Re: [time-nuts] Unified VCXO Carrier Board

[Neil Schroeder]

I would be pleased to contribute a 100 MHz wenzel onyx for testing if
that'd be of value. I don't see myself getting to it anytime soon and this
project directly benefits almost half the things on my "never to do but
wish I could" list
On Sun, Oct 25, 2015 at 7:00 PM Bruce Griffiths 
wrote:

> On Sunday, October 25, 2015 09:21:02 AM Charles Steinmetz wrote:
> > I wrote:
> > >>According to the simulation, the resistor has no effect on the output
> > >>amplitude until it is well below 1k ohms
> >
> > Bruce replied:
> > >even 10k increases the output signal amplitude by 130mV or 2.6%.
> > >However that is smaller than the tilt/sag in the high level output due
> to
> > >feedthrough via Cbe of the input transistor when it is off.
> >
> > Bruce is correct, although I don't consider 130mV to be a significant
> > effect on a 5v logic level.  My fault, I guess, for saying "no"
> > effect instead of "no significant" or "no material" effect.
> >
> > But, do we really need to dispute every insignificant, niggling
> > little detail like this?  Even in science, there must be *some*
> > allowance for the use of everyday language instead of requiring
> > absolute explicit clarification of every possible point, or all
> > communications would be unbearably tedious from all of the
> > qualifications.  I say this as someone who is often criticized for
> > overclarifying to the point of being pedantic and tedious.
> >
> > There was simply no need, nor excuse, for the prior (incorrect)
> > suggestion that a resistor to ground from Point "A" would not be
> > effective in canceling the small asymmetry of the circuit, OR for the
> > suggestion that such a resistor would be a useful means to adjust the
> > output amplitude (this because of (i) the concomitant ill effect on
> > symmetry and (ii) the much more direct and efficacious means of
> > achieving the result by adjusting R6 or R1 and R2).
> >
> > Best regards,
> >
> > Charles
> >
> >
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> Charles
>
> There was no such suggestion, merely  a note that the amplitude was also
> affected by this. This effect is important in that its probably advisable
> to
> ensure that the input protection diodes of any gate being driven by the
> output don't enter into conduction (I discovered that at least for the
> 74HC04 that the propagation delay jitter increased dramatically once the
> input protection diodes began to conduct). Thus an increase in output
> amplitude by a few hundred mV could be detrimental to the performance
> of the driven logic device.
>
> Whilst the symmetry adjustment effect is real its actually achieved by
> adjusting the ratio of the emitter currents of the 2 transistors (its not a
> threshold effect due to Vbe changes -they are too small but an adjustment
> of the differential switching delays of the 2 transistors).
> Consequently adjusting the ratio of emitter currents of Q1 and Q2 is best
> made via a pot (200 ohm??) connected between the upper ends of R1 and
> R2 (reduce R1 and R2 to 910 ohm) with its wiper connected to the C5, C6,
> C7, R7 node.
> Adjusting the wiper position has very little effect (tens of mV) on the
> output amplitude whilst allowing adequate range of adjustment of the
> output signal duty cycle.
>
> Adjusting the value of R6 can be counter productive in that it spoils the
> match to a 50 ohm load achieved via simple 2:1 (turns ratio) stepdown RF
> transformer for the purposes of measuring the PN of the circuit.
>
> Bruce
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Re: [time-nuts] When NTP goes wrong...

[Neil Schroeder]

I would like to respond in a generic and sweeping way - having not read in
the detail Bob layed out for us required to fully analyze the situation -
to the notion that circuit level access or prior topological knowledge is
required to exploit this or any other spoofing attack.  On a corporation or
education network, I could generate such malformed packets with almost no
effort as long as i had my Mac or a similarly not-windows device, or access
to one.  I estimate it'd take less than 5 minutes for me to do for the
majority of targets - which means any motivated party could within an hour
or two. I'm not warranting I would succeed - hopefully there would be a
real firewall SOMEWHERE in the path from the open internet to a real
physical host.

IP routers are, by design, completely disinterested in source information
and the additional overhead of becoming aware and meaningfully acting on it
is significant - hence multimillion dollar price tags on single linecards
in most Internet-scale devices.  Additionally, the amount of knowledge
required to effectively benefit from it while avoiding massive
architectural issues is frequently impractical if not to distribute to the
necessary infrastructure devices.

Long story short: this sort of processing is only practical at the
very.ingress interfaces to a network.  In the case of a Level 3 sized
carrier that would mean the number of interfaces that are not protected
from such a packet would number literally in the millions.  Level 3 is a
poor example of an vulnerable path - i would be hard pressed to circumvent
their security strategies due to effective onion-like layering - but
AT's?  No problem.  All I need is one host that is willing to play and is
on a segment without reverse path forwarding  - which is all of them, in my
experience.  Once i am past the first hop I can get the rest of the way
there.

The network should not *ever be the solution *to a host vulnerability.  It
can provide a break-fix level of response but as I believe it was PHK said
- the only effective mitigation strategy starts with a real firewall
followed by a very aggressively managed host.  The level of protection
offered by standard anti-spoofing ACLs or advanced RPF detection is merely
insurance.

Other effective strategies include NEVER allowing the internet to connect
directly to a host.  A simple reverse proxy or server load balancer
combined with a RFC 1918 numbering scheme on host networks is a VERY
powerful tool.  Such L4-7 inspection engines are just the ticket to foiling
an evil exploit.

NS



i Sun, Oct 25, 2015 at 2:01 PM Paul  wrote:

> [This is my final contribution to this topic since real time-nuts using NTP
> run their own S1 servers driven by their Thunderbolts (et.seq.) and don't
> need to worry about this]
>
> On Sun, Oct 25, 2015 at 11:27 AM, Florian Teply  wrote:
>
> > >
> > > >But if I read that article on ars technica correctly, it looks like
> > > >it is something inherent to the ntp protocol itself and the
> > > >definitions it makes.
> >
>
> Only loosely.  It might appear that RFC5095 admits certain attacks using
> the 'debug' interface however the 'source'* document says (referring to the
> 'nonce' check)
>
> "While it seems reasonable to expect this check to be performed on the KoD
> packet as well, RFC 5905 [41, Sec. 7.4] does not seem to explicitly require
> this."
>
> I believe this is an incorrect interpretation but in any case I think it's
> clear the RFC is ambiguous and the published "fix" is to explicitly
> validate the nonce.  Other fixes include completely disabling the 'debug'
> interface. Implicit in this is the need to update the NTPv4 RFC.
>
> I advise those concerned to read RFC5095, the BU paper* (don't worry about
> the 68 references) and check the NTP security notice** to draw your own
> conclusions about this problem keeping in mind Wojciech's recent comments.
>
> *http://www.cs.bu.edu/~goldbe/papers/NTPattack.pdf
> **http://support.ntp.org/bin/view/Main/SecurityNotice
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Re: [time-nuts] UPS for my time rack

[Neil Schroeder]

Depending on your actual power throughput needs- PTCs can be a challenge as
Bob mentions.  You will have a tough time meeting the power requirements of
a Thunderbolt with many you'll see.   Now efuses (think TPS24/25xxx)  or
mosfets with a controller (think LTC43xx) can be a good choice but don't
hesitate to use a real honest to god fuse that blows out and waits for you
to come replace it if that is what you would need

I personally do as suggested in the thread above to some degree- I do AC to
DC conversion once for all my time and frequency stuff then have batteries
local to important gear and (in older stuff) a diode(s) or (in newer stuff)
a real hotswap controller.  But whenever something is really important
there's whatever fuse is needed.

Finally if you are of the type to be adventuresome -
http://cds.linear.com/docs/en/datasheet/4110fb.pdf  or

- Google for Freescale's, ON Semi's or TI's *offline* UPS Reference
designs.  Yes they invert DC to AC, but you can drive the inverter gates
with a microcontoller's PWM output. meaning no matter how jagged your
utility's wave may be you can create a perfect, beautiful 50 or 60 Hz sine
of your own - devoid of most noise.

NS

On Wed, Oct 14, 2015 at 12:01 AM Bob Camp  wrote:

> Hi
>
> One option for the “fuse” part of the DC supply system are PTC resettable
> fuses. You *do* indeed need to be careful about voltage and current ratings
> on these gizmos. If the only objective is to “not have smoke” when there
> is a short,
> that can reduce the variables to a manageable level. If your wire will
> handle 20A for
> long enough to get the gizmo to limit and your load is typically < 5A
> there are
> parts you can find.
>
> A few cautions:
>
> The trip points are very temperature dependent. If you need to handle -20C
> in the winter
> and +40C in the summer, that will narrow things down quite a bit.
>
> Mounting matters quite a bit. If you go with SMD parts, be careful of
> traces that act as
> heatsinks. This is one case that the part needs to get hot.
>
> There are to many variables on most of the spec sheets to simply pick one
> and move on.
> The only good way to do it is to get several and run repeated tests on
> them Min carry current
> will occur at your highest temperature. Worst case trip will occur at your
> lowest temperature.
>
> Consider that the “carry current” may not be the real limitation.
> Resistance in the supply lead
> of an OCXO is a bad idea. This may limit your current well below the point
> that the fuse actually
> trips.
>
> This sounds like a pretty scary list. To some degree it is. These parts do
> have their place. That
> does not mean they work everywhere and anywhere.
>
> Bob
>
> > On Oct 13, 2015, at 2:54 PM, Poul-Henning Kamp 
> wrote:
> >
> > 
> > In message <4FD0F30EBAEF49609DF207E3EE61C15B@pc52>, "Tom Van Baak"
> writes:
> >
> >
> >> I used to rely on one massive UPS (along with natural gas generator)
> >> for my entire lab. Eventually I found it more reliable and convenient
> >> to have localized power backup. By local I mean backup for a single
> >> shelf, or even a single instrument.
> >
> > The big gain is avoiding the DC->AC conversions.
>
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Re: [time-nuts] UPS for my time rack

[Neil Schroeder]

Those traco power units are fantastic. Absolutely great.

For smaller applications Murata makes 3W ones quite similar and Wurth
Electronik is also in that market.

On Wed, Oct 14, 2015 at 12:00 PM Poul-Henning Kamp 
wrote:

> 
> In message <20151013225202.1e70a...@aluminium.mobile.teply.info>, Florian
> Teply
>  writes:
>
> >DC-DC converters with very
> >good efficiency exist for quite some time now.
>
> The one I just put in my HP5065A does 60W with 90+% efficiency
> in a 2x1x.5 inch package:
>
> http://phk.freebsd.dk/hacks/HP5065A/20150930_dcdc/index.html
>
> >Umm, around here, at least for ham radio operators, it seems many
> >standardize now on PowerPole connectors for 12V DC.
>
> They're quite neat, but I wish there were something a little less
> heavy-duty for the 1-2 Amp range.
>
> --
> 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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[time-nuts] Two V(in)s walk into a bar...

[Neil Schroeder]

Lets take a hypothetical device, like specifically a PRS10, but could be
any time/freq device like a PLL or an amplifier or all of these.

Isolating power supplies with some dexterity can greatly improve noise
control, and less peformance related, can help us protect very very
expensive circuits from their less bourgeois support ICs.  Many of us may
choose to implement them as modular devices for easy relocation or
replacement.

Main question: if I want to isolate the quiet and noisy power supplies, or
just supply them differently, can they share a common return?

The basic answer has to be yes.  Eventually everything has to get back to
ground, and the Earth itself is a fair equalizer of all things on it.  I
can clearly join analog and digital back at the input supply.  But if I had
them isolated, do those iso grounds have to stay with their iso supplies?

Take the PRS10 - it has two cables for Vin - power and signal supplies -
but only one return cable.  Can i isolate, via transformers couplers what
have you the two supplies yet return the common ground to one or the other?

The signals handle themselves - they each have a ground wire of their own,
or does that handle it ?  Are each of those opportunities for a loop?

I know it'd work with just keeping separate DVcc and AVcc supplies that
join at some point, and then that return can join at the star ground like
everyone else.  If you are designing the module, you can handle the
isolation inside and just have one input supply and return then isolate new
supplies internally and eliminate the second cable.  Or two in vcc, two out
gnd.  Those all make sense.

 I think the single return option on the PRS10 is what's hanging me up
here.

Does isolation offer any real further benefit than AVxx and DVxx that is
even worth pursuing outside the extreme use cases?

Lots of words.  Thanks.

NS
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Re: [time-nuts] Motorola Oncore UT+ firmware upgrade backup power questions

[Neil Schroeder]

I didnt see this well answered - the device loads firmware at each start
cycle.  If i am not mistaken you can even use ntp.


On Mon, Mar 16, 2015 at 1:34 AM, Adrian Godwin artgod...@gmail.com wrote:

 Seiko and some other manufacturers used Supercaps for a while in their
 Kinetic watches. Electrically they're fine, but they turned out to have a
 shorter life than rechargeable batteries. They even replaced capacitors
 with lithium rechargeables when servicing the older models.

 In a backup situation they might do better : I believe the problems were
 caused by allowing them to discharge and exposing them to high
 temperatures, neither of which should occur in a timenut application (as
 long as they're not inside a stabilisation oven). However, don't think of
 them as a complete solution to ageing nicads - they're still a wet
 electrolytic and probably have a finer internal structure than a nicad, so
 are still subject to chemical ageing.



 On Mon, Mar 16, 2015 at 3:51 AM, Hal Murray hmur...@megapathdsl.net
 wrote:

 
  csteinm...@yandex.com said:
   The Energizer AA and AAA lithium primary batteries (Li/FeS2) have a
  shelf
   life exceeding 10 years,
 
  Like many things, it's temperature dependent.
 
  A classic trick is to store batteries in your freezer.  Aside from better
  shelf life, you can probably find them in the dark.
 
 
  --
  These are my opinions.  I hate spam.
 
 
 
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Re: [time-nuts] USB problems and solutions - Some what Off Topic -- USB-C

[Neil Schroeder]

 so easy to ignore. We’ll see what actually happens …..
 
  Bob
 
  On May 30, 2015, at 11:28 AM, Neil Schroeder gign...@gmail.com
 javascript:; wrote:
 
  USB-C will offer a number of things that I believe will be of benefit
 to
  time nuts everywhere:
 
  1) High current 5V up to 3A on every port
  2) High voltage/current up to 20V/5A optionally on every port -
 sufficient
  to power some rubidium oscillators natively, and a small boost to get
 the
  rest of them.
  3) a native UART channel - no more freaky USB interrupts/polling to get
  your pulses
  4) single omnipurpose connector ends with no insertion dependencies
  5) Better, simpler device enumeration - while I haven't seen how it
  addresses this personally, the stuff i have read is very promising.
 
  Due to the switched controller nature of the interface, you should have
  less nonstandard crap that may cause your computer to hang or other
 issues
  related to drivers. The controller arbitrates a lot more setup
 details, and
  the number of those on the market will be limited compared to usb
  peripheral ICs.
 
  This may be off topic from your off topic, but it seemed a good
 opportunity
  to share this  info.
 
