Something tells me those crystals cost more than 10 cents... and were probably
quite a bit worse than today's 10 cent Chinese processor crystals. Young'uns
today have no idea how good they have it... and get off my lawn! I just sorted
through a $10 (shipped from China) bag of 100 crystals
I forgot to mention that you can also configure Lady Heather by editing the
heather.cfg file. You can place the command line options that you want to
use, one per line, in this file. The options must start in column 1 and begin
with a '/' or '-', otherwise they will be considered as
Version 4.0 does not work with anything but TSIP (Trimble) type receivers. The
next release (v 4.10?) will work with all sorts of receivers. It will also
compile for Windows, Linux, and now macOS (aka OS/X) (using XQuartz as the X11
server).
If you can compile a Linux C program, macOS
Yes, the next release (should be out in a couple of weeks) supports numerous
receiver types. Included are:
Native binary formats:
Trimble TSIP devices - (Thunderbolts, Resolution T family, various telecom
GPSDOs like the NTWB, NTPX, etc)
Datum Starloc II (ugh!)
Ublox
Motorola (6, 8, 12
Here is a plot of the Thunderbolt cold starting with the "initial DAC voltage"
setting set to the peak value of the initial spike (and not the 10.00 MHz
setting). The upward spike when the unit starts tracking sats (it took around
twice as long to start tracking sats) is gone, but the DAC
I asked this very question a few years back... the consensus was to lower power
dissipation into the typical 50 ohm load.
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well done.
On Wed, Sep 14, 2016 at 12:27 AM, Mark Sims
<hol...@hotmail.com<mailto:hol...@hotmail.com>> wrote:
You can set the view interval to any value with the "V" keyboard command
(default is one second per pixel, 1 minute per horizontal division).
Above the plot area
While on the subject of how GPS receivers do or don't report the day that a
leapsecond will occur, I fired up a Nortel/Trimble NTWB receiver to see what
it said. It has the standard Trimble packet (0x58:0x05) from which one can
calculate the day, but Lady Heather was reporting "Leap
One thing you can do with a Thunderbolt is to let it settle into to disciplined
equilibrium to 10.000 MHz, check the DAC voltage serring, and then switch
off disciplining and manually control the EFC DAC. This will improve the phase
noise at the expense of frequency drift which may or may
I hope to get the next version out in the next couple of weeks...
Ahhh, the subtile wonders of calculating when a leapsecond happens... A
couple of receivers (like 12 channel Motorola receivers) are nice enough to
directly tell you the date of the leapsecond. Tthe Z3801A and Z3812A get it
Yes. The device supports a SCPI command set. The next version of Lady
Heather supports it... well at least my modified Z3812A does.
You probably don't need an RS422 converter. You can cobble an RS-232
connection into the RS-422 port. This usually works, but some hardware serial
ports
Okee dokeee... here it is. Not much difference. The initial step is
smaller, but it still spikes. After that things are pretty much the same.
After it cool down, I'm doing another run with the initial voltage set to the
peak of the spike.
One slight difference was with the new
I just ran a tbolt (which has been off for a couple of months) and logged the
state for a couple of hours... and then remembered something about the initial
DAC value setting that I had figured out long ago... it has little to nothing
to do with oscillator disciplining.The tbolt drives the
Here's a little info on Lady Heather's oscillator autotune function for the
Thunderbolt GPSDO:
The autotune function tries to optimize the settings for the oscillator
disciplining parameters, antenna signal mask angle, and the signal level
amplitude mask beyond what the default setting (which
You might want to try some lithium AA cells. They start out around 1.65V.
They are MUCH less prone to leakage than any "alkaleak" battery and have a very
long shelf-life (i.e. good for low drain memory backups). As always, when
adding a backup battery to a GPS, verify that the battery
The Z3801A status page takes 3 seconds to process/send. Not surprising that
the time is a bit off. Lady Heather only requests the SYST:STAT message once
per minute (at hh:mm:33 seconds) because it blocks the unit from doing anything
else while it is handling it. The main things extracted
Yes, rollovers should not be a problem and should only affect the date display.
