Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Hal Murray]

jim...@earthlink.net said:
> I imagine that there's a way to "constantly" press the button with a
> jumper, too. 

It's easier than that.  Just turn off the bootable flag on the eMMC.  Then it 
automagically tries the SD card.



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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Bob kb8tq]

Hi

One of the big shocks shopping for some of this stuff is that the single piece 
price may be 
5X  the “volume price”. That’s not true of everybody, but it’s true of a lot of 
vendors. This sort
of thing does not apply only to GPSDO’s. 

On top of that, we get used to buying some items for “salvage” prices that are 
well below 
the original volume price. A GPSDO that we buy on eBay for $40 may have sold 
originally 
for $500 in volume. The single piece price (20 or 30 years ago) could have been 
$3,000. 

You could argue that this does not make any sense. You could also wonder how 
any get out
into the market with that sort of pricing. The answer may well be that if you 
are a large OEM
already doing a million dollars a year worth of business with the outfit, you 
can get a “loaner” 
for evaluation. 

Bob

> On Oct 18, 2017, at 8:39 PM, W7SLS  wrote:
> 
> Hello,
> 
> Might be my first post.  Thanks for the group wisdom.
> 
> I did not see any pricing on the web page for 
> http://www.spectruminstruments.net/TM4.pdf 
> , and the site seems to be (c) 
> 2007 (a decade ago).
> 
> Before I contact that vendor, I’m curious about:
> 
>   - any ballpark ideas on cost?
>   - any reason to prefer that over, say, a Jackson Labs Fury, or?
> 
> My current setup is an eBay $130 GPSDO into an repurposed video distribution 
> amplifier, to feed HP and Tek signal generators, frequency counters, etc.  I 
> might be doing something wrong, but Lady Heather reports 63,000 (not a typo) 
> ppb accuracy.   Not awful, but nowhere near the numbers discussed on this 
> forum. hence my interest in something else.
> 
> Thanks for considering,
> 
> Scott W7SLS
> 
>> On Oct 18, 2017, at 7:47 AM, Rob Seaman  wrote:
>> 
>> http://www.spectruminstruments.net/TM4.pdf 
>> 
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[W7SLS]

Hello,

Might be my first post.  Thanks for the group wisdom.

I did not see any pricing on the web page for 
http://www.spectruminstruments.net/TM4.pdf 
, and the site seems to be (c) 2007 
(a decade ago).

Before I contact that vendor, I’m curious about:

- any ballpark ideas on cost?
- any reason to prefer that over, say, a Jackson Labs Fury, or?

My current setup is an eBay $130 GPSDO into an repurposed video distribution 
amplifier, to feed HP and Tek signal generators, frequency counters, etc.  I 
might be doing something wrong, but Lady Heather reports 63,000 (not a typo) 
ppb accuracy.   Not awful, but nowhere near the numbers discussed on this 
forum. hence my interest in something else.

Thanks for considering,

Scott W7SLS

> On Oct 18, 2017, at 7:47 AM, Rob Seaman  wrote:
> 
> http://www.spectruminstruments.net/TM4.pdf 
> 
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Re: [time-nuts] True Position Time Figure of Merit

[Stephan Flor via time-nuts]

Thank you Mark. I will read through it.Steve 

On Wednesday, October 18, 2017 4:01 AM, Mark Sims  
wrote:
 

 This forum thread has most of our reverse engineering info on these GPSDO's:

http://www.eevblog.com/forum/projects/gpsdo-loss-of-satellitesfix-troubleshooting/
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[jimlux]

On 10/18/17 4:17 PM, Hal Murray wrote:


jim...@earthlink.net said:

This is one of the reasons I use beaglebone greens - soldered in eMMC so  no
need for SD card ...


The advantage of the SD card is that you can easily start over when your
"disk" gets trashed.

"Easy" of course is dependent on your opinion and talents.  I think you can
boot a BeagleBone from SD by holding down a button and put things back
together from there.  So no wires or extra hardware required, but you have to
research a new layer of HOWTOs.


precisely so - hold the button and power up.

You can set up so that the contents on the SD just boot, or rewrite the 
flash (10-15 mins).
I imagine that there's a way to "constantly" press the button with a 
jumper, too.


Building that SD card image is a bit more complex than it needs to be. 
You can download the image trivially, but modern consumer OS'es 
basically don't make it easy to directly write to a device, and what 
you're basically doing is burning a image to the SD card.


