[time-nuts] Generating a solid PPS from 10Mhz source

[Jerome Blaha]

Hey Guys,

Is there an easy circuit to build that can consistently deliver a 1 PPS from a 
10MHz source with excellent resolution and repeatability?  My first application 
is to test different 10MHz oscillators without a TIC always attached and then 
compare the PPS output change over time against a master GPSDO PPS with an 
HP53132A.

The circuit used for PPS generation would have to deliver consistent PPS output 
with preferably not more than 100ps noise or jitter, assuming a perfect source. 
 I'm totally guessing that for this resolution, the PPS would have to be 
generated and accurate to within 0.001Hz every second.  If this is too 
difficult, maybe the integration time can be increased to generate one pulse 
every 10second or every 100,000,000.00 cycles?

Finally, is a square 10Mhz reference any better in this case than a sinusoidal 
input for generating the PPS?

Thanks,
Jerome

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Re: [time-nuts] Fixing broken HP5065A LED clock

[Poul-Henning Kamp]

In message 
, paul swed 
writes:

>Poul-Henning is that just the back board of the clock?
>I guess I did not realize there were actually 2 boards.

There are 3 and 2 board versions of the LED clock.  Mine is the 2-board
version.

See the section about MM5313 here:

http://phk.freebsd.dk/hacks/HP5065A/20151225_clock/index.html

I think you can use my PCB to make the 3-board a 2-board
but you'd have to change some constants in the firmware to send out
50Hz rather than 1Hz.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Generating a solid PPS from 10Mhz source

[John Ackermann N8UR]

Tom Van Baak has developed dividers based on simple PIC chips that will 
produce 1 PPS from several input frequencies.  These dividers have 
remarkably low jitter, down in the couple-of-picosecond range, and are 
very simple.


I've implemented life support circuitry around two versions of Tom's 
code, both available as kits from TAPR:


The TADD-2 is a 4x6 inch board with 6 BNC outputs, each of which can be 
set to provide 1, 10, 100, 1K, or 10K PPS from either a 5 or 10 MHz input:

http://tapr.org/kits_tadd-2.html

The T2-Mini is a tiny board with a single input and output.  The default 
firmware allows PPS output for 1, 2.5, 5, or 10MHz input:

http://tapr.org/kits_t2-mini.html

Both of these devices have a low-jitter sine-to-square converter on the 
input, and work over a wide input amplitude range, so just about any 
sine wave will drive them.


John


On 1/13/2016 4:22 AM, Jerome Blaha wrote:

Hey Guys,

Is there an easy circuit to build that can consistently deliver a 1 PPS from a 
10MHz source with excellent resolution and repeatability?  My first application 
is to test different 10MHz oscillators without a TIC always attached and then 
compare the PPS output change over time against a master GPSDO PPS with an 
HP53132A.

The circuit used for PPS generation would have to deliver consistent PPS output 
with preferably not more than 100ps noise or jitter, assuming a perfect source. 
 I'm totally guessing that for this resolution, the PPS would have to be 
generated and accurate to within 0.001Hz every second.  If this is too 
difficult, maybe the integration time can be increased to generate one pulse 
every 10second or every 100,000,000.00 cycles?

Finally, is a square 10Mhz reference any better in this case than a sinusoidal 
input for generating the PPS?

Thanks,
Jerome

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Re: [time-nuts] Generating a solid PPS from 10Mhz source

[Edesio Costa e Silva]

Hi!

Try TVB's picDiv at http://www.leapsecond.com/pic/picdiv.htm

Edésio

On Wed, Jan 13, 2016 at 09:22:09AM +, Jerome Blaha wrote:
> Hey Guys,
> 
> Is there an easy circuit to build that can consistently deliver a 1 PPS from 
> a 10MHz source with excellent resolution and repeatability?  My first 
> application is to test different 10MHz oscillators without a TIC always 
> attached and then compare the PPS output change over time against a master 
> GPSDO PPS with an HP53132A.
> 
> The circuit used for PPS generation would have to deliver consistent PPS 
> output with preferably not more than 100ps noise or jitter, assuming a 
> perfect source.  I'm totally guessing that for this resolution, the PPS would 
> have to be generated and accurate to within 0.001Hz every second.  If this is 
> too difficult, maybe the integration time can be increased to generate one 
> pulse every 10second or every 100,000,000.00 cycles?
> 
> Finally, is a square 10Mhz reference any better in this case than a 
> sinusoidal input for generating the PPS?
> 
> Thanks,
> Jerome
> 
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Re: [time-nuts] Generating a solid PPS from 10Mhz source

