[time-nuts] I am a nut

[Joseph Gray]

I just got an HP 8920B service monitor to replace what I had before.
It has the High Stability oscillator option. After running the self
tests, I was doing a quick check of the internal reference. With my
frequency counter locked to a GPSDO, I see that the 8920B reference is
0.2 Hz high. OMG! I'd adjust it, but this thing came calibrated and I
don't want to mess with it quite yet.

Just thought I'd share my obsession :-)

Joe Gray
W5JG
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Re: [time-nuts] HP 10544A Repair

[Richard (Rick) Karlquist]

On 3/1/2016 4:13 AM, Bob Camp wrote:


Is it worth getting it super close? Probably not without a temperature test 
setup.

Bob


Right.

It is entirely possible that if you did a temperature test
in an environmental chamber, you would find that you
could get a better tempco by adjusting oven set point
to have a slight offset from the turnover.  In this regime,
the crystal drift would cancel out the tempco of the
electronics.  This all depends on the crystal tempco,
the electronics tempco, and the respective thermal gains
to the crystal and the electronics.  But there will be
an adjustment giving zero tempco (at least around a single
ambient temperature).  My old boss at Agilent used to
call this sort of thing a "hero experiment", which he
used as a pejorative term.

Rick
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Re: [time-nuts] Inside a CTS 1960017 OCXO

[Gregory Muir]

Bob,

I was referring to the bulk of the conversations on this device where people 
were finding 60 Hz related artifacts.

Greg

>On Date: Mon, 29 Feb 2016 21:11:19 -0500
>From: Bob Camp wrote:
>
>Hi
>
>On some parts the spur shows up in the 40 to 80 Hz range. 
>That pretty much rules out the line frequency.
>
>Bob

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Re: [time-nuts] Inside a CTS 1960017 OCXO

[Bob Camp]

Hi

The spectrum plots and scope plots do not look like a blocking oscillator. They 
look very much 
like an internal spur generated by something in the circuit taking off at low 
frequency. 

Bob


> On Mar 1, 2016, at 10:09 AM, Alex Pummer  wrote:
> 
> sometimes high frequency oscillators could get in certain mode of operation 
> the "blocking oscillation" see here: 
> https://en.wikipedia.org/wiki/Blocking_oscillator, also it could happen, that 
> the high frequency oscillation does not stops entirely, just undergoes an 
> amplitude fluctuation, that could cause side bands on both side of the 
> carrier. Blocking oscillation could happen because of to strong positive 
> feedback -- due to design error or component error. The dumping of that 
> product on e-Bay also could be a sign of a to late recognized error
> 73
> KJ6UHN
> 
> On 2/29/2016 2:04 PM, Gregory Muir wrote:
>> Not sure if I am missing something here or not but an early mention was made 
>> regarding synching the test equipment used to the 60 Hz line to see if the 
>> purported 60 Hz anomaly is actually synchronous or asynchronous.  I haven't 
>> heard anything regarding this since then.
>> 
>> Greg
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Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

[Neil Green]

On 29 Feb 2016, at 10:46 am, Hal Murray  wrote:

> What distro are you starting with?
> 
> I'm using Debian.  Their kernel includes PPS support, both Wheezy and Jessie.

I’m using Raspbian Jessie. PPS over GPIO is now recognised in the stock kernel 
but kernel PPS isn’t. I compile a kernel that disable dynamic ticks and enables 
KPPS.

>> I had a DS3231 lying around so, ...
> 
> Are you setup to make long term measurements?  It will be interesting to see 
> how it drifts.

Measurements will be purely anecdotal, and I most likely won’t start observing 
until I’m happy that I’ve optimised the circuit. This is probably frustrating 
to an experienced time nut, but I lack any sophisticated measuring equipment 
beyond NTP’s loopstats/peerstats/clockstats files.
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Re: [time-nuts] GPS Outage

[Magnus Danielson]

Hi Jim,

On 03/01/2016 03:24 PM, jimlux wrote:

On 2/29/16 10:56 PM, Magnus Danielson wrote:



On 02/29/2016 11:31 AM, Martin Burnicki wrote:

Hal,

Hal Murray wrote:


martin.burni...@burnicki.net said:

Strange that at least 3 independant firmware trees/development
teams should
chose the same magic wk860.



I don't find it strange. If the next firmware version is based on the
previous version and none of the developers has stumbled across this
potential problem earlier ...


That sounds like poor software engineering.  Or poor engineering
management.

The wk860 is supposed to represent the build time of the software ...


Do you *know* this, or are you just *assuming* this? ;-)


so it will
work for 20 years from when it was built rather than 20 years from
when the
10 bit week counter last rolled over or 20 years from when the
constant was
last updated.


There are also approaches where the proper extension of a week number
doesn't just work within a single 1024 week cycle with some hardcoded
limit, like this simple example:

if ( wn < 860 )
   wn += 1024;

There may always be pieces of code which generate a faulty result under
certain conditions, and no stumbles across this even in reviews until it
really happens.

I'm not aware of *any* project where each single line of code is checked
once again whenever a new release is rolled out.


Rather, in all projects I've seen there is a tendency to trust existing
code and only extend it. Re-validating it is usually regarded as money
in the sea. That old code can have incorrect assumptions that you
eventually expose as you change its environment is a re-occurring
learning experience.



Ariane 5...


Indeed. Most of the cases the failure isn't as spectacular.

Cheers,
Magnus
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Re: [time-nuts] GPS Outage

[jimlux]

On 2/29/16 10:56 PM, Magnus Danielson wrote:



On 02/29/2016 11:31 AM, Martin Burnicki wrote:

Hal,

Hal Murray wrote:


martin.burni...@burnicki.net said:

Strange that at least 3 independant firmware trees/development
teams should
chose the same magic wk860.



I don't find it strange. If the next firmware version is based on the
previous version and none of the developers has stumbled across this
potential problem earlier ...


That sounds like poor software engineering.  Or poor engineering
management.

The wk860 is supposed to represent the build time of the software ...


Do you *know* this, or are you just *assuming* this? ;-)


so it will
work for 20 years from when it was built rather than 20 years from
when the
10 bit week counter last rolled over or 20 years from when the
constant was
last updated.


There are also approaches where the proper extension of a week number
doesn't just work within a single 1024 week cycle with some hardcoded
limit, like this simple example:

if ( wn < 860 )
   wn += 1024;

There may always be pieces of code which generate a faulty result under
certain conditions, and no stumbles across this even in reviews until it
really happens.

I'm not aware of *any* project where each single line of code is checked
once again whenever a new release is rolled out.


Rather, in all projects I've seen there is a tendency to trust existing
code and only extend it. Re-validating it is usually regarded as money
in the sea. That old code can have incorrect assumptions that you
eventually expose as you change its environment is a re-occurring
learning experience.



Ariane 5...




 Modern approaches to testing helps, and working on

the backlog of testing can help to disclose such problems, but only if
the test-code writer has the mindset that covers the problem at hand.
It's easy to make bold statements, reality is much more humbling
experience in the long run. Good test-benches will aid you as you want
to make larger clean-ups of old code. Larger clean-ups helps to expose
old bugs as you actually look at the code as a designer again. It is
also humbling to see what errors a younger yourself did and how you now
don't do such design anymore as you have been bitten badly by the bug.





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Re: [time-nuts] Effect of the Antenna Delay in setting in Z380!A

[Tom Holmes]

Hi Dave...

Group delay really applies to any device, and mathematically is the rate of 
change of phase vs. frequency. It is usually of interest for bandpass devices, 
but no reason it can't be used for a piece of coax. The word 'group' comes from 
the idea of being interested in the delay over a range, or group, of 
frequencies, with no large gaps being implied.

For a bandpass device, the requirement is often that the delay be constant over 
the bandpass range, especially for digital signals. 

If you have an instrument that can measure time intervals, such as the HP 5335 
counter, you can measure your cable delay to close enough accuracy, per Bