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
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 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 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
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
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
>
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
I have both. They seem to work well and appear to be genuine Ublox stuff. I
highly suspect that somebody in China bought, for dirt cheap, a product
production line closeout of something that used LEA-6T modules and stuffed
them in those drone gizmos... there is no reason to use an
One thing to consider about using a module with a built-in ceramic patch
antenna is that usually the antenna cannot be removed and the modules have no
support for an external antenna. If you do have problems getting a signal it
can be very difficult to add an external antenna. You might want
No, not really. I would get one of these... 1/3 the price, comes with
antenna.A timing receiver is way overkill for a clock. USB is a pain for
microcontrollers to work with. Get it working with with the 8M, upgrade
later to the M8T if you feel the need.
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
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
Back when that local high school kid was arrested for bringing his "home made"
alarm clock to school, I bought a "bomb clock game" off of Ebay. It looks
like 7 sticks of dynamite with a circuit board with LEDs strapped to it. The
game part is you press a button and it starts counting down 10
They default to speaking Motorola binary data. The burst of data at power-up
is the Motorola @@Cj version info string. You then have to send it some
commands to enable various messages. There is a command to enable Zodiac
binary mode. I don't think that they speak NMEA.
I don't think so. The day and year is there, only the month is 0. They guy
selling them has them available in sealed factory case lots. They look new.
They are in sealed anti-static bags. My guess is they came from somebody's
product line closeout.
I did notice that several of their
Another big honkin' wart on DATUM's nose:
The unit responds to the standard Trimble TSIP command to select output in UTC
or GPS time. But, and I don't like this big but... I cannot deny, it always
reports that it is in GPS time mode! You have know way of knowing what kind of
time it is
Ok, these things are a little less horrid than they first presented themselves
as. Whenever Lady Heather sends a command to change a setting, it follows it
up with a command to read that setting back from the receiver. It turns out
that the Datum units don't have any (or possible a very
"@ @ W b 0x01 cksum 0x0D 0x0A" will switch from Motorola mode to Zodiac mode.
The checksum is the XOR of all bytes after the @@ and before the cksum byte.
The 0x?? values represent binary bytes. The spaces are for clarity and are not
sent.
A simple and rather effective power line monitor: get an old cheap laptop with
some sort of sound input capabilities with at least a semi-usable battery, an
AC output wall wart, and a couple of divider resistors. Record the AC line
as audio during your experiments. You can analyze the
Is it an edge-card type connector? If so, how many pins and what spacing? It
might be possible to use or modify one of the extenders that I made for the
HP5370, Tek TM500 stuff, and some other equipment.
To appease our new (hopefully) benevolent Martian overlords, Lady Heather can
now work in Mars time... and I have it running right now while connected to a
Jupiter timing receiver.
-
> Hmm. I have a SC-01.. One could hook it up to a Arduino trivially.
And run it on Mars
Do you have any equations for calculating Jovian (or Pluto) time and date from
UTC / GPS / TAI time? Lady Heather does not want to slight any of our other
potential planetary overlords (but could whip their bloated gaseous asses in a
fight)
I just added code to Lady Heather to calculate time in Terrestrial Time (TT)
and Geocentric Terrestrial Time (TCG). The difference is basically the time
dilation effect of a time referenced to the center of the earth. Now I'm
adding Barycentric Dynamic Time (TDB) which is TT referenced to
They are based upon a telco surplus "UCCM" GPSDO board. Both Symmetricom and
Trimble made (mostly) compatible units. I prefer the Trimble units... they
store their settings in EEPROM. The Symmetricom units don't... and have to do
a long re-survey every time you power them up. Plus the
All the affordable GPSDOs out there are surplus telecom devices...
Thunderbolts, Z38xx's, NTP, etc. They were built to rigorous telco
standards and can be excellent performers. Just because they are surplus, does
not make them junk.
The latest round of surplus GPSDOs to hit the
Charles,
You are confusing these units with those made by that ham in China (can't
remember his callsign, begins with a "B"). The guts of these boxes is a telco
GPDDO board made by either Trimble or Symmetricom (you can tell because of the
6.0V power requirement).And that reference to a
I don't think there is a way to control the loop parameters except maybe some
PFORTH commands. The Trimble units can be put into holdover via software.