[Ole Petter Ronningen]

Sounds like a PICDIV is just about right:
http://www.leapsecond.com/pic/picdiv.htm

Ole

On Wed, Jan 13, 2016 at 10:22 AM, Jerome Blaha 
wrote:

> Hey Guys,
>
> Is there an easy circuit to build that can consistently deliver a 1 PPS
> from a 10MHz source with excellent resolution and repeatability?  My first
> application is to test different 10MHz oscillators without a TIC always
> attached and then compare the PPS output change over time against a master
> GPSDO PPS with an HP53132A.
>
> The circuit used for PPS generation would have to deliver consistent PPS
> output with preferably not more than 100ps noise or jitter, assuming a
> perfect source.  I'm totally guessing that for this resolution, the PPS
> would have to be generated and accurate to within 0.001Hz every second.  If
> this is too difficult, maybe the integration time can be increased to
> generate one pulse every 10second or every 100,000,000.00 cycles?
>
> Finally, is a square 10Mhz reference any better in this case than a
> sinusoidal input for generating the PPS?
>
> Thanks,
> Jerome
>
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Re: [time-nuts] Lady Heather Server On Raspberry Pi 2 Model B?

[Chris Caudle]

On Wed, January 13, 2016 8:30 am, Nick Sayer wrote:
>> No, ntpd would be getting time from the serial port, not from the
>> network socket.
>
> You're right. I may be wrong, but I would expect that either gapd or
> ser2net would want to open the serial device exclusively, which would
> spoil things.
...
> You might investigate whether you could make some sort of intermediate
> service that could be a client of gpsd and provide the listening socket
> for LH.

That is the right approach, and someone has already done that.
If I had seen this before I completely forgot, but my old friend N5TNL
pointed me to:
Original code written for BSD:
http://ralphsmith.org/~ralph/thunderbolt.tar.gz

Patches for linux and info by Leigh Klotz (WA5ZNU):
http://wa5znu.org/2011/08/tbolt/

The  original announcement for the BSD version was almost 6 years ago by
Ralph Smith:
https://www.mail-archive.com/time-nuts@febo.com/msg26128.html

The follow-up by Leigh was right at 4 years ago:
https://www.febo.com/pipermail/time-nuts/2012-January/062566.html


Summary is the thunderboltd service runs and communicates with the
Thunderbolt, provides a network port for Lady Heather to connect to for
remote display and control of the Thunderbolt, and places the time into a
shared memory region for ntpd to pick up.

It works on x86, so I'm getting ready to install an ARM compiler to see if
it compiles cleanly for ARM.  I don't have the right RS232 level
translator yet to connect my Thunderbolt to my ARM system (BeagleBone
Black in my case, not RPi), so I can't check it out directly yet.

-- 
Chris Caudle



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Re: [time-nuts] Generating a solid PPS from 10Mhz source

[Nick Sayer via time-nuts]

Just shy of a half dozen folks have asked, so I'll post here as soon as I 
finish cleaning it up. I'll put it on Github when it's ready. I just need a day 
or two. 

Sent from my iPhone

> On Jan 13, 2016, at 6:43 AM, Nick Sayer via time-nuts  
> wrote:
> 
> If anyone is interested in the equivalent functionality using an ATTiny25 
> (for instance, if you’re already heavily invested in AVR instead of PIC, like 
> I am), ping me. I’ve privately written code to solve almost the same problem 
> and it could easily be adapted into doing the same job.
> 
>> On Jan 13, 2016, at 5:23 AM, Edesio Costa e Silva  
>> wrote:
>> 
>> Hi!
>> 
>> Try TVB's picDiv at http://www.leapsecond.com/pic/picdiv.htm
>> 
>> Edésio
>> 
>>> On Wed, Jan 13, 2016 at 09:22:09AM +, Jerome Blaha wrote:
>>> Hey Guys,
>>> 
>>> Is there an easy circuit to build that can consistently deliver a 1 PPS 
>>> from a 10MHz source with excellent resolution and repeatability?  My first 
>>> application is to test different 10MHz oscillators without a TIC always 
>>> attached and then compare the PPS output change over time against a master 
>>> GPSDO PPS with an HP53132A.
>>> 
>>> The circuit used for PPS generation would have to deliver consistent PPS 
>>> output with preferably not more than 100ps noise or jitter, assuming a 
>>> perfect source.  I'm totally guessing that for this resolution, the PPS 
>>> would have to be generated and accurate to within 0.001Hz every second.  If 
>>> this is too difficult, maybe the integration time can be increased to 
>>> generate one pulse every 10second or every 100,000,000.00 cycles?
>>> 
>>> Finally, is a square 10Mhz reference any better in this case than a 
>>> sinusoidal input for generating the PPS?
>>> 
>>> Thanks,
>>> Jerome
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
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> 
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Re: [time-nuts] Tait reference