OTOH, the instructions ARE on the "getting started" page of the 
beaglebone site.

http://beagleboard.org/getting-started

but it's way too many steps, and there's way too many "using your 
favorite xyz utility"







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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Hal Murray]

jim...@earthlink.net said:
> This is one of the reasons I use beaglebone greens - soldered in eMMC so  no
> need for SD card ...

The advantage of the SD card is that you can easily start over when your 
"disk" gets trashed.

"Easy" of course is dependent on your opinion and talents.  I think you can 
boot a BeagleBone from SD by holding down a button and put things back 
together from there.  So no wires or extra hardware required, but you have to 
research a new layer of HOWTOs.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[jimlux]

On 10/18/17 2:09 PM, Adrian Godwin wrote:

On Wed, Oct 18, 2017 at 9:11 PM, Gary E. Miller  wrote:


Yo Hal!

On Wed, 18 Oct 2017 12:26:27 -0700
Hal Murray  wrote:


For getting started, you also need:
   SD card reader/writer
   keyboard and mouse (Pi has USB)
   display adapter (Pi is HDMI)
   display


Yeah, just for setup.  Shall we include the price of the desk it sits
and the building it is in?



You can set a Pi up headless from scratch by putting an empty file called
'ssh' in the boot directory of the raspbian SD card. It then enables the
ssh daemon on startup.


This is one of the reasons I use beaglebone greens - soldered in eMMC so 
no need for SD card, no HDMI interface - the expectation is that you're 
using it headless/serial console style. And the eMMC is preloaded with 
Debian Jessie (or perhaps something newer)


The only ugly thing is the USB Gadget interface, which works fine, but 
always seems a bit weird - The USB serves triple duty - disk access to 
part of the file system, IP network interface, serial console port.


So on a Mac, you can mount it as a disk, ssh or "screen" to it via 
either ip or the /dev/cu.usbmodem


There's also a standard ethernet interface. Which by default comes up 
using DHCP and zeroconf, so you can plug it in to your network at home, 
and then look for it with "ping beaglebone.local".


And the beaglebone has lots of GPIO.







Of course, then you need another computer to talk to it with ..


Unless you're a real hardcore embedded person, in which case you just 
make and break a connection between two wires on the TxD line to send 
ascii, and you use the blinks of an LED or the intermittent tingle on 
your tongue from the RxD to decode it.



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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Tom Van Baak]

> picPET -- Precision Event Timer http://www.leapsecond.com/pic/picpet.htm

Thanks for the plug. Yes -- it does sub-microsecond relative time-stamping 
simply: one Schmitt-trigger TTL input pin and one RS232 output pin. But -- it's 
a $1 chip, not a black box. And the timestamps aren't UTC either. So I think it 
misses some requirements that Rob mentioned.

Another alternative is to use UBX-TIM-TM2 messages from ublox timing receivers.

Still, as much as I like ublox or picPET or John's high-res Arduino-based TICC 
or homebrew NTP / Pi project, I suspect they are not the turn-key commercial / 
industrial black box that Rob is looking for.

/tvb

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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Adrian Godwin]

On Wed, Oct 18, 2017 at 9:11 PM, Gary E. Miller  wrote:

> Yo Hal!
>
> On Wed, 18 Oct 2017 12:26:27 -0700
> Hal Murray  wrote:
>
> > For getting started, you also need:
> >   SD card reader/writer
> >   keyboard and mouse (Pi has USB)
> >   display adapter (Pi is HDMI)
> >   display
>
> Yeah, just for setup.  Shall we include the price of the desk it sits
> and the building it is in?
>

You can set a Pi up headless from scratch by putting an empty file called
'ssh' in the boot directory of the raspbian SD card. It then enables the
ssh daemon on startup.

Of course, then you need another computer to talk to it with ..
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Adrian Godwin]

> Ethernet, add $25.
>
>
Perhaps less  :

http://www.ebay.co.uk/itm/122596979464
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[time-nuts] GPS 19x HVS Receiver/Antenna, NEMA 0183, 10 Hz update rate

[Gregory Beat]

I noticed that an eBay reseller in Las Vegas (Garmin Marine dealer) has sold 
over 275 of the Garmin GPS 19x HVS Position Receiver/Antenna packages at a 
discounted price.
eBay auction # 171415290499

Anyone try these units out?
===
There are also a few Garmin NEMA2000 units (Marine CAN bus attempt by NEMA)
from a Chinese reseller, auction # 162703815781
—

greg, w9gb
chicago

Sent from iPad Air
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Bob Bownes]

A black box was asked for. Who cares what the OS inside is if you never
need to mess with it. A surprising number of things run linux variants.
Pretty much every smart phone is linux or unix...