The Symmetricom units require you to disconnect the antenna (or possibly use a
SCPI command to manually set the DAC voltage... Lady Heather
I found some test data and tried those values with my code. They agree to
within a millisecond... and that difference is caused by my JD to Gregorian
routine that adds a millisecond to the JD input to compensate for possible tiny
double precision math errors... All of Lady Heather's times
For all those curious about all these weird and wonderful astronomical time
scales this is a good start:
http://arxiv.org/pdf/1005.4415v3.pdf
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The Jupiter receiver defaults to Motorola output, but can be switched to
Zodiac. It talks at 9600:8:N:1
Frankly, it is the wrong receiver to use, particularly with an indoor antenna.
I would go with a modern GPS receiver with standard NMEA output and a 1PPS
signal. They are MUCH more
I've found that the HP-5065A rubidium makes for a pretty decent power line
monitor. Mine will trip the "continuous operation" indicator on power glitches
that most power line monitors ignore (including some rather high dollar ones).
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
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
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
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
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
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
It appears that they are brand new... no signs of ever being handled or
installed. The anti-static bag is sealed with a yellow warning sticker. The
date codes in the firmware/software ID message indicates year 2000. The
manufacture date message returns 0's in all the fields.
They have a
No, they are set up to default to Motorola command set. And all messages must
have the proper checksum and CR LF sequence. When the receiver is in Zodiac
binary mode, it wont take Motorola commands and vice versa.
Ublox timing receivers let you specify the RF delay of your antenna / amplifier
/ receiver electronics independent of the cable delay. They are the only low
cost receivers that seem to have this feature.
___
Lady Heather can display solar times. Set the time zone name to SST or SDT
(there is also a command line option). Heather can also calculate and display
the sun and moon positions and moon phase. The next release has some
improvements to the equation of time calculation. Also, be aware
I got a couple of requests for the schematic... apparently the old link is
dead. Here is Warren's original drawing. Buy the man a beer... The only
change that I made was using a single high-beta (say 1000) transistor to drive
the heater. Warren used two transistors. All the part numbers
I also added the HP10811 double oven board to Dirty PCB's shared projects. 10
boards will cost you a whopping $25 (They usually send you couple of extras if
they had good yields).
http://dirtypcbs.com/view.php?share=22492=f5a69b7619ce8f139bb9d1ea789ad45e
Once upon a time I came across a document from National Semiconductor that
talked about their transistor product line. At the time they made less than
100 different transistor dies... but sold them under 10,000+ different part
numbers.Some were just packaging variations. Maybe some
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 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
They can be if you store them in something like an ammo box. If they "go off"
in the sealed box the pressure builds, the reaction rate increases
exponentially, and voila... shrapnel time. There's a video out there showing
the results.
Most people recommend storing them in nomex/kevlar
I have a LOT of experience in testing and using 18650 cells. It is a horrible
place for the un-initiated to be. The market is so saturated with dangerous
fakes and inferior, over-speced cells that finding a genuine cell is a
vanishingly small probability. Hopefully the seller mentioned
I built a switched capacitor balancer. It takes some time to balance a wildly
out-of-balance pack but does a great job of maintaining balance during charging
and discharge. I run the balancer during pack charging and discharging. I
tried it charging an 8S LiFePO4 pack with 7 fully charged
I'd say 80% of the outside design work I do have little ditties in the
contracts that say NO development to be done on net connected systems. New
Eagle requires a net connection to keep working. Also the EULA seems to say
they can slurp your designs at will and ship them off to who knows
I doubt that it is something TAPR would do. Building complete systems gets
into all sorts of issues (mainly regulatory). But it is easy enough to build.
They sell a nice case that the RPI3 and touchscreen mounts in. The
PI+touchscreen+case sells for around $110. The TICC(s) connect to
At one time Timelab worked well for me under Wine. It's been years since I
tried it.
I recently got in a TAPR TICC and am in the process of adding time interval
counter support to Lady Heather. It's not even remotely as nifty as Timelab
(and never will be), but it does run under Windows /
Here's an hour of Thunderbolt data... with labels for the xDEVs. On narrow
screens only the 1-10-100-1000... divisions are labeled and not 1-2-5-10-20...
Otherwise the longer labels run together.
I also enabled the PPS plot which is basically the PPS jitter.
The Star-4 PPS seems to be
Yes, if your TICC reference oscillator is of lowish quality you should run the
TICC in time interval mode and it can analyze one device.