  NS9
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Re: [time-nuts] USB problems and solutions - Some what Off Topic

[Neil Schroeder]

USB-C will offer a number of things that I believe will be of benefit to
time nuts everywhere:

1) High current 5V up to 3A on every port
2) High voltage/current up to 20V/5A optionally on every port - sufficient
to power some rubidium oscillators natively, and a small boost to get the
rest of them.
3) a native UART channel - no more freaky USB interrupts/polling to get
your pulses
4) single omnipurpose connector ends with no insertion dependencies
5) Better, simpler device enumeration - while I haven't seen how it
addresses this personally, the stuff i have read is very promising.

Due to the switched controller nature of the interface, you should have
less nonstandard crap that may cause your computer to hang or other issues
related to drivers. The controller arbitrates a lot more setup details, and
the number of those on the market will be limited compared to usb
peripheral ICs.

This may be off topic from your off topic, but it seemed a good opportunity
to share this  info.

NS9
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Re: [time-nuts] IRIG-B audio decoder circuits and ICs sought

[Neil Schroeder]

A bc635 can be had on eBay for almost nothing. It's not a pleasant piece of
gear, but this is one task it can help you with greatly.

Tools exist to let you analyse the stream extensively, and the Api is
trivial to learn -but not super featured at the high level.

On Tuesday, May 19, 2015, Tim Shoppa tsho...@gmail.com wrote:

 See for example the Truetime 820 decoder. Discriminators, One-shots, and
 Flip-Flops with pots to tweak the levels.

 Tim N3QE

 On Tuesday, May 19, 2015, Joseph Gwinn joegw...@comcast.net
 javascript:; wrote:

  I'm studying up on how IRIG-B decoder circuits work.  What are the good
  approaches, the bad approaches, especially in the presence of noise?
  (I asked on the NTP group, with little result beyond the C/C++ decoder
  software written for the audio channel of a 1990s Sun workstation,
  which it ate alive: 50% cpu load.)
 
  Are there decoder ICs available?
 
  The closest to a decoder IC I've found is some FPGA code from a partner
  of Microsemi (nee Symmetricom):
 
  ..
 
 http://www.microsemi.com/products/fpga-soc/design-resources/partners/semquest
  
 
  All marketing and little technical information.  I'll have to find out
  the details.
 
 
  I find very little, though I did find one intriguing idea using a
  Costas Loop to lock to the 1 KHz carrier, and a posting suggesting
  squaring the input signal and phase-locking to the 2 KHz result.  Most
  recent articles on IRIG decoders come from Chinese sources, mostly in
  the AC power industry.
 
  Joe Gwinn
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Re: [time-nuts] Comparing the BeagleBone Black Raspberry Pi as NTP servers

[Neil Schroeder]

The other key key key item is make sure you hand build yourself a 3.14 or
.16 kernel.

NS

On Mon, Mar 23, 2015 at 2:30 AM, Attila Kinali att...@kinali.ch wrote:

 On Sun, 22 Mar 2015 16:41:56 -0400
 Paul tic-...@bodosom.net wrote:

  1) Did you start out using the attached patch antenna?  D Drown implies
  successfully using the patch on the Adafruit until it was soldered in
  place.  He fixed that by switching to an external antenna.  I've never
 had
  any success with attached patch antennas but my receivers are inside.


 The BBB is known to have a bad EMI behaviour. You should not put
 any sensitive RF components near it, without proper shielding.

 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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Re: [time-nuts] Comparing the BeagleBone Black Raspberry Pi asNTP servers

[Neil Schroeder]

I can confirm similar issues with each of my BBBs.  They just can't seem to
get the jitter down.

I've tried a variety of combinations of Debian and Ubuntu, and even
replaced the clock on one with an Si5338.

On Sun, Mar 22, 2015 at 6:29 AM, Mike George mgeo...@tuffmail.us wrote:

 David:

 On this page:

 http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#BBW.
 2FBBB_.28All_Revs.29

 they list an alternative console only image:

 https://rcn-ee.com/rootfs/bb.org/release/2015-03-01/
 console/bone-debian-7.8-console-armhf-2015-03-01-2gb.img.xz

 It might be easier starting with that if you don't intend to use graphics.

 Mike

 On 3/22/2015 03:46, David J Taylor wrote:

 David:
 On the BBB, were you running the fully loaded release, or the minimum
 console version of the OS?
 Which specific version of the OS?

 Thanks,
 --- Graham
 =

 Graham,

 The download was:

  bone-debian-7.8-lxde-4gb-armhf-2015-03-01-4gb.img.xz (547,024,548 bytes)

 which was from the Recommended Debian Images from:
 http://beagleboard.org/latest-images.  Perhaps there are some services
 or background tasks I can disable to reduce the CPU steady load from its
 present 16% average level?

 73,
 David GM8ARV


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Re: [time-nuts] NTP stratum 1 appliances with different (GPS, etc) cores...

[Neil Schroeder]

Ones ive deployed:

End run.  BSD
Microsemi S350 LINUX
Meinberg MRS LINUX

Others:
Spectra com
Brandywine

The three i used were all very good. You want more re details I will put
some effort into it.
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Re: [time-nuts] Soekris without a GPS receiver.

[Neil Schroeder]

You need to do a console mode install on the system itself or you have
problems - you can do a debootstrap on another machine and get going... but
heres  the thing - you need FreeBSD to use the Soekris appropriately.
Otherwise you're using a 486 from 2001 just to cause yourself pain.

All you need is FreeBSD Crochet - its not a tough process.  Check it out,
then immediately use the same tool to build yourself an image for the
Beaglebone you should order :-)

https://github.com/kientzle/crochet-freebsd

Alternately, CF cards are HUGE now.  I have a 16G in my Soekris and that's
PLENTY big to run a full operating system on.  Don't even have to do
NanoBSD - although naturally, you'll pay for it in performance and memory
use if you don't.

NS

On Fri, Jan 2, 2015 at 5:05 AM, Hal Murray hmur...@megapathdsl.net wrote:


 david-tay...@blueyonder.co.uk said:
  Chris, I completely agree with you.  Were it possible to install a
 normal
  OS easily, I would have done so, but the device only has a CF card slot,
 and
   there is no secondary boot device, so you end up trying to install the
 OS
  on  the memory stick image you have booted from, and this does not seem
 to
  work.  ...

 I think the idea is that you do the install on some other system, using
 something like a USB to CF adapter.


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Re: [time-nuts] schematics of frequency counter

[Neil Schroeder]

I would reconsider the LDOs while you have some time to play with them.
The TPS79333DBVR is not even remotely ultralow noise at most offsets,
despite what TI may say.

For 5V5 and under up to about 600ma, I would suggest you take a look at the
ADM7155 (adjustable) or ADM7154 (fixed). If you need 800ma, the 7150 is
here for you.

http://www.analog.com/en/power-management/linear-regulators/adm7155/products/product.html
http://www.analog.com/en/power-management/linear-regulators/adm7150/products/product.html

The TI part has nearly 35 uVRMS of noise  at just 2.8a with not very good
PSRR.  The 7155 will produce less than  1.0 μVRMS Total Integrated Noise
from 100 Hz to 100 KHz and 1.6 from 10 to 100 KHz,and that's without an RC
noise compensation network.  Its a fabulous part for a sensitive
application like yours.

I'm hoping I am right in assuming that the noise performance of the LDOs is
a concern, and don't mean to even dare suggest that you've done anything
but a great job! :-)

NS

On Sat, Dec 27, 2014 at 5:34 AM, Li Ang lll...@gmail.com wrote:

 Hi Charles,
In my circuit, the VCC is 5v. I've noticed my bias and emitter resistor
 is something need to be changed. I will play with the resistors and see if
 it improves. Thanks.

 2014-12-27 6:42 GMT+08:00 Charles Steinmetz csteinm...@yandex.com:

  Li Ang wrote:
 
   RF pnp transistor is harder to get. I would like the front end works
  at 300MHz.
 
  My questions:
  1) why the difference of DC bias of the 2 NPN matters?  I thought only
 the
  frequency part is useful to a counter, amplitude information is useless
  right?
 
 
  You want the circuit to switch near the mid-point of the input sine wave,
  and at exactly the same place every time.  How you bias the transistors
  determines how well this is accomplished.
 
  You also want the output to switch fast and cleanly between a low voltage
  very near 0v (ground) to a high voltage very near 3v (Vcc, logic high).
  An NPN cannot do that, biased the way that you have them connected (the
  emitter of the output transistor Q301 can only pull the output down to a
  little less than 1v due to R315, which may sort of work but is not a
 proper
  way to run 3v logic).  This operation also saturates Q301, which is bad
 for
  performance.  See simulated results below.
 
  In order for an NPN to provide a useful output for 3v logic, (i) its
  emitter must be grounded, and (ii) it must either be run into saturation
 or
  use a Baker clamp.  Running the transistor into saturation must be
 avoided,
  particularly if you want to reach 300MHz, and a Baker clamp raises the
  logic low output voltage to 0.5v (not a good thing with 3v logic).
 So,
  it is very much better to use a PNP differential pair.  For a 300MHz
  circuit, I would use BFT93 (and even that barely gets you to 300MHz).
 
   2) what's is the C4 in your circuit for?
 
 
  C4 makes Q1 and Q2 a differential (emitter-coupled) pair at RF
  frequencies, but not at DC.  So, the circuit has no gain at DC and
  therefore the DC errors between Q1 and Q2 cause much less output error
 than
  they would if the emitters were connected directly together.
 
   3) If the noise is more important than the gain, what kind of transistor
  should I choose? The Ft near 300MHz ones(BFS17, 2SC9018) or Ft far
 beyond
  300MHz ones(BFP420, BFP183,BFR93) ?
 
 
  Far beyond.  The Ft is the frequency where a transistor completely runs
  out of gain.  You want to operate at a much lower frequency where the
  transistor still has substantial gain, particularly with fast RF
  transistors, which generally have much lower DC hfe than general-purpose
  transistors like 3904 and 3906.  Note that the simulation of the circuit
  you published (simulated results below) barely works at even 20MHz.  As I
  noted above, even the BFT93 barely gets you to 300MHz with a 1Vrms input.
 
  Best regards,
 
  Charles
 
 
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Re: [time-nuts] Set time on Solaris computer from HP 58503A

[Neil Schroeder]

Of *course* you can sync to better than a millisecond on the LAN.  There's
not a machine worldwide at my employer more than 600 micros off from each
other, and the machines at my house are within 50.

You wanna start talking the sync-e+1588 test I'm doing?  We're speaking in
nanos then.

My LTE Lite is the only USB pps I have presently - and it pulls my time
well over 200 milliseconds off reference.  That's a massive change from the
1 or less I am from the internet and the 50 micros from the other boxes.

NS

On Sun, Dec 14, 2014 at 10:30 AM, Chris Albertson albertson.ch...@gmail.com
 wrote:

 I would still like to experiment with it. As I wrote earlier I bought this
  for a frequency reference,  not a clock, but I would not object to a bit
 of
  fun messing around with it.
 
 
 If the goal is just getting good enough time onto the Solaris machine then
 use NTP and some pool servers on the Internet.  You get about 10
 millisecond level accuracy and the cost is zero.  If you have solaris
 running you might even have this all setup and running.  If not do this as
 the first step and verify it works.

 If 10ms is unacceptable, next step is to connect the PPS signal.  Doing
 this will move you from milli to micro second level accuracy.   It is easy
 if the Solaris machine has a real serial port.   If you have to go through
 a USB dongle you loose about an order of magnitude accuracy but this is
 still very good.

 There is zero point in buying a special computer to run NTP.  Just use any
 computer you own that is already running 24x7.  Of course if you don't have
 a computer that runs 24x7 then you would look for one that uses very little
 power.

 Don't worry to much if the USB connection skews the time on the NTP server
 by some tens of microseconds, your server can't transfer time to your other
 computers on the LAN any better than millisecond level so a few tenths of
 an millisecond hardly mater.

 My opinion of computer time is that for normal use being a few milliseconds
 off is OK because the typical monitor is refreshed no faster than 100Hz so
 you have lag cause by screen refresh times even if the internal clock is
 dead-on perfect.  Same for disk time stamps, these is lag in the IO system
 too


 --

 Chris Albertson
 Redondo Beach, California
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Re: [time-nuts] Set time on Solaris computer from HP 58503A

[Neil Schroeder]

Based on my recent testing - including Solaris - you will be better off
with the Internet unless your USB adapter is far better behaved than the
several I have here

On Sunday, December 14, 2014, Hal Murray hmur...@megapathdsl.net wrote:


 drkir...@kirkbymicrowave.co.uk javascript:; said:
  Can anyone advise if this is possible,  and if so what software is
 needed?
  Any idea what sort of accuracy would be achievable?

 I'm not familiar with Solaris.  I've never worked with a 58503A, but I have
 worked with the Z3801A and KS-24361.

 I'd try ntpd.  There is probably a version that comes with Solaris.

 USB probably doesn't support PPS.  I'd expect time to be within ballpark of
 10s of ms, roughly what you would expect with a good network connection so
 use that as a sanity check.

 You will need to setup your ntp.conf to use the HP driver, 26.

 You will need to setup your 58503A to use UTC in T2 mode.
   :diag:gps:utc 1  (and reboot?)
   :ptime:tcode:format F2

 You can check the GPS/UTC setting on the status page, and check the T2
 setting by sending:
   :PTIME:TCODE?



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Re: [time-nuts] Ublox time/freq aiding was Re: Linear voltage regulator hints...

[Neil Schroeder]

The oscillator in he m8f is a vctcxo and can be steered with feedback or
controlled by the host.

Also the m8f can send compliant DAC words to a TLV8515 and and MCP part via
i2c for external
VCXOs. It accepts their return signal on what would normally  be its
feedback in ports.

On Sunday, December 14, 2014, Bob Camp kb...@n1k.org wrote:

 Hi

 There is also a little note down in the (many) notes section:

 Not all features are available with all firmware versions.

 It applies to all of the external inputs (like USB and SPI).

 Since the oscillator in the uBlox is a TCXO and not a VCTCXO, the aiding
 feature would not help in the case of biasing the unit with a hot air gun.
 It would still loose lock as the TCXO went nuts.

 The ideal outcome would be a system that reported against the external
 input rather than the internal TCXO. Since they digitize the external pin
 with the TCXO, the outcome is pretty coarse (10’s of ns). That’s not going
 to help us much.

 Bob

  On Dec 14, 2014, at 4:26 AM, Simon Marsh subscripti...@burble.com
 javascript:; wrote:
 
 
  On 14/12/2014 04:08, d...@irtelemetrics.com javascript:; wrote:
   Note that most high-end GNSS timing receivers go one better and
 simply have an external input for the clock. That way you feed your own lab
 clock into the receiver. If you have Rb/Cs/maser you would use that as the
 reference. It's what the national timing labs do, along with dual-frequency
 and post-processing and all the other tricks of the trade.
 