What is the output format you would like for your timestamp? disk, network
file system, serial all can be made to work.

One could probably build 10-20 for a couple thousand dollars and make
enough to make it worth the trouble, depending on the output format of the
timestamp.

Pi Zero - $10
SD card - $8
GPS - $4
2x16 LCD display - $5
Enclosure - $15 for small box, $20 for ABS rack mount, $35 for aluminum
Hardware, nuts, bolts, screws, etc - $5
Power Supply - $5
Custom Interface card with buffering for TTL signal, other signal input
method, opto isolator, serial port for config & control, rs-232 out for
timestamp, serial and PPS from GPS, connectors, etc - $20-25 built.
Cables, etc - $5
Small rubber duck or GPS puck antenna $5

Ethernet, add $25.

Pi has USB/HDMI, but you can run it headless too.

Total BOM ~$100 (expensive case)
Development - ~week @$75/hr = $3,000 (board design, prototype, code +
documentation)
Manufacturing, packaging, etc ~$50/unit

Shipped cost/unit, 20 units = $150materials, $150 labor = $300.
40 units = $225

Obviously BOM costs go down w volume, but you'd have to hit at least
quantity 50 to get a good break on enclosures and the custom boards.

So the big variable is how many will you need and what are you willing to
pay the developer. $75/hr is more or less going contract rates in my world.
$125-$150 not unheard of.

One off, no labor cost, cheap. Under $40 if you provide your own enclosure,
antenna, etc.


On Wed, Oct 18, 2017 at 3:26 PM, Hal Murray  wrote:

>
> > For under a $100 you could get a Raspberry Pi, a GPS HAT, and connect
> your
> > input to a GPIO pin.  Configure ntpd to log the real PPS and the input as
> > another 'PPS'.
>
> Is there an option to log all individual PPS events?
>
>
> The $100 for a Pi might be significantly low.  It depends on what you have
> in
> your toy box.
>
> Aside from the Pi and GPS HAT, you also need power and a micro SD card.
> For
> black box applications, you probably want a case.  You may need an external
> GPS antenna.
>
> For getting started, you also need:
>   SD card reader/writer
>   keyboard and mouse (Pi has USB)
>   display adapter (Pi is HDMI)
>   display
>
> I have an old KVM switch.  It uses PS2 rather than USB, so I need a PS2 to
> USB adapter.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Gary E. Miller]

Yo Hal!

On Wed, 18 Oct 2017 12:26:27 -0700
Hal Murray  wrote:

> > For under a $100 you could get a Raspberry Pi, a GPS HAT, and
> > connect your input to a GPIO pin.  Configure ntpd to log the real
> > PPS and the input as another 'PPS'.   
> 
> Is there an option to log all individual PPS events?

# ppswatch /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
timestamp: 1508356708, sequence: 591837, offset:  1412510
timestamp: 1508356709, sequence: 591838, offset:  1381010
timestamp: 1508356709, sequence: 591838, offset:  1381010
timestamp: 1508356710, sequence: 591839, offset:  1397496
timestamp: 1508356710, sequence: 591839, offset:  1397496

Just redirect to a log file.

> The $100 for a Pi might be significantly low.  It depends on what you
> have in your toy box.

Looking at Amazon, quantity one, I see:

RasPi3 $35
GPS Hat w/ remote antenna and cord: $30
16BG miscro sd card: $9
RaspI + HAT case: $10
USB charger: $8
USB charge cable: $2
Cat5 ethernet cable: $2

Looks like $96 to me.  You can save some if you buy in bulk,

Plus labor, which after the first one is small.

> For getting started, you also need:
>   SD card reader/writer
>   keyboard and mouse (Pi has USB)
>   display adapter (Pi is HDMI)
>   display

Yeah, just for setup.  Shall we include the price of the desk it sits
and the building it is in?



RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin


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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Tim Shoppa]

picPET -- Precision Event Timer http://www.leapsecond.com/pic/picpet.htm

On Wed, Oct 18, 2017 at 1:33 PM, Rob Seaman  wrote:

> Attila Kinali wrote:
> > On Wed, 18 Oct 2017 08:47:58 -0600
> > Rob Seaman https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts>> wrote:
> >
> > > I’m at the annual planetary sciences meeting (in Provo this year) and
> several
> > > groups have expressed interest in duplicating our setup (details of FO
> > > converters, Schmitt triggers, etc, omitted) in a “cheap black box” to
> quote
> > > one fellow. Lots of people contribute productively to NEO observations,
> > > including amateurs and small teams with little funding. Improving their
> > > timekeeping would help keep rocks from falling on you and your family.
> >
> > What is this black box supposed to do? Just provide a PPS? IRIG-B?
> > Or does it need to have time-stamping capabilities? If so, how many
> > channels?
> >
> > What are your time precision/accuracy requirements?
> >
> > What how cheap is "cheap"? What is the volume?
>
> Thanks for the quick reply. I should have included the subject line in the
> message:
>
> "inexpensive, black box, GPS or NTP based TTL time capture”
>
> Telescope domes are filled with equipment, in particular the camera
> shutter, that can be instrumented to issue a pulse suitable for hardware
> time capture. We use Meinberg IRIG PCIe cards to trap these and read the
> timestamps using their library routines under Linux. “Black box” to the
> person I was talking to meant no IRIG in the dome, no Linux, and no PCIe
> slot, but rather a self-contained unit that syncs to GPS. When last he
> implemented such a feature at another telescope he didn’t even have time
> capture, but rather the device issued a trigger at a specified moment, so
> the timestamp and the shutter opening were inverted. He also seems to
> prefer the timestamps be issued on a serial connection, not via library.
>
> Unlike laboratory instrumentation, a telescope environment needs to be
> both very automated and very forgiving. Money may also be constrained.
> However, telescopes are also often very flexible and I am willing - no,
> eager - to consider completely different arrangements of equipment.
>
> So, reliable timestamping of a TTL input is the ulitmate goal. One channel
> would be sufficient, but multi-channel would not invalidate an option. PPS
> or IRIG-B (DCLS IEEE-1344) are not required, but might form an intermediate
> part of the solution. Reference could be GNSS or possibly NTP.
>
> Precision varies, but milliseconds down to microseconds. Accuracy should
> match the precision, meaning UTC accurate to same. Extra credit for
> multiple timescale support.
>
> Cheap is what I want to know. I see the previous thread on BB-black and
> could imagine a solution using the real time capabilities of that for a few
> hundred bucks, but these are not experimenters, per se. That’s why they
> want a black box. Volume is one to several, but could imagine a bulk order
> if savings were significant. Hundreds of dollars might be the price point.
>
> Thanks!
>
> Rob Seaman
> University of Arizona
>
>
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Hal Murray]

> For under a $100 you could get a Raspberry Pi, a GPS HAT, and connect your
> input to a GPIO pin.  Configure ntpd to log the real PPS and the input as
> another 'PPS'. 

Is there an option to log all individual PPS events?


The $100 for a Pi might be significantly low.  It depends on what you have in 
your toy box.

Aside from the Pi and GPS HAT, you also need power and a micro SD card.  For 
black box applications, you probably want a case.  You may need an external 
GPS antenna.

For getting started, you also need:
  SD card reader/writer
  keyboard and mouse (Pi has USB)
  display adapter (Pi is HDMI)
  display

I have an old KVM switch.  It uses PS2 rather than USB, so I need a PS2 to 
USB adapter.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Hal Murray]

The "no Linux" complicates things.  Ignoring that...

Assuming you have a PC with good time, you can use the PPS capture technology 
to get a time stamp from any signal.  I use it to monitor power line 
frequency with a simple python script.

If you want GPS on that PC, that will use the first serial port.  You will 
need another serial port for each signal you want to monitor.  If ms accuracy 
is good enough, you can use a USB serial port.


You could use a Raspberry Pi instead of a PC.  Some assembly required.

A serial port is electrically rugged.  The IO pins on a Pi are delicate.

The GPS HAT from Adafruit has a small prototyping area.  It should be 
reasonable to add a level shifter and lightning protection.  Again, if ms is 
good enough you can use a USB serial adapter.

