[time-nuts] Trimble Thunderbolt no longer determines thecorrect date

[ed briggs]

The current model Thunderbolt E #60333-50, v1.04 firmware has a 
last valid date on the 22nd December 2029.

It is probably  a good idea to specify what firmware you  have in these 
discussions as different versions will have different properties, and some of 
the used Thunderbolts are quite old.



On Jul 28, 2017, at 9:05 AM, 
"time-nuts-requ...@febo.com" 
> wrote:

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Today's Topics:

  1. Trimble Thunderbolt no longer determines thecorrectdate
 (Mark Sims)
  2. Symmetricom X72 and Lady Heather results (Mark Sims)


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Message: 1
Date: Fri, 28 Jul 2017 02:32:44 +
From: Mark Sims >
To: "time-nuts@febo.com" 
>
Subject: [time-nuts] Trimble Thunderbolt no longer determines
   thecorrectdate
Message-ID:
   
>

Content-Type: text/plain; charset="iso-8859-1"

Actually,  Lady Heather's rollover compensation code has no limit on the 
correction.  It can compensate for any number of rollovers.   In fact you can 
use it to adjust the receiver time by any number of seconds (including 
fractional seconds).

The default behavior is to trigger after 10 seconds of consecutive time 
messages where the time is before year 2016.  The 10 second filter is to avoid 
false triggers from corrupted packets.   This means that for the first 10 
seconds after starting Heather on a Tbolt,  the date will be wrong.  When 
rollover compensation is in effect, the date is shown in yellow and a "ro" flag 
appears next to it.   It would nice if somebody could come up with a patched 
firmware...

You can get a false rollover detection if you start monitoring a receiver 
before it has acquired the almanac since most receivers output time based upon 
the GPS epoch if they don't have an almanac.



The current version of Mark's Lady Heather program has code to detect this and 
fix it so you're good to go for the next 19.6 years.

--

Message: 2
Date: Fri, 28 Jul 2017 01:27:07 +
From: Mark Sims >
To: "time-nuts@febo.com" 
>
Subject: [time-nuts] Symmetricom X72 and Lady Heather results
Message-ID:
   
>

Content-Type: text/plain; charset="iso-8859-1"

I'm in the process of adding support to Lady Heather for the Symmetricom X72 
(and SA22) rubidium oscillators.  I have a most of the functionality working.  
The X72 has a "health" message that dumps a couple dozen values.  The values 
are labeled with some rather cryptic names that give some hint about what they 
are,  but no where in their (miserable) documentation do they elaborate on what 
the values mean.   Does anybody have any info on them.

The X72 is user interface is a very frustrating an infuriating thing to work 
with.   The device has several glaring omissions in what it does...  like no 
way to read back any settings that you have made and no way to save most of 
them in EEPROM and no command to restore the unit to its factory default state.

Attached is a plot showing most of the non-static health values... it looks 
like most of them are highly correlated with temperature.  Without heavily 
average-filtering the display,  the values look a lot like noise.
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End of time-nuts Digest, Vol 156, Issue 34
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Re: [time-nuts] ADEV query Timelab and TICc

[ed briggs]

The 1 PPS signal is derived from an 81 MHz clock (12 ns) on the GPS chip 
according to the  Skytraq manual.  So that would mean n * 12ns.

From: time-nuts-requ...@febo.com
Sent: ‎3/‎20/‎2017 9:00 AM
To: time-nuts@febo.com
Subject: time-nuts Digest, Vol 152, Issue 32

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Today's Topics:

   1. Re: ADEV query Timelab and TICC (Orin Eman)
   2. ADEV query Timelab and TICC (Mark Sims)
   3. Re: ADEV query Timelab and TICC (gandal...@aol.com)
   4. Re: ADEV query Timelab and TICC (Dave Martindale)


--

Message: 1
Date: Sun, 19 Mar 2017 22:09:57 -0700
From: Orin Eman 
To: Tom Van Baak ,  Discussion of precise time and
frequency measurement 
Subject: Re: [time-nuts] ADEV query Timelab and TICC
Message-ID:

[time-nuts] 58503a and Yixunhk

[ed briggs]

I’ve never had a problem with this vendor.  I’ve purchased a Z3801a, and a 
Z3805a and both work fine, and I have the equipment to measure that.  I’ve also 
purchased several items of agilent test gear from this vendor, and they all 
worked fine, and were accompanied by a test and calibration form which was 
accurate.  On two occasions when I’ve had questions, I sent mail and received 
prompt answers.