  I think it would be agreat idea also. It's a wonder that more of the
 'timing' receivers don't have that external clock option! I wonder what
 these Ublox parts use for a clock? Is it something frequency compatible
 with a 10Mhz source??? (Hmm, can we pry one apart to figure it out! ;) )
 
  Ublox modules have a 48mhz internal clock.
 
  There is the following interesting paragraph in at least the 7  8 data
 sheets:
 
  ---
 
  1.8.2 Aiding
  The EXTINT pin can be used to supply time or frequency aiding data to
 the receiver.
 
  For time aiding, hardware time synchronization can be achieved by
 connecting an accurate time pulse to the EXTINT pin.
 
  Frequency aiding can be implemented by connecting a periodic rectangular
 signal with a frequency up to 500 kHz and arbitrary duty cycle (low/high
 phase duration must not be shorter than 50 ns) to the EXTINT pin. Provide
 the applied frequency value to the receiver using UBX messages.
 
  ---
 
  I haven't been able to find any information about what this actually
 does though. Anyone know ?
 
  Cheers
 
 
  Simon
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Re: [time-nuts] Which First GPSDO to buy?

[Neil Schroeder]

In a relative newcomer to this intense of a crowd :-).  But j also found
that I'm not quite  instrumented (yet) to tackle the accuracy problem.  As
such Im focusing where i can  on what I know (power, systems, the like)
while I accumulate the other gear.

As such I can say the thunderbolt and now the lte lite have been rock
solid.

On Friday, December 12, 2014, Anthony Roby ar...@antamy.com wrote:

 I'm in the same beginners' category as you.  I'd do more but have other
 projects on the go and have found I would need more equipment (GPIB
 interfaces, a spectrum analyzer etc) to get much further.  That said, I
 like the Lucent KS24361 and have a few bits and pieces on order to tap into
 J8 on the board of REF-1 and double the 5MHz for use in the lab.  I picked
 up a decent antenna on eBay, it's probably not in an ideal spot but that
 was a tradeoff between aesthetics on the house / access to pull a coax down
 to the basement / height of my ladder, and it seems to work fine.  Power
 supply was also auction-sourced for less than $20 and runs nicely.  I think
 eventually I'll make a panel and install the unit in my basement rack.

 I have no need for the time-nuts accuracy, but I have to say I've found
 this whole area fascinating and have learned a ton over the past couple of
 months toying around with this stuff and absorbing the expertise from the
 group here.

 Anthony

 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com javascript:;] On
 Behalf Of Hal Murray
 Sent: Friday, December 12, 2014 6:49 PM
 To: Discussion of precise time and frequency measurement
 Cc: hmur...@megapathdsl.net javascript:;
 Subject: Re: [time-nuts] Which First GPSDO to buy?



 kc0...@gmail.com javascript:; said:
  For a newcomer to this field, which GPSDO would be better to purchase
  as  a first-time acquisition: ...

 I'd suggest the Lucent KS24361.  Lots of people here have them so it will
 be easy to get advice.


 Aside from the GPSDO, you also need a power supply and antenna, and coax to
 get to the antenna.  It will work a lot better if the antenna is in a good
 location.  GPS is 1.5 GHz, so you have to pay attention to loss in the
 coax.


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Re: [time-nuts] Beaglebone NTP server

[Neil Schroeder]

Graham make sure you read up on dtb and fdt. Many if not most distros don't
have what you might call a default.

On Tuesday, December 9, 2014, Graham / KE9H ke9h.gra...@gmail.com wrote:

 Dan: Thanks. I don't know where you were quoting from, but it was the
 answer I needed.

 Paul: I found BB-BONE-GPS-00A0.dts, so I will start editing/hacking from
 there.
 I plan to run under Debian 7.7 or 8-Testing.

 Thanks,
 --- Graham

 ==

 On Tue, Dec 9, 2014 at 5:33 PM, Paul tic-...@bodosom.net javascript:;
 wrote:

  On Tue, Dec 9, 2014 at 12:59 PM, Graham / KE9H ke9h.gra...@gmail.com
 javascript:;
  wrote:
 
   I guess I am asking if the kernel pps-gpio has a specific preferred
  pin,
   or whether it can be mapped to any available gpio pin.
  
 
  The provided-with-stock-dtb pin is: 0x40 which is P9 pin 15.
  I use the only free pin on P8 or P9: 0x7c which is P8 pin 26
 
  There are various maps/charts/lists around with the pins.  Just decompile
  /lib/firmware/BB-BONE-GPS-00A0.dtbo and fiddle if you want a different
  pin.  The Debian relases come with dtc, I don't know about Angstrom.
 
  e.g.
  
 http://www.embedded-things.com/bbb/beaglebone-black-pin-mux-spreadsheet/
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Re: [time-nuts] 10MHz LTE-Lite - PPS accuracy?

[Neil Schroeder]

I don't think so - should just work

Did you already have ntpd running when you attached?  And do you have the
full PPS module stack including ldisc?

It works on every platform I got. :-)

As to better than Internet time - I cannot get it closer than 2 or 3 ms. I
have MANY internet time sources whose offset is not close to that bad

On Wednesday, December 10, 2014, Paul tic-...@bodosom.net wrote:

 On Wed, Dec 10, 2014 at 12:17 PM, gign...@gmail.com javascript:;
 wrote:

  Quite simply - if you either execute ldattach pps /dev/ttyUSBx, or are
  running GPSD (recommended) it will bind the USB appropriately to a ppsapi
  instance.
 

 I can get a /dev/ppsN but ppstest says time-out.  I saw some hints that the
 USB DCD

 might depend on the chipset .  I don't like gpsd so I try to avoid it but I
 might try it.

 Thanks.

  Do not do it.  You will not approve of the results.
 

 I don't intend to use it in production.
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Re: [time-nuts] Beaglebone NTP server

[Neil Schroeder]

It can be but suffers from enough jitter to be unusable.

All current BBB out of the box kernels have PPS-gpio. Google PPS gpio DTS
bbb.

Enjoy :-)

On Sunday, December 7, 2014, Chris Albertson albertson.ch...@gmail.com
wrote:

 On Sun, Dec 7, 2014 at 12:09 PM, folkert folk...@vanheusden.com
 javascript:; wrote:

 
  On my rpi the jitter is between 2 and 10us iirc but it is a while since
  I tested it. A quick peak shows me currently 3us jitter. Not bad for a
  userspace solution imho.


 Really?   The PPS to GPIO interface is handles in user space?  It is not
 interrupt driven?
 In the implementations I've seen the critical real time work is done inside
 the PPS interrupt handler and then of course ntpd runs in userland and can
 take as much time as it needs

 --

 Chris Albertson
 Redondo Beach, California
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Re: [time-nuts] Convert Stanford Research SR620 time-interval counter to SR625 ???

[Neil Schroeder]

I certainly won't cry foul. There's places where rolling your own can put
key assets at risk - it I had 4 I would push the issue but I only have one
atomic reference and I'd rather not blow it up

If anyone has things they need blown up I am available for the cost of
beer. As electronics get more advanced and smaller they certainly have
become MUCH more delicate.


On Wednesday, December 3, 2014, Paul tic-...@bodosom.net wrote:

 On Wed, Dec 3, 2014 at 3:54 PM, David I. Emery d...@dieconsulting.com
 javascript:;
 wrote:

  Do you have any rough number as to what they charged you for
  this ?
 

 The price at the SRS store is $150.  A great deal compared to $100 for a
 manual or heatsink.
 Granted the board is a bit more complex than a DE-9 and a couple of BNC
 connectors. I just looked at the retail for a PRS-10 and got over it.
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Re: [time-nuts] Any tutorial available for Lady Heather displays?

[Neil Schroeder]

It does not. Trust me.

I learned what little I know about this time stuff on a res t then an SMTX
and a thunderbolt - and found myself having  to learn all the concepts
elsewhere and even having to piece together how Trimble implements certain
things by observation.

Had i chosen the HP and Moto route it would have been a lot less painful
thanks to their documentation habits.


On Tuesday, December 2, 2014, Hal Murray hmur...@megapathdsl.net wrote:


 mflaws...@cox.net javascript:; said:
  I want to learn more in general about timing, deviation, steering,
 GPSDO's,
  etc.,

 Many years ago, I learned a lot by reading the manual for the Z3801A.  It's
 an owners/operators manual rather than a tutorial, but you can learn a lot
 by
 reading between the lines.  There is a ham radio web site with a lot of
 good
 info, including the manual and a good story that goes with a tour through
 the
 oscillator.

 There are also several HP app notes and articles in the HP Journal.  One
 covers the history: GPSDOs started as a way for power companies to figure
 out
 where lightning had hit their lines.  All you have to do is measure the
 time
 the breakers trip accurately enough and you can drive the repair truck to
 the
 correct tower.

 The TBolt documentation probably covers a lot of the same ground.  I think
 it's split over several documents.  The protocol documentation might be a
 bit
 thick, but again, you can learn a lot by reading between the lines.

 For general fun reading about timing, I recommend:
   Time Too Good to Be True, Daniel Kleppner
   Physics Today, March 2006, page 10
   http://scitation.aip.org/journals/doc/PHTOAD-ft/vol_59/iss_3/10_1.shtml


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Re: [time-nuts] 10 MHz oscillators vs 100 MHZ

[Neil Schroeder]

Wenz will happily well you anything in stock. I just picked up my first
original owner OCXO - a 100mhz onyx.

On Wednesday, December 3, 2014, Azelio Boriani azelio.bori...@gmail.com
wrote:

 I think that Ulrich should teach us how to make such an oscillator,
 not the other way round...

 
 http://www.tu-cottbus.de/fakultaet3/de/fakultaet/institute/stiftung/prof-dr-ing-habil-dr-hc-mult-ulrich-l-rohde.html
 

 On Wed, Dec 3, 2014 at 8:11 AM, Gerhard Hoffmann dk...@arcor.de
 javascript:; wrote:
  Am 03.12.2014 um 00:28 schrieb John Miles:
 
  NEL has great OCXOs.  Also worth checking out Wenzel (they own Croven
  Crystals and will sell them separately), Rakon, and Vectron.
 
  I haven't seen any 100 MHz OCXOs rated for -145 at 100 Hz, but -135 can
 be
  had.
 
 
  We had a few from Pascall that where at -145 @100@100M
 
  
 
 http://www.pascall.co.uk/content/S635399087054759815/Low-noise%20osc%20app%20note.pdf
 
  (interesting!)
 
  regards, Gerhard
 
 
 
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Re: [time-nuts] Convert Stanford Research SR620 time-interval counter to SR625 ???

[Neil Schroeder]

Slightly deviated topic : I haven't really ever been able to talk to my
prs10 via serial and change or check my PLL status/settings.  Any tips
here??checked the internal jumpers and resistors.


On Thursday, November 27, 2014, Bob Camp kb...@n1k.org wrote:

 Hi

  On Nov 27, 2014, at 8:05 PM, Don Latham d...@montana.com javascript:;
 wrote:
 
  I’ve just replaced the SR620 oxco option 01 with a Morion, by simply
 adding a 7812 to the 15 v heater feed. Locks well with either gpsdo or
 cesium external source. Don’t forget to turn on the external option and set
 the frequency for 5 or 10 MHz. It took about 5 days for the Morion to
 reasonably settle down.
   I agree about the Rb, has to be set with Gpsdo anyway, and I’ve already
 had 2 of them go South.

 I’ve had much better luck with Rb’s once I started heat sinking them
 properly. I pretty much ignored that issue early on and would regularly
 loose them. So far I have not lost one with a decent heat sink (and sub 40C
 baseplate).  Without heat sinking, some of them are up around 60-70C on the
 baseplate. Internal temps are even higher.

 Bob

 
  Prescalers from RFBay.
 
  Don
 
  On Nov 27, 2014, at 4:25 PM, Brooke Clarke bro...@pacific.net
 javascript:; wrote:
 
  Hi David:
 
  For me the key benefit of the SR620 is the 16 digit display.  That
 implies a lot of digits in the reference (although not all 16 of them) so I
 always use an external reference.
 
  When I turn the PRS-10 upside down the crystal changes frequency and
 the Rb corrects the crystal, see:
  http://www.prc68.com/I/PRS10.shtml#Accel
  http://www.prc68.com/I/Images/FC_ROT.jpg
 
  Mail_Attachment --
  Have Fun,
 
  Brooke Clarke
  http://www.PRC68.com
  http://www.end2partygovernment.com/2012Issues.html
  http://www.prc68.com/I/DietNutrition.html
  Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
  On 27 November 2014 at 22:15, Brooke Clarke bro...@pacific.net
 javascript:; wrote:
  Hi David:
  Hi Brooke
 
  If you look just to the right of the SR620 you will see a separate
 box that
  contains the PRS10.
  Ah, I missed that!!!
 
  I was thinking it fitted inside the SR620, but obviously not.
 
  The PRS10 can work as either a Rb GPSDO or as a time stamping
 device.  For
  the SR620 any GPSDO would make a good external reference.
  It would have been nice to have a better reference inside, as
  sometimes I move equipment around, and don't always want to take more
  than necessary, so having a better reference inside would have been a
  nice thing, but I see it is not what I thought.
 
  This unit I purchased has the option 01, the ovenized VCXO, but of
  course that is not going to have the long-term stability of a Rb
  source.
 
  I see one of the SR625 add-ons on eBay,
 
 
 http://www.ebay.com/itm/STANFORD-RESEARCH-SYSTEMS-SR625-2GHz-PRESCALER-/281486714451?pt=US_Marine_Aircraft_Radioshash=item4189ea6653
 
  but it does not look in good condition, so I'm not paying $700 for it.
 
  Dave
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Re: [time-nuts] Convert Stanford Research SR620 time-interval counter to SR625 ???

[Neil Schroeder]

I am convinced it's a grounding problem as well but I'm overly paranoid
about frying my not-cheap oscillator experimenting with it if others had
experience.

I went through a couple of them prior to getting one with a fully
functional photo acquisition system so I wasn't gonna quibble over a few
bits on a serial interface when the oscillator obviously work.

On Wednesday, December 3, 2014, yDavidkk I. Emery d...@dieconsulting.com
wrote:

 On Wed, Dec 03, 2014 at 02:53:50PM -0500, Paul wrote:
  On Wed, Dec 3, 2014 at 12:08 PM, Neil Schroeder gign...@gmail.com
 javascript:; wrote:
 
   I haven't really ever been able to talk to my
   prs10 via serial
  
 
  I took the easy way out and bought the interface board (directly from
 SRS).

 Do you have any rough number as to what they charged you for
 this ?



 --
   Dave Emery N1PRE/AE, d...@dieconsulting.com javascript:;  DIE
 Consulting, Weston, Mass 02493
 An empty zombie mind with a forlorn barely readable weatherbeaten
 'For Rent' sign still vainly flapping outside on the weed encrusted pole -
 in
 celebration of what could have been, but wasn't and is not to be now
 either.

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Re: [time-nuts] LTE Lite SkyTraq chip info

[Neil Schroeder]

Poul are you teferring  to the lte lite specifically?  My Resolution SMT GG
will go single sat or OD mode with only non GPS sats available.