However, I have seen devices/software that use GPS fail to work because of what
appears to be an invalid date. It seems that they are validating the data from
the receiver and if, for instance, the date is
Happy until the next power glitch... the setting does not seem to persist
between boots. There may also be other conditions that causes it to forget
your date.
And when setting the date, you should disconnect the antenna first, then power
on. Once the unit starts tracking satellites you
I did a little math on the dates and it looks like the rollover happened in the
last couple of days...
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Sometime (I didn't have it connected) in the last couple of weeks my Z3801A
went into gps week rollover. It now reports the year as 1997. It had been
working propely. Lady Heather caught the anomaly and automatically added 1024
weeks worth of seconds to the date/time which compensated for
Oops, that last message went to the wrong list...
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http://www.theregister.co.uk/2016/09/03/intel_drone_show_thx_faa/
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If you don't like how the Tbolt adjusts the oscillator on your Tbolt... do it
yourself. You can set up the Tbolt for manual DAC control and implement your
own control loop. Warren Sarkison and I implemented a alternate control PID
for the Tbolt DAC. Yep, it's in Lady Heather. It's been
You never said what accuracy you need for your time. Lady Heather's time set
function should get you down to the 40 msec area. You can configure it to set
the time once, periodically, or whenever receiver time and system time diverge
by "x" milliseconds.The time set is a "jam sync" of
Actually the main factor of determining observed sunset/sunrise times vs
calculated ones are temperature gradients of the local atmosphere rather than
than the absolute temperature/humidity/pressure... sunset being more disturbed
than sunrise. Local effects of several minutes have been
Yes, at times I used a two stage linear regulator. The first stage had
excellent low freq rejection and the final stage too care of the high freq
stuff.
Some times a full linear supply is not a viable option due to power
dissipation/size issues or the utter convenience of using a switching
You have to be careful choosing a linear regulator to clean up a switching
supply. Many just wind up passing the noise through. Pay attention to the
noise, PSRR and CMRR vs frequency specs, etc
Take a look at the "voltage regulation" section of that home built VNA page for
an example:
> You will be aware of the three different definitions of sunset, of course.
Actually 5... Physical, Official, Civil, Natutical, and Astronomical.Plus
Lady Heather lets you specify an arbitrary horizon angle.
> It calculates positions for the moon as well.
Lady Heather also does the
I recently added code to Lady Heather to precisely calculate the sun position,
sunrise/solar noon/sunset times and the Equation of Time... Egad, what a deep,
dark rabbit hole that leads one down. And woe be unto thee that trusts any of
the online calculators. Results can be over 10 minutes
The -12V is used to drive the RS-232 signals... it also eventually gets to the
EFC dac so it can swing below ground. Also, the +12V gets to the DAC. Pay
close attention to generating noise on these lines.
Also, when I did Lady Heather's temperature control PID (with great help from
Warren
Last month there was a discussion here about using a GPS to drive a
hyper-accurate nixie tube clock with a lot of the discussion revolving around
the effects of human perception and reaction times. Here is blog post that
discusses some of the gotchas software and hardware can impose. There
Try driving your counter frequency reference input with the LPRO or comparing
the LPRO with the GPSDO. The LPRO is (most likely) much more accurate the
counters' internal timebase.
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Well, what now gets shown / plotted depends upon the receiver type.
For Thunderbolts the standard plots are the DAC (EFC) volatge, temperature
sensor reading, and the PPS and OSC offset values from the primary timing
message (the OSC plot defaults to OFF since it generally looks like a lot
The Ublox modules (at least some of them) can support an external oscillator
and have messages for controlling oscillator parameters and disciplining.
> This is actually done. But you need to design the GPS receiver from the
ground up to use a very high quality
It gets there by downing a fifth of bourbon and staggering around endlessly...
Or you should be able to do a /gq on the command line.
