. Do you have
reference?

What would be the difference between timing and navigation versions of
cheap commercial receivers?

1) Timing receivers are often stationary, navigation receivers are
typically not stationary for extended periods of time. So a timing
receiver can benefit from a time only solution. Ie you have a known
(x,y,z)/(lat,lon,h) position and solve only for time, reducing the unknown
from (x,y,z,t) to only (t). The known position can be had from a) full 4D
single fix solution or better from b) a site survey taking the mean
position from many hours of measurements or also good from c) an
independently surveyed position of the antenna position. This mode will of
cause improve time when there are fewer than 4 satellites tracked.

2) Timing versions might get an upgraded oscillator. Maybe a TCXO instead
of a standard XO.

3) Navigation receivers integrations will not require high accuracy PPS
output from the receiver. If you can save some cents on PPS generation
hardware by having 500ns resolution of the PPS instead of 1-10ns
resolution - the navigation receiver will not even have hardware resources
to generate a decent 1PPS.

To my knowledge, the accuracy of (x,y,z,t) is given by the "geometrics" of
the satellites tracked. The receiver reports this in the DOP (dilution of
precision). There is PDOP (3d position), HDOP (horizontal position), HDOP
(vertical position) and TDOP (Time). There is not much the receiver can do
in normal operation with four or more tracked satellites to select between
position and time accuracy. The relationship is given by the geometry of
the measurements!

For a navigation receiver, there must be a time solution that is (scaled
by c) more or less at the same accuracy as the position. Having 3 meter
accuracy means the receiver time is good to 10ns. However the navigation
receiver does not need to communicate this timing accuracy to the outside.
It does not have to calibrate filter/processing delays. Slowly varying
delays in analog filters due to temperature changes can also be ignored.
Delays due to LNA and cables can also be ignored if you have a spec at
1PPS of 1us.

--

Björn


> Hi
>
> Indeed the solution is done once per second or so. In the solution they
> weight the significance of position versus time. If you accept a larger
> time error in the solution, you can come up with a smaller location error.
>  Is that a bit of mathematical sleight of hand? - of course it is. Can you
> keep doing it forever? - no you can't. Eventually you need to get the time
> back up to date.
>
> Put another way - if all that was going on was the same solution process
> in every receiver - there would be no differences in results. Software is
> software. The hardware in a low cost timing receiver is the same as the
> hardware in a low cost "location only" receiver. The difference is the
> firmware. You can indeed shoot timing firmware into some location
> receivers and turn them in to timing receivers.
>
> Bob
>
> On Dec 29, 2012, at 12:14 AM, Michael Perrett  wrote:
>
>> Bob,
>> That is simply not accurate - if the solution rate is 1/second, then all
>> parameters are solved in that time frame. There are 4 indpendent
>> variables
>> and minimal processing power is required to solve all four equations.
>> Although I am not very familiar with commercial receivers, that is what
>> happens in the Rockwell, Trimble and IEC military units. If the output
>> is
>> more than once per second it is *usually* an output of the Kalman
>> Filter,
>> not a "true" measurement.
>>
>> Michael / K7HIL
>>
>> On Fri, Dec 28, 2012 at 6:20 PM, Bob Camp  wrote:
>>
>>> Hi
>>>
>>> …. except… A navigation GPS doesn't care much about the time solution.
>>> Updating the location is a much higher priority than updating the time.
>>> The
>>> typical "solution" is to let the time estimate coast for a while and
>>> update
>>> it much less often than the location.
>>>
>>> Bob
>>>
>>> On Dec 28, 2012, at 7:18 PM, Magnus Danielson
>>> 
>>> wrote:
>>>
 On 28/12/12 23:35, Bob Camp wrote:
> Hi
>
> The GPS does an estimate against the local crystal frequency. It
>>> generates the PPS off of it's estimate. The less often it updates the
>>> estimate the more odd things you see as the crystal drifts.

 A typical GPS off the shelf solves the position solution every second,
>>> having a 1 Hz report rate. This includes clock corrections. Some GPSes
>>> is
>>> capable of higher report-rates.

> Of course, the crystal can have trouble all it's own. If the crystal
>>> has a rapid rate of frequency change over a narrow temperature range,
>>> the
>>> GPS simply can't keep up with the crystal.

 Most GPS receivers only have TCXOs, and even if tossing in an OCXO,
>>> excessive heat can throw the frequency and hence the GPS solution way
>>> of
>>> the ma

Re: [time-nuts] Strange GPS behaviour

[bg]

Hi,

> On 12/28/12 9:14 PM, Michael Perrett wrote:
>> Bob,
>> That is simply not accurate - if the solution rate is 1/second, then all
>> parameters are solved in that time frame. There are 4 indpendent
>> variables
>> and minimal processing power is required to solve all four equations.
>> Although I am not very familiar with commercial receivers, that is what
>> happens in the Rockwell, Trimble and IEC military units. If the output
>> is
>> more than once per second it is *usually* an output of the Kalman
>> Filter,
>> not a "true" measurement.
>>
>
> how is the output of a Kalman filter not a "true measurement".. it's
> essentially the composite of many measurements, weighted by the
> uncertainty of those measurements, and, if properly setup, the
> uncertainty of the filter output is less than any of the component
> measurements.

Often these receivers can output either a filtered solution or an
"unfiltered" solution.

The kalman filter will do measurement updates once a second with
pseudorange and delta range measurements. In between - to get 10Hz or
whatever - they will use the kalman filter to predict the
position/velocity.

> Or by "true measurement" do you mean a "point solution" at an instant in
> time, which I don't think you would get from any receiver that uses any
> form of tracking loop, because what is the output of that tracking loop
> but some estimate of the observable, filtered through the loop filter.
> After all, you need to measure/estimate both code phase and rate.

Sure, the pr/dr measurements are filtered both by the tracking loop and by
the integration time. But that filtering is on another scale than using a
filter to predict outputs at a higher rate than what the point solution is
available at.

--

  Björn


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Re: [time-nuts] clock-block any need ?

[bg]

Magnus,

> Doing ~200 us for a non-trival network with real data on it sound about
> right.
>
> What kills many assumptions is that the noise-forms fail most of the
> normal assumptions about "noise". It's not zero mean, it does not have a
> static mean, it does not have a static variance, it is not symmetric, it
> is not independent of other traffic, it is not "just another service".
>
> Cheers,
> Magnus

But NTP is very much aware of the measurements coming from a complicated
statistical source. Look for 'wedge scattergram'.

   http://www.eecis.udel.edu/~mills/database/brief/algor/algor.pdf
   http://www.eecis.udel.edu/~mills/database/brief/distlec/distlec.ppt

--

Björn


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Re: [time-nuts] Thunderbolt oven / non-stable operating temperature

[bg]

Warrenm
>
> tvb posted>
>>Were you able to test how quickly, or how well, the filter learned the
>> tempco of the OCXO?
>
> Only at a couple of very general data points.
> Using a very Bad unit, the Kalman filter had an effect, although not very
> good in under 1/2 day.
> After a week or so on a good unit, it helped maybe 3 to1 with ageing and
> Temperature TC.

Not contributing vs your information in detail or quality. But here is
some terse information from Trimble regarding holdover for the Tbolt.

   "This voltage steers the oscillator correcting for temperature and
aging effects by using a Kalman Filter.  The Kalman filter works by
observing the behavior of an oscillator over temperature and time while
GPS is locked.  This is called the training period."

   http://trl.trimble.com/docushare/dsweb/Get/Document-8428/

kind regards,


 Björn




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Re: [time-nuts] FE-5860a internal RF connector?

[bg]

A premade U.FL to SMA cable worked fine for me, a few years ago in my
5680A. However as mentioned a few days ago, there are _many_
variations/generations of this unit. FEI might have changed the connector.

--

   Björn

> Was wondering if anyone ever confirmed the type of RF connector found
> internally in the FE-5860a?
>
> I've seen several posts calling it a Hirose U.FL, but the linked thread
> suggests that it might actually be an OSMT connector:
> http://www.vklogger.com/forum/viewtopic.php?t=10289
>
> Or is everyone simply soldering cable directly to the center pin?
>
> Thanks,
> James
>
> --
> *Integrity is a binary state - either you have it or you don’t.* - John
> Doerr
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Re: [time-nuts] Best phase detector / mixer for 100MHz?

[bg]

> Jim Lux wrote:
>> On 11/26/12 10:11 AM, Demian Martin wrote:
>>> I asked Wenzel about mixers for phase noise measurement and they
>>> directed me
>>> to Marki Microwave as what they use:
>>> http://www.markimicrowave.com/2770/Mixers.aspx  I have not obtained or
>>> tested any myself but it's a pretty solid recommendation I think.
>>
>>
>> Isn't Marki making the old WJ mixers?  That seems to be what someone
>> told me a few years ago: they basically have all the tooling and
>> designs, etc.
>
> That's interesting, because MaCom Technology Solutions seems to
> be making WJ models as well.  A few years back, there was another
> company (I think the name started with an S) that seemed to have
> inherited the WJ line.  The company currently called WJ has
> nothing to do with these mixers at all.
>
> Rick

Did you see this information from Mini Circuits on WJ mixer replacements?

 
http://217.34.103.131/pdfs/Surface-Mount%20Mixers%20Are%20WJ%20Replacements.pdf

--

Björn


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Re: [time-nuts] GPS splitter measurements

[bg]

Paul,

> Azelio,
> Not at all the satellite splitters can be smart or passive. I use a
> passive
> so it has 1 dc path. But all of the other ports have dc blocks built in.
> The smarter units will direct the highest DC to the antenna. Its really
> diodes and I stay clear of those. To smart for there own good.

The S14WI chose the lowest port with a DC present. (smarter than diods...
;-))

> Plus with 3.3v and 5 v... it gets messy. I actually use the whole thing as
> a passive. Have a line amp ahead of the splitter to make up for splitter
> loss. Feed it with its own supply that also feeds the antenna.

> On some gps units you do have to add a dc load to trick them into
> believing
> an antenna is connected.

This is included in (all) decent splitters. The load is usually 200ohms.
The S14WI will actually remove the load towards the receivers when it
detects a short/open condition towards the antenna.

> Regards
> Paul
> WB8TSL
>
> On Thu, Oct 11, 2012 at 7:15 PM, Azelio Boriani
> wrote:
>
>> To test this kind of items, you have to play with DC-blocks and
>> bias-tees.
>> Rather tedious but necessary. I know as at times I have to test
>> questionable GPS antennae that return after lightning strikes.
>>
>> On Fri, Oct 12, 2012 at 1:09 AM, paul swed  wrote:
>>
>> > Magnus what would the possibility be of measuring an 8 way satellite
>> > splitter? The $7 wonders with dc pass through. That looks like a very
>> nice
>> > network analyzer you have.
>> > Regards
>> > Paul
>> > WB8TSL
>> >
>> > On Thu, Oct 11, 2012 at 7:05 PM, Magnus Danielson <
>> > mag...@rubidium.dyndns.org> wrote:
>> >
>> > > On 10/12/2012 12:16 AM, Azelio Boriani wrote:
>> > >
>> > >> Please take care that the S14WI is "smart": if it doesn't sense a
>> DC
>> > >> current on the antenna port then it reports that to the user ports
>> and I
>> > >> think it can even power off the internal amplifier, this can
>> account
>> for
>> > >> the observed loss instead of the gain.
>> > >>
>> > >
>> > > I did consider this. but did not have the time and energy to follow
>> that
>> > > up at the time. It was only when I got home that I could dig up the
>> > > datasheet and manual of the S14WI. Didn't want to fry it in the lab.
>> > >
>> > > I rather do an incomplete lab quick and safe. I reports warts and
>> all.
>> > >
>> > > I'll see if I get time to re-do it tomorrow.
>> > >
>> > > Regardless, I want to get things going. More people than me should
>> be
>> > able
>> > > to do this.
>> > >
>> > >
>> > > Cheers,
>> > > Magnus
>> > >
>> > > __**_
>> > > time-nuts mailing list -- time-nuts@febo.com
>> > > To unsubscribe, go to https://www.febo.com/cgi-bin/**
>> > > mailman/listinfo/time-nuts<
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>> > > and follow the instructions there.
>> > >
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Re: [time-nuts] RFX GPSDO - Anybody played with one of these?

[bg]

> On 10/2/12 10:35 PM, b...@lysator.liu.se wrote:
>>> On 10/2/12 2:36 PM, saidj...@aol.com wrote:
 Hello Paul,

 thanks much for the feedback!

 Yes, we think we have identified a nice combination of oscillators,
 GPS,
 and firmware that seems to work pretty well. The GPSTCXO units cannot
 be
 compared to a lower cost $150 Thunderbolt in terms of phase noise or
 stability
 of course, and they have CMOS 10MHz outputs, but then the  TB's cost
 around
 $1500 new I guess.

 We think the GPSTCXO's and LC_XO type units will work quite well
 wherever
 standard OCXO's are used today, and power/size/weight are an  issue.