On Tuesday, November 25, 2014, Poul-Henning Kamp p...@phk.freebsd.dk wrote:

 
 In message 7da89.51b7dfcf.41a65...@aol.com javascript:;, S. Jackson
 via time-nuts writes
 :

 Now that the cat is out of the bag - notice that on these boards we used
 the special -T timing version which is more than twice as expensive than
 the
 normal navigation version used by others..

 That reminds me:  I have yet to see anthing that uses Galileo or
 GNONASS in a position-hold mode, are those constellations still
 not competitive with GPS in that niche ?

 --
 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] CentOS 7, Motorola GPS receiver and NTP

[Neil Schroeder]

 Check out the synergy m12 eval board. It's about $100 with the m12m on it
and a little less if you're going to install your own.

The most recent ftdi in-tree driver will automatically support the
adapter.  Previous versions you need to echo the VPI to the sys
tree  interface of the ftdi_sio driver - which is trivial to do in
rc.local.


On Wednesday, November 26, 2014, Paul tic-...@bodosom.net wrote:

 On Wed, Nov 26, 2014 at 11:49 AM, xaos x...@darksmile.net javascript:;
 wrote:

  Question: How do I setup NTP with a 1 PPS from serial port
  and the Motorola receiver hooked up?
 

 You'll want to review the documents at ntp.org and the list 
 http://lists.ntp.org/listinfo/questions.
 The folks there will be happy to assist you.

 There are two important points:

 1) Until 4.2.8 is released you'll want to build a recent version of 4.2.7.
 Don't use 4.2.6

 2) Review the many and varied posts on the subtleties of using PPS via ATOM
 or as part of a refclock like ONCORE 
 http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver30.html.  It can
 have surprising side-effects.
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Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps

[Neil Schroeder]

My approach in progress is LVPECL driver from the master clock to a low
cost clock cleaner PLL with a low phase noise VCXO (mine are crysteks and
abracon depending on what I felt like at the moment).

Does that sort of approach match your requirement?  It isn't as low cost as
a dist amp but the results should theoretically be quite good. I'm not
instrumented to REALLY test the fine edges of performance but...



On Sunday, November 23, 2014, Bill b...@hsmicrowave.com wrote:

 Hi Bob,

 Thanks for your comments.

 The devices in my lab that can benefit from the low phase 10 MHz source
 are 1) the spectrum analyzer(s), 2) a  Comstron direct synthesizer, 3) the
 synthesized signal generators and the test source(s) used to drive
 microwave multipliers and signal sources. All these devices will see the 10
 MHz phase noise (improvements) within the narrowest PLL the devices use.

 After spending bucks for a low noise 10 MHz source, I can't afford to
 use one for each instrument. Besides it would hurt to go through the
 trouble of buying a low phase noise 10 MHz reference and lose it in a poor
 distribution amplifier(s). Also, the advantages of running all instruments
 from the same 10 MHz source are well known.

 So while I was hoping to short circuit some of the design/prototyping
 effort in the hopes someone on this thread had been there,  I'll just hit
 the books and do some prototyping and noise testing and see what I come up
 with.

 Regards...Bill

 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com javascript:;] On
 Behalf Of Bob Camp
 Sent: Sunday, November 23, 2014 7:08 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps

 Hi

 While OCXO’s that have -170 dbc/ Hz specs are fairly common, they normally
 go deep inside a box of some sort. It’s a rare off the shelf device that
 takes in the output of a distribution amp *and* requires that sort of phase
 noise.

 What’s your target device(s)?

 Why do I ask? Well, a device that has a -170 dbc floor combined with a
 -170 dbc oscillator will give you -167. A device with a -200 dbc floor will
 still “degrade” a -170 dbc oscillator. That’s a fairly big change in
 circuit complexity (and cost) for a 2.9 something db improvement. The list
 of devices that might make it worth spending (say) a few hundred dollars a
 channel versus under a buck a channel is pretty short. That may put a bound
 on this.

 One example may help: If you are running phase noise testing, forget about
 multi channel distribution amps. They will add a ground loop(s) / pickup
 loop(s) that you will be fighting forever and ever. Do that sort of stuff
 straight off the oscillator. There is no rational amount of money (ummm ….
 e … how much do you have?) you can spend to get around this. A second
 (or eighth) oscillator is cheaper than even some of the simple approaches
 that don’t work very well. The type of OCXO you are talking about is a 
 $50 item on eBay.

 Bob


  On Nov 23, 2014, at 9:17 PM, Bill b...@hsmicrowave.com javascript:;
 wrote:
 
  Thanks to all for the response but the distribution amp additive noise
 can be a real problem since the 10 MHz to be distributed is -170 dBC/Hz at
 10 KHz and needs to be preserved if at all possible.
 
  BTW, the Ettus Octobox doesn't have a spec for additive phase noise, so
 that's out.
 
  Again thanks...Bill
 
  -Original Message-
  From: time-nuts [mailto:time-nuts-boun...@febo.com javascript:;] On
 Behalf Of Bob
  Camp
  Sent: Sunday, November 23, 2014 1:09 PM
  To: Discussion of precise time and frequency measurement
  Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps
 
  Hi
 
  For any “real world” source being distributed, simple high speed CMOS
 buffers will not add enough noise to matter at 10 MHz. That of course also
 assumes that the target gear is the normal bunch of instruments that we all
 play with.
 
  Bob
 
  On Nov 23, 2014, at 11:47 AM, Bill b...@hsmicrowave.com javascript:;
 wrote:
 
  What's the latest opinion (data) on available low additive phase
  noise
  10 MHz amplifiers for 10 MHz distribution?
 
 
 
  Regards and thanks.Bill
 
 
 
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Re: [time-nuts] ocxo

[Neil Schroeder]

Did we answer the q? about schematics?

All of SRS's products have their block diagram and parts list with a
detailed circuit description in their user manual.  Sneak preview: its all
resistors.

NS

On Sun, Nov 23, 2014 at 4:22 PM, Don Latham d...@montana.com wrote:

 No question about that. The morion does run a little warmer than the old
 unit
 apparently did. Fan is temp-controlled, so I think OK. will monitor box
 temp
 with a digital :-) thermometer, very poor resolution, but probably ok.
 When I get the last obs done. will do a little blurb to the group.
 Don

 Bob Camp
  Hi
 
  That sounds fine. Without knowing just what they did or didn’t do, it’s
 always
  worth being a bit careful.
 
  Bob
 
  On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote:
 
  Running very nearly continuously for about 4 days now. The self-measured
  jitter is mean 0 and sdev of 8 ps. I don't think there is a problem
 with the
  Morion. I'm using my newly acquired cs source and a couple of z3801's
 for
  checking. 1 bit on the SR's frequency calibration dac seems to be about
 4-5
  parts in 10^-10 if I'm reading things right. Next test is a z3801
 driving
  the
  external freq port on the sr to see if the frequency change direction
 of the
  morion is OK.
  The scope display output from the SR620 is great!
  Lots to learn. Also have one of Said's units coming. Gone nuts for time,
  won't
  do anything much new, but it's new to me. All this to drive
 moonbounce...
  Don
 
 
  Bob Camp
  Hi
 
  If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be
  important at all. It’s just something to watch for. If you start seeing
  data
  in two groups, each one 20 ps wide and separated by maybe 200 ps, you
 are
  seeing a problem from the 5 MHz.
 
  Running the box for a while before doing a full detailed cal is a very
 good
  idea. It’s a bit warm inside and some of the stuff is temperature
  sensitive.
  You want it to reach equilibrium.
 
  Bob
 
  On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote:
 
  Ah. Got it finally!  Doh. Just finished trying out the Morion this
  afternoon.
  Electrically works very well. Used a 7812 to drop the +15 volts from
 the
  option 1 ocxo, there is enough power headroom to bring the Morion up
 from
  cold
  and run it comfortably. As you said, the control voltage for the
 original
  is
  indeed 5 v, and can be set by the internal d/a. The output of the
  oscillator
  passes through an emitter follower voltage adjuster and through a
 low-q
  filter
  to three stages of ECL buffer and then out to the 10 MHz system bus
 clock.
  Another path proceeds to a relay-switched divide by 2 to the phase
  detector
  so
  an external 5/10 MHz source can lock the internal oscillator.
  The external 5/10 MHz source proceeds to the phase detector thru an
  identical
  buffer chain without the switched divider.  The remainder of the clock
  circuits is a multiplier to 90 MHz.
 
  I'll run the autocal tomorrow and then get some jitter stats if
 possible.
  This
  is an early specimen, s/n about 700 or so. I can imagine seldom used,
 and
  sitting on standby for 20 years or so, pushing the ocxo out of
 tolerance.
 
  The saga continues; I may have to look for a 10 MHz replacement on
 epay,
  there
  isn't room to put in an Hp, unfortunately.
  Don
 
 
 
 
  Bob Camp
  Hi
 
  At least the Morion’s I have seen have 5 MHz crystals in them rather
 than
  10
  MHz. They have a 10 MHz output due to an internal doubler. Since the
  circuit
  is not perfect, there is cycle to cycle variation in the 10 MHz.
 It’s way
  more
  jitter (measured in picoseconds) than the oscillator has due to phase
  noise.
  My concern is that a counter might be bothered by this is some subtle
  way.
 
  Bob
 
  On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote:
 
  Hi Bob: no. cobble, not double :-)  A little research has me
 thinking I
  can
  easily adapt a morion. I can try it at least by starting with the
 morion
  on
  an
  external power supply and patching the output and control voltages
 in to
  the
  sr.
 
  The sr620 has a control circuit which apparently accomplishes your
  suggestions; they claim to use the internal oscillator for short
 term
  and
  lock it to a supplied external source for longer term. Probably
 has a
  long
  time constant on the built-in phase lock to do this.
 
  Anyhow, autocal calibrates everything except, guess what, the 10 mhz
  source.
  Thats done separately.
  So a bootup self check shows OK even if the frequency standard is
 way
  off.
 
  Onward and upward.
  Don
 
  Bob Camp
  Hi
 
  I believe that the SR620 uses a “true” 10 MHz OCXO. I would be
 careful
  using a
  5 MHz doubled to 10 OCXO. The counter may or may not be happy with
  sub-harmonic induced jitter.
 
  Best bet at the specs:
 
  +12V power
  0-5V EFC
  Sine wave out +7dbm
 
  +/- 5x10^-9 0 to 70C
 
  Pinout - trace what you have.
 
  Bob
 
  On Nov 21, 2014, at 6:59 PM, Don Latham 

Re: [time-nuts] ocxo

[Neil Schroeder]

No but a little math based on your ocxo's range can help... but measuring
it in person does give you the best numbers.

More precision and more bits WON'T hurt here and the application notes from
the leading crystal makers suggest a DAC front ended by a precision op amp
with and that the xo be followed by a buffer.  So I took the nuclear option:

http://www.analog.com/static/imported-files/circuit_notes/CN0257.pdf

My Wenzels don't have a reference out and neither do any of my VCXOs, but
my $30 Vectron from Ebay does - so my circuit for it is modified to accept
its reference voltage (its also plugged into an ADF4001 now)

NS


On Sun, Nov 23, 2014 at 4:56 PM, Bob Camp kb...@n1k.org wrote:

 Hi

 About the only other question would be the proper resolution for the DAC.
 There’s not much of a way to to answer that one without playing with a
 woking original OCXO.

 Bob

  On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote:
 
  No question about that. The morion does run a little warmer than the old
 unit
  apparently did. Fan is temp-controlled, so I think OK. will monitor box
 temp
  with a digital :-) thermometer, very poor resolution, but probably ok.
  When I get the last obs done. will do a little blurb to the group.
  Don
 
  Bob Camp
  Hi
 
  That sounds fine. Without knowing just what they did or didn’t do, it’s
 always
  worth being a bit careful.
 
  Bob
 
  On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote:
 
  Running very nearly continuously for about 4 days now. The
 self-measured
  jitter is mean 0 and sdev of 8 ps. I don't think there is a problem
 with the
  Morion. I'm using my newly acquired cs source and a couple of z3801's
 for
  checking. 1 bit on the SR's frequency calibration dac seems to be
 about 4-5
  parts in 10^-10 if I'm reading things right. Next test is a z3801
 driving
  the
  external freq port on the sr to see if the frequency change direction
 of the
  morion is OK.
  The scope display output from the SR620 is great!
  Lots to learn. Also have one of Said's units coming. Gone nuts for
 time,
  won't
  do anything much new, but it's new to me. All this to drive
 moonbounce...
  Don
 
 
  Bob Camp
  Hi
 
  If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be
  important at all. It’s just something to watch for. If you start
 seeing
  data
  in two groups, each one 20 ps wide and separated by maybe 200 ps, you
 are
  seeing a problem from the 5 MHz.
 
  Running the box for a while before doing a full detailed cal is a
 very good
  idea. It’s a bit warm inside and some of the stuff is temperature
  sensitive.
  You want it to reach equilibrium.
 
  Bob
 
  On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote:
 
  Ah. Got it finally!  Doh. Just finished trying out the Morion this
  afternoon.
  Electrically works very well. Used a 7812 to drop the +15 volts from
 the
  option 1 ocxo, there is enough power headroom to bring the Morion up
 from
  cold
  and run it comfortably. As you said, the control voltage for the
 original
  is
  indeed 5 v, and can be set by the internal d/a. The output of the
  oscillator
  passes through an emitter follower voltage adjuster and through a
 low-q
  filter
  to three stages of ECL buffer and then out to the 10 MHz system bus
 clock.
  Another path proceeds to a relay-switched divide by 2 to the phase
  detector
  so
  an external 5/10 MHz source can lock the internal oscillator.
  The external 5/10 MHz source proceeds to the phase detector thru an
  identical
  buffer chain without the switched divider.  The remainder of the
 clock
  circuits is a multiplier to 90 MHz.
 
  I'll run the autocal tomorrow and then get some jitter stats if
 possible.
  This
  is an early specimen, s/n about 700 or so. I can imagine seldom
 used, and
  sitting on standby for 20 years or so, pushing the ocxo out of
 tolerance.
 
  The saga continues; I may have to look for a 10 MHz replacement on
 epay,
  there
  isn't room to put in an Hp, unfortunately.
  Don
 
 
 
 
  Bob Camp
  Hi
 
  At least the Morion’s I have seen have 5 MHz crystals in them
 rather than
  10
  MHz. They have a 10 MHz output due to an internal doubler. Since the
  circuit
  is not perfect, there is cycle to cycle variation in the 10 MHz.
 It’s way
  more
  jitter (measured in picoseconds) than the oscillator has due to
 phase
  noise.
  My concern is that a counter might be bothered by this is some
 subtle
  way.
 
  Bob
 
  On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote:
 
  Hi Bob: no. cobble, not double :-)  A little research has me
 thinking I
  can
  easily adapt a morion. I can try it at least by starting with the
 morion
  on
  an
  external power supply and patching the output and control voltages
 in to
  the
  sr.
 
  The sr620 has a control circuit which apparently accomplishes your
  suggestions; they claim to use the internal oscillator for short
 term
  and
  lock it to a supplied external source for longer 

Re: [time-nuts] rs-422 rs-232 to fast ethernet converter

[Neil Schroeder]

If you feel like building :

http://www.ti.com/tool/tida-00226

You can integrate that further than a cots one


On Sunday, November 23, 2014, Joseph Gray jg...@zianet.com wrote:

 Didier has a good suggestion as to the serial to Wifi adapter. I may
 order one for my Z3801. Looking on Amazon, I see these two units that
 are more reasonably priced:


 http://www.amazon.com/Keynice-Ethernet-Intelligent-Communication-Wireless/dp/B00JTUVA0G/ref=pd_sim_sbs_e_1?ie=UTF8


 http://www.amazon.com/Ethernet-Serial-RS232-RS485-Converter/dp/B00ATV2DX2/ref=pd_cp_pc_1

 Joe Gray
 W5JG


 On Sun, Nov 23, 2014 at 11:59 AM, Graham planoph...@aei.ca javascript:;
 wrote:
  Thanks Didier,
 
  Good suggestions and I have been considering something similar.
 
  cheers, Graham ve3gtc
 
 
  On 2014-11-23 13:26, Didier Juges wrote:
 
  Graham,
 
  There are a number of WiFi to serial modules like the one I use on my
  Thunderbolt monitor: The Microchip WiFly RN-XV-171. Once configured
  (typically using a PC), they will present a TCPIP port (TCP or UDP) from
  which you can get and send data directly to the serial port.
 
  Alternately, you can use Digi XBee modules that work like wireless RS232
  isolators. I use the XSC Pro 900 MHz for a number of projects, including
  data loggers that are out of WiFi range. You can get well over a mile in
  open space with those. They are limited to 19200 bauds at the most.
 
  Didier KO4BB
 
  On November 22, 2014 4:47:15 PM CST, Graham planoph...@aei.ca
 javascript:; wrote:
 
  I have been contemplating how I will would like to interface to the
  KS-23461 devices using rs-422.
 
  One option is a rs-422 to USB cable. Seems easy enough.
 
  But another option I keep stumbling across is a rs-422/rs-232 to fast
  ethernet such as:
 
 
 
 http://www.transition.com/TransitionNetworks/Products2/Family.aspx?Name=SDSFE3110-120
 
  Frankly, I have no first hand knowledge or experience with these
  devices. First glance suggests that it might just be what I want - easy
 
  access to the KS-23461 ports through a connection to my local network
  without having a PC of some sort close by.
 
  So, any first hand experience with such devices? Good idea or bad?
 
  cheers, Graham ve3gtc
 
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Re: [time-nuts] Lucent KS-24361 24V DC power requirements

[Neil Schroeder]

I drive my prs10 with a parallel pair of ldos balanced by an op amp. I'll
draw it out and post it if you like.

On Friday, November 21, 2014, Azelio Boriani azelio.bori...@gmail.com
wrote:

 At most you need 2.4A (when the two OCXOs are heating up): a 2.5A
 supply is needed.

 On Fri, Nov 21, 2014 at 6:25 PM,  planoph...@aei.ca javascript:;
 wrote:
  Good day all,
 
  I have been following the discussions as best as I could. I recell seeing
  the question asked or at least theorized as to what is the power
  requirements of these units - either individually or together.
 
  I have reviewed all messages or at least all that I can find in these
  threads but I couldn't find a definitive answer unless of course the
  answer is in one of the responses hiding where I haven't looked.
 
  I purchased a set of these modules and they are currently in transit but
  I don't have a 24V DC supply at the moment.
 
  So, in order to try and get ahead before the arrival of these modules I
  would like to at least plan out if not get a suitable power supply
  ready. I don't want to over specify by too much and worse yet, under
  specify.
 
  Has anyone actually made any power used measurements of these modules? 2A
  average, 4A peak? Somewhere inbetween or more?
 
  cheers, Graham ve3gtc
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[time-nuts] ADF4001/4002 startup questions

[Neil Schroeder]

Morning nuts-

I'm aware several of you use the ADF4002 for a simple small PLL in your
radios.  Could any of you share some example bits or maybe even the code
you use during startup?   I know what my latch values should be, but I
don't seem to be getting them wrapped in the right control bits.

I am a hardware guy, this software stuff is coming to me slowly.  Thanks
for any help, feel free to reply directly.

NS
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Re: [time-nuts] ADF4001/4002 startup questions

[Neil Schroeder]

I got myself a bus pirate - thanks for bringing that forward in my brain.

I got a lot of great responses thank you everyone.

On Wednesday, November 19, 2014, Bob Camp kb...@n1k.org wrote:

 Hi

 The 4001 is pretty forgiving of order of load issues. I’ve always just
 followed the order in the AD app notes and it’s worked fine.

 I’d recommend getting any of the USB logic level scopes and tacking it
 onto what you have. The ones I have seen are plenty fast enough for this
 kind of thing. The software that comes with them lets them run as a logic
 analyzer with deep enough memory to see the whole load process. If you are
 half as prone to error as I am, it will pay for it’s self pretty fast.

 Bob

  On Nov 19, 2014, at 12:35 PM, Neil Schroeder gign...@gmail.com
 javascript:; wrote:
 
  Morning nuts-
 
  I'm aware several of you use the ADF4002 for a simple small PLL in your
  radios.  Could any of you share some example bits or maybe even the code
  you use during startup?   I know what my latch values should be, but I
  don't seem to be getting them wrapped in the right control bits.
 
  I am a hardware guy, this software stuff is coming to me slowly.  Thanks
  for any help, feel free to reply directly.
 
  NS
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Re: [time-nuts] Si570 question

[Neil Schroeder]

Jim-

Do you need to tune it?  The 571 is the VCXO - but if you're feeling
adventuresome you  could drive the 570 as an NCO (numerical) via its i2c
interface.

NS

On Tuesday, November 18, 2014, Jim Lux jim...@earthlink.net wrote:

 On 11/18/14, 11:19 AM, Orin Eman wrote:

 I have one of these: http://sdr-kits.net/PA0KLT_Description.html

 built with the CML output Si570 that goes to 1417 MHz (!)

 There is a schematic in the assembly manual that's linked to from that
 page.  They use 100n and 1n capacitors in parallel on Vdd and 4K7 pullups
 on SCL/SDA.  They have 100n DC blocks directly on the output pins.

 Into a 50 ohm load, the CML outputs produce about 4dBm as I recall.
 Obviously, the CMOS output will be different.

 There is a review of a different Si570 kit on the Clifton Labs site:

 http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm

 I got similar results comparing my kit against an HP 8640B.  The Si570
 beats the 8640B close in just as shown on the Clifton Labs site.

 Some Softrock SDR radios also use the Si570.  They use a single 10n
 capacitor on Vdd and 2K2 pullups...:

 http://www.wb5rvz.org/ensemble_rxtx/03_lo

 I have the Softrock Ensemble RXTX.  It works fine on RX, but unfortunately
 I have not been able to get satisfactory image rejection on TX.  I suspect
 the FST3253.

 So, it looks like decoupling isn't that critical - 10n or 100n||1n in
 these
 examples.  1K pullups on SDA/SCL seem to be overkill and anything
 reasonable = 4K7 should work.

 Orin.


  thanks... looks like it's time to stop analyzing and go find a piece of
 copper clad to stick this thing down on.  I see a lunchtime project coming
 up,


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Re: [time-nuts] How to clock a Beaglebone Black from an external reference

[Neil Schroeder]

Also, simon the plls can be entirely bypassed. The circuits aren't clearly
exposed but I believe you could get the peripheral clock covered and
definitely the Ethernet clock -  interesting  from a 1588 perspective.

On Friday, November 14, 2014, Simon Marsh subscripti...@burble.com wrote:

 Most processors can be clocked from a variety of sources and we know that
 with a bit of hacking it can be possible to connect them up to a
 time-nut-standard reference (either directly for simple microprocessors or
 with a synthesizer/pll).

 The Beaglebone Black is my weapon of choice when it comes to embedded
 boards and being able to lock it to an external reference should give some
 obvious benefits, such as being a great NTP server (e.g. a more modern
 equivalent of the Soekris boards) to having access to a large number of
 timers  peripherals synchronised to the reference. The BBB requires a
 24mhz clock to operate, so the end goal here will be to get it running from
 a 10mhz reference multiplied up by a PLL.

 The TL;DR summary is that despite the scary amount of tiny surface mount
 components on the board, the modifications actually turned out to be quite
 simple and, on first look, the result is great performance.

 So here's how to do it.

 Modification Details

 The BBB contains a TI Sitara AM3358 SoC and section 6.2 of the relevant
 datasheet (http://www.ti.com/lit/ds/symlink/am3358.pdf) details the
 various clocking options for the core. The key bit of information is that
 the core will automatically use an external crystal or an LVCMOS clock
 source and does not require any specific configuration to be made either
 way.

 The schematic for the BBB is readily available (
 https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SCH.pdf)
 and the upper left corner of page 3 details how the crystal on the board is
 connected.

 Together, the datasheet and schematic suggest that hooking up the BBB to
 an external LVCMOS source should be as easy as simply removing the existing
 crystal and attaching the source to OSC0_IN (pad 2 of the crystal). The
 crystal is marked as Y2, has a couple of supporting capacitors (C25  C26),
 and an associated resistor (R17).

 The crystal is nicely marked up on the board itself and is easy to spot.
 It's on the underside and attached are a couple of photos for reference.
 The photo is of a Rev C. Element 14 BBB; earlier revisions of the board
 have a different, large, black crystal but the board layout is the same.

 The main risk with removing the crystal is the proximity of all the tiny
 surface mount parts, but it turned out to be very simple with a basic hot
 air gun and some tweezers. I also removed R17 (the spec of dust sat between
 C25  C26), as the SoC datasheet stated OSC0_OUT should be left
 unconnected. The whole process was suprisingly easy, took less than a
 minute and I didn't need to resort to any magnifying aids.

 The location of C25  C26 help understand the orientation of the crystal,
 the external source needs to be attached to the pad nearest C25. This is
 the left hand pad in the photos. After the crystal has been removed, the
 remaining pads are nice and big making soldering of a coax cable
 straightforward.

 A final photo shows the crystal and R17 removed, and with coax attached.

 Test  Performance

 In order to check the change was working, I clocked the BBB using a
 MicroCrystal OCXO connected to a cheap PLL-on-a-chip. The PLL I used has
 woefully few specs with regards to jitter etc, but had the virtue of being
 to hand, operated at 3.3v and directly provided a 2.4 multiplier to get
 24mhz needed for the BBB. The BBB was connected to an adafruit GPS breakout
 and the lot was left out overnight on an open desk running NTP and using
 the gps as a PPS source.

 I'd intended to provide some nice graphs from NTP, but in practice the NTP
 jitter flatlined at 4us and the offset all night was practically flat as
 well, showing only occasional variation with maximums of +- 2us. This was
 great from a performance view, suggesting performance is better than NTP
 can report, but does make for some dull graphs.

 The frequency plot was barely more interesting but is attached; the scale
 is ppm and shows a drift of less than 0.1 ppm over 12 hours; this I think
 is consistent with the spec of the OCXO. Note the room is not air
 conditioned and my heating comes on between 6am and 7am; there is a nice
 lack of impact, as you would hope. For comparison, my RasPI NTP server
 varies about 1ppm, with offsets of +- 50us corresponding to temperature
 variations.

 Overall, this was quite a trivial test but nicely succesful.

 Internally the BBB has quite a few different clock domains so, longer
 term, it will be interesting to see if the impact of the SoC internal PLLs
 can be measured. Whilst not an issue for something as high level as NTP,
 the PLLs will determine the detail of how the reference stability transfers
 to peripherals like the BBB timers and PRU.

 

Re: [time-nuts] How to clock a Beaglebone Black from an external referenceL

[Neil Schroeder]

This is fantastic.  If anyone is interested i would be happy  to share my
design for a couple of PLL/oscillator boards in cape form factor that would
feed this perfectly.  I've been waffling on my choice of microcontroller
but in the spirit of this application I'll likely go  with an msp430.


On Friday, November 14, 2014, Simon Marsh subscripti...@burble.com wrote:

 Most processors can be clocked from a variety of sources and we know that
 with a bit of hacking it can be possible to connect them up to a
 time-nut-standard reference (either directly for simple microprocessors or
 with a synthesizer/pll).

 The Beaglebone Black is my weapon of choice when it comes to embedded
 boards and being able to lock it to an external reference should give some
 obvious benefits, such as being a great NTP server (e.g. a more modern
 equivalent of the Soekris boards) to having access to a large number of
 timers  peripherals synchronised to the reference. The BBB requires a
 24mhz clock to operate, so the end goal here will be to get it running from
 a 10mhz reference multiplied up by a PLL.

 The TL;DR summary is that despite the scary amount of tiny surface mount
 components on the board, the modifications actually turned out to be quite
 simple and, on first look, the result is great performance.

 So here's how to do it.

 Modification Details

 The BBB contains a TI Sitara AM3358 SoC and section 6.2 of the relevant
 datasheet (http://www.ti.com/lit/ds/symlink/am3358.pdf) details the
 various clocking options for the core. The key bit of information is that
 the core will automatically use an external crystal or an LVCMOS clock
 source and does not require any specific configuration to be made either
 way.

 The schematic for the BBB is readily available (
 https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SCH.pdf)
 and the upper left corner of page 3 details how the crystal on the board is
 connected.

 Together, the datasheet and schematic suggest that hooking up the BBB to
 an external LVCMOS source should be as easy as simply removing the existing
 crystal and attaching the source to OSC0_IN (pad 2 of the crystal). The
 crystal is marked as Y2, has a couple of supporting capacitors (C25  C26),
 and an associated resistor (R17).

 The crystal is nicely marked up on the board itself and is easy to spot.
 It's on the underside and attached are a couple of photos for reference.
 The photo is of a Rev C. Element 14 BBB; earlier revisions of the board
 have a different, large, black crystal but the board layout is the same.

 The main risk with removing the crystal is the proximity of all the tiny
 surface mount parts, but it turned out to be very simple with a basic hot
 air gun and some tweezers. I also removed R17 (the spec of dust sat between
 C25  C26), as the SoC datasheet stated OSC0_OUT should be left
 unconnected. The whole process was suprisingly easy, took less than a
 minute and I didn't need to resort to any magnifying aids.

 The location of C25  C26 help understand the orientation of the crystal,
 the external source needs to be attached to the pad nearest C25. This is
 the left hand pad in the photos. After the crystal has been removed, the
 remaining pads are nice and big making soldering of a coax cable
 straightforward.

 A final photo shows the crystal and R17 removed, and with coax attached.