I’m sorry to hear you are having difficulties with your 58503a, but on the 
basis of my experience, I would not call this vendor disreputable, as others 
seem to be suggesting.  I’d suggest sending him an email.  If you have to 
return the unit, I suspect he’ll honor the return terms and conditions which 
accompanied the offering.  If you are having problems with the DC-DC converter, 
you might also point that out to him since he seems to have parts from time to 
time.


Others may have had other experiences, but my experiences with this vendor have 
all been positive. 


ed
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Re: [time-nuts] What's best an HP 58503A, Z3805A, or Z3801A

[ed briggs]

Some Furuno GPS in these GPSDOs  (in particular the z3815a) were recently 
reported to suffer from a roll-over problem which causes the year to be 
incorrect.  So you might want to check that before purchasing.  It's a pity, 
the Furuno is a better receiver than the UT+.   You can search the archives of 
this list for further information.
 
Also, in the units marked 'z380x upgraded to 58503a', it seems the firmware was 
updated to 58503a firmware even though
the front panel says z3805. I have one of these units, and it indeed reports it 
is a 58503A to the command interface.  Whether or not the 58503a firmware is 
any better than the Z3805a firmware, I have no idea. 
 
Good luck!
 
ed
  
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[time-nuts] Lucent GPDSO TTI ps graph and efc is this sick?

[ed briggs]

The EFC is probably not sick, it is still in the middle of it's range, and has 
moved only a small amount.  I would let it run for another week and see if it 
starts to head back down.   As I mentioned in a previous post, I had to run my 
z3816a for several weeks before it settled down.  After that period of time, my 
Z3816 settled into the EFC range of 581240-581280 and a predicted uncertainty 
in the 100-200ns/24 range - but it took a month to get there)
 
Important note: it seems that the Lucent *reports the PPS TI error differently* 
than previous units. This will make comparisons between this unit and the older 
unit difficult.   
 
Another time-nut sent me the data file from Z38xx attached to a Lucent GPSDO, 
and I noticed that most of the values TI values had only zeros to the right of 
the decimal point.  (almost all but not all).  This made the data look like the 
TI jumped around in discrete steps of 1.0 * 10e-8 .  That is the reason you see 
the 'strata' and 'plateaus' in your plot that you don't see in previous 
z3801,3805,3816 plots.  The peaks in the +/- 40 ns range are the same as on my 
Z3816a (which uses the same GPS receiver).
 
The data file also had quite a few 0.0 TI values, which bounced then to 
1.0e-8 etc.  So somewhere in the data paths, someone is doing the equivalent of 
a floor(TI error). So if you calculate averages on this kind of data and 
compare it to averages or SD on previous units, the results will be misleading.
 
It's possible that the program Z38xx is incorrectly parsing these values and 
'stripping the digits to the right' performing a floor(TI).   I can't tell 
because I only have the data after Z38xx parsed it.  Somebody who has one of 
these units and Z38xx could open the debug screen and capture it to a file and 
see if the '1 PPS to TI ns relative to GPS has zeros to the right of the 
decimal point most of the time, or the response to the :PTIM:TINT? is 
'stepping' as I described above.
 
BTW - what do you see as the predicted uncertainty.
 
Regards
 
Ed
  
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[time-nuts] Lucent KS 24361 and Z 3816a Performance

[ed briggs]

I wanted to share an observation about my Z3816a which may be relevant to KS 
24361 users.
Both units use the same oscillator and GPS receiver.   
 
When I first powered up my Z3816a, I noticed there were very infrequent Time 
Interval offset spikes
of 100 ns or more.  Once every 4 days to start, then once a week, then longer.  
  
 
Researching the time-nuts posting, I found others who had seen this and had 
offered different explanations, 
including bad GPS receiver,  damage to connections during transit, receiver 
overload, mistreatment by the surplus vendor.
 
In my case, it was neither of these. Simply allowing the unit to run for a 
month remove all the spikes. In my Z3816a now shows a predicted uncertainty in 
the 100-200ns/24 hour range. No spikes.  
 