[Adrian Godwin]

Good news - my purchase arrived quickly, contains an FE5660A 10MHz
oscillator and shows both the internal standard lock light and the internal
reference lock light within a few minutes. It runs from 13.8 volts and
takes about 1.2A.

The f1 and f2 lock lights don't come on, but that's not a big issue. I may
just rewire those outputs as a distribution amplifier in any case.


On Tue, Jan 12, 2016 at 5:46 PM, Adrian Godwin  wrote:

> If so, let's hope the sudden surge of purchases will encourage the dealer
> to find some more :)
>
>
> On Tue, Jan 12, 2016 at 1:39 PM, Clint Jay  wrote:
>
>> That's a very happy coincidence and one I'd hoped to hear.
>>
>> The pictures in the auction seem to show a lack of tarnish on the Ref Out
>> and Ref In BNCs which suggests they have had plugs on them, looping the
>> internal reference, other little bits of information also pointed to that,
>> the remnants of a sticker on the front of one unit seems to say
>> 'RUBID01...', past auctions of T801 units have been labelled with things
>> like 'RUBID048', the hex switches seem to be set correctly for use with an
>> internal reference as well so I was quietly confident they had the Rb
>> option fitted.
>>
>> Now I just have to cross my fingers that mine arrive with the Rb in good
>> conditon. The seller also states 'working order' so there's possible scope
>> for a refund if it doesn't.
>>
>> On 12 January 2016 at 12:24, GandalfG8--- via time-nuts <
>> time-nuts@febo.com>
>> wrote:
>>
>> > Are these the references with a rubidium oscillator ?  They seem  to
>> have
>> > similar models with OCXOs etc.
>> > http://www.ebay.co.uk/itm/111862884745
>> >
>> > ---
>> > Well now, how's this for a happy coincidence.
>> >
>> > I've just received an email from a friend who bought a Tait T801 from
>> that
>> > very same auction, asking about the rubidium module that he  found
>> inside
>> > it:-)
>> >
>> > Regards
>> >
>> > Nigel
>> > Gm8PZR
>> > ___
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>> >
>>
>>
>>
>> --
>> Clint.
>>
>> *No trees were harmed in the sending of this mail. However, a large number
>> of electrons were greatly inconvenienced.*
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Re: [time-nuts] Lady Heather Server On Raspberry Pi 2 Model B?

[Nick Sayer via time-nuts]

> On Jan 12, 2016, at 4:20 PM, Chris Caudle  wrote:
> 
>>> On Jan 12, 2016, at 7:17 AM, Chris Caudle  wrote:
>>> Can ntpd using a Thunderbolt as a time source run cooperatively with LH
>>> accessing the same Thunderbolt over ser2net?  That seems like the best
> 
> On Tue, January 12, 2016 4:01 pm, Nick Sayer via time-nuts wrote:
>> I'm going to guess no, because only one thing can connect to the
>> ser2net socket at a time.
> 
> No, ntpd would be getting time from the serial port, not from the network
> socket.

You’re right. I may be wrong, but I would expect that either gapd or ser2net 
would want to open the serial device exclusively, which would spoil things.

>  The idea would be that ntpd was getting the clock time from the
> serial port, but the time messages would be interleaved with whatever data
> the Thunderbolt was sending back in request to the LH commands.

You might investigate whether you could make some sort of intermediate service 
that could be a client of gpsd and provide the listening socket for LH. If 
you’re fortunate, LH may be able to just connect up to gpsd directly. gpsd has 
the wherewithal to interleave client access, if I am not mistaken.