>>>
>>>
>>> Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO?
>>> (7km/s)  The total Doppler isn't usually the issue (the GPS satellites
>>> are moving faster, after all), but the receiver may not work for high
>>> velocities, high altitudes?
>>
>> GPS SVs moves at around 4km/s, but nevertheless there are still COCOM
>> limits implemented in nearly all receivers (never break both 504m/s and
>> 18km height)
>>
>
> Doh. of course. higher is slower
>
>
> In any case, though, nothing stops Jackson Labs from selling one that is
> export controlled and has no restrictions.

Not more than some paperwork for Jackson Labs to source a "no limit"
uBlox. And then checking that the uBlox actually performs as expected in
that environment. Well, I am not sure the doppler search range is wide
enough in a standard firmware. (+-4km/s vs +-11km/s relative vel.)

On the "black sheep" Javad online shop they quote an extra $1k for this.


--

Björn


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Re: [time-nuts] RFX GPSDO - Anybody played with one of these?

[bg]

> On 10/2/12 2:36 PM, saidj...@aol.com wrote:
>> Hello Paul,
>>
>> thanks much for the feedback!
>>
>> Yes, we think we have identified a nice combination of oscillators, GPS,
>> and firmware that seems to work pretty well. The GPSTCXO units cannot be
>> compared to a lower cost $150 Thunderbolt in terms of phase noise or
>> stability
>> of course, and they have CMOS 10MHz outputs, but then the  TB's cost
>> around
>> $1500 new I guess.
>>
>> We think the GPSTCXO's and LC_XO type units will work quite well
>> wherever
>> standard OCXO's are used today, and power/size/weight are an  issue.
>>
>
>
> Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO?
> (7km/s)  The total Doppler isn't usually the issue (the GPS satellites
> are moving faster, after all), but the receiver may not work for high
> velocities, high altitudes?

GPS SVs moves at around 4km/s, but nevertheless there are still COCOM
limits implemented in nearly all receivers (never break both 504m/s and
18km height)

--

   Björn


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Re: [time-nuts] Symmetricom 58532A and 58536A group delay figures

[bg]

With a warmed up tbolt and Lady Heather it is perfectly possible to
"measure/watch" the delay by swapping the splitter in and out of the
antenna cable chain.

--

   Björn

>>> Interesting that it's so far off from the 40 ns in the data sheet.
>
>> I think the usually quote worse case.
>
> Both data sheets said "typical".
>
>
> Worst case makes sense for things like delays through digital gates where
> you
> have to add up the total delay to see if your design will meet timing.
> But
> if you are trying to correct for actual delays, the typicals are probably
> more useful.
>
> Note that typicals can change over time if the manufacturer switches to a
> newer/cheaper/faster process, or you get a batch from a different vendor.
> The numbers in the data sheet may not match current reality.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] WWVB Now a Monopoly

[bg]

Dont you have GPS/Cs locked cell networks anymore in the US?

http://www.endruntechnologies.com/cdma.htm

--

Björn

> In the real world, if GPS does not work, the WWVB change means you either
> have to buy the XW stuff or go do something else.
>
> YMMV
>
> -John
>
> =
>
>
>
>> On 9/26/12 7:11 PM, J. Forster wrote:
>>> But if someone here designed and built a $100 receiver and offered it
>>> to
>>> the group, that could well violate some of their IP.
>>>
>>> As to building a home brew receiver and certifying a onsie so your
>>> lab's
>>> cal is traceable, I'd certainly not trust a cal done that way.
>>>
>>> Doing spacecraft communications is hardly the same thing.
>>>
>>
>>
>>
>> Well..if you're trying to do NIST traceable cals in a legally acceptable
>> way, then it's very unlikely that any homebuilt receiver that infringed
>> the patent would be acceptable, from a patent standpoint. The general
>> exemption to practice the invention is for development of a new
>> invention, not to make use of it for other reasons (otherwise, the
>> patent wouldn't be particularly useful in terms of exclusivity).
>>
>> OTOH, if you cobble up a (non-infringing) receiver and validate its
>> performance analytically, why wouldn't that be acceptable for a
>> traceable calibration.  It's no different than using a homebuilt quartz
>> oscillator as a transfer standard, is it?
>>
>> Now, if you're selling calibration services, it would be a tougher sell
>> to your customers: they'd have to believe in your analysis or oscillator
>> building. This is in the sense that if I use a HP 105, the long history
>> and tradition of HP is essentially standing behind the design and the
>> published performance standards; a homebuilt standard has a higher bar
>> for the great unwashed public.
>>
>> If you want traceability for, say, a journal article, then I think the
>> bar is set differently.  For state of the art stuff, the article usually
>> describes the calibration approach, and it's up to the reader to decide
>> if you did it adequately.
>>
>>
>>
>>
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>>
>
>
>
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Re: [time-nuts] HP-106 and Sulzer Quartz Crystals

[bg]

There are some BVAs in Sweden,

   http://www.febo.com/pipermail/time-nuts/2012-August/069068.html

The measured pair was found in european parts of the same auction site.

--

   Björn

> In 2006 (I wasn't aware of this list at that time) there was here the
> opportunity to have a BVA. Recently the only thing related was some BVA
> blanks available (from US) on the usual auction site for $38 IIRC.
>
> On Wed, Sep 19, 2012 at 10:26 PM, Bob Camp  wrote:
>
>> Hi
>>
>> I would *hope* there are still a few left in France.
>>
>> Bob
>>
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>> Behalf Of Azelio Boriani
>> Sent: Wednesday, September 19, 2012 4:21 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] HP-106 and Sulzer Quartz Crystals
>>
>> My home is about 300Km south of the Oscilloquartz facilty and all the
>> BVAs
>> that I know of are in the US.
>>
>> On Wed, Sep 19, 2012 at 10:09 PM, paul swed  wrote:
>>
>> > Great pix and now I do know what to look for.
>> > I have to say I am actually partial to the old HP5360 oscillators.
>> > They really were the time-bug that bit me. I have 7 of them or so.
>> > Regards
>> > Paul
>> > WB8TSL
>> >
>> > On Wed, Sep 19, 2012 at 4:00 PM,  wrote:
>> >
>> > > Hi Paul,
>> > >
>> > > Here are two other links
>> > >
>> > > http://www.oscilloquartz.com/file/pdf/8607.pdf
>> > > http://www.lysator.liu.se/~bg/timenuts/IMG_5119.JPG
>> > >
>> > > They are a bit shorter but bulkier than a FTS1x00-series USO.
>> > >
>> > > --
>> > >
>> > >Björn
>> > >
>> > > > Azelio thanks now I know what to look for. Have to say I don't
>> actually
>> > > > ever see oscilloquartz equipment in the US. Now to look under the
>> > > > fleamarket table and grab a 8600 for $5. ;-) Oddly I have picked
>> up
>> > some
>> > > > nice oscillators that way and just missed some good ones by other
>> hams.
>> > > > Regards
>> > > > Paul
>> > > >
>> > > > On Wed, Sep 19, 2012 at 3:25 PM, Azelio Boriani
>> > > > wrote:
>> > > >
>> > > >> Or, better, this:
>> > > >> http://www.oscilloquartz.com/file/pdf/8600.pdf
>> > > >>
>> > > >>
>> > > >> On Wed, Sep 19, 2012 at 9:20 PM, Azelio Boriani
>> > > >> > > > >> >wrote:
>> > > >>
>> > > >> > Try this:
>> > > >> > http://www.oscilloquartz.com/file/pdf/2230.pdf
>> > > >> > upper left corner of the .PDF
>> > > >> >
>> > > >> > On Wed, Sep 19, 2012 at 9:12 PM, paul swed
>> 
>> > > >> wrote:
>> > > >> >
>> > > >> >> Ok OK how about a pix of one of these BVAs so I know what to
>> look
>> > for
>> > > >> at
>> > > >> >> the hamfest.;-)
>> > > >> >> Regards
>> > > >> >> Paul
>> > > >> >> WB8TSL
>> > > >> >>
>> > > >> >> On Wed, Sep 19, 2012 at 2:53 PM, Tom Van Baak (lab)
>> > > >> > > > >> >> >wrote:
>> > > >> >>
>> > > >> >> > http://leapsecond.com/museum/osa8607/
>> > > >> >> >
>> > > >> >> > /tvb (iPhone4)
>> > > >> >> >
>> > > >> >> > On Sep 19, 2012, at 11:16 AM, "Ron Ward"
>> > >
>> > > >> wrote:
>> > > >> >> >
>> > > >> >> > > Thanks John:
>> > > >> >> > > WOW, I didn't realize that some oscillators are now at
>> >  7X10-14.
>> > > >> >> > > Thanks,
>> > > >> >> > > Ron
>> > > >> >> > >
>> > > >> >> >
>> > > >> >> > ___
>> > > >> >> > time-nuts mailing list -- time-nuts@febo.com
>> > > >> >> > To unsubscribe, go to
>> > > >> >> > https:/

Re: [time-nuts] HP-106 and Sulzer Quartz Crystals

[bg]

Hi Paul,

Here are two other links

http://www.oscilloquartz.com/file/pdf/8607.pdf
http://www.lysator.liu.se/~bg/timenuts/IMG_5119.JPG

They are a bit shorter but bulkier than a FTS1x00-series USO.

--

   Björn

> Azelio thanks now I know what to look for. Have to say I don't actually
> ever see oscilloquartz equipment in the US. Now to look under the
> fleamarket table and grab a 8600 for $5. ;-) Oddly I have picked up some
> nice oscillators that way and just missed some good ones by other hams.
> Regards
> Paul
>
> On Wed, Sep 19, 2012 at 3:25 PM, Azelio Boriani
> wrote:
>
>> Or, better, this:
>> http://www.oscilloquartz.com/file/pdf/8600.pdf
>>
>>
>> On Wed, Sep 19, 2012 at 9:20 PM, Azelio Boriani
>> > >wrote:
>>
>> > Try this:
>> > http://www.oscilloquartz.com/file/pdf/2230.pdf
>> > upper left corner of the .PDF
>> >
>> > On Wed, Sep 19, 2012 at 9:12 PM, paul swed 
>> wrote:
>> >
>> >> Ok OK how about a pix of one of these BVAs so I know what to look for
>> at
>> >> the hamfest.;-)
>> >> Regards
>> >> Paul
>> >> WB8TSL
>> >>
>> >> On Wed, Sep 19, 2012 at 2:53 PM, Tom Van Baak (lab)
>> > >> >wrote:
>> >>
>> >> > http://leapsecond.com/museum/osa8607/
>> >> >
>> >> > /tvb (iPhone4)
>> >> >
>> >> > On Sep 19, 2012, at 11:16 AM, "Ron Ward" 
>> wrote:
>> >> >
>> >> > > Thanks John:
>> >> > > WOW, I didn't realize that some oscillators are now at  7X10-14.
>> >> > > Thanks,
>> >> > > Ron
>> >> > >
>> >> >
>> >> > ___
>> >> > 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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Re: [time-nuts] GPSDO Component Selection

[bg]

Hi Bob,

This argument has been done before on time-nuts... sorry for repeating.

There are geodetic quality GPS reveivers, like the Ashtech Z12-CORS (with
external 5-20MHz input - not the true Z12 Metronome) available for a few
hundred dollars occasionally. I got my Z12 CORS for free, from a site
where it had been replaced by modern GPS/GLONASS receivers.

I also found three Novatel Millenium OEM3 for ca $100 a piece, which in
their days were used by national time labs. Unfortunately two of them has
developed a problem with a custom IC.

I am far from having the economic freedom to purchase a new H-Maser or
Cesium. However I still have a HP5065A running in the basement. When new
in the early 1970ties, you could probably have traded the rubidium for the
house it is now running in.

Conclusion: used geodetic gps equipment are no more expensive, than many
of the oscillators we play with. They might actually once have been used
in the same national time lab... ;-)

--

   Björn



> Hi
>
> Indeed true for most non-geodetic gps units. Put another way - true unless
> you have a lot of money.
>
> Bob
>
> On Sep 9, 2012, at 7:25 PM, b...@lysator.liu.se wrote:
>
>> Hi Bob,
>>
>> Probably true for Motorola Oncores. Not very true for geodetic
>> receivers.
>>
>> Until you have a receiver clock that is on par with the satellite clocks
>> AND you are short on visable satellites. This might be true if you can
>> load up a modern cesium in your vehicle, and go for a downtown "urban
>> valley" type of scenario.
>>
>> On a stationary site, your expensive clock will not matter to much,
>> since
>> your solution is already pretty over-determined with some 60
>> measurements
>> on each epoch. (9 GPS +6 Glonass)*2(L1/L2)*2 (code + phase)
>>
>> --
>>Björn
>>
>>> Hi
>>>
>>> Position accuracy and timing accuracy are two very different things.
>>> Firmware is optimized to improve either one. "Position" firmware is
>>> often
>>> pretty poor for timing.
>>>
>>> Bob
>>>
>>> On Sep 9, 2012, at 5:05 PM, Chris Albertson 
>>> wrote:
>>>
 On Sun, Sep 9, 2012 at 1:14 PM,   wrote:

> True for a cheap oem navigation receiver. Not true for a geodetic
> quality
> receiver, who usually have some options (external frequency input,
> PPS_in)
> to make them the best timing receivers available. However they are
> much
> more expensive than the typical single frequency timing reciver.