To analyze/compare two devices with one TICC you really need a very high
quality reference oscillator...
I have a couple of FTS oscillators that have
A nasty bug crawled into my ear last night and muttered something like:
"Put the TICC counter circuit, a 1/5/10/15 Mhz PICDIV divider, input squarer,
terminator relay, etc on a module.Make a motherboard that 4-8 of those
modules can plug into along with an ATMEGA processor. Output the data
I just added the capability of Heather to monitor and control a GPS device
while simultaneously calculating ADEVs from an external time interval counter
like the TAPR TICC (it can also work with the time interval analyzer only).
This mode lets Heather calculate true adevs instead of
There are apparently companies out there that specialize in low volume
semi-custom enclosures. They are a lot like the cheap PCB manufacturers that
we are now blessed with in their economies of scale. I think the guy
mentioned the price for this power supply enclosure was around $35 (BTW,
Lady Heather has detected a GPS week rollover event... 10 seconds of
consecutive years less than 2016. When this happens Heather adds 1024 weeks to
the receiver date until it is past 2016. This can happen when Heather is
connected to a receiver that is starting up and sending invalid dates
Yes, that is the board in the unit. It is boxed up by BG7TBL and sold on
Ebay. It uses the highest spec ATDC version of the Star-4 with the highest
spec 8663 DOCXO.
Yes, it should. Heather can input from a serial/USB connection or TCP/IP.
Your GPIB interface needs to stream data in a "talk-only" mode.
Currently my TIC reader can handle either time interval (period) data or time
stamps. It knows about TICC data with channel identifiers on the values
The Ublox multi-GNSS receivers are incredibly picky about the channel
allocations. Basically if you don't use the default channel min/max values
they either won't work or are very flakey. I tried values other than
min=4/max=8 for Galileo and nothing worked. Also, if you have SBAS enabled
I don't have an M8T, only an M8.
Heather defaults to showing up to 14 satellites. You can specify more sats or
a dual column display using the SI or GCT commands or you can click the mouse
on the satellite info table.
You can also use the SG command to set the GNSS configuration, but version
Beware of Atom based devices... Many of the Atom chips have a problem where a
couple of the critical clock output signals have a design problem and they
start failing after around 18 months. This problem just became public in the
last month or so when Cisco warned of impending failures in a
The protocol gets saved in a serial EEPROM. The firmware is apparently in
masked rom and cannot be upgraded. Trimble has some ancient utilities that let
you change the protocol between GPS (only does GGA and VTG sentences unless you
paid for custom firmware), TAIP (which Lady Heather now
I recently added code to Lady Heather to support up to 10 external com links
(serial or TCPI/IP). One is the receiver port, one will be a TICC, and two
are "echo" ports. One echo port echoes all the raw data sent by the receiver
and the other does the same thing except the data is formatted
The TSIP protocol is the same one we all know and love. But some of the values
in the commands are different, particularly the set_io_options command that
sets which commands that the receiver sends automatically and in what format it
sends them. I suspect that, alone, would make dropping in
On the chip with the "MX" marking on it, what f/w version does it show
(usually v5.02 or v5.10)? I have a couple of CM3's configured for TAIP output,
but I have the programs for switching them to TSIP or NMEA.
---
> The module is basically a Trimble SveeSix-CM3 and is
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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Heather has an automatic GPS week rollover detection feature. If it sees 10
consecutive time messages with a year before 2016, it assumes that the receiver
has week rollover issues and adds 1024 weeks to the time until the year is past
2015. This is indicated by the "ro" flag on the date
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
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
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
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
Oops, that last message went to the wrong list...
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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
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
http://www.theregister.co.uk/2016/09/03/intel_drone_show_thx_faa/
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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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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:
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
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
> 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
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
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
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
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
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
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
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
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
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
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
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
Can you say "Mr Rogers' Neighborhood?" I knew you could...
He (along with creepy Mr McFeelie) always ran segments on how some item was
made. Geared towards pre-schoolers, but always worth watching.
-
Compare the Science channel's new "How Do They Do It" to the older
Lady Heather has support for setting the system clock from the GPS receiver.
The next release has support for analyzing and compensating for the GPS /
system / com port message delay. It does not use the 1PPS signal.
It can get the Windoze clock to under 40 msecs (two times the typical
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
901 - 1000 of 1485 matches
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