So, if you see similar spikes on your KS 24361, you might want to resist the 
urge to power it off and 'try stuff' until next month.  The oscillators in 
these units may not have been used on 12 years, and it maybe they need time 
(and a little controlled heat) to get comfortable in their new environment.
 
This is offered in the hope it may save some unnecessary head-scratching, and 
not as a refutation of alternative  theories.
 
Ed
 
 
  
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[time-nuts] Lucent KS-24361 GPS and Performance

[ed briggs]

I am curious about which GPS and rev is used in these units. Could someone post 
the response from :DIAG:IDEN:GPS? from one of these units?
Also, I'm curious if anyone has a Z38XX plot for one of these devices that has 
been in operation for greater than 48 hours,  I'm particuarly interested in the 
plot of the PPS TI  EFC chart as well as the plot of the holdover uncertainty 
for a period of (say) 2880 minutes or longer  to see how this unit compares to 
my Z3816a.
If someone does and could post it, I'd be much obliged
cheers
Ed
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Re: [time-nuts] GPS Lightning Protection

[ed briggs]

Dave M,
The advice about a 'system approach' is essential, or the lightning discharge 
may go through your building wiring instead of through your ground rod.  Or, a 
lightning strike down the street may follow the power line,  pass through your 
home wiring, GPS receiver,  and into your GPS antenna ground. 
A nice overview of the basics of such a system approach for residential 
locations is presented in the IEEE Guide to Surge protection. 
www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf
Since some time-nutters may be experimenting in residential settings, this 
guide may be more useful than guidance for industrial settings.
There are now approved ground bonding assemblies available for about $10 US 
dollars. (They're called 'Intersystem Bonding Termination' devices.).  This can 
simplify the creation of a single ground point, and can help eliminate the 
clutter telephone and CATV grounding attachments to the electrical service 
ground.  Get a licensed electrician to install it; don't modify your electrical 
service ground on your own.
Also, you mentioned something about connecting a copper wire to Aluminum. That 
may present problems or even be illegal in your area unless it is done 
correctly.  In the U.S. you should check a recent edition of NFPA 780 and your 
local electrical  code. 
Also, if your home has lightning rods, these need to be included in the design.
Regarding gas discharge tubes, these are widely used, and they are often 
designed to fail 'shorted', so you can  tell if they've failed by loss of 
signal. Replacement gas discharge tubes are available from the manufacturers.
The gas discharge units for GPS systems are designed to let the  DC control 
voltage pass through ( usually 5 volts, some systems use 12 (eg some 
Symmetricom receivers)) and clamp any voltage higher that this.  Note that the 
voltage referred to here is the difference between the shield and center 
conductor of the coax.  You should look for an arrestor that handles the GPS 
frequency, and passes the DC voltage (non DC blocking) but limits surges to 6 
or 15 volts (depending on your GPS supply voltage) , but not 300 or 600 volts 
that is common for suppressors designed for service with  low power 
transmitters.  
Some systems use two lightning arrestors, one at the antenna to protect it 
fromsurges appearing on the feedline, and one at the point of entry/single 
ground point. 
Once you have a look at the IEEE guide, and the NFPA guide, you'll shudder when 
you read internet postings like :  'I just connected a lightning supressor to 
my radio and ran a wire to  a 4 foot ground rod outside my window.  It seems to 
be working fine'.

Best of Luck!
Ed




  On Oct 16, 2014, at 7:34 PM, Dave M dgmin...@mediacombb.net wrote:
  
  I'm looking for effective coaxial lightning arrestors for my GPSDO antennas.
  I've seen several types; those completely enclosed in a one-piece metal 
  enclosure (no replaceable components) and those having a replaceable gas 
  discharge tube seem to predominate the list.
  I'm looking closely at the gas discharge tube types, and am curious as to 
  their effectiveness and durability.  I'd like to know stuff like; are they 
  effective in dissipating a static charge, how do I know when the gas tube 
  needs to be replaced, are the gas tubes of a special type, are replacement 
  gas tube easily available, etc.
  
  I'm interested in opinions and experiences with arrestors and 
  recommendations for which type is most effective.
  
  Thanks for comments,
  Dave M 
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