Some Pi setups occasionally trash their "disk".  Sometimes they run for 
months.  I think the usual problem is poor power.  If the Pi is doing nothing 
else, you can make a backup copy of the SD card and put things back together 
by following a simple recipe.

--

You also said no IRIG.  In case it helps, you can get IRIG out of a PC.



-- 
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Gary E. Miller]

Yo Rob!

On Wed, 18 Oct 2017 11:33:28 -0600
Rob Seaman  wrote:

> That’s why they want a black box. Volume is one to several, but could
> imagine a bulk order if savings were significant. Hundreds of dollars
> might be the price point.

For under a $100 you could get a Raspberry Pi, a GPS HAT, and connect
your input to a GPIO pin.  Configure ntpd to log the real PPS and the
input as another 'PPS'.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin


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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Bob Bownes]

So, if I hear you right, you want a ttl input to trigger a timestamp,
accurate to ms or µs to a file, correct?

Bob


On Wed, Oct 18, 2017 at 1:33 PM, Rob Seaman  wrote:

> Attila Kinali wrote:
> > On Wed, 18 Oct 2017 08:47:58 -0600
> > Rob Seaman https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts>> wrote:
> >
> > > I’m at the annual planetary sciences meeting (in Provo this year) and
> several
> > > groups have expressed interest in duplicating our setup (details of FO
> > > converters, Schmitt triggers, etc, omitted) in a “cheap black box” to
> quote
> > > one fellow. Lots of people contribute productively to NEO observations,
> > > including amateurs and small teams with little funding. Improving their
> > > timekeeping would help keep rocks from falling on you and your family.
> >
> > What is this black box supposed to do? Just provide a PPS? IRIG-B?
> > Or does it need to have time-stamping capabilities? If so, how many
> > channels?
> >
> > What are your time precision/accuracy requirements?
> >
> > What how cheap is "cheap"? What is the volume?
>
> Thanks for the quick reply. I should have included the subject line in the
> message:
>
> "inexpensive, black box, GPS or NTP based TTL time capture”
>
> Telescope domes are filled with equipment, in particular the camera
> shutter, that can be instrumented to issue a pulse suitable for hardware
> time capture. We use Meinberg IRIG PCIe cards to trap these and read the
> timestamps using their library routines under Linux. “Black box” to the
> person I was talking to meant no IRIG in the dome, no Linux, and no PCIe
> slot, but rather a self-contained unit that syncs to GPS. When last he
> implemented such a feature at another telescope he didn’t even have time
> capture, but rather the device issued a trigger at a specified moment, so
> the timestamp and the shutter opening were inverted. He also seems to
> prefer the timestamps be issued on a serial connection, not via library.
>
> Unlike laboratory instrumentation, a telescope environment needs to be
> both very automated and very forgiving. Money may also be constrained.
> However, telescopes are also often very flexible and I am willing - no,
> eager - to consider completely different arrangements of equipment.
>
> So, reliable timestamping of a TTL input is the ulitmate goal. One channel
> would be sufficient, but multi-channel would not invalidate an option. PPS
> or IRIG-B (DCLS IEEE-1344) are not required, but might form an intermediate
> part of the solution. Reference could be GNSS or possibly NTP.
>
> Precision varies, but milliseconds down to microseconds. Accuracy should
> match the precision, meaning UTC accurate to same. Extra credit for
> multiple timescale support.
>
> Cheap is what I want to know. I see the previous thread on BB-black and
> could imagine a solution using the real time capabilities of that for a few
> hundred bucks, but these are not experimenters, per se. That’s why they
> want a black box. Volume is one to several, but could imagine a bulk order
> if savings were significant. Hundreds of dollars might be the price point.
>
> Thanks!
>
> Rob Seaman
> University of Arizona
>
>
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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Rob Seaman]

Attila Kinali wrote:
> On Wed, 18 Oct 2017 08:47:58 -0600
> Rob Seaman  > wrote:
> 
> > I’m at the annual planetary sciences meeting (in Provo this year) and 
> > several 
> > groups have expressed interest in duplicating our setup (details of FO 
> > converters, Schmitt triggers, etc, omitted) in a “cheap black box” to quote
> > one fellow. Lots of people contribute productively to NEO observations, 
> > including amateurs and small teams with little funding. Improving their 
> > timekeeping would help keep rocks from falling on you and your family.
> 
> What is this black box supposed to do? Just provide a PPS? IRIG-B?
> Or does it need to have time-stamping capabilities? If so, how many
> channels?
> 
> What are your time precision/accuracy requirements?
> 
> What how cheap is "cheap"? What is the volume?