 I looked at every link and can't see where they give a timing accuracy
 spec on the PPS with respect to UTC.   Possition accurracy is very
 good and we might assume the timing is as good.  But they don't say it
 is.  What's interesting is these GPSes will accept an accurate clock
 input in order to give better location data.   That is the opposite of
 a timing GPS where you tell it accurate location data so that it can
 get better timing.   Cutting down the unknown in one lets you do
 better in the other.   I assume these all cost well over $50.  You can
 get a pretty good timing GPS for $30 and it WILL have the PPS error
 specified.

 To the OP.  None of this matters a lot because PPS is a standard input
 signal.  It is easy to swap out a GPS receiver later.  Same with the
 OCXO.  From a control point of view they are all pretty much the same.
 You can swap them out later


 Chris Albertson
 Redondo Beach, California

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>>>
>>>
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>>
>>
>>
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Re: [time-nuts] GPSDO Component Selection

[bg]

Hi Bob,

Probably true for Motorola Oncores. Not very true for geodetic receivers.

Until you have a receiver clock that is on par with the satellite clocks
AND you are short on visable satellites. This might be true if you can
load up a modern cesium in your vehicle, and go for a downtown "urban
valley" type of scenario.

On a stationary site, your expensive clock will not matter to much, since
your solution is already pretty over-determined with some 60 measurements
on each epoch. (9 GPS +6 Glonass)*2(L1/L2)*2 (code + phase)

--
Björn

> Hi
>
> Position accuracy and timing accuracy are two very different things.
> Firmware is optimized to improve either one. "Position" firmware is often
> pretty poor for timing.
>
> Bob
>
> On Sep 9, 2012, at 5:05 PM, Chris Albertson 
> wrote:
>
>> On Sun, Sep 9, 2012 at 1:14 PM,   wrote:
>>
>>> True for a cheap oem navigation receiver. Not true for a geodetic
>>> quality
>>> receiver, who usually have some options (external frequency input,
>>> PPS_in)
>>> to make them the best timing receivers available. However they are much
>>> more expensive than the typical single frequency timing reciver.
>>
>> I looked at every link and can't see where they give a timing accuracy
>> spec on the PPS with respect to UTC.   Possition accurracy is very
>> good and we might assume the timing is as good.  But they don't say it
>> is.  What's interesting is these GPSes will accept an accurate clock
>> input in order to give better location data.   That is the opposite of
>> a timing GPS where you tell it accurate location data so that it can
>> get better timing.   Cutting down the unknown in one lets you do
>> better in the other.   I assume these all cost well over $50.  You can
>> get a pretty good timing GPS for $30 and it WILL have the PPS error
>> specified.
>>
>> To the OP.  None of this matters a lot because PPS is a standard input
>> signal.  It is easy to swap out a GPS receiver later.  Same with the
>> OCXO.  From a control point of view they are all pretty much the same.
>> You can swap them out later
>>
>>
>> Chris Albertson
>> Redondo Beach, California
>>
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>
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Re: [time-nuts] GPSDO Component Selection

[bg]

> On Sun, Sep 9, 2012 at 1:14 PM,   wrote:
>
>> True for a cheap oem navigation receiver. Not true for a geodetic
>> quality
>> receiver, who usually have some options (external frequency input,
>> PPS_in)
>> to make them the best timing receivers available. However they are much
>> more expensive than the typical single frequency timing reciver.
>
> I looked at every link and can't see where they give a timing accuracy
> spec on the PPS with respect to UTC.

Here is an older quote for geodetic quality time receivers.

   http://www.bipm.org/static/gpst/mail/13Jul99.1

   Table 5.  Inferred RMS day-boundary clock
   variations attributable to individual receivers
   ===
 USNJ (Javad) 216 ps
 USNO (AOA TR)630 ps
 USNB (Ashtech)   574 ps
   ===

and some other links.

http://tycho.usno.navy.mil/ptti/ptti2003/paper7.pdf
http://tycho.usno.navy.mil/ptti/ptti2007/paper29.pdf

https://goby.nrl.navy.mil/IGStime/index.php

> Possition accurracy is very
> good and we might assume the timing is as good.  But they don't say it
> is.  What's interesting is these GPSes will accept an accurate clock
> input in order to give better location data.  That is the opposite of
> a timing GPS where you tell it accurate location data so that it can
> get better timing.

You got it wrong, the external frequency input is primarily there to let
you compare accurate clocks. There are few applications that really
require an OCXO or better for position uses.

>  Cutting down the unknown in one lets you do
> better in the other.   I assume these all cost well over $50.

That I said already... ;-) But then you will find a gem from time to time
on the big epay river.

--

   Björn


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Re: [time-nuts] GPSDO Component Selection

[bg]

Chris,

> On Sun, Sep 9, 2012 at 6:18 AM, Don Oconnor  wrote:
>> Hello,
>>
>>
>>
>> I would like to design and build a microcontroller based GPSDO. And I
>> have a couple of questions some of you may be able to answer.
>>
>>
>>
>>
>>
>> 1. I am going to use Trimble SMT GPS timing module but I'm
>> curious. Does a GPS timing receiver produce a more precise 1 PPS output
>> than a standard GPS tracking receiver in a static location? Or does it
>> just produce a 1 PPS signal that is more accurate to GPS time?
>
> Both of the above by several orders of magnitude.  The best timing
> mode GPSes today have the PPS within a few tens of nanoseconds of UTC
> (one sigma) while the typical navigation mode GPS has the PPS within a
> few microseconds.   Also the timing mode GPS can do things like a self
> survey to determine location.  The finding a soltion for time within
> _knows_ it is not moving removes some uncertainty in the result.   I'd
> say it would be almost pointless to use a nav receiver in a GPSDO
> especially when decent timming mode receivers sell for under $20.

True for a cheap oem navigation receiver. Not true for a geodetic quality
receiver, who usually have some options (external frequency input, PPS_in)
to make them the best timing receivers available. However they are much
more expensive than the typical single frequency timing reciver.

Look at:

 http://www.septentrio.com/products/receivers/polarx4-tr-pro

 http://www.topconpositioning.com/products/networks/network-systems/net-g3a

 http://www.novatel.com/solutions/timing/#whatWeOffer

 http://javad.com/downloads/javadgnss/sheets/Delta-G3T_Datasheet.pdf

 
http://javad.com/downloads/javadgnss/how-to/hardware/Receiver_Clock_Synchronizing_Configuration_Example.pdf

--

   Björn


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Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[bg]

Hi Nigel,

>
> With regards to the Oncore VP carrier phase measurement option, I'm  not
> too sure that the 8821B does actually make use of that.

The "Z" is a pure software option, to enable the phase capability already
in all of the VP receivers. So you pay extra, but get exactly the same
hardware. Since they optimised away IRIG and other function, I find it
unlikely they would have premium Z options in the VP if it was not used. I
should try to snoop on the communication between the VP and the
microcontroller in the 8821.

--

   Björn


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Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[bg]

Hi Nigel,

Yes, I have the same version. We might have got it from the same UK epay
source. The GPS did not work reliably, and I did start testing that module
outside the Trak unit, and also tried VP(8chan) receivers that I had. Did
not really conclude why the GPS did not behave properly. I was, like you,
disappointed by the lack of IRIG and other features that are in the
standard units. I also drew the conclusion this was a "high volume"
special model, where it was cost effective to eliminate all - for the
specific application - unuseful outputs.

However it is a very decent size OCXO inside.

The phase measurement Oncore model is interesting, since I have seen very
few GPSDOs that use phase information. It gives the possibility to reduce
the short term GPS noise to cm/s level. However this is probably lost in
the PPS generation hardware, since the Oncore does not lock its internal
crystal to the external OCXO.

--

Björn

> Hi Bjorn
>
> Is yours also the cut down 2.084MHz version, or do you have a "proper"
> 8821B with a more useful GPSDO frequency and all the outputs fitted?
> I think this one was originally used in a trunked radio  system.
>
> I've just checked and the fitted VP Oncore is  the B8121Z116, so perhaps
> the same module, but I'd forgotten until I  looked again that the unit is
> without the IRIG-B output as well  as the Low-Rate output that normally
> allows a
> variety of pre-set pulse rates,  hence my "cut down" comment.
>
> The Low-Rate ouput speciification suggests some interesting  possibilities
> for experiments in conditioning other oscillators, as  amongst some very
> slow pulse rates it also offered an option of 1  MPPS.
> Unfortunately, not only are the connectors not fitted but quite a lot of
> presumably associated PCB components in that area are also missing.
>
> Do you have a manual for the 8821B?
> I've only ever found a manual for the 8821A, although I suspect the  only
> significant difference may be the fitting of the larger B7A OCXO  to the
> 8821B, which necessitated the height increase to 2U, but it would be nice
> to be
> able to compare them.
>
> regards
>
> Nigel
> GM8PZR
>
> In a message dated 21/08/2012 21:05:02 GMT Daylight Time,
> b...@lysator.liu.se
>  writes:
>
> Hi  Nigel,
>
> Have one of those Trak 8821B too. It is a bit interesting since  the
> Motorola Oncore VP inside mine has the Z option (phase  measurement).
>
> --
>
> Björn
>
>
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Re: [time-nuts] Z3815A Internal SMA 10Mhz Output

[bg]

Hi Nigel,

> Then there's the variant of the Trak Microwave 8821B, as just one
> example,
> that uses a 16.384MHz OCXO from which they derive  a 2.048MHz output
> without 10MHz anywhere in sight.
> When I bought one of those a few years ago I assumed that  all 8821Bs
> would
> be 10MHz GPSDOs, or some nice round figure  anyway, and it never even
> occured to me to ask whether it might be  otherwise, which in this
> particular
> instance turned out to be a rather  expensive mistake:-)

Have one of those Trak 8821B too. It is a bit interesting since the
Motorola Oncore VP inside mine has the Z option (phase measurement).

--

Björn


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Re: [time-nuts] T-Bolt Temperature

[bg]

It would be a worthy hack (in the classic sense) to extract the Tbolt
firmware and patch it to work with the current temperature chips.

--

 Björn

> Hi
>
> Just in case this inadvertently heads of in the wrong direction….
>
> Lady Heather displays exactly what the TBolt firmware comes up with. The
> disconnect with the new sensor chip is between the TBolt firmware and the
> chip it's self.
>
> Bob
>
> On Aug 16, 2012, at 10:37 PM, Arthur Dent 
> wrote:
>
>>> Do you know the part number of a chip to replace the DS1620?
>>
>> The part number is the same, DS1620. What is important is the
>> revision of the DS1620. When Dallas Semiconductor/Maxim
>> 'improved' the chip and went from REV-D (or D2) to REV-E they
>> made a change in the way the data was sent to the outside world.
>> Lady Heather displays the temperature from REV-E chips in
>> distinct step instead of a smooth curve.
>>
>>  I have used REV-C2 chips as replacement and they work just
>> fine. Note the chip revision has little or nothing to do with the
>> Trimble REV letter on the outside of the Thunderbolt case, the
>> latest Thunderbolt revision from 2005 just happens to be a
>> REV-E.
>>
>> -Arthur
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[time-nuts] TADD-1 replacement status

[bg]

Hi,

Have not seen any recent updates on the new TAPR 10MHz distribution
amplifier design/production. What is the current status?

--

   Björn


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Re: [time-nuts] FRK specs.....

[bg]

Hi Don,

>
> Bert:
> Interesting.
>
> I, too, have a couple of the HP 10811 oven-oscillators sitting on the
> shelf for several years, waiting for a project. I want to 'discipline'
> them, but really do not know how.

Also look at John's modification of a Thunderbolt.

http://www.ke5fx.com/tbolt.htm


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   Björn


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Re: [time-nuts] FTS 1200

[bg]

Bert,

Good that you got the EFC working!   But I would be a bit suspicious of
needing -13V.

It seems from:
  
http://www.ece.gatech.edu/academic/courses/ece4007/08fall/ece4007l01/al4/datasheets/symmetricon_oscillator_instructionsheet.pdf

that the default EFC configuration is (0 to +10)V with a range of 4e-7
(2Hz). From the same document there are a lot of other EFC configurations,
but none that goes outside of +-10V.

My 1200 has about 3.5Hz tuning range on (0,10)V. Se attached jpg. I did
not check behavior on negative EFC voltage.

--

   Björn

> John,
>  that did the trick I can tune it with a negative voltage, minus 13  gives
> me plus 2 Hz but this unit came out of a FTS 5000 and it had a positive
> tuning voltage.
> Bert
>
>
> In a message dated 8/9/2012 9:13:29 P.M. Eastern Daylight Time,
> jmi...@pop.net writes:
>
>>  John
>> Oven did reduce in current and I can not imagine that it would be  that
>> close with an overheated oven. At 0 V it is within .5 Hz of what  they
> normally
>> are. Ground has no effect but even 0.8 V on pin 2  stops oscillation
>
> That's a suspicious-sounding voltage.  Are you  sure you're not
> forward-biasing the varicap?  Maybe some of these  OCXOs were specified
> for
> use with negative EFC voltage.
>
> If so, then  driving the diode with a negative voltage should raise the
> operating  frequency (which is what you want.)
>
> -- john,  KE5FX
> www.miles.io
>
>
>
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Re: [time-nuts] FTS 1200

[bg]

Hi Bert,

So the EFC does not work at all?  (or did I miss something obvious?)

/Björn

> The unit starts high and over 20 minutes comes down to 4.975 with 0 V
> on the EFC. Any voltage on pin 2 and it quits oscillating.
> Bert
>
>
> In a message dated 8/9/2012 7:06:48 P.M. Eastern Daylight Time,
> li...@rtty.us writes:
>
> Hi
>
> As the unit warms up, you should be able to tell weaner  it starts off
> above 5 or below 5 MHz. There are enough different crystal cuts  that
> *might* be
> in there that checking it at turn on is the easy approach. If  it starts
> low and is off low, the heater may be the  issue.
>
> Bob
>
> On Aug 9, 2012, at 6:53 PM, ewkeh...@aol.com  wrote:
>
>> Bjoern
>> No not able to tune it to 5 MHz.
>>  Bert
>>
>>
>> In a message dated 8/9/2012 6:48:59 P.M.  Eastern Daylight Time,
>> b...@lysator.liu.se writes:
>>
>> Hi  Bert,
>>
>>> I have a FTS 1200 that is off by  about 2 Hz.   Have  decided to take a
>>> closer look.  Does any one have technical  Information I should  study
>>>  before I
>>> open it up.
>>> Thanks
>>> Bert  Kehren
>>
>> The efc range on my FTS 1200 goes from about   -1.5Hz to +2Hz (0V to
> +10V).
>> Is your FTS1200 of even with max (or min)  efc  voltage?
>>
>> --
>>
>> Björn
>>
>>
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Re: [time-nuts] FTS 1200

[bg]

Hi Bert,

> I have a FTS 1200 that is off by about 2 Hz.  Have  decided to take a
> closer look. Does any one have technical Information I should  study
> before I
> open it up.
> Thanks
> Bert Kehren

The efc range on my FTS 1200 goes from about -1.5Hz to +2Hz (0V to +10V).
Is your FTS1200 of even with max (or min) efc voltage?

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Re: [time-nuts] HP 58503A

[bg]

Doug,

> I ran into a wiki description of GPS using WGS84 a couple days ago. It
> included a mention of ESEC and it was something like: Earth Static,
> Earth Centric. I think I was following a link about the Z3801A.
>
> It referred to the fact that lat-lon is referenced to a static grid on
> the Earth and doesn't change as the Earth rotates on its axis or around
> the sun. Earth static and Earth centric.

That reference frame is called Earth Centered Earth Fixed  (ECEF). And
that is what GPS is using "internally". However it is not lat/lon/h, but
cartesian with origo in the earth center, xy in the equatorial plane and z
pointing towards the north pole.

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

--

   Björn



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Re: [time-nuts] FTS1200, OSA8600, OSA8601 phase noise and ADEV measures

[bg]

> Bottom line, the large low-frequency spurs in the FTS plot at 1.4 and 2.9
> Hz
> will be caused by one of these conditions:
>
> 1) A problem with the reference source(s)
>
> 2) A problem with the FTS oscillator itself
>
> 3) A normal characteristic of the FTS oscillator (maybe its spur specs
> weren't very good to begin with?)

It seems the FTS1200 is only slightly out of spec compared to

 
http://www.ece.gatech.edu/academic/courses/ece4007/08fall/ece4007l01/al4/datasheets/symmetricon_oscillator_instructionsheet.pdf

  
http://rubidium.dyndns.org/~magnus/time/timelab/FTS1200_OSA8600_OSA8601_20120802_1.png
>
> 4) An RF crosstalk or leakage problem with the cables/adapters used
>
> 5) A power-supply regulation issue
>
> 6) Coupling between inadequately-bypassed power leads.  This is a big
> problem with some OCXOs where they apparently forgot to use bypass
> capacitors inside the can.  I usually solder a 0.1 uF ceramic chip cap
> right
> at the point of entry, if in doubt.
>
> 7) Some as-yet-unexplored effect related to beatnotes in dual-reference
> measurements.
>
> It may be possible to rule out cases (2) and (3), and definitely case (7),
> by temporarily switching back to the normal single-reference
> configuration.
>
> -- john, KE5FX
> www.miles.io
>

--

Björn


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Re: [time-nuts] 5MHz ocxo

[bg]

Hi,

Note that the 1804M, also has a 1PPS output. This is coming directly from
the GPS module 1PPS. The Trimble SV6 module I have in my units is only
good to 1us, almost a 1000 times worse than a Tbolt. I am not sure if the
SV6 has a "sawtooth" error message giving a good estimate on how wrong the
current 1PPS pulse is/was. However improving the 1PPS output accuracy and
jitter could for some uses be a useful mod.

--

   Björn

> On 25/07/12 23:36, Ed Palmer wrote:
>> Take another look at flea bay.  If you search for < "5 mhz" oscillator
>> > and weed out the trash there are a few decent looking units.
> I had searched for 5MHz ocxo which is why I didn't see the ones you
> found. Having said that the result is slightly frustrating as, although
> there are a few 5MHz ocxo's in the list none will fit the case which is
> only 1U
>>
>> As for repairing the original, go for it.  You can't make it any
>> worse.  I would use a utility knife to scrape away as much solder as
>> possible but don't use the sharp edge of the blade, use the back of
>> the sharp edge so that it cuts more like a cutter on a lathe or
>> milling machine.  Once you've got the excess out of the road, my tool
>> of choice is a micro-torch.  Pre-heating with a heat gun might be a
>> good idea, too.  If you search the archives you'll find more ideas on
>> opening these things.
> Thanks I'll have a look



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Re: [time-nuts] HP-5065a advise and purchase decision

[bg]

Tom,

> Chris,
>
> The HP 5065A is one of the best Rb ever made.
>
> /tvb (iPhone4)

Have you or any other list member had the opportunity to take measurements
on the ElmerPerkin/EG&G Space rubidiums (in a lab environment)?

   http://www.excelitas.com/Downloads/DTS_Frequency_Standards_RAFS.pdf

--

Björn


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Re: [time-nuts] Widdershins

[bg]

Direct GPS signals,  RHCP, good! Reflections (multipath) LHCP bad!  ;-)

--

Björn

> It's also connected to handedness. widdershins means to go leftwise,
> deasil righthanded or rightwise. lefthandedness bad, righthandedness
> good.
> Threads righthanded usually, bunches of other stuff.
> Don
>
> Bill Hawkins
>> Around 1530, it was considered very bad luck to walk around a church
>> widdershins (see the Wikipedia article). I think it goes back earlier
>> than that, to a time well before clocks.
>>
>> If widdershins means counter-clockwise, how did they know which way
>> clocks ran?
>>
>> The answer lies in northern hemisphere sundials. When clocks with
>> faces were invented, they ran in the same direction as the shadow
>> of the gnomon on a sundial.
>>
>> Widdershins also means anti-sunwise, which would be blasphemous to
>> people that used to believe that the sun was a powerful god.
>>
>> There's lots of angles to this time stuff.
>>
>> Bill Hawkins
>>
>>
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>
>
> --
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> R. Bacon
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
>
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Re: [time-nuts] Thunderbolt cabling questions

[bg]

> On Sun, Jun 10, 2012 at 2:50 PM,  wrote:
>
>> ... 3m
>> of antenna cable is no problem. Antenna position is more important than
>> the exact type of antenna. I'd rather have a decent antenna at a very
>> good
>> site, than a very good antenna at a slightly worse antenna site
>
>
>
> 3M is trivial.  30M will work fine too.
>
> I agree about the location really mattering more than anything else.  What
> I did was drill a 2" hole through the roof up from the attic and push a 10
> foot gallanvised iron plumbing pipe up.   The antenna sits on thop ithe
> pipe and is higher then the roof top ridge and then the cable go down the
> center of the pipe.  I pipe flange on top  of the pipe makes a perfect
> mounting platform.   I used a timing antenna comes inside a white pointed
> plastic radome.  These sell for just under $30 on eBay.   Maybe it is
> coincidence or not but the four holes pin the standard pipe flange match
> up
> with the four holes in the bottom of my antenna and there is enough room
> inside the hole in the center for an "N" connector.   It is worth getting
> the antenna "done right" because it is the most important part of the
> entire system. Those dome type antenna are worth it.  the shape is
> designed to shed both bird poop, and snow.  Birds can be an issue with a
> flat top antenna, no snow here.
> Chris Albertson
> Redondo Beach, California

The Trimble Bullit antenna has a 1" thread that will mate with a plumbing
pipe directly. The F-connector will fit through it. Be a bit careful,
since the pipe will have conical threads you might break the antenna if
using to much force.

--

Björn


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Re: [time-nuts] Thunderbolt GPS rollover

[bg]

Hi again Mark,

> Most GPS receivers base their rollover point from their data of
> manufacture/firmware creation/etc.   The week rolls over 1024 weeks after
> that.   They tend to not be dependent upon when the actual GPS week rolls
> over.  Better receivers have ways of inferring the actual week after a
> rollover occurs...  it appears that the Thunderbolt does not do this.
> Also,  most GPS receivers do not cease to work after a rollover...  they
> just report a bad date.
>
> From the Thunderbolt manual:
> The first week number roll-over will occur as August 21, 1999 (GPS)
> transitions to August 22, 1999 (GPS). The ThunderBolt adjusts for this
> week rollover by adding 1024 to any week number reported by GPS which is
> less that week number 936 which began on December 14, 1997. With this
> technique, the ThunderBolt will provide an accurate translation of GPS
> week number and TOW to time and date until July 30, 2017.

A neat solution to this would be if the time-nuts could reverse engineer
enough of the Tbolt to mod the firmware and fix any upcoming roll-over
issues. Anyone know if Trimble has issued any firmware upgrades to the
general public? Both my Nortel GPSTM 45000-boards have later firmwares
inside than in the printing on the physical board.

--

   Björn


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Re: [time-nuts] Trimble/Nortel 45000 GPSDO

[bg]

Hi Mark,

> I got in a couple of those Nortel GPSDO modules (marked 45000-00-B8
> GPSTM).   These are the single board version of the NTGS50AA modules that
> have a separate small front panel board.They are hardware and software
> compatible (mostly).   Some immediate differences popped up.  The 45000
> board is at least 6dB LESS sensitive than the NTGS50AA (maybe 4dB less
> than a Thunderbolt).  This might not be a good receiver if you have signal
> level problems.

My Nortel GPSTM units are also less sensitive that normal Tbolts. Have not
quantified it in a controlled way. Are your GPSTMs also late revisions?
Newer than the NTGS50AAs?  If so that is strange, since performance
(sentitivity at least) is worse. Hmmm... it is not quite clear that the
full length PCB is more expensive to build than the separate cards, with
cable (including 4 20cm SMB coaxes)

I think it would be interesting to compare the different versions, to find
out why there is such a big impact on sensitivity.


> Mine came in with the 34310-T oscillator.   The NTGS50AA came with the -T2
> oscillator (but may be shipped with the -T).   Like the -T2,  the -T seems
> to not be temperature sensitive.   Although it is way too early to tell,
> the -T started aging in at a 1E-8 parts/day.   The -T2 started at around
> 1E-9 parts/day and settled down after three weeks in the 5E-12 parts/day
> range.

Mine have oscillators marked "STP 2254, Spec 34310 C1", and "49422-CR". I
have yet to arrange with a stable laptop to run LH on continously.

--

Björn


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Re: [time-nuts] Thunderbolt cabling questions

[bg]

Hi Chris,

Even if this is the datasheet of a later version, it gives an overall
picture of what you ask about.

   
http://trl.trimble.com/docushare/dsweb/Get/Document-383329/022542-010B_Thunderbolt-E_DS_0807.pdf

The Tbolt perform (even) better with stable temperature surroundings. 3m
of antenna cable is no problem. Antenna position is more important than
the exact type of antenna. I'd rather have a decent antenna at a very good
site, than a very good antenna at a slightly worse antenna site.

My Tbolt with internal 24VDC PSU draws 200mA at 24V -> ca 5W. This is in
steady state at about 22C.

--

   Björn
>
>
>   10/06/2012 22:26
>
> My Thunderbolt, PSU and antenna should arrive this week. I would like
> to put out it outside my shack, which is an upstairs room in a bungalow.
> Outside of the plasterboard walls of my room is a big empty roof space.
> Can
> I put the TB in there, with it's PSU and feed the antenna wire out
> under a ridge tile and have the antenna itself on an aluminium bracket
> with a clear sky view on the ridge of the roof.? It would mean a cable
> from the output of the TB back into my room of about 10 or so feet.
> Anything I need to watch for, does the PSU run particularly warm? How
> much current do they draw off the mains, it's not going to cost a bomb
> leaving it on 24 hours a day, is it? Thanks.
>
> --
>Best Regards,
>Chris Wilson.
> mailto: ch...@chriswilson.tv
>
>
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Re: [time-nuts] NTGS50AA RS422

[bg]

Murray,

> Bjorn,
> I don't know of an RS422 connection at the back of the NTGS50AA. There is
> a
> 'CMOS' level serial output (essentailly a monitor point) on the top pin,
> 7th
> row along from the end the power is applied. There are also 10MHz PECL
> outputs at the other end of the connector.
>
> I use either Trimble's GPS Monitor software or the latest Lady Heather,
> and
> I connect to the front panel RS232 connector.
>
> 73,
> Murray ZL1BPU

I have sofar only used power on the back connector. Tboltmon works
out-of-the-box on the front RS232. Does GPS Monitor have extras compared
to Tboltmon? I have not yet got Lady Heather to work, have not spent much
time on it though.

I got the RS-422 from Sams message (16th of April).

> Serial Interfaces:
> Port A is RS-422 @19200 SCPI (available on the 110 pin connector on the
> main board)
> Port B is RS-232 @9600 TSIP (DB9 connector on Breakout board)

This Port A (or monitor port) does it go directly to the Trimble CPU ASIC?
Are there perhaps a hidden second serial port also on the normal Tbolts?

It would be nice to put the known infromation on the GPSTM boards on a
webpage so that newcomers do not have to start from the beginning.

--

Björn


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Re: [time-nuts] Trimble/Nortel GPSTM (NTGS50AA) - working with Lady Heather.

[bg]

Sam, Mark, Murray and others,

Which pins on the large "CPCI" connector holds the RS422 serial port.
Power is on row 1 and 4.

--

   Björn

> There was some discussion in Dec 2011 regarding the Trimble/Nortel GPSTM
> (NTGS50AA) which fizzed out after it was mentioned that Lady Heather would
> not work with these units. I was undeterred and purchased some anyway.
>
> I have started playing around with these and have discovered that by
> asking it Sat status (0x10, 0x3C, 0x10, 0x03) at ~300ms intervals the unit
> will start streaming data after a few seconds. Once the Trimble is in this
> state Lady Heather detects the GPSDO and seems to work normally... Except
> the TC and DAMP fields which are reported as 0.0 and GAIN which is
> reported as -3.500 Hz/V (Tboltmon reports the correct values) I have read
> that this also happens with older Thunderbolts?
>
> I have written a small Windows app (available on request, off list) that
> sends the required packets to the GPSTM and by wrapping it in a batch file
> I have it opening Lady Heather once the unit is in the required state.
> (Only required once, or after running Tboltmon)
>
>
> Details of my 3, Trimble NTGS50AA's are:
>
> Firmware:
> App: 2.68  - 16 Dec 2004
> GPS: 10.4 - 15 Dec 2004
>
> GPS receiver has 8 Channels.
>
> Default disciplining parameters as reported by Tboltmon:
> Time Constant (sec): 100.0
> Damping: 1.2
> Ko (Hz/V) 1.20
> Min Voltage: 0.0
> Max Voltage: 6.0
> Initial DAC Voltage: 3.00
> Jam Sync Thresh (ns): 0.0
> Max Freq Offset (ppb): 45.0
>
> These GPSDO's uses the Trimble 34310 DOCXO which I think is the Vectron
> OC-050?
>
> There are 4 SMB RF connectors on the main board:
> 1. GPS Antenna Input
> 2. 10.000 MHz Output
> 3. 9.834 MHz Output
> 4. 0.5 Hz (Even Sec)  PP2S Output. Unfortunately requesting the unit to
> output 1PPS does nothing. (yet)
>
> The 9.8304MHz output may be handy.. divided by 300 it's 32.768 KHz ;)
>
> Power Supply:
> The NTGS50AA requires 36-75 VDC (48V nominal) and has a on-board Lucent
> DC-DC converter to supply the required +/-12 and +5 volts.
>
> Serial Interfaces:
> Port A is RS-422 @19200 SCPI (available on the 110 pin connector on the
> main board)
> Port B is RS-232 @9600 TSIP (DB9 connector on Breakout board)
>
> LED indicators:
> There are 5 LED's on the breakout board that contains the DB9 connector.
> 1. Power
> 2. Not used, but switch-able via software
> 3. Not used, but switch-able via software
> 4. Lock
> 5. Holdover
>
> Temperature Sensor:
> DS1620 Rev D
>
> Jumpers:
> There is a 8 pin header (JP1) on the main board that would accept 4
> jumpers.. I haven't tried them but it is tempting to see what happens when
> I enable them.
>
>
> //Sam
>
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Re: [time-nuts] NTGS50AA, better than Thunderbolt

[bg]

Hi Mark,

> My second NTGS50AA came in from Old Cathay.  Seems to be working OK.  A
> couple weeks of oscillator aging will tell more.   This one originated
> from Guatemala City, Guatemala (the other one also came from Guatemala)
> The seller on Ebay has scaled back his dirty capitalist pig escalation in
> price down to $100...  shipping still at the 100% markup of $60 (unit was
> was $69/$30 before the excitement).
> Note that these units do have the pads for SMA connectors if you want to
> replace the oscillator.

I got two Trimble boards from HK. They seem to be an earlier version of
the NTGS50AA. There is one BIG full length PCB, no separate daughter board
with LEDs and DB9 serial port. See Ebay #300678217853.

They run fairley well, have not let them settle down really. There are
some very slight differences between the boards. PWB markings 45000-00-C
rev H and 45000-00-B rev C. The newer has FW 3.62 and OCXO are Trimble
49422-CR, date 0436. The older board has FW 3.55 and OCXO marked Trimble
STP 2254, SPEC 34310 C1, date 0247.

Running Tboltmon you get a GUI page for controlling the LEDs. Never saw
that for the ordinary Tbolts. So it seems the Tboltmon is aware of these
variations. :-) It is a 8 channel GPS.

Has anyone compared these full length GPSTM Thunderbolts with the smaller
layout NTGS50AA versions?

--

Björn



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Re: [time-nuts] Why are 1PPS signals so skinny?

[bg]

Mark & Azelio,

Or even 10V into 50ohm, 20us... See figure 3-4 in ICD-GPS-060.

http://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf

More modern 3-5.5V into 50ohm, 20us.
 
http://contracting.tacom.army.mil/majorsys/jab/DAGR%20Interface%20Specification.pdf

Above are two standards demanding short skinny 1PPS pulses. Are there any
other standards with distinct shape requirements on 1PPS pulses?

--

   Björn

> Feed a 5V 1Hz square wave into a 50OHM load and look at the power drain.
> Do
> the same with a 100uS pulse and smile at the difference.
>
> On Mon, May 14, 2012 at 5:23 PM, Mark Sims  wrote:
>
>>
>> My first inclination,  if I were building a timing receiver,  would be
>> to
>> make the PPS output a nice,  symmetrical square wave.   But pretty much
>> all
>> GPS timing receivers output an anorexic,  dinky little heroin addicted
>> supermodel sized pulse (from 1 to 150uS wide is typical).


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Re: [time-nuts] Tbolt failure modes

[bg]

Thanks everyone!

> On 05/12/2012 03:37 PM, Mark Sims wrote:
>>
>> It sounds like the -12V supply is used to generate the DAC low voltage
>> reference.  If it is floating,  the DAC output will be unstable.  If it
>> is at a solid voltage,  the DAC output will be stable.  The standard EFC
>> range for a tbolt is -5V to +5V,  but since almost all Tbolts are
>> running the osc with a positive EFC voltage,  it will work with the -12V
>> line grounded.
>>
>> I suspect that  although it may appear to be working,  the DAC output
>> may not be as stable as with a negative rail available since whatever is
>> generating the negative DAC reference voltage will be well below its
>> dropout voltage.
>>
>> One thing to try is to do an oscillator autotune with the -12V line
>> grounded  and at -12V.  Your DAC gain will probably double (or half)
>> since the DAC output range is now 0V..5V instead of -5V to 5V.  The
>> tbolt firmware knows what the expected dac voltages rails are (readable
>> via an undocumented TSIP message) are and also has settings for what
>> range to allow the EFC to swing.
>
> Well, all this is well, but doesn't reflect well on Björns problems I
> think, I did look at his postings in this thread and he seems to have
> valid -12V.
>
> What is an issue is that the big ASIC seems either powerless or kept not
> running.
>
> Either a 3,3V regulator went down, got shorted or something, or clock
> failed or reset line not released.
>
> I am a bit interested in this myself, but don't have the time to drive
> down to him this weekend.
>
> Cheers,
> Magnus

I have checked the voltages. They are the same, measuring on the defect
unit and a working one. Have also swapped the receiver boards between
different PSUs. There is no problem running a working receiver with the
PSU of the defect one. Hence I agree with Magnus and others suggesting the
CPU (big Trimble asic) is not running.

Today I do not have access to the right instruments, but just measuring
with a DMM - there are differences at TP8, TP9 and TP10. And as mentioned
previously the CPU-chip is to cold, compared to a working unit.

I do not have time to pursue the CPU problem right now. Hope to come back
later with an update.

thanks,

Björn


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Re: [time-nuts] TU-60 Instruction to set NMEA output

[bg]

Hi Merv,

> Hi,
>
> I am new to timenuts.
>
> Is anyone able to give me the binary command sentence/code to send to my
> Jupiter TU-60 to change it's output from Binary to NMEA please?
>
> I assume it has to be a binary command starting with @@ but I am unable to
> find a suitable command using Tac32 control software.
>
> Merv  VK6BMT

I used to have an older Jupiter receiver. Does your receiver have the same
2x10 pin interface as shown in table 4 of the linked datasheet?

   http://gpskit.nl/documents/rockwell/jupiter-gps-board.pdf

On that receiver, you could chose power up mode (NMEA or Jupiter binary)
with a hardware jumper. Se below schematic (SW2) how the adapter board I
used implemented the NMEA/binary choise.

   http://gpskit.nl/images/thekit-schematics-large.gif

--

   Björn


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Re: [time-nuts] Trimble Resolution SMT - good/bad/indifferent?

[bg]

> On 5/11/12 2:38 AM, Hal Murray wrote:
>>
>>> Why in the hell would anybody build a 50 channel receiver?  At most you
>>> MIGHT see 12 usable GPS sats...  I don't think that I've seen over 10.
>>> WAAS
>>> should be fairly useless for a timing receiver.
>>
>> I can think of a couple of reasons.  I'm sure there are more.
>>
>> One would be marketing type bragging rights.  I can scan more channels
>> than
>> you.
>>
>> Another area would be cold-start time.  If you have to search N slots,
>> more
>> searchers runing in parallel is likely to speed things up.
>>
>>
> Searchers and trackers are often different logic, these days..
>
> Searching is very efficiently done with a FFT correlator, because you
> can search all lags simultaneously with NlogN effort as opposed to
> O(N/2) effort with a sequential search.  Same for Doppler.
>
> But once you've acquired, you track with a conventional
> Early/Prompt/Late scheme.
>
> When you get into full-up implementations, where there is coupling
> between the tracking loops (think of a 2 frequency receiver.. L1 and L5
> will have related doppler), there are other "economies of scale" possible.

Here is an example of tracking loops coupled even more.

http://www.javad.com/downloads/jns/papers/coop_tracking.pdf

--

Björn


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Re: [time-nuts] (no subject)

[bg]

>
> I like "Less than $20... Not for Sale"  Sounds like vaporcrap to me...
> -
> Or 216 channels (GPS L1/L2/L2C/L5; GLONASS L1/L2; Galileo E1/E5A):
> http://www.javad.com/jgnss/products/triumph.html

Have used Delta receivers in production at a former employment. They are
very capable receivers.

http://www.javad.com/jgnss/products/receivers/delta.html


--

Björn


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Re: [time-nuts] question about Thunderbolt geo acuracy

[bg]

Attilla,

> On Thu, 10 May 2012 22:50:15 +1000
> swingbyte  wrote:
>
>> Hope this isn't too chat roomy, however, I have need of a survey precise
>> geolocation type gps.  I was wondering if the precise timing abilities
>> extend to its precision in position output?  I have a thunderbolt and
>> one of those conical white aerials from china and would like to know if
>> this combination will give me accurate height data.
>
> How fast do you need it?
>
> One project i'm involved with uses a LEA6-T with its phase data output
> and averaging over several hours to get x/y resolutions in the 2-4mm
> range.
> I'm quite sure you can do something similar with altitude as well.
>
>   Attila Kinali

That is relative positions over a baseline of ca 100m. Not absolute
positions.