The next version of Lady Heather I am working on makes getting to the sat
signal quality display easier... G Q from the keyboard will toggle it (in
addition to
The Trimble GPSDOs and most of the SCPI ones (like the Z3801A) have "jam sync"
commands that force the receiver to do an immediate time sync (the Z3801A
requires the device to be in holdover before it will accept a jam sync). Some
also have commands where you an also specify thresholds where
If you start Lady Heather from a command line prompt, the cfg file should be in
the directory you are in. If you start it clicking on an icon or the start
menu, it should be in your My Documents folder (which depends upon the OS
version you are running). You can find out for sure by typing ?
Navspark claims the 10 MHz signal is very accurate frequency-wise (1E-9), but
has poor jitter characteristics and if you need low phase noise you need to add
a cleanup PLL. Their website has flash videos of the output, but all wise
people have hopefully removed flash support from their systems
The NVS NV08C GPS receiver module is a rather nice little 32 channel
GPS/GLONASS/SBAS receiver that has an output message that gives you the raw
satellite bit streams. They can be had for around $60 bare module ($120 on a
breakout board from sylphase.com). They also support carrier phase
Pretty much all the telecom GPSDO's are driven by an on-board, isolated DC-DC
converter. Some are 24V nominal input, some are 48V (a few are even 18-72V).
The '+' / '-' designation is pretty much irrelevant since the converter inputs
are isolated and are not referenced to chassis ground...
The NTBW50AA (and most other telecom GPSDO's) will run on 48V. This will
solve your problems for dirt cheap. They are very high quality
industrial/medical supplies (not cheap junk wall-warts) that currently sell
from distributors for over $80.
And it does NOT say they DON'T use the '838. No where do they mention an '822.
They do mention an '838 and the data-sheet they link to is for the '838.
Their listing seems to meet the legal definitions of deceptive advertising and
bait-and-swith sales. If they were in the US, they would
Just checked mine... it's an 822A. They sell it as an '838... bastards... I
just ordered one of yours. My RS-232 GPS breakout board already has a
connector with Adafruit pinouts on it, so makes life easy.
---
> If you're talking about the NS-T, the picture on their store
I measured the message end-time offset on the Navspark version (USB, virtual
115,200 baud) at 153.8 msecs, standard deviation of 7.1 msecs... I don't know
how the real serial port version would compare.
The Adafruit was 460 msecs, 50 msec standard deviation.
-
> I've been
I just did a test on my cheapest (3 for $15-$20) GPS module... a V.KEL Sirf III
receiver. Indoors, on the lower level floor, away from windows, etc. I was
getting 25-35 dBc levels with the patch antenna properly oriented. With the
module flipped over and the antenna surface on a hardwood
You might want to try a modern GPS receiver. I have some cheap (< $10-20) GPS
modules with on board patch antennas that work indoors, sitting on the floor
of the bottom level of a two story stucco-over-wire mesh house, away from
windows, surrounded on all sides by tall trees, with the
Probably the best way for most people to keep their clock accurate is to use
something like NTP with a local GPS receiver that provides a 1PPS signal that
you can get into your computer (not always an easy thing to do and get working
properly). Done properly, this can get you into the
Lady Heather has the ability to set the system clock from any just about any
GPS receiver. It can set the clock every day, hour, minute, or when system
time and receiver time diverge by more than "x" milliseconds. Most stock
Windows systems have a clock granularity of +/- 15.6 milliseconds,
Well, the whole point of the exercise is to see how well you can do if you
DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server
available... only the humble messages coming from a 10 dollar GPS receiver.
Try getting a net connection in the middle of the Gobi desert
Yes, I find it confusing also. I've been reporting the value that Lady
Heather uses to do most of her evil internal message off machinations with...
For those, the negative offset value is the "natural" polarity. I'm probably
going to change it around to something humans (including me)
As mentioned in the post the times reported are the time stamp in the receiver
packet minus the system clock time when it was received... negative value
indicate the message arrives after the PPS. The polarity of the reported value
is consistent with how Lady Heather makes use of the
Attached is a plot of the timing message arrival times of the Trimble
Resolution-T receiver running in TSIP mode. Like the Adafruit Ultimate, its
firmware seems to do little to get the timing message out at a fixed reference
point.