 Test  Performance

 In order to check the change was working, I clocked the BBB using a
 MicroCrystal OCXO connected to a cheap PLL-on-a-chip. The PLL I used has
 woefully few specs with regards to jitter etc, but had the virtue of being
 to hand, operated at 3.3v and directly provided a 2.4 multiplier to get
 24mhz needed for the BBB. The BBB was connected to an adafruit GPS breakout
 and the lot was left out overnight on an open desk running NTP and using
 the gps as a PPS source.

 I'd intended to provide some nice graphs from NTP, but in practice the NTP
 jitter flatlined at 4us and the offset all night was practically flat as
 well, showing only occasional variation with maximums of +- 2us. This was
 great from a performance view, suggesting performance is better than NTP
 can report, but does make for some dull graphs.

 The frequency plot was barely more interesting but is attached; the scale
 is ppm and shows a drift of less than 0.1 ppm over 12 hours; this I think
 is consistent with the spec of the OCXO. Note the room is not air
 conditioned and my heating comes on between 6am and 7am; there is a nice
 lack of impact, as you would hope. For comparison, my RasPI NTP server
 varies about 1ppm, with offsets of +- 50us corresponding to temperature
 variations.

 Overall, this was quite a trivial test but nicely succesful.

 Internally the BBB has quite a few different clock domains so, longer
 term, it will be interesting to see if the impact of the SoC internal PLLs
 can be measured. Whilst not an issue for something as high level as NTP,
 the PLLs will determine the detail of how the 

Re: [time-nuts] SRS TSD12

[Neil Schroeder]

Be cautious on these. Take a lesson from my idiocy;

I read this email, said h atomic oscillator, and headed to eBay. Found
a listing for a reasonable price, read through too quickly, and bought
one...

...a non working one meant for parts.

They're interspersed with the working ones and look similar so be careful!



On Tuesday, November 11, 2014, Shaun Merrigan shaunmerri...@outlook.com
wrote:

 Folks,

 I have noted that a number of Stanford Research TSD12 Rubidium standards
 are available on the auction site.  I searched the TN archives and the
 interweb and came up with little useful information.
 Does anyone have any information about these units?  Is it a rebadged
 PRS-10 made for the Telecom market?

 The connector pinout is identical to the PRS10, at least.

 TIA,

 Shaun M

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Re: [time-nuts] 10 MHz OCXO recommendations

[Neil Schroeder]

Just to add a note on the original question : there are some brand new
never used Vectron 8091s available for a reasonable  price now and it's
drift and jitter  have been on par with my Wenzel.

I am not yet set up to measure it's phase noise or other general rf
characteristics but according to its cut sheet they're quite good.


On Tuesday, November 11, 2014, Mark Spencer m...@alignedsolutions.com
wrote:

 Sorry a few more points to mention.

 If for some reason I am particularly concerned about the stability of an
 OCXO reference I will compare it to another OCXO and on occasion to a GPSDO
 as well while measuring a Device Under Test.  This gives me some comfort
 that if am looking at the performance of a particular Device Under Test
 that any drift in the OCXO I am using as a reference would have been
 detected.   (It also gives me a reason to keep my stack of HP5370 and
 HP5335 counters running.) I don't expect this approach to give me absolute
 certainty of picking up drift or jumps in my reference but it does give me
 some comfort.

 While I suspect this approach would not go over very well in a commercial
 lab vs buying a high performance cesium standard or H Maser (:  for hobby
 use it seems to work for me.   Timelab is also useful for collecting
 analyzing the data from the various counters.  I also trigger all the
 counters from the same 1pps source.

 I typically compare my best OCXO's to my best GPSDO on a more or less
 continuous basis (from a time nuts perspective it's of some interest to
 look at their long term drift.)  From time to time I also cross check my
 best GPSDO against another GPSDO (:

 Regards Mark Spencer

 Sent from my iPad

 On 2014-11-11, at 4:26 PM, Charles Steinmetz csteinm...@yandex.com
 javascript:; wrote:

  Mark wrote:
 
  I find the concept of occasionally adjusting a good OCXO  which in turn
 is used as a reference works well for me.I have some that haven't
 needed adjustment for over 2 years (they are still well within one part per
 billion of being on frequency.)
 
  A few of us have advocated this approach on the list, and there is good
 reason for it.  A GPSDO offers two advantages: (1) it is self-adjusting,
 therefore easy to own and use; and (2) it has better stability at long tau
 than the OCXO alone.  The price you pay for those advantages is poorer
 stability at low tau than the OCXO alone, which can be anywhere from slight
 with a good design (e.g., Thunderbolt, Z3801) to shockingly bad with a bad
 design (including many DIY attempts).
 
  If one does not need the very best performance at long tau -- and most
 time-nuts do not -- a free-running OCXO that you adjust manually every now
 and then can be the best reference available to the average time nut.
 (Long tau can be anywhere from 100 seconds to several thousand seconds,
 depending on the particular OCXO.)  Plus, not spending money on GPS
 discipline allows you to spend more on the OCXO to get better stability at
 low tau, and a more extended upper limit on low tau (say, better than GPS
 all the way to 2000 seconds instead of 200 seconds).
 
  Personally, I do use GPS discipline to keep my best OCXO in perpetual
 adjustment, but that is mostly for convenience.  Usually, I turn
 disciplining off when I'm taking data.  Only when I'm doing something where
 the data are averaged for longer than about 3000 seconds do I leave it on
 (3000 seconds is based on the stability of my particular OCXO).
 
  Remember, GPS has a well-defined stability floor, and is not better than
 a good OCXO at averaging times (tau) less than 100 or even 1000 seconds --
 so GPS discipline cannot do anything to help the stability of a good OCXO
 at shorter tau than that.  (Yes, it may be able to help a lousy OCXO or
 TCXO at lower tau -- but you can get a better OCXO than that for $20, so
 why bother?)  There is so much focus on GPSDOs that I think many time nuts
 do not realize this fundamental fact.
 
  A few rules of thumb:
 
  --  An OCXO is the best low-tau reference most amateurs can afford
  --  GPS discipline cannot help at low tau because it is noisy
  --  Most of us do not need extreme stability at long tau
 
  And some general conclusions:
 
  --  Get the best OCXO you can find
  --  Enclose it (thermally isolated from the enclosure)
  --  Don't try to whip a so-so OCXO into shape with GPS discipline
 
  Finding a really good OCXO may take some effort.  Some models are more
 likely to be really good than others (like the BVA that Mark mentioned,
 and some others that have been vetted in large numbers), but even then
 there can be large differences from sample to sample.  So, one may need to
 sort through a number of them to find a really good one.  If one doesn't
 have access to a clearly better oscillator for comparison, using the
 three-cornered hat technique with one's best oscillators is probably the
 best method available to the amateur time nut.  Note that quartz
 oscillators tend to exhibit best stability if 

Re: [time-nuts] future NTP programs...

[Neil Schroeder]

I don't think ntp requires nor should have anything like a dedicated multi
system monitoring  platform of its own.

The fact is that today's modern data collection methods are more than
adequate - ntpd need only store its values in an accessible place and
a graphite agent or ajna or your choice of robust system data mining tools
can scrape them regularly and store them for posterity.

A server-local cli infrastructure is clearly invaluable to the
troubleshooting process.  But overall health monitoring is a wheel not in
need of an overhaul


On Monday, November 10, 2014, Magnus Danielson mag...@rubidium.dyndns.org
wrote:

 Poul-Henning,

 On 11/11/2014 01:15 AM, Poul-Henning Kamp wrote:

 
 In message 546152ac.8090...@rubidium.dyndns.org, Magnus Danielson
 writes:

  Monitoring as such is an important task, and some of the NTP clients
 might be servers in other contexts, and then it makes sense to monitor
 that they got their NTP time into shape.


 For which there has existed a system call for 20 years now:

   ntp_gettime() has as argument a struct ntptimeval * with the
 following
   members:

   struct ntptimeval {
   struct timeval time;/* current time (ro) */
   long maxerror;  /* maximum error (us) (ro) */
   long esterror;  /* estimated error (us) (ro) */
   };

   These have the following meaning:
   time   Current time (read-only).
   maxerror   Maximum error in microseconds (read-only).
   esterror   Estimated error in microseconds (read-only).


 Sure. So that's what another daemon could be pulling out.

 I'm just saying that the NTP processing and the NTP monitoring may not
 need to run by the same daemon necessarily, just because we did that in the
 past. Pulling things from the kernel provide more isolation, and the
 monitor daemon can have special code to handle security issues of
 monitoring, without making the processing dito suffer from it, beyond
 making sure the data is available somewhere.

 Cheers,
 Magnus
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Re: [time-nuts] Divide by five

[Neil Schroeder]

Go on - actually stepping or mixing then filtering the output?  Or
numerically deriving an offset?

I am well on my way to en ensemble of sources - and my plan has always been
to build a diverse set of circuits and attempt to  capture the best of
each.  I just wasn't sure the best approach.

At one point I was considering phase locking all of them together - but
again that seemed less than straightforward.  You can do it PLL back to
back, but is there a way to have a loop that contains multiple clocks?  I
would think the telephone game would apply.

NS

On Sat, Nov 8, 2014 at 6:35 PM, Bob Camp kb...@n1k.org wrote:

 Hi

 One of the more interesting uses for something like a Cyclone V would be a
 front end board to drive a KS-24361 from an ensemble of sources. That’s
 what David Allan’s original idea was when he started the whole software
 empire that turned into the Z3801 and all the rest.

 Bob

  On Nov 8, 2014, at 8:36 PM, Bert Kehren via time-nuts 
 time-nuts@febo.com wrote:
 
  We do most our projects with Altera G/A.
  The biggest benefit is that if something does not work on first pass
  changing the G/A logic is much faster, less costly than a new board
 layout.
  Bert Kehren
 
 
  In a message dated 11/8/2014 6:17:29 P.M. Eastern Standard Time,
  kb...@n1k.org writes:
 
  Hi
 
  I’ve done a lot of designs with Altera parts. They are  fine parts, but
  they are not magic. On the CPLD parts, be careful of the speed  grade
 and be
  sure you do a timing analysis on your design before you buy any
 hardware. All
  the design tools are schematic entry capable and free on the  web.
 There’s
  not a big speed bump when you start using them (like say needing  to go
  learn VHDL…).
 
  Once you get using them, the CPLD's are quite  handy for a wide range of
  projects, way beyond a simple divide by 5. Their  bigger cousins (the
 FPGA’s)
  aren’t that much more (under $35) and they will do  a LOT, especially in
 the
  newer series. The Cyclone 2’s had a minimum rated PLL  input of 20(?)
 MHz.
  The later parts bumped that down to 10 MHz. Much more  TimeNuts
 compatible.
 
  Bob
 
  On Nov 8, 2014, at 5:58 PM, cfo  xne...@luna.dyndns.dk wrote:
 
  On Sat, 08 Nov 2014  09:58:36 +0100, Francesco Messineo wrote:
 
 
  can anyone suggest a (cheap if possible) programmer and software  for
  these modern PLD?
 
  Thanks and best  regards Frank  IZ8DWF
 
  I'd suggest ALTERA parts , but  only because they are the cheapest
 boards
  on *bay , XILINX boards are  2 x the Altera price on *Bay.
 
  An EPM240 CPLD Board $9   (240 cells let you do quite a lot)
  http://tinyurl.com/qcusb69
 
  There's also an EPM-570 Board , but the price is almost the same as  the
  below FPGA , and then the FPGA is the thing to get.
 
 
  A CycloneII EP2C5T144 FPGA board (With 2 onbard PLL's) $18 -  Super
 value
  for the money
  http://tinyurl.com/pd326ct
 
  An ALTERA Programmer  $6
  http://tinyurl.com/po2qhq2
 
 
  The only caveat is that  they are NOT 5v tolerant , they can do 3v3 or
  less.
 
 
  ALTERA has the free QuartusII WEB Edition , and it works fine under
 both
  Windows  Linux (i'm using Mint17 x64 ... Ubuntu 14.04 based  under the
  hood)
 
  I am a VHDL beginner , and  completed this (free) course s few month
 back
 
  Course
  http://tinyurl.com/per8lm5
 
  Forum
  http://tinyurl.com/pw3b9bv
 
 
  I have just did a divide  by 5 with the EP2C5T144 FPGA board , using one
  of the PLL's. I did  use so few resources, that it reported 0% of the
  4608
  Cells utilized,  and 1 of 2 PLL's used.
 
  *** SNIP *
  Fitter StatusSuccessful - Sat Nov  8 23:11:59 2014
  Quartus II 64-Bit Version13.0.1 Build 232 06/12/2013 SP 1 SJ Web
  Edition
  Revision Namediv5pll
  Top-level  Entity Namediv5pll
  FamilyCyclone  II
  DeviceEP2C5T144C8
  Timing Models Final
  Total logic elements0 / 4,608 ( 0 % )
  Total combinational functions0 / 4,608 ( 0 % )
  Dedicated  logic registers0 / 4,608 ( 0 % )
  Total registers   0
  Total pins6 / 89 ( 7 % )
  Total virtual  pins0
  Total memory bits0 / 119,808 ( 0 %  )
  Embedded Multiplier 9-bit elements0 / 26 ( 0 %  )
  Total PLLs1 / 2 ( 50 % )
  *** SNIP  *
 
  Actually i like Xilinx ISE WebPack better , but  the cheap
  *Bay/Aliexpress
  boards are ALTERA Boards , so i have both  tools installed on my linux
  machine.
 
 
  If you  don't feel like learning VHDL or Verilog , you can do the layout
  in  Schematic. ALTERA QuartusII does have an extensive 74xx lib built
  in
  the schematic engine.
 
  See my ansver to assignment 10  , for a QuartusII schematic entry of a
  50M
  divider. Using use 4 x  HC390 dividers in a divide : 100 / 100 / 100 /
 50
  configuration.
  http://tinyurl.com/ntdkcst
 
 
  Be  sure to get these versions of the tools , as both have upgraded
 their
  tools , and the new tools doesn't support the older (cheaper chips).
 
  Altera QuartusII  : Version 13.0sp1  (13.1+ doesn't 

Re: [time-nuts] Divide by five

[Neil Schroeder]

I would very, very, very much enjoy perusing that library, if you'd be as
kind ;-)

Particularly just a few basics for the Xilinx. I also have a few CVHD-950s
In need of some parenting!

On Saturday, November 8, 2014, Gerhard Hoffmann dk...@arcor.de wrote:

 Am 08.11.2014 um 09:46 schrieb Said Jackson via time-nuts:

  

 The  x163 seems to be in better supply than the '161.

 For example:  http://www.nxp.com/documents/data_sheet/74LVC163.pdf 
 At 3.0 - 3.6V  150 MHz guaranteed, 200 MHz typ.

 I have done a fanout board for the Xilinx Coolrunner XC2C64 to 100 mil
 square pads.
 The small chip in the Background is the core voltage regulator, The plug
 fits to
 the Xilinx USB configuration cable. Enough to create 1pps from 100 MHz.

  https://picasaweb.google.com/lh/photo/4Bpcfouj8WH0shNGIyuVUtMTjNZETY
 myPJy0liipFm0?feat=directlink 

 The other small boards are 100 MHz Crystek CVHD-950 locked to 10 MHz using
 LVC163

 Doubler 100 MHz --- 200 MHz  13dBm in - 13 dBm out using 2*BF862
 push/push grounded gate

 Doubler 200 MHz - 400 MHz  13 dBm in 13 dBm out, HSMS-282F, SAW Filter on
 400 MHz, ERA-4 amplifier

 All are week-enders, Layout printed on Laser printer to foil,
 presensitized FR-4 0.5mm from Bungard, home etched.
 The bottom side ist ground only.
 I can use these snippets in my Altium Designer to combine them to larger
 projects; the modules keep
 their layout and need only to be handled as a block. I have collected
 quite a block library over the years. :-)

 regards, Gerhard



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Re: [time-nuts] Divide by five

[Neil Schroeder]

On the topic of SMD/SMT surfboards - has anyone seen one that has pad areas
designed for crystals or oscillators?Most of the pads are for
resistors, and that might be fine for a crystal in the strictest sense -
just the crystal no resonator - but I have 4, 6, and 8 pad guys here that
just aren't spaced right for that.

If nobody has, will break out Eagle and make an attempt to create one.

NS

On Fri, Nov 7, 2014 at 3:32 PM, Brooke Clarke bro...@pacific.net wrote:

 Hi:

 I have some info on working with SMD parts at:
 http://www.prc68.com/I/SMT.shtml
 The key thing is to get parts with a reasonable pitch, 0.1 is a standard
 DIP pitch.
 0.050 (1.27 or 1.25 mm) is half DIP and is easy to do with a fine tip
 soldering iron and small dia. solder that I normally use for other stuff.
 The use of a stereo zoom microscope or a magnifying glass/light or 3.25
 diopter reading glasses is a big help.

 On eBay there are many surface mount surfboard that allow you to mount a
 SMT and then treat it like a SIP so you can use prototyping boards.

 Another option is to make a ring counter out of transistors.
 http://www.prc68.com/I/comp.shtml#Lamp
 The beauty is that each transistor is toggling at 2/N of the clock
 frequency.

 Mail_Attachment --
 Have Fun,

 Brooke Clarke
 http://www.PRC68.com
 http://www.end2partygovernment.com/2012Issues.html
 http://www.prc68.com/I/DietNutrition.html
 Chris Albertson wrote:

 On Fri, Nov 7, 2014 at 1:12 PM, Joseph Gray jg...@zianet.com wrote:

  Can anyone recommend a chip that
 is fast enough and comes in DIP?


 Some SMDs are easy to solder by hand.  Others such as ball grid array is
 impossible.

 An easy SMD prototype board can be made by sawing the edge connectors off
 some old RAM memory or PCI boards and gluing down a parallel row of them.
 Dead bug style works well with SMD also.

 We are going to have to get used to working with these.


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Re: [time-nuts] Prototype boards. Was: Re: Divide by five

[Neil Schroeder]

Sparkfun in the United States also sells off large bags of their discards
for this very purpose - generally sorted by the type of work you wish to
practice.  http://www.sparkfun.com/.

This is where I went wrong.  I got a lot of great stuff and jumped right in
on it.  Fortunately we're not talking an AD9458 here but I did torch some
things that were inconvenient.

On a similar tack, I did just order a couple of reflow controllers for your
average toaster oven to test.  Will share the results here if desired.

NS

On Fri, Nov 7, 2014 at 7:42 PM, Chris Albertson albertson.ch...@gmail.com
wrote:

 On Fri, Nov 7, 2014 at 6:39 PM, Bob Camp kb...@n1k.org wrote:

  Hi
 
  Tools are one thing that makes it happen. Practice is another thing that
  we often forget about being in the mix. Start slow and simple.


 The best and certainly lowest cost practice can be on old, dead consumer
 electronics.  Got a dead pc mother board?  Practice removing a ew parts and
 re-soldering them.  They are easy to remove using a heat gun, the hot air
 will melt the solder and then you have hundreds of zero cost practice
 parts.

 --

 Chris Albertson
 Redondo Beach, California
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[time-nuts] Trimble EOLs SMTx and SMT GG

[Neil Schroeder]

A quick search revealed nobody has noted the Res SMTx and SMT GG have been
announced as EOL by Trimble.

The replacement parts are the anticipated Res SMT 360 and - no doubt in
response to Mr. Jackson's LTE-Lite - the ICS-SMT 360, a complete GPSDO in
an SMT format with and 10 and 40 MHz out as well as the standard PPS and
TSIP.

The Res SMT GG didn't get a very long run...

NS
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Re: [time-nuts] HP5334 parport linux tool

[Neil Schroeder]

VERY HELPFUL.  I just picked up this counter and have done a lot of time
just staring at that D shell connector with a slight tinge of despondence.

NS


On Sun, Nov 2, 2014 at 6:54 PM, Tom Wimmenhove tom.wimmenh...@gmail.com
wrote:

 I just recently got myself a HP 5334B universal counter and wanted to
 communicate with it using my PC. I don't have any GPIB hardware but I found
 GLExPIB (https://code.google.com/p/glexpib/source/checkout) that uses a
 standard parport.
 I hacked and modified the library slightly and wrote a simple interactive
 command line tool to communicate with the counter.
 It's a simple command line tool that has an interactive mode to send
 commands and receive measurements. It also includes a wiring diagram for
 the (passive) cable drawn by the author of GLExPIB.

 I thought I might share this with you guys because I'm sure there are
 people on this list that have the same counter. (It might work with general
 GPIB equipment, but I have no way to test it).

 Download link: http://www.tomwimmenhove.com/otherstuff/
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Re: [time-nuts] Really fast ADC needed

[Neil Schroeder]

Agilent and Hitite make the only monsters that I am aware of being
commercially available.

I have heard tell of implementing time interleaved ADCs and
magical wonderous but barely stable fpga ideas. Could ask around.




 hol...@hotmail.com wrote:

 A friend of mine is looking for an ADC that can do 5 bits at 20-40
 gigasamples/second...  there is a timing related component to the project.
 Any ideas of who makes a decent beastie?  It needs to supply continuous
 data so things like a fancy scope won't do...
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Re: [time-nuts] GPS for ntp

[Neil Schroeder]

Andrew-
I'm actually referring to using either the eCAP function or one of the
integrated dmtimer triggers - which are, from some accounts, more accurate
than a gpio.

Google beaglebone dmtimer pps.

NS

On Mon, Oct 20, 2014 at 11:56 PM, Andrew Rodland and...@cleverdomain.org
wrote:

 On Mon, Oct 20, 2014 at 10:50 PM, Neil Schroeder gign...@gmail.com
 wrote:
  The one thing that hasn't yet happened is making the beaglebone timestamp
  on the linux side in a way that works for ntp.
 
  Custom code no problem. Freebsd PPSAPI no problem. Linux, nothing there
  yet.
 
  I have been working on it but if anyone has some insight its appreciated.
 

 It appears to support gpio class devices, with interrupts, so the
 pps-gpio driver (in-tree since 3.2) should work just fine. The only
 thing that's needed (other than building the driver) is a bit of code
 in the board support file to register the device. Various folks have
 done it for the rpi (http://ntpi.openchaos.org/pps_pi/ for example),
 and I've done it for the UDOO Dual
 (https://gist.github.com/arodland/518f037e4f24b1984286). The BBB is
 probably about as easy.

 I'm not sure if there's other hardware that lets you do better than
 grabbing an interrupt, but that will get you in the microsecond range
 or a bit better, anyhow.
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Re: [time-nuts] GPS for ntp

[Neil Schroeder]

The one thing that hasn't yet happened is making the beaglebone timestamp
on the linux side in a way that works for ntp.

Custom code no problem. Freebsd PPSAPI no problem. Linux, nothing there
yet.

I have been working on it but if anyone has some insight its appreciated.

On Monday, October 20, 2014, Bob Camp kb...@n1k.org wrote:

 Hi

 There is a *lot* of detail on this in the archives.

 Quick rundown - the Soekris has some custom code and “stuff” that makes it
 better for NTP than any of the other boards.

 For any normal use, a couple of microseconds is likely “good enough. For
 that, many boards and GPS’s will do just fine. Yes people have gotten NTP
 running on just about every board that will run Linux.

 Bob

  On Oct 20, 2014, at 9:39 PM, Joseph Gray jg...@zianet.com
 javascript:; wrote:
 
  What does everyone think of this GPS module for ntp use? According to the
  specsheet, it uses a Ublox Neo-7N.
 
 
 http://www.ebay.com/itm/RY725AI-10Hz-UART-USB-interface-GPS-Glonass-QZSS-antenna-module-flash-memory-/181562403752
 
  I'm thinking about using it for a Beaglebone ntp server. I know there was
  some discussion about Beaglebones a while back. Has anyone gotten ntpd
 with
  PPS and time stamping running on a Beaglebone yet (like on the Soekris
  Net4501)?
 
  Does anyone want to take a wild guess as to the best/worst case UTC
 offset
  I might get with such a setup? I realize that I'd have to try it to
 really
  find out, but guesses and advice from those more knowledgeable is always
  appreciated.
 
  What I'm really after is to eventually have several Beaglebones scattered
  around the area as part of a TDOA DF network. I have spare radios to
  dedicate to the task. Each fixed node will timestamp incoming
 transmissions
  and then relay that information to a central location. The central system
  will use the data to calculate the location of the transmitter.
 
  Does anyone here have any experience with this sort of thing? Would you
  recommend a better way of accurately timing the transmissions vs using
 ntp
  on each Beaglebone?
 
  I know that TDOA is used by the cellular companies. Is anyone aware of
 some
  user level projects or source code for this? I've Googled a bit, but
  haven't turned up much. There was one thesis about an Amateur doing part
 of
  this, but he didn't have much detail on the satellite nodes and didn't
  describe anything about the centralized processing part.
 
  I have one Beaglebone White that I got cheap, so I have something to get
  started with. Later, as I figure out things, I'll buy a few Beaglebone
  Blacks.
 
  Joe Gray
  W5JG
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Re: [time-nuts] LTE-Lite module

[Neil Schroeder]

How much would we guess that Wenzel blue-top would run you?

Relative to the low cost GPSDO,  my understanding is the Wenzel parts are
priced appropriately to their quality.



On Fri, Oct 17, 2014 at 11:32 AM, S. Jackson via time-nuts 
time-nuts@febo.com wrote:


 Hello Jim,
 let me answer through Time Nuts as this may interest  other parties as
 well.
 Yes, using a fast flip flop to generate 10MHz out of  the 20MHz TCXO 3.0V
 CMOS output from the LTE-Lite module will preserve the phase  noise
 (actually
 improve it by up to 6dB due to the 20log(n/m) noise improvement)  and will
 not add any spurs if you use the clean 3.0V output from the LTE-Lite
 module
 or an external clean power supply (please note the LTE-Lite TCXO RF  output
 is 3.0V due to the internal 3.3V to 3.0V Low Noise regulator feeding the
 TCXO and buffer).
 Use fast logic such as 74AC74, 74FCT74, or the like.  We do exactly that on
 our ULN-2550 boards to generate 50MHz and 25MHz out of the  100MHz, and
 using a fast CMOS divider will result in additive phase noise  that will be
 below the crystal oscillator phase noise floor.
 That will result in significantly better phase noise and  much lower spurs
 than using the synthesized 10MHz output from the board, and one  74' chip
 can generate both 10MHz and 5MHz out of the 20MHz LTE-Lite output. This  is
 exactly what we would do here if we needed a clean 10MHz from the 20MHz
 LTE-Lite board.
 I believe you can order low-noise divide-by-2  blue-top boxes from Wenzel
 already packaged-up and connectorized as  well.
 Hope that helps,
 Said
 Hi Said
 I was one of those looking for 10Mhz but I just thought  again now that it
 might be just as well to divide the standard 20Mhz output by 2  using a FF.
 I think that would preserve all the desirable characteristics of the  20Mhz
 signal which I understand to just be square wave at CMOS 3.3v levels
 anyway. Is that correct?
 Thanks
 Jim
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Re: [time-nuts] Price of LTE Lite GPSDO vs Trimble Thunderbolt.

[Neil Schroeder]

How do you feel your module compares to that old Thunderbolt, Said?

NS

On Fri, Oct 17, 2014 at 1:13 PM, S. Jackson via time-nuts 
time-nuts@febo.com wrote:

 Pete,

 that is not inflation, that is supply and demand. The Trimble Mini-T  was
 priced at $945 on Trimble's standard price list for 1 to 9 pieces, and the
 Thunderbolt was likely twice that much when sold new, so you have to
 compare
 that to the LTE-Lite pricing.

 The Thunderbolt units offered by Tom via TAPR to Time Nuts at that  time
 were old rejects that had done their duty already, were fully paid-off  and
 would have been scrapped and recycled by the Telecom otherwise, and Tom
 invested a huge amount of his time testing them and  packaging/shipping
 them at
 no charge, so that pricing was completely  random and lucky for us to be at
 the right time at the right moment.

 In fact the complete used Thunderbolt package now lists for up to $498 on
 Ebay..

 No problem on offering these kits factory-new with warranty at what  we
 hope is a fair price,
 Bye,
 Said


 In a message dated 10/17/2014 12:49:32 Pacific Daylight Time,
 p...@petelancashire.com writes:

 First  three cheers to LTE for making these available.

 It reminds me when  Motorola made a developers kit for the then
 new 68HC11 MCU available for  $68.11.

 I know of one design win they got that more then made of their  marketing
 costs.

 Another that hit me is with inflation the LTE Lite  is not much more then
 what many of us paid for our Thunderbolts.

 For  those new to the list  ...

 https://www.febo.com/pipermail/time-nuts/2008-May/031100.html

 http://www.leapsecond.com/pages/tapr-tbolt/

 In  2008, $124, the LTE Lite in 2014 $195.

 With 'real' inflation (not the  11% you get online) the $71 difference is
 not much more.

 My two  backup Thunderbolts cost me $145 each, just before they hit $200
 then  became history.

 Again thanks to Said and JLT  

 -pete
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Re: [time-nuts] GPS jump

[Neil Schroeder]

I'm trying to determine semantics and I was likely mistaken.

They regularly update them both a variety of technologies - TWTCC and
others. Then DC of course sends to COS.

 Is it actually possible to phase lock two oscillators together cross the
distance from DC  to  Colorado Springs? (2400 kilometers or so). ?


On Friday, October 10, 2014, Brian Inglis brian.ing...@systematicsw.ab.ca
wrote:

 On Oct 9, 2014, at 7:43 PM, Jim Palfreyman jim77...@gmail.com wrote:


  We look after 5 separate hydrogen masers spread all over Australia and we
 collect tic phases between the masers and the GPS.

 On around ~Oct 7 we have noticed that the normal steady straight line
 (with
 standard daily noise) took a noticeable downward turn - on all 5 masers.