Thanks for the quick reply. I should have included the subject line in the 
message:

"inexpensive, black box, GPS or NTP based TTL time capture”

Telescope domes are filled with equipment, in particular the camera shutter, 
that can be instrumented to issue a pulse suitable for hardware time capture. 
We use Meinberg IRIG PCIe cards to trap these and read the timestamps using 
their library routines under Linux. “Black box” to the person I was talking to 
meant no IRIG in the dome, no Linux, and no PCIe slot, but rather a 
self-contained unit that syncs to GPS. When last he implemented such a feature 
at another telescope he didn’t even have time capture, but rather the device 
issued a trigger at a specified moment, so the timestamp and the shutter 
opening were inverted. He also seems to prefer the timestamps be issued on a 
serial connection, not via library.

Unlike laboratory instrumentation, a telescope environment needs to be both 
very automated and very forgiving. Money may also be constrained. However, 
telescopes are also often very flexible and I am willing - no, eager - to 
consider completely different arrangements of equipment.

So, reliable timestamping of a TTL input is the ulitmate goal. One channel 
would be sufficient, but multi-channel would not invalidate an option. PPS or 
IRIG-B (DCLS IEEE-1344) are not required, but might form an intermediate part 
of the solution. Reference could be GNSS or possibly NTP.

Precision varies, but milliseconds down to microseconds. Accuracy should match 
the precision, meaning UTC accurate to same. Extra credit for multiple 
timescale support.

Cheap is what I want to know. I see the previous thread on BB-black and could 
imagine a solution using the real time capabilities of that for a few hundred 
bucks, but these are not experimenters, per se. That’s why they want a black 
box. Volume is one to several, but could imagine a bulk order if savings were 
significant. Hundreds of dollars might be the price point.

Thanks!

Rob Seaman
University of Arizona


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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Attila Kinali]

On Wed, 18 Oct 2017 08:47:58 -0600
Rob Seaman  wrote:

> I’m at the annual planetary sciences meeting (in Provo this year) and several 
> groups have expressed interest in duplicating our setup (details of FO 
> converters, Schmitt triggers, etc, omitted) in a “cheap black box” to quote
> one fellow. Lots of people contribute productively to NEO observations, 
> including amateurs and small teams with little funding. Improving their 
> timekeeping would help keep rocks from falling on you and your family.

What is this black box supposed to do? Just provide a PPS? IRIG-B?
Or does it need to have time-stamping capabilities? If so, how many
channels?

What are your time precision/accuracy requirements?

What how cheap is "cheap"? What is the volume?

Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Rob Seaman]

Howdy,

I’ve been working for the Catalina Sky Survey for a couple of years. For many 
years, CSS has been one of the most productive discoverers of Near Earth 
Objects (NEOs), that is, of asteroids and comets that are potentially hazardous 
to the Earth.

As you might imagine there are numerous interesting aspects to this project, 
and timekeeping is one. We use Meinberg clocks and IRIG PCIe cards to capture 
TTL signals from the stepper motor controller of the large camera shutters to 
attach accurate and reasonably precise UTC time tags to each celestial search 
field. Our telescope control also depends on knowing the time. Etc.

I’m at the annual planetary sciences meeting (in Provo this year) and several 
groups have expressed interest in duplicating our setup (details of FO 
converters, Schmitt triggers, etc, omitted) in a “cheap black box” to quote one 
fellow. Lots of people contribute productively to NEO observations, including 
amateurs and small teams with little funding. Improving their timekeeping would 
help keep rocks from falling on you and your family.

Any suggestions for a minimally expensive, maximally performing such 
arrangement? Or alternative architectures? One group has used:

http://www.spectruminstruments.net/TM4.pdf 


Thoughts?

Many thanks!

Rob Seaman
University of Arizona

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[time-nuts] True Position Time Figure of Merit

[Mark Sims]

This forum thread has most of our reverse engineering info on these GPSDO's:

http://www.eevblog.com/forum/projects/gpsdo-loss-of-satellitesfix-troubleshooting/
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