As Tom pointed out, this is only an issue if you are
It is only tracking the GPS sats, running at 1Hz rate. Almost every GPS
receiver that can run faster than 1Hz has warnings that the 1PPS output is only
valid/stable if the device is configured for 1Hz output.
My Ublox 8 receiver tracks GPS/Glonass/Beidou/SBAS sats. I have seen it
A couple of people have asked about the poor message arrival time performance
of the popular Adafruit Ultimate GPS receiver. I modified Lady Heather to
analyze the message arrival times using a histogram instead of a simple
average. When I looked at the histogram data (.01 msec resolution),
Easy, I have a 4 value array. It keeps count of the number of times each
0.1 msec step between -2000 .. 2000 msecs was seen. If two or more bins wind
up with the same max count, I report the average of those bin times, otherwise
it's the bin with the highest count. I also dump the
I have added some code to my message time offset measurement routine to
calculate a histogram of the values (along with the average and standard
deviation). I'm now using the peak histogram bin(s) to determine the message
offset time. The histogram technique has the advantage of ignoring
The Skylab is effectively useless for sub-second timing. The message arrival
time periodically jumps around, up to +/- 300 msecs. There are a couple of
values that it seems to prefer, but any value can be seen.
NMEA works a lot better on most receivers that I expected. They send several
Lady Heather keeps the date/time time in two sets of variables. One is the
receiver time message values in UTC (or GPS) time. The other is local time
(UTC/GPS adjusted for time zone or time scale) that is used for the clock
displays. There are integer year,month,day, hours,minutes,seconds
I found what was causing the apparent ramps in the message offset time for the
Motorola mode receivers and the Z38xx receivers. Here is the updated and
corrected info. Note that a couple of receivers do have some minor ramp
sawtooths in their message timing. They are less than +/- 10 msecs
Heather will take either time format, but requests the receiver to send T2
format.
I originally thought the SCPI receivers would be right on time due to my
original measurements of their message jitter, but when I started measureing
the actual message arrival times... surprise, surprise,
Here are the results of measuring the difference between the time code in a GPS
receiver time message and the arrival time of the last byte of the message.
Negative values mean that the receiver sends the timing message after the 1PPS
pulse that it describes. The table also shows the standard
And somebody paid well over 10 times the market rate to lease server space that
was one building closer to the NYSE computers. My idea to put an end to this
bogo-trading nonsense is to add a random delay to all the trades.
> Someone recently built a new fiber route
Apple's new file system timestamps files with nanosecond resolution. A lot of
Linux file systems also do that now. The nanosecond ain't what it used to
be... I can imagine people wanting picosecond timestamps in the near future.
Who knows, maybe we'll have something like NTP compensating
I have a Z3812A that I added back in the GPS receiver and modified it (moving
6 zero ohm resistors) to work as a standalone GPS. Basically it's now a
stand-alone Z3811. I have Lady Heather working with it now. The hack of
using the RS-422 output to directly drive a RS-232 serial port does
The closest thing to an official Lady Heather site if John Mile's ke5fx.com
I also want to put it it up on Github when the code settles down some.
The good Lady Heather doesn't accept donations of the monetary kind.
Receivers not currently hoarded in her dungeon are appreciated.
I am the creator author of Lady Heather. The code in Lady Heather started out
from a program that I wrote to control Magellan GPS receivers (like the
OEM-5000) back in days of the first Gulf War... it ran under DOS as a text mode
only program.
When TAPR did their group buy for Trimble
Lady Heather now works with Venus receivers in mixed binary / NMEA mode. So
now it can display the sky view data (via NMEA sentences) while running in
Venus binary mode. I also added support for parsing the $PSTI NMEA sentence
that contains the sawtooth correction info. Why somebody
Yes, no Venus binary messages for sky view or sawtooth correction. Those are
only available in NMEA. But to make effective use of a timing receiver you
should be running it in binary where you can properly monitor and control it.