  On 2013-10-03 05:33, Jim Palfreyman wrote:


  Noticed an above average bump in our H-Maser vs GPS graphs - from sites
 all over Australia.

 Recent coronal mass ejection or US government shutdown not updating
 GPS?
 Anyone else seen it?


  drop out gap between about 04.21-04.26 UTC?
 clockstats.20131003:
 56568 15684.876 127.127.20.4 $GPRMC 042124 A ...
 56568 16004.862 127.127.20.4 $GPRMC 042644 A ...
 peerstats.20131003:
 56568 15684.876 127.127.20.4 961a -0.02270 ... 0.05344
 56568 16004.862 127.127.20.4 961a -0.13150 ... 0.15721
 loopstats.20131003:
 56568 15684.876 -0.02270 0.899 0.07071 0.70 4
 56568 16004.862 -0.13150 0.898 0.08830 0.000114 4



 Did anyone else who tracks H-masers notice this as well?

 Is it JPL making corrections?


  Le 10 oct. 2014 à 03:09, Bob Camp a écrit :


  GPS is steered by the Air Force last time I checked.
 A really good place to check is the NIST Time and Frequency pages that
 show both real time and historical data for each GPS sat compared to NIST
 time:
 http://www.nist.gov/pml/div688/grp40/gpsarchive.cfm
 Hopefully it’s accessible via that link from a variety of locations.
 Since the NIST data is independent of the steering (two different
 outfits involved) it should not be vulnerable to a “our ground segment
 broke and we steered everything to match” sort of error.


 On 2014-10-09 23:06, mike cook wrote:

I remember Jim reported a similar issue back in october last year:


 That dates are close enough to make you wonder if it is not part of
 some cycle.


 From: http://www.usno.navy.mil/USNO/time/gps/gps-info
 GPS SYSTEM TIME
 GPS system time is given by its Composite Clock (CC).
 The CC or paper clock consists of all operational Monitor Station and
 satellite
 frequency standards. GPS system time, in turn, is referenced to the Master
 Clock
 (MC) at the USNO and steered to UTC(USNO) from which system time will not
 deviate
 by more than one microsecond. The exact difference is contained in the
 navigation
 message in the form of two constants, A0 and A1, giving the time
 difference and
 rate of system time against UTC(USNO,MC).

 Page also gives links to GPS time data ftp://tycho.usno.navy.mil/pub/
 gps/utcgps30.dat
 which shows a 2ns jump in UTC(USNO)-GPS smoothed over 2 days from Oct 7-8,
 but that
 appears normal; the 1ns differences from Oct 2-7 appear anomalous.

 Looking at the NIST 10 min data, from Oct 3-8 the gap between GPS samples
 and NIST
 closed about 1.5ns/day, dropping now to about .5ns/day: the graph shows
 the values
 sliding down to the right, and now levelling off about zero.

 So are NIST and USNO steering each other?

 --
 Take care. Thanks, Brian Inglis
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Re: [time-nuts] GPS jump

[Neil Schroeder]

No. They don't directly if that's what you mean.  They do regular time
transfers, likely more regularly than most due to accessibility to a common
view and common interest.

The GPS consolation is actually a sub-(sub?)-scale of UTC(USNO_MC) called i
think USNO_OSC?  Have to check.

They have been building out the  timescale ensemble at Schriever
significantly over yhe last 5 or so years. They were up to 26 references
planned last  i spoke with anyone back home - the delta being primarily
H-masers.

I think that's a good move. Despite Timefreq being just  about  2 hours
away, that master clock's survivability  was never certain.  Shipping the
timescale to Colorado Springs from Wisconsin Ave/Bethesda did contain risk,
and they are mitigating it.

I was once told - total anecdote and certainly 15 years ago - that despite
proximity and willingness they rarely exchange views or collaborate
experimentally between Colorado Springs and Boulder. Silly in  my mind but
it is an a active weapons platform and the logistics may not be conducive.

NS



On Friday, October 10, 2014, Brian Inglis brian.ing...@systematicsw.ab.ca
wrote:

 On Oct 9, 2014, at 7:43 PM, Jim Palfreyman jim77...@gmail.com wrote:


  We look after 5 separate hydrogen masers spread all over Australia and we
 collect tic phases between the masers and the GPS.

 On around ~Oct 7 we have noticed that the normal steady straight line
 (with
 standard daily noise) took a noticeable downward turn - on all 5 masers.


  On 2013-10-03 05:33, Jim Palfreyman wrote:


  Noticed an above average bump in our H-Maser vs GPS graphs - from sites
 all over Australia.

 Recent coronal mass ejection or US government shutdown not updating
 GPS?
 Anyone else seen it?


  drop out gap between about 04.21-04.26 UTC?
 clockstats.20131003:
 56568 15684.876 127.127.20.4 $GPRMC 042124 A ...
 56568 16004.862 127.127.20.4 $GPRMC 042644 A ...
 peerstats.20131003:
 56568 15684.876 127.127.20.4 961a -0.02270 ... 0.05344
 56568 16004.862 127.127.20.4 961a -0.13150 ... 0.15721
 loopstats.20131003:
 56568 15684.876 -0.02270 0.899 0.07071 0.70 4
 56568 16004.862 -0.13150 0.898 0.08830 0.000114 4



 Did anyone else who tracks H-masers notice this as well?

 Is it JPL making corrections?


  Le 10 oct. 2014 à 03:09, Bob Camp a écrit :


  GPS is steered by the Air Force last time I checked.
 A really good place to check is the NIST Time and Frequency pages that
 show both real time and historical data for each GPS sat compared to NIST
 time:
 http://www.nist.gov/pml/div688/grp40/gpsarchive.cfm
 Hopefully it’s accessible via that link from a variety of locations.
 Since the NIST data is independent of the steering (two different
 outfits involved) it should not be vulnerable to a “our ground segment
 broke and we steered everything to match” sort of error.


 On 2014-10-09 23:06, mike cook wrote:

I remember Jim reported a similar issue back in october last year:


 That dates are close enough to make you wonder if it is not part of
 some cycle.


 From: http://www.usno.navy.mil/USNO/time/gps/gps-info
 GPS SYSTEM TIME
 GPS system time is given by its Composite Clock (CC).
 The CC or paper clock consists of all operational Monitor Station and
 satellite
 frequency standards. GPS system time, in turn, is referenced to the Master
 Clock
 (MC) at the USNO and steered to UTC(USNO) from which system time will not
 deviate
 by more than one microsecond. The exact difference is contained in the
 navigation
 message in the form of two constants, A0 and A1, giving the time
 difference and
 rate of system time against UTC(USNO,MC).

 Page also gives links to GPS time data ftp://tycho.usno.navy.mil/pub/
 gps/utcgps30.dat
 which shows a 2ns jump in UTC(USNO)-GPS smoothed over 2 days from Oct 7-8,
 but that
 appears normal; the 1ns differences from Oct 2-7 appear anomalous.

 Looking at the NIST 10 min data, from Oct 3-8 the gap between GPS samples
 and NIST
 closed about 1.5ns/day, dropping now to about .5ns/day: the graph shows
 the values
 sliding down to the right, and now levelling off about zero.

 So are NIST and USNO steering each other?

 --
 Take care. Thanks, Brian Inglis
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Re: [time-nuts] First few measurements of my Arduino Due GPSDO

[Neil Schroeder]

Are all the devices you're using or considering capable of hardware
timestamps?  Or are you doing it in software today?



On Wednesday, September 24, 2014, Andrew Rodland and...@cleverdomain.org
wrote:

 Yes indeed, that board is dead. Luckily, though, I had a substitute
 (see some conversation around Sep 10 on the other thread about
 adapting a UDOO to do the job -- it's a board that has both the Due's
 SAM3X and an i.MX chip running Linux, with serial and GPIO shared
 between them) and I've made some slower progress using that, mostly
 tweaking the control loop for smoother response, and improving the
 health-monitoring / holdover logic.

 More excitingly, a board that I ordered from China even before killing
 the EtherDue arrived yesterday. It's a Due clone called Taijiuino
 that brings out the SAM3X's own Ethernet MAC pins, instead of using an
 offboard Ethernet controller like the EtherDue does. I'm optimistic
 that this will give me much finer control over packet timestamping and
 lower the ethernet-induced NTP jitter by an order of magnitude or so,
 which would really give me something to show for this project. The
 only downside is I have to write the Ethernet driver first! Definitely
 hoping to have something to report there.

 On Sun, Sep 14, 2014 at 5:35 PM, Shane Morris edgecombe...@gmail.com
 javascript:; wrote:
  I'll be looking for that blog post. By the way, how did the burnt out
  EtherDue go? I remember saying after you had taken your last set of
  pictures that you'd popped it...!
 
 
  On Mon, Sep 15, 2014 at 6:48 AM, Andrew Rodland and...@cleverdomain.org
 javascript:;
  wrote:
 
  Neil,
 
  I'm working on a blog post now, I'm hoping to have it complete by
  Monday or Tuesday. I'll send a followup here when it's posted.
 
  On Sun, Sep 14, 2014 at 11:47 AM, Neil Schroeder gign...@gmail.com
 javascript:;
  wrote:
   I have nothing constructive to add at this time but I would truly
 enjoy
   reviewing your design and build logs/notes.
  
  
  
   On Sunday, September 14, 2014, Andrew Rodland 
 and...@cleverdomain.org javascript:;
   wrote:
  
   Hi all,
  
   I've got some figures in from my clock, and I figured I would post
   them here in hopes of getting some eyes on them and some help with
   interpretation.
  
   Reference is a Spectracom NetClock 9183 with OCXO option. Frequency
 is
   good to better than 10^-9, PPS is specified as +/- 50ns.
  
   Instrument is an HP 5335A (in lovely condition given that it was
 built
   in 1985 according to the serial number) in time difference mode.
  
   My clock is quantized at 10MHz, so you wouldn't expect better than
   100ns accuracy. But I added -50ns to the offset in software, making
 it
   zero in on the edge where the offset is 0 counts 50% of the time and
   -1 count the other 50%. (Dithering provided by noise in the system
 and
   the Resolution-T's own sawtooth). This seems to have worked better
   than expected.
  
   (On a side note: this means that the gain of my control loop is
   obviously pretty non-linear inside of 1us. Anything I should read
   about that?)
  
   So far I've done two 24-hour runs, one with PLL and FLL constants at
   3600s, and one with them at 7200s.
  
   Phase plot:
   3600s: http://i.imgur.com/LLfYgXe.png
   7200s: http://i.imgur.com/zUbgNHc.png
  
   Both keep within +/-20ns the majority of the time, which is better
   than I expected given the specs of both clocks. 1us offset is
   deliberately added at the PPS output of my clock to make the 5335A
   happy.
  
   Frequency plot:
   3600s: http://i.imgur.com/7GoXdoF.png and
  http://i.imgur.com/rjBa7gf.png
   7200s: http://i.imgur.com/KcyGT3r.png and
  http://i.imgur.com/GZH4Pcl.png
  
   Both have similar envelopes that seem to reflect the quantization
 more
   than anything (100s averaging shrinks the envelopes by very close to
 a
   factor of 100x). 7200s looks like it has some kind of oscillation
 with
   2000s period, which is worth looking into.
  
   MDEV:
   3600s: http://i.imgur.com/RmAcAwT.png
   7200s: http://i.imgur.com/xO7aYf9.png
  
   ADEV was a perfectly straight line so I didn't bother. MDEV displays
 a
   little more structure, but I'm not really clear on the
 interpretation.
  
   TDEV both: http://i.imgur.com/YamRIui.png
  
   I like TDEV. Same information as MDEV but since it turns slope=-1 to
   slope=0  it makes this kind of graph more readable. The two plots are
   within each other's error bars, so any difference between them might
   be imaginary, but they depart at 1000s, which probably corresponds to
   the 2000s oscillation.
  
   I guess I'm seeking general input on where I should go next -- do the
   graphs tell me anything interesting? Should I keep working on the
   control loop even though it already manages to keep things within
 half
   a clock tick? Or should I start looking for ways to reduce the
   Ethernet jitter since that's the dominant source of error in the use
   that I care about?
  
   Andrew

Re: [time-nuts] First few measurements of my Arduino Due GPSDO

[Neil Schroeder]

I have nothing constructive to add at this time but I would truly enjoy
reviewing your design and build logs/notes.



On Sunday, September 14, 2014, Andrew Rodland and...@cleverdomain.org
wrote:

 Hi all,

 I've got some figures in from my clock, and I figured I would post
 them here in hopes of getting some eyes on them and some help with
 interpretation.

 Reference is a Spectracom NetClock 9183 with OCXO option. Frequency is
 good to better than 10^-9, PPS is specified as +/- 50ns.

 Instrument is an HP 5335A (in lovely condition given that it was built
 in 1985 according to the serial number) in time difference mode.

 My clock is quantized at 10MHz, so you wouldn't expect better than
 100ns accuracy. But I added -50ns to the offset in software, making it
 zero in on the edge where the offset is 0 counts 50% of the time and
 -1 count the other 50%. (Dithering provided by noise in the system and
 the Resolution-T's own sawtooth). This seems to have worked better
 than expected.

 (On a side note: this means that the gain of my control loop is
 obviously pretty non-linear inside of 1us. Anything I should read
 about that?)

 So far I've done two 24-hour runs, one with PLL and FLL constants at
 3600s, and one with them at 7200s.

 Phase plot:
 3600s: http://i.imgur.com/LLfYgXe.png
 7200s: http://i.imgur.com/zUbgNHc.png

 Both keep within +/-20ns the majority of the time, which is better
 than I expected given the specs of both clocks. 1us offset is
 deliberately added at the PPS output of my clock to make the 5335A
 happy.

 Frequency plot:
 3600s: http://i.imgur.com/7GoXdoF.png and http://i.imgur.com/rjBa7gf.png
 7200s: http://i.imgur.com/KcyGT3r.png and http://i.imgur.com/GZH4Pcl.png

 Both have similar envelopes that seem to reflect the quantization more
 than anything (100s averaging shrinks the envelopes by very close to a
 factor of 100x). 7200s looks like it has some kind of oscillation with
 2000s period, which is worth looking into.

 MDEV:
 3600s: http://i.imgur.com/RmAcAwT.png
 7200s: http://i.imgur.com/xO7aYf9.png

 ADEV was a perfectly straight line so I didn't bother. MDEV displays a
 little more structure, but I'm not really clear on the interpretation.

 TDEV both: http://i.imgur.com/YamRIui.png

 I like TDEV. Same information as MDEV but since it turns slope=-1 to
 slope=0  it makes this kind of graph more readable. The two plots are
 within each other's error bars, so any difference between them might
 be imaginary, but they depart at 1000s, which probably corresponds to
 the 2000s oscillation.

 I guess I'm seeking general input on where I should go next -- do the
 graphs tell me anything interesting? Should I keep working on the
 control loop even though it already manages to keep things within half
 a clock tick? Or should I start looking for ways to reduce the
 Ethernet jitter since that's the dominant source of error in the use
 that I care about?

 Andrew
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