---


 Björn


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Re: [time-nuts] question about Thunderbolt geo acuracy

[bg]

Hi Tim,

The answer is NO. Even though decent accuracy can be had with long
averaging. It was discussed a few years ago on this list.

--

   Björn

> Hi all,
> Hope this isn't too chat roomy, however, I have need of a survey precise
> geolocation type gps.  I was wondering if the precise timing abilities
> extend to its precision in position output?  I have a thunderbolt and
> one of those conical white aerials from china and would like to know if
> this combination will give me accurate height data.
>
> Thanks
>
> Tim
>
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Re: [time-nuts] Can M12+T be improved?

[bg]

> In message <727909549.133407.1336592785570.JavaMail.mail@webmail11>,
> billdobson
> @uk2.net writes:
>
>>   The idea is to remove the onboard TCXO and replace it by a
>>   16.368MHz clock synthesysed from the OCXO,
>
> I asked one of the motorola engineers about this long time ago for
> the UT+, and he said pretty flatly that it wouldn't work.
>
> He said that it is not really a TCXO but an XO with it's temperature
> measured and the frequency looked up in a table in the onboard
> microcontroller, and therefore the temp-calibration would have to
> be redone and he wouldn't tell me the commands to do so.
>
> Those commands may have leaked subsequently, and the M12 may be
> different from the UT in this respect, but I doubt it is enough
> to just preplace the TCXO.

So the UT+ really has a "synthetic" TCXO. Having a OCXO that should not be
needed. Where is the temp sensor? Is it possible to disable?

There is an old article where an Oncore VP is phase locked to an external
Cs oscillator.

 http://www.pttimeeting.org/archivemeetings/1999papers/paper35.pdf
 http://tycho.usno.navy.mil/ptti/ptti2000/paper9.pdf


--

Björn


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Re: [time-nuts] Allen Osborn Turborogue SNR-12 RM

[bg]

Hi Thomas,

AOA used to be in Westlake Village, north of LA. They were bought by ITT
some years ago. ITT more recently split, I think they should be within ITT
Exelis. Maybe you could contact them?

   
http://www.exelisinc.com/capabilities/GPS-Payload,-Receiver-and-Control-Systems/Pages/default.aspx

To convert data, try tecq. There is also some information available on
downloading etc,

http://facility.unavco.org/software/teqc/examples/CB.html
http://facility.unavco.org/software/download_transfer/aoa/aoa.html

Another idea could be to check if there is any manuals left on old CORS
sites that used to run SNR-12 receivers.

--

Björn

> I recently picked up a Allen Osborn Turborogue SNR-12 RM which I believe
> is a Metrology quality L1 L2 carrier phase receiver but I have so far
> found no documentation. Is anyone familiar with these instruments and
> possibly know where I could locate a manual.
> Thanks;
> Thomas Knox



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Re: [time-nuts] Tbolt failure modes

[bg]

> Agreed, the CPU is not working... check the 3.6864MHz crystal under the
> CPU. If it is possible to locate the reset signal...

Time to get some sleep... I found the crystal. It is not easily probeable
when mounted on the PSU board. Also the power rail has to short pins to
accept the external 3 voltage PSU fitting the 1-board version of the
Tbolt. Will need to adapt something.

--

   Björn


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Re: [time-nuts] Tbolt failure modes

[bg]

Hi Magnus,

> On 05/08/2012 11:58 PM, Bob Camp wrote:
>> Hi
>>
>> The first thing to check is the soldering job on the DB-9 connector.
>> Second thing to check is the RS-232 level translator IC. (RS-232 in
>> should create TTL etc)
>
> Does not explain why the OCXO remains stuck as if it was untrained.
>
> I suspect that the CPU never starts or hangs early.
>
> Cheers,
> Magnus

The big Trimble IC (U2) close to the RS232 port, is also noticeable colder
to a finger tip on the faulty unit, compared to a working unit.

--

  Björn


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Re: [time-nuts] Tbolt failure modes

[bg]

Hi Bob,

The DB-9 looks fine even with magnifying glass.
The good one has a MAX232EWE IC, the faulty has a TC232EOE. I see 
RS232-level coming in at pin 13 and going inside the Tbolt at pin 12 (ttl
level).So there should be no problem there.

Have also swapped PSU board, so the problem is inside the actual GPSDO board.

The 232 level IC is a dual channel RX/TX translator. Anyone know what the
second 232 port is used for?

--

   Björn

> Hi
>
> The first thing to check is the soldering job on the DB-9 connector.
> Second thing to check is the RS-232 level translator IC. (RS-232 in should
> create TTL etc)
>
> Bob
>
> On May 8, 2012, at 5:52 PM, b...@lysator.liu.se wrote:
>
>> Hi group!
>>
>> Just got a few Thunderbolts. It is a few PN 39448-61 and one PN
>> 38223-61.
>> Date codes from 9932 to 0025. This is the "normal" version with a 24VDC
>> power board and Tbolt board integrated in a small AL box with red
>> markings. One of the receivers is having a problem. Measuring from the
>> outside there is:
>>
>> 1) Takes the same amount of power as the working units.(to the
>> resolution measured)
>> 2) Has 10MHz output.
>> 3) Has 4.9VDC on antenna center pin.
>> 4) -8.9VDC stable on rs232 Tx pin (pin2 in DB9)
>> 5) 10MHz is 0.7Hz off after many power on hours with known good antenna
>> 6) TP9 & TP10 (close to the GPS board power connector) has 4.9VDC
>> 7) Tboltmon will not talk to the board.
>> 8) There is no serial output at all from the Tbolt.
>>
>> Differences compared to a good Tbolt
>>
>> 1) Tboltmon will ofcause communicate.
>> 2) After locking 10MHz will be very close to nominal
>> 3) TP9 and TP10 shows a square wave (ca 7V pp, 9.795625000kHz)
>>
>> I have looked at Tom's page at
>>
>>  http://www.leapsecond.com/tbolt-faq.htm
>>
>> Brooke's at
>>
>>  http://www.prc68.com/I/ThunderBolt.shtml#IC
>>
>> and John's at
>>
>>  http://www.ke5fx.com/tbolt.htm
>>
>> Are there other good Thunderbolt sites?
>>
>> Has anyone done debugging of faulty Tbolts? Comments on what might be
>> wrong with my faulty unit? (I am not that experienced in hardware
>> debugging...)
>>
>> --
>>
>>  Björn
>>
>>
>>
>>
>>
>>
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[time-nuts] Tbolt failure modes

[bg]

Hi group!

Just got a few Thunderbolts. It is a few PN 39448-61 and one PN 38223-61.
Date codes from 9932 to 0025. This is the "normal" version with a 24VDC
power board and Tbolt board integrated in a small AL box with red
markings. One of the receivers is having a problem. Measuring from the
outside there is:

  1) Takes the same amount of power as the working units.(to the
resolution measured)
  2) Has 10MHz output.
  3) Has 4.9VDC on antenna center pin.
  4) -8.9VDC stable on rs232 Tx pin (pin2 in DB9)
  5) 10MHz is 0.7Hz off after many power on hours with known good antenna
  6) TP9 & TP10 (close to the GPS board power connector) has 4.9VDC
  7) Tboltmon will not talk to the board.
  8) There is no serial output at all from the Tbolt.

Differences compared to a good Tbolt

  1) Tboltmon will ofcause communicate.
  2) After locking 10MHz will be very close to nominal
  3) TP9 and TP10 shows a square wave (ca 7V pp, 9.795625000kHz)

I have looked at Tom's page at

http://www.leapsecond.com/tbolt-faq.htm

Brooke's at

http://www.prc68.com/I/ThunderBolt.shtml#IC

and John's at

http://www.ke5fx.com/tbolt.htm

Are there other good Thunderbolt sites?

Has anyone done debugging of faulty Tbolts? Comments on what might be
wrong with my faulty unit? (I am not that experienced in hardware
debugging...)

--

Björn






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Re: [time-nuts] FS700 antenna

[bg]

Magnus,

> Hi Stan,
>
> On 05/05/2012 08:18 PM, Stan, W1LE wrote:
>> The classical approach:
>>
>> Look at the spectrum and notch or filter out what is not wanted.
>>
>> The FS-700 does have a set of filters and a front panel LORAN output
>> (w/gain)
>> to monitor with a spectrum analyzer for filter settings.
>>
>> I like the AUSTRON model 2048 LF Multifilter, just like a 1X4 RF
>> multicoupler
>> with a series of 8 notch filters for ~70 thru 130 KHz, with a peak
>> indicator and a spherics indicator light.
>> Notch filters can be switch selected on the front or some are on the
>> real panel.
>
> The FS700 has a 6 filters on it's input. Considers hooking myself up and
> see how much signal I see and if there is noise. I highly suspects that
> my antenna signal isn't exactly great.
>
>> For intermittent signals like noises, the peak indicator lamp gets my
>> attention.
>
> Sounds handy.
>
> Cheers,
> Magnus

I could probably have it hooked up to one of these

 
http://www.procom.dk/products/base-station-antennas/0-25-mhz/omnidirectional-antennas/bcl-1-ka

You do not want to loan your new toy away for a few weeks? ;-)

Btw does the FS700 receive the Russian Chayka signals? I think there is a
Russian station at about the same distance as the closest Norwegian Loran
station from Stockholm. Also the path from Norway is pure land, from
Russia it is mostly water.

--

   Björn


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Re: [time-nuts] Setting up PRS10 with M12+T GPS

[bg]

> Björn,
>
> On 05/03/2012 12:30 AM, b...@lysator.liu.se wrote:
>> Magnus,

 Tbolt   PRS10A PRS10B
 1pps  --> PPSIN
   PPSOUT -->   PPS IN

 PRS10A slowly following the Tbolt (PRS10A PT8)
 PRS10B "quickly" following the PRS10A (PRS10B PT0)

 Ok?
>>>
>>> Yes, but if this is a free-running thunderbolt (I think you said
>>> something about that) then PT8 will be a bit slow. For a tracking
>>> thunderbolt PT8 may work, even if it takes time for it to track in.
>>
>> No a GPS locked Tbolt.
>
> Thanks for that clarification, I am obviously a bit tired.
>
>> A free-running Tbolt was just an example of a very
>> low noise 1PPS source, where I would find it useful to have a "PT-1"
>> bias
>> calibration mode bypassing the PLL, and moving the PPSOUT directly with
>> the PPSIN.
>
> So this does not suffice?:
>
> Page 33:
> "When provided with an accurate and stable 1pps source, the unit will
> automatically align its 1pps output to the 1pps input and then adjust
> the frequency of the rubidium reference to maintain the alignment over
> time."
>
> Page 17:
> "After receiving 256 consecutive "good" 1pps inputs, the 1pps pulse
> delay is set to the last of the 256 time-tag values."
>
> I interpret this as this:
>
> When the 256s PPS has been approved, the last-time-tag is used to adjust
> the output delay such that the output signal is aligned, within the
> precision of the time-offset value.
>
> Then, the PLL is running. Either the output delay is not shifted and
> only the PPS alignment is done on approval, or it is updated in the
> background. The text only supports the former explicitly, but it would
> be nice to verify if it is either of these.
>
> Doing phase-jump of PPS like this on start-up is expected. I've even has
> a measurement on it somewhere.

It is surely working alright in the long run. I am not convinced it is
appropriate for applications where you fire up the PRS for a few hours and
then do a few hours of measurements.

Even if it jumps the 1pps, early on the PLL will still be 100s of ns away
from its reference. There should be a better way to make this, than how I
run the PRS...

--

   Björn


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Re: [time-nuts] Setting up PRS10 with M12+T GPS

[bg]

> Yes, all made clear.
> Trigger on Ch.4, I see. You have written "green: 10MHz PRS10B" but it must
> be A, otherwise it seems that the PPS and the 10MHz of the PRS10 are not
> phase aligned. Moreover, the PRS10B seems to track the PRS10A with "some
> delay" as the 10MHz from A spreads on more than 5nS (useful, the infinite
> persistence, isn't it? I use it a lot)
>
>

I had

locked Tbolt 1PPS going into PPS_IN of PRS10A
PPS Out of PRS10A going into PPS_IN of PRS10B.

I watched/measured
1) PPS out from Tbolt on ch 1  (yellow)
2) 10MHz out from PRS10A on ch 2 (green)   // Corrected
3) 10MHz out from PRS10B on ch 3 (blue)// Corrected
4) 1PPS out from PRS10 B on ch 4 (red)

I should do some proper measurements with TIC, instead of just 'watching'
on the scope. Yes the 1pps and 10MHz is ofcause stable within the same
PRS10. But should not the 10MHz zero crossing be aligned with the 1PPS?
Cables were not perfectly matched, but should be within 2-3ns of each
other.

Yes, persistance is very nice!