Whoever did the Venus binary commands did not think things
I have implemented support for all of the relevant Venus binary messages.
It's just that I don't have a Venus timing receiver to test the timing receiver
specific messages (which are only three messages that control the self-survey
/ position hold modes). Oh, and besides the lack of a
I'd get the $80 assembled unit from Navspark first and see if it works for you.
If not, you won't have wasted your time and money on doing a PC board.
Lady Heather can now talk to Venus receivers in binary mode (also handles
generic NMEA receivers). I don't have a Venus timing receiver so
Navspark will sell you one in on a board for around $80. They claim 6 ns
timing accuracy. Also 0.01 ppb on the 10 MHz output. I sent Navspark a couple
of questions about their USB interface and they never responded...
http://navspark.mybigcommerce.com/ns-t-precision-timing-gps-receiver/
I saw no problems with Ublox Neo 6M, LEA-5T, LEA-6T, Ublox 7, or Ublox 8
receivers.
A Synergy M12+ did not report the leap pending in the @@Bj message, but did in
the @@Gj message.
-
Anyone know if the M12T or Lea Bloc GPS chips have the same problem as the
I bit bang serial all the time... it is much easier if to do if you are only
banging serial output. Reading serial streams at higher bit rates while doing
other useful stuff can be challenging... particularly if you don't have a timer
handy.
I once coded up a PIC to output a time code /
A lot of the newer GPS modules can accept "dead reckoning" data from external
sensors and integrate that into their location solutions. The receiver does
all the Kalman filtering foo for you. Also you can get receivers with up to
50Hz position updates (you have to run the com link at very
I added the ability of Lady Heather to calculate the time offset of the timing
message from "wall clock" time. It calculates the difference between the
system clock time to the time that the (end of) the timing message arrived.
The result is only as good as your system clock, so the system
I got in a Z3812A (aka Lucent KS-24361 REF-0) and installed a Motorola UT+ in
it following the excellent guide by Peter Garde (google is your friend) and
have it working as a standalone GPSDO...basically it now a REF1 unit). The
mod mostly involves moving half a dozen 0 ohm resistors (I
The Z3801A bug reporting the wrong day for the leap second is has to be in the
Z3801A firmware and not the GPS receiver... that receiver does not have a
message that reports the date of the leapsecond or the almanac data needed to
calculate it. It only has the message that says a leapsecond
I get the Z3801A leap pending flag from the #T1 or #T2 time stamp in the
:PTIM:TCOD? response. For the date, either :PTIM:LEAP:DATE? or
:PTIM:LEAP:GPST? depending upon the unit type.
And now for some more receiver leapsecond shenanagins:
The Ublox receivers work well. You can calculate the
The GPS satellites are now reporting the pending leapsecond...
The Z3801A has it messed up... it says the leap will occur on 30 Sep 2016 (73
days). The Z3801A has two different messages that report the leap day... both
are wrong.
Navspark has some affordable ($80) modules that do "raw" (carrier phase)
output.Also RTK modules for $50 that can give you real-time centimeter
accuracy and GPS derived attitude and bearing between two units.Alas, they
don't seem to do L1/L2 or accept an external clock. They claim +/-
A lot of GPS receivers either don't support the ZDA message, or turn it off by
default. And many (most?) that do send it send the time with millisecond
resolution.
The NMEA sentences for sending date and time were very poorly thought out.
Several different sentences can contain the time
I ran some tests on the message timing of some V.KEL gps receivers in both NMEA
and binary mode. These receivers are the cheapest ones I have (3 for $15 -
$20, shipped). They use a SIRF III chip and have an on-board ceramic patch
antenna. They performed amazingly well. No problems tracking
While on the subject of antenna cable delay and sawtooth values, I have only
seen Trimble document the sign of the value that you enter to compensate for
cable delays (for Trimble devices you enter a negative value). Other
receivers may require a positive or negative value. Also, some
I think they are all pretty much the same unit. I don't know if any of the
oscillator models is any better. I assume they are all equivalent and actual
performance (like any OCXO) is luck of the draw.