> 
> LH would also be seeing the time messages, but it sees those anyway, so I
> think the only concern would be the behavior of ntpd when all the data
> from LH commands is going by.  Possibly a second concern of whether ntpd
> sends any commands to the Thunderbolt that might cause LH to be confused
> by responses to commands LH did not send.
> 
>> If I were going to do it, what I might do is connect up the PPS output of
>> the tbolt to a GPIO pin of the RPi and configure that pin for the pps
>> device and set up ntpd for that.
> 
> You still have to get wall clock time from somewhere, PPS just delineates
> the seconds, it doesn't name the seconds.

Of course. You just have ordinary ntp peers for that.

> For some cases you could have ntpd get the starting time from another
> network source and just use PPS to keep track of the seconds after that,
> but then you would still have corner cases of knowing when leap seconds
> occurred, maybe others.

Well ntp ostensibly takes care of that too.

> And of course if you relied on network access to other time servers you
> could not operate on an isolated network.

That’s true. My goal, though, was just to contribute to the ntp pool, so 
connectivity is assumed.

> 
>> That way, LH can have the serial
>> interface all to itself. I've done this with a far more ordinary GPS
>> module to make a public stratum 1 server out of a Pi Zero for the NTP pool
>> (ntp.kfu.com).
>> 
> 
> How did it get the correct time set at startup?  Did it have to query
> other network servers to set the time, then the PPS controlled the clock
> after that?

Yup.

> Can it be a "stratum 1" server if it has to rely on another server to get
> the correct time when it starts up?  I guess it could if it doesn't serve
> time until it has checked with other stratum 1 servers to make sure the
> time is correct.

That’s exactly right - it doesn’t claim stratum 1 until it gets an ntp lock 
over the network (at which point it can claim stratum 2 normally), and then it 
starts to take the pps updates and claims stratum 1.

> 
> Sorry, didn't mean to go off into those weeds, but that isn't the system I
> want.
> I want a machine which can get the correct current time without reference
> to another system, which means that ntpd must get the time information
> from somewhere, either by directly reading the serial port, or passed
> through from gpsd which is reading the serial port, or some similar setup.
> The PPS driver would be connected directly to ntpd.

The issue with the serial data stream in my case is that there’s no 
synchronization in it that’s sub-second accurate. That is, there’s no way to 
know which leading edge of which bit in the NMEA sentence is lined up with the 
start of the GPS second. And even if you get that, the serial driver doesn’t 
have any mechanism to accurately time-stamp the incoming characters - at least 
not nearly as well as the pps device. Now, that may not be the case with the 
tbolt, but with the module that that server’s using, trying to actually sync 
acceptably with gpsd is an exercise in futility. It’s much faster to just 
ignore the serial data and get synced initially over the network.

> 
> -- 
> Chris Caudle
> 
> 
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Re: [time-nuts] Generating a solid PPS from 10Mhz source

[Nick Sayer via time-nuts]

If anyone is interested in the equivalent functionality using an ATTiny25 (for 
instance, if you’re already heavily invested in AVR instead of PIC, like I am), 
ping me. I’ve privately written code to solve almost the same problem and it 
could easily be adapted into doing the same job.

> On Jan 13, 2016, at 5:23 AM, Edesio Costa e Silva  
> wrote:
> 
> Hi!
> 
> Try TVB's picDiv at http://www.leapsecond.com/pic/picdiv.htm
> 
> Edésio
> 
> On Wed, Jan 13, 2016 at 09:22:09AM +, Jerome Blaha wrote:
>> Hey Guys,
>> 
>> Is there an easy circuit to build that can consistently deliver a 1 PPS from 
>> a 10MHz source with excellent resolution and repeatability?  My first 
>> application is to test different 10MHz oscillators without a TIC always 
>> attached and then compare the PPS output change over time against a master 
>> GPSDO PPS with an HP53132A.
>> 
>> The circuit used for PPS generation would have to deliver consistent PPS 
>> output with preferably not more than 100ps noise or jitter, assuming a 
>> perfect source.  I'm totally guessing that for this resolution, the PPS 
>> would have to be generated and accurate to within 0.001Hz every second.  If 
>> this is too difficult, maybe the integration time can be increased to 
>> generate one pulse every 10second or every 100,000,000.00 cycles?
>> 
>> Finally, is a square 10Mhz reference any better in this case than a 
>> sinusoidal input for generating the PPS?
>> 
>> Thanks,
>> Jerome
>> 
>> ___
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