--

   Björn


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Re: [time-nuts] Setting up PRS10 with M12+T GPS

[bg]

Magnus,
>>
>> Tbolt   PRS10A PRS10B
>> 1pps  -->PPSIN
>>  PPSOUT -->  PPS IN
>>
>> PRS10A slowly following the Tbolt (PRS10A PT8)
>> PRS10B "quickly" following the PRS10A (PRS10B PT0)
>>
>> Ok?
>
> Yes, but if this is a free-running thunderbolt (I think you said
> something about that) then PT8 will be a bit slow. For a tracking
> thunderbolt PT8 may work, even if it takes time for it to track in.

No a GPS locked Tbolt. A free-running Tbolt was just an example of a very
low noise 1PPS source, where I would find it useful to have a "PT-1" bias
calibration mode bypassing the PLL, and moving the PPSOUT directly with
the PPSIN.

--

   Björn


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Re: [time-nuts] Setting up PRS10 with M12+T GPS

[bg]

Hi Magnus,

>> |---|
>> |   |
>> |   PRS10APRS10B   |
>> |--->PPS IN PPS OUT-->PPS IN PPS OUT--|
>>
>>
>> hoping that the font doesn't mess up the ASCII schematic...
>
> PRS10A PRS10B
> PPSOUT --> PPSIN
> PPSIN  <-- PPSOUT
>
> I believe he meant.

No I would never do that! Take one! let the other follow the first one.

>
> I also believe he used a separate source for the later experiment.

Tbolt   PRS10A PRS10B
1pps  -->   PPSIN
PPSOUT --> PPS IN

PRS10A slowly following the Tbolt (PRS10A PT8)
PRS10B "quickly" following the PRS10A (PRS10B PT0)

Ok?

--

   Björn


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Re: [time-nuts] Setting up PRS10 with M12+T GPS

[bg]

>>The phase of the PPSOUT and the generated 10 MHz will probably not align
> up, >something which is critical to some applications.
> Yes, for example the DVB-T SFN requires the PPS and 10MHz phases to be
> aligned, better, not to move. This requires to slightly alter the 10MHz to
> keep the PPS aligned.
>
> Let me ask Bjorn: did you succeed in aligning the two PRS10?

Somewhat... I had a "stable" offset between the 10MHz PRS10 signals of
almost 8ns, moving +-2.5ns over some hours.

Moreover,
> what
> do you mean by "each other", a scheme like this:
>
>
>
> |---|
> |   |
> |   PRS10APRS10B   |
> |--->PPS IN PPS OUT-->PPS IN PPS OUT--|
>
>
> hoping that the font doesn't mess up the ASCII schematic...

Almost, I also let the PRS10A be steered by a Tbolt.

PLL settings 8 on PRS10A, and 0 on PRS10B, which should make PRS10B quick
enough to follow any wiggle the PRS10A do slowly following its Tbolt
supplied PPS_in.

I had

locked Tbolt 1PPS going into PPS_IN of PRS10A
PPS Out of PRS10A going into PPS_IN of PRS10B.

I watched/measured
1) PPS out from Tbolt on ch 1  (yellow)
2) 10MHz out from PRS10B on ch 2 (green)
3) 10MHz out from PRS10A on ch 3 (blue)
4) 1PPS out from PRS10 B on ch 4 (red)

see attached screendump from a 500MHz Scope.  I did not have enough time
to completely remove offsets between 10MHz signals from PRS10A & B. More
tuning should have been done on the PRS10A wrt the Tbolt PPS also.

Any comments?

--

   Björn

> On Wed, May 2, 2012 at 11:07 PM, Magnus Danielson <
> mag...@rubidium.dyndns.org> wrote:
>
>> Hi Azelio,
>>
>> On 05/02/2012 10:30 PM, Azelio Boriani wrote:
>>
>>> Magnus, you are correct but can I avoid to list our beloved
>>> counters/analyzers? The time-nut main tool is the TIC.
>>>
>>
>> Hehe, yes. But you can do great things even with a spare HP5335A for
>> instance. It's quite respectable with about 1 ns resolution in this
>> context.
>>
>> I have not tried using the SIA-3000 for TIC purposes. Just "getting
>> into"
>> the machine GPIB-wise is a bit of a challenge.
>>
>>  Anyway, to correct the PPS input for the PRS10 the hardware approach is
>> a
>>> must: so a delay line and a microprocessor are needed. Unless the SRS
>>> can
>>> develop a suitable software for the PRS10 (an inverted TTL serial line
>>> is
>>> already present) to read the M12+.
>>>
>>
>> Well, look at the Spectratime SRO-100, which already has that feature.
>>
>> http://www.spectratime.com/products/isync/gps-disciplined/SRO-100
>>
>> Architecture-wise it is very similar to the FEI 5680, a 60 MHz VCXO, DDS
>> for FLL and then DDS for output. PPS input and output makes you think
>> about
>> PRS-10. The PPS input has about 1 ns resolution.
>>
>> Now, there is a few things which differs from the PRS-10. It move it's
>> internal (and later also its output) PPS to align up to the PPS
>> reference.
>> It hence does not need an output alignment. This makes the 7,5 MHz clock
>> (133 ns cycle) less critical. BTW I do the same in my products. The
>> phase
>> of the PPSOUT and the generated 10 MHz will probably not align up,
>> something which is critical to some applications.
>>
>> Also, it can take info from Jupiter-T, OnCore, M12+ and SuperStar II
>> receivers for detailed timing info.
>>
>> Cheers,
>> Magnus
>>
>>
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Re: [time-nuts] Setting up PRS10 with M12+T GPS

[bg]

Jerry, Magnus,

> Considering the M12+T PPS noise, you won't need anything stellar. A
> PICTIC II will do just fine... or if you trust the PRS-10 readings, run
> from that.
>
> What would make this better would to use a sawtooth-correction to PPS
> delay setup, as the PRS-10 measurement resolution will be about on par
> with that. Would lower the effects of hanging-bridges, even if one
> suffers less when dealing with a rubidium.
>
> Adjust the PRS-10 PLL bandwidth/time-constant, the default value is most
> probably not optimum, you can go further up in time. Do check the manual.

But do not have a large PLL time-constant, while you are checking basic
functionality. Time-constants are shown in a table on page 35 in the
manual.
With default (PT=8) settings it will take hours for the pll to get close
in. Any tinkering with moving the pulse (PP) or delay calibration (TO)
will take forever to show if you got the sign right or hade the right
offset size... ;-(

Calibrate the Time offset (TO) according to the example on page 32 in the
manual, by looping the 1pps_out to 1pps_in on the PRS10, keep in mind that
you should use the cable, buffers, etc that later will take your GPS 1PPS
to the 1PPS_in on the PRS, so that you really take care of all delay from
the GPS 1pps to the PRS10, including internal PRS10 delays, that might
have changed from previous calibration.

Also have in mind that the 1pps disciplining wants 256 good measurements
in a row just to start closing the PLL.

Take the time constant down to 0, and make yourself confident that all
offset calibrations are right and that you are tracking the right edge of
the GPS 1PPS etc. After all tinkering to get the basics right then
increase the time-constant to filter out 1PPS noise and outliers.

To check performance later, you could check that the PRS10 timetag (TT)
stays very low, by polling each second and logg these values.

I am not at all an expert on PRS10. Have spent the weekend trying to get
two units to sync to each other. I would like to have a simple (quick
feedback) way of making sure that most time bias'es are removed. A
free-running Tbolt for example gives a low noise 1PPS, and quickly
tracking that, would make bias elimination much less time consuming.

Anyone having an efficiant scheme for setting up a PRS10?

--

Björn
>
>> On Wed, May 2, 2012 at 9:46 PM, Jerry Mulchin  wrote:
>>
>>> I need some guidance from the collective.
>>>
>>> I just finished rebuilding my PRS10 lab standard and it is now using a
>>> M12+T GPS module.
>>> I have completed my site survey and it is now in "hold position mode",
>>> TRAIM is enabled
>>> with 500ns alarm setting and the 1PPS is enabled during non-TRAIM alarm
>>> conditions.
>>>
>>> The PRS10 is set for default 1PPS steering, but all of the other
>>> parameters are just as
>>> I received the unit 5 years ago.
>>>
>>> My questions are these;
>>>
>>> 1.) Should I reset the PRS10 to its Default settings or just adjust
>>> selected parameters to
>>> align the unit for proper operation with the M12+T unit? And if that is
>>> the case, what parameters
>>> need adjusting?
>>>
>>> 2.) Are there any special settings, other than what WinOncore sets,
>>> that I
>>> should make to the
>>> M12+T unit?
>>>
>>> 3.) After all this is completed, how do I know that the PRS10 is
>>> properly
>>> tracking GPS and
>>> maintaining frequency accurately? I don't have a Cesium reference, but
>>> I
>>> do have an un-disiplined
>>> LPRO-101, but I don't think that really helps me determine frequency
>>> accuracy.
>>>
>>> I will be adding the sawtooth correction eventually to the M12+T 1PPS
>>> output, but observed
>>> negative sawtooth with WinOncore shows +/- 14ns changes with some
>>> bridging
>>> occasionally.
>>>
>>> While I don't ever want to claim NIST traceability, I would like to be
>>> a
>>> close as possible, and I
>>> guess that is the bottom line need here. So what else do I need to do
>>> to
>>> get as close as possible?
>>>
>>> Thanks for any help.
>>>
>>>
>>>
>>>
>>> Jerry Mulchin
>>>
>>>
>>>
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Re: [time-nuts] Ashtech 3DF GPS

[bg]

Hi Stan,


> On more or less of a whim, I found and bought an Ashtech 3DF GPS. The
> interesting thing about this particular GPS is that it uses four separate
> GPS antennas mounted in a diamond pattern about 1 meter on a side and can
> compute not only the "usual" stuff, but also heading, roll, and pitch
> angles. I had heard of this being possible, but never actually seen it
> done.
> There are no accessories included with this unit, other than the power
> cord.
>
> Does anyone know where I can find a manual for it?

Look for manuals in

ftp://ftp.ashtech.com/OEM,%20Sensor%20&%20ADU/

perhaps it is this one? Or an earlier version.
   
ftp://ftp.ashtech.com/OEM,%20Sensor%20&%20ADU/ADU2/Reference%20Material/adu2.pdf


> Will this GPS work with just four ordinary active antennas or are the
> antennas special?

Will probably work with almost any antenna, but for good performance use a
geodetic quality rover antenna.

> Given the complexity of the additional data massaging it does to extract
> the
> angular data, does this also mean that it will have more accurate position
> and or timing performance?

No, its specialty is to determine the relative positions of the four
antennas. This will give heading, roll and pitch of the vehicle the system
is mounted on.

> Does it need all four antennas to be able to do anything at all, or can it
> compute position and time with just one antenna connected?

It will probably do position and time with just the "master" antenna
connected.

> Thanks,
> Stan

Good luck!

--

Björn


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Re: [time-nuts] Sw for pm6680B

[bg]

Hi,

> Hi the Gang,
>
> I just got not cheap but for a quite reasonnable price a legacy Fluke
> PM6680B counter.
> This toy seems to be very interesting to play with, I already have a
> 5370B but this new toy I got seems to be more fancy to play with, have
> to be confirmed.
> I know there is a software from Fluke names TimeView, is it possible to
> get a copy of it?
> Are there any other software running under Windows XP and/or w7 I could
> use?
> Any help will be appreciated.
>
> All the bests to you.
> Pierre-Francois, F5BQP

John Miles' Timelab now works fine with my PM6681.

" V1.010 of 12-Mar-12
Added support for the Philips/Fluke PM6680 counter"

http://www.ke5fx.com/timelab/readme.htm

I do not see a reason to use TimeView.

--

Björn


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Re: [time-nuts] Trimble recommends RG-59 Antenna Cable.

[bg]

Hi Ken,

> Hi Time-Nuts guys,  I was reading the Trimble Thunderbolt manual section
> 2.1.3 (Antenna Cable).  Trimble recommends using RG-59 cable which is 75
> ohm coax.  Is this a typo or is this correct?  I thought that the Trimble
> Thunderbolt would use a 50 ohm cable and antenna.
>
> Thankyou
>
> Ken Kubick
>
> kenkub...@hotmail.com

That is correct. That is also why the companion Trimble Bullet antenna is
available with F-connector. However the Tbolt runs very well on 50ohm
cables/connectors as well.

--

Björn


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Re: [time-nuts] Trimble Thunderbolt GPS Antenna

[bg]

Hi Ken,

>
> Hi,  Time-Nuts guys I just baught a Trimble Thunderbolt on ebay.  I am in
> need of an antenna,  there are so many on ebay I am not sure which one to
> get. Maybe someone could point me in the right direction?
>
> Thankyou
>
> Ken Kubick

How long antenna cable do you need in your location?
How low-loss antenna cable will you use?

The orginal antenna to the Tbolt is the Trimble Bullet antenna.

   http://trl.trimble.com/docushare/dsweb/Get/Document-8420/Bullet-III_DS.pdf

   Ebay #220997989191

Here is a former HP/Agilent antenna that has worked fine for me.

   
http://www.symmetricom.com/products/gps-solutions/gps-timing-products-and-accessories/58532A-GPS-L1-Reference-Antenna/

Generally most GPS antennas will work. (Searching for "GPS timing antenna"
will give you some choice)

Here is a very nice antenna. Rather good gain at 33dB, LNA power from
2.5VDC to 24VDC - which means it can take the oldtimer GPS receivers
giving 12V or 15V and new giving 3.3V or lower. (Like Antcom antennas, no
dealings with that particular seller.)

   Ebay #150753929036

Datasheet

   http://antcom.com/productsheets/2G15A-XTB-1-N_D.pdf

Good luck!

--

Björn


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Re: [time-nuts] GPS, USGS Early Earthquake Warning

[bg]

Hi Brooke,

> Hi Tom:
>
> They do use two different seismometers at each location, a large movement
> and a sensitive.
> http://www.prc68.com/I/Seismometer.shtml
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/Clarke4Congress.html

It is a bit fun that the Earthquake Detector product "QA-2000" shares
product name with the Honeywell (Sundstrand) Inertial accelerometer
"QA-2000"...

http://quakealarm.com/
http://www.inertialsensor.com/inertial-navigation-accelerometers.php


--

 Björn


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Re: [time-nuts] PRS-10 input and output calibrations

[bg]

With factory default settings with 2 PRS-10s, connecting 1PPS_out from one
unit to 1PPS_in on the other, would not align the 1PPS_out pulses. They
were off by several hundred of ns. It was probably an operator error
somewhere. We just did not find the error in the time frame we had
available.

--

   Björn


>   Björn, what do you mean with "We never got one to track the other in a
> reliable way"?
> Thai is, how can it be that a PRS10 cannot track another PRS10? What do
> you
> get when trying to track one with the other?
>
> On Sun, Apr 22, 2012 at 8:44 PM, Poul-Henning Kamp
> wrote:
>
>> In message <4f93f032.2040...@rubidium.dyndns.org>, Magnus Danielson
>> writes:
>>
>> >The input calibration would be something in the similar way,
>>
>> What I did:
>>
>> Detune an OCXO slightly (I actually have a 9.7 MHz OCXO from
>> IsoTemp), feed it to PPSDIV, disable the discipline code in the
>> PRS10, collect the measured input time stamps over some hours.
>>
>> Either you get a nice ramp, or you get som kind of demented staircase,
>> in which case you try to figure out which of the calibration constants
>> to mess with.
>>
>> An alternative is to feed the PRS10 output to a HP333x Synthesizer
>> and have that generate your 10-epsilon MHz for the PPSdiv.
>>
>> This general "vernier" method can be used to measure all sorts of tricky
>> stuff, from interrupt latencies in operating system kernels to
>> stuff like the above.
>>
>> --
>> 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] PRS-10 input and output calibrations

[bg]

Magnus,

Interesting! Have a couple of PRS-10s at work that we wanted to lock
together. We never got one to track the other in a reliable way.

--

   Björn

> Fellow time-nuts,
>
> Anyone who has tried to calibrate the PPS input and PPS output
> interpolators of the PRS-10?
>
> The output calibration seems pretty easy to do, just a TIC to measure
> the PPS to 10 MHz and then sweep through the output delay values to
> cover a little more than the 400 ns range.
>
> The input calibration would be something in the similar way, a simpel
> method would be to use a coax cable between output and input, and then
> use the internal output offset to measure the range of the input
> interpolator. However, the input interpolator is a decade better than
> the output interpolator. However, considering that I have a 5359A just
> waiting to be used, I think I use a fixed output PPS delay and trigger
> the 5359A with and then sweep that one.
>
> I would then use the collected data to find suitable correction values.
>
> Comments and suggestions? Experience?
>
> Cheers,
> Magnus
>
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Re: [time-nuts] Lucent 40 dB Antenna

[bg]

Hi Joe,

40dB is not needed when you have a short (<10m) /good antenna cable. Then
26dB will be plenty fine. Howver going to 20 or 30+ meters using standard
RG58 will be a problem with 26dB. Ofcause what matters is the attenuation
at L1 with your cable. Better cable can be longer...

You do not need an spectrum/network analyzer. Take a your antenna and
receiver to a good site, if you installation site might be marginal. Your
C/N0 (snr) should be around or above 50dBHz for high elevation satellites.
Then compare the C/N0 values for you antenna at your workshop, to see how
much worse than "perfect" that site is. If using a Tbolt remember to
change from Trimble AMU into dBHz.

Note that LNA dB amplification not generally translate direcly into dB
carrier to noise ratio.

--

   Björn

PS I got a small batch of HP timing antennas new in box for around $25 a
piece some years ago... :-) DS

> Mine arrived in the same manner.  It works but I can't tell any real
> difference between it and my 26 dB antenna, switching between them when
> mounted on the corner of the roof of my workshop.
>
> Joe
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Steve Krull
> Sent: Friday, April 13, 2012 1:40 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Lucent 40 dB Antenna
>
> Just got mine, from "Just_for_survive" on eBay. Poorest packing job I've
> ever seen for an international package. Three wraps of newsprint and a
> thin padded envelope. I'll know this weekend if its operational.
>
> Steve
>
>
>
> On Tue, Apr 10, 2012 at 11:14 PM, Chuck Forsberg WA7KGX N2469R wrote:
>
>> My Lucent antenna arrived today.  I scrounged some adapters
>> and connected it to my Thunderbolt.  Two birds were visible
>> with AMU > 4 when I held the antenna.  My Droid 3 could not
>> see any birds through the wet roof.
>>
>> The unit has some dings and scrapes but no visible corrosion.
>>
>> I am tempted to take it apart but don't wish to break a unit
>> which seems to be working well.
>>
>> Has anyone compared this antenna with the mushroom that
>> came from China with the used Thunderbolts???
>>
>> --
>> Chuck Forsberg WA7KGX N2469R c...@omen.com   www.omen.com
>> Developer of Industrial ZMODEM(Tm) for Embedded Applications
>>   Omen Technology Inc  "The High Reliability Software"
>> 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430
>>
>>
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Re: [time-nuts] Thoughts on lightning protection measures....

[bg]

Said,

The ground is a decent thermal isolator. And will in nordic countries not
often go deeper than about 1 meter. You need to build your houses
foundation "deep" enough to stand on non frozen ground. Otherwise your
house will move to much with the seasons and likely break. It is not that
hard to get your ground pole deep enough to avoid freezing problems.

-- 

   Björn

> Hi Attila,
>
> if I remember correctly, the issue is that the "ground" at the house is
> not a "real" ground when the earth is frozen, as the resistance of frozen
> earth goes up substantially over non-frozen earth. So it's like not having
> grounded the wires at all.
>
> This is a real issue for cables brought to the house (cable TV, telephone,
> etc etc) as those cables are grounded somewhere else on the other side,
> and
> thus  there may be 1000's or even 1's Volts between the two "grounds",
> even (or  especially) for just a proximity strike. As mentioned by someone
> else, all bets  are off anyway's for direct hits, not much will survive a
> direct hit.
>
> It's been a long time since I designed cable TV receivers, but the specs
> are here, and I think there are some explanations in there somewhere:
>
> _http://www.nordig.org/specifications.htm_
> (http://www.nordig.org/specifications.htm)
>
> bye,
> Said
>
>
>
>
> In a message dated 4/12/2012 09:54:40 Pacific Daylight Time,
> att...@kinali.ch writes:
>
> Hmm?  That sounds interesting. In switzerland, and AFAIK in most  european
> countries, power feeds have to be grounded at the entry of the  house
> (ie the neutral conductor is grounded). This should protect the
> electrical
> equipment from such ground jumps as you discribe. Or do i miss  something?
>
> Attila  Kinali
>
>
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Re: [time-nuts] Re-radiating a GPS signal...??

[bg]

It is well known that vertical accuracy is worse by about 1.8 times the
horizontal accuracy. It is true this is geometrically caused. In indoor
scenarios high sensitive receivers have a vertical bias due to excessive
multipath. More or less all received signals have bounced multiple times
to reach the receiver in the worst scenarios. This however has nothing to
do with a rerad-system, where your rerad signal will be much stronger than
the natural one. Otherwise there would be no need for a rerad-system in
the first place. Also a correctly installed rerad-system will not give
excessive multipath problems. Vertiacal biasing is not caused by
(correctly) installed rerad systems.

--

Björn

> Purely geometrically, the fix solution is computed as the intersection
> point of spheres with the radii determined by the propagation time, and
> the centers by the positions of the satellites (practically not all
> spheres intersect in the same geometrical point, so an average is
> computed).
> If the GPS Rx would receive simultaneously all satellites, considered
> evenly distributed on a sphere, then the added path delays would mostly
> cancel out - but if only the visible satellites are accounted for, we
> will have an unbalanced system, approximated to an hemispehere, in which
> the horizontal error will be low, as the longer paths cancel mostly out,
> but for the vertical one it's not the case.
>
> Any GPS receiver will exhibit lower vertical precision than the
> horizontal one.
> The same phenomenon, of low precision, and biasing of position is
> evident if just a part of the constellation is used (an obstacle
> obscures a large part of the sky).
>
> The internal delays of the Rx are mostly fixed and known, so they can be
> accounted for, and compensated in the firmware fix solution, but the
> cable length is a variable (depending on the installation) factor, not
> accounted for.
>
>
> On 4/12/2012 7:15 PM, b...@lysator.liu.se wrote:
>> Not at all!
>>
>> The (first) receiving antenna defines the position you get out of a long
>> antenna cable or a reradiating system. The delays in LNA, filters,
>> cables,
>> rerad antenna, free air between rerad antenna and final receiving
>> antenna
>> ALL goed into the receiver clock error. This is clear both from a
>> theoretical point, from most standard GPS texts and from practical
>> experience from multiple installations I have used over the years.
>>
>> If you disagree, please provide evidence.
>>
>> --
>>
>>Björn
>>
>>> Not quite, the delay of the antenna cable is affecting less the
>>> horizontal position (it depends also on the current received
>>> constellation geometry), but mostly the height ASL of the fix point,
>>> prolonging simultaneously all the paths from the satellites with a
>>> fixed
>>> value.
>>> Also, the propagation speed in a cable is significantly lower than in
>>> free space - the perceived delay increase is ~1.5 times for usual
>>> cables
>>> (~.67 velocity factor), and the computed fix point would have a lower
>>> height ASL than the real one.
>>>
>>> Those relaying systems are merely good for an approximate location fix,
>>> mostly for not loosing the GPS signal in covered areas so that the
>>> reacquire of the real signal is faster, with almost no perceived
>>> discontinuity.
>>>
>>>
>>> On 4/12/2012 6:11 PM, David McGaw wrote:
 The time/position fix would be from the location of the receiving
 antenna of the repeater, degraded only by noise.

 This should work if both antennas have good back-side rejection
 (choke-rings are particularly good for this but perhaps any good
 timing
 antenna could meet this), the re-transmitting antenna is close to
 being
 directly under the receiving antenna, and the system gain is low
 enough.
 The problem I would see in a room that is not fully shielded is
 interference between the direct and retransmitted signals at the
 receiver under test.

 David N1HAC

 On 4/12/12 10:17 AM, MailLists wrote:
> GPS being extremely time-dependent, any delay introduced will affect
> positioning precision. Also, the signal is too weak for such an
> amplification/echo cancelling signal chain.
> Passive relaying, or using at most a simple amplifier with low enough
> gain, and short signal delay, remain the only feasible concepts.
>
> On 4/12/2012 4:48 PM, Azelio Boriani wrote:
>> Passive UHF TV repeaters were in use in Italy too. Nowadays, for the
>> DVB-T
>> TV, active gap-fillers are used instead. Active gap-fillers are
>> same-channel repeaters with the necessary, sophisticated echo
>> suppression
>> technique. We have developed our echo suppression signal processor
>> on
>> a
>> Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS
>> CDMA.
>>
>> On Thu, Apr 12, 2012 at 3:29 PM, Alan
>> Meliawrote:
>>
>>> If the isolation is good and the "clear view" sig

Re: [time-nuts] Best location for a GPS antenna...?

[bg]

Rerad-systems are getting controlled in Europe too.

http://www.etsi.org/deliver/etsi_en/302600_302699/302645/01.01.01_60/en_302645v010101p.pdf

Any reports on how quick this is going? Where I live, there are rules, but
not many are aware of them.
--

   Björn

> You must read:
> http://transition.fcc.gov/eb/Orders/2005/DA-05-2998A1.html
>
> Which discusses a FCC complaint with Navtech for selling GPS reradiating
kits.
> An exert is presented below:
>
>
>  ``Please note: re-radiation kits are currently only
>  available for purchase to International Customers and in
>  cases where the U.S. Government is the end user.''


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