Those boards run on 6VDC. The Trimble units use a 5V oscillator (which lots of
places
The Tektronix TM509/5009 (and I think the 5010) counter modules have a National
Semiconductor noise generator chip in them. It injects noise into the counter
to get around counter oscillator/input frequency synchronization. I was once
given a TM509 with a bad noise generator chip... Some
Or use the sawtooth compensation value to control an external variable delay
line circuit to move around the PPS signal from the receiver. This can get
interesting to implement if the receiver can output negative values for the
sawtooth compensation (hint: add a bias to the sawtooth value to
My LEA-6T board came out of one of those cheap Chinese drone pucks. It has a
ceramic patch antenna on board. I have it sitting on the floor of the lower
floor of a two-story, stucco over wire mesh house (not close to any windows).
Same for some Sirf, Venus, and standard Ublox receivers.
Yes, turning on the display filter only gives an indication that one could
gain some some benefit if they were to use the message arrival timing to
implement some sort of NTP-ish algorithm to their 1PPS-less clock.
I have added some options to Lady Heather calculate the adevs of the message
Most definitely... if I turn on Lady Hather's display filter (which does a
sliding average of "n" readings) the standard deviation and jitter values drop
dramatically. With a 60 second filter the deviation was down to around .15
msecs and the peak-peak jitter below a millisecond. Average
I have seen some reports of some Skylab GPS boards that had some rather sketchy
GPS code. A friend had one that was off around 0.5 degrees in longitude...
but only if your location was between +/- 90 degrees longitude. He was on the
east coast and had the problem. He sent it to me (96
That plot was from a 12 hour run. I've done 48+ hour runs and did not see
anything strange. I'm not currently measuring the offset of the message from
the 1PPS, just the stability/jitter in the timings of the last byte of the
timing message. If the timing message offset time from 1PPS
Ooops, that tboltjit.gif plot was actually from a Trimble Resolution-T SMT
timing receiver running with an indoor antenna, not a Thunderbolt. The
Thunderbolt with an outdoor antenna is about twice as good.
I just added the ability to feed the timing jitter value to Lady Heather's real
time
I added the ability for Lady Heather to measure a plot the difference of the
arrival times of each timing message (actually the time when Lady Heather
receives the last byte of the timing message from the operating system). The
end-of-message arrival time is time stamped to nominally
Very few people have the ability to build Lady Heather for Windoze from
source... pretty much everybodyl uses the binary. Having people build from
source is not an option (except on Linux, it's relatively painless and the
tools are easily available and free, plus Linux users tend to know what
Heather's gotta work with XP (and maybe Win98)... too many people (including
me) run it on old trashy laptops, so no fancy pants new fangled Windoze calls
allowed...
In the past I've avoided the use of QueryPerformanceCounter due to potential
issues with AMD processors, multi-core processors
I just added some code to Lady Heather to record and plot the time that the
timing message arrived from the receiver (well, actually the time that the
screen update routine was called, maybe a few microseconds difference).I
am using my existing GetMsec() routine which on Windoze actually
A company that I founded, at one time shipped about half the world's supply of
PC graphics cards. We got several requests from the film and TV industry for
display devices that produced images that could be filmed. Our cheap-ass
solution was a card that output 24 Hz video and the camera was
The Z38xx and similar SCPI receivers are a special case. Their time code
message is specifically synchronized to the 1PPS. If you enter the :PTIM:TCOD?
command to get the time message, the receiver "blocks" for up to a second until
the 1PPS time. They also have a second serial port
The noise of a turbulent air flow increases at the EIGTH power of the
velocity... it's one of the largest exponents seen in natural phenomena.
> the linear speed of the air has a lot of effect on the noise
>
For a clock that is observed by eye, the NMEA message on most receivers comes
out close enough to the second to not need the 1PPS. I think there is even a
section in the NMEA spec that says how close to the second the message should
come out. Receivers that output binary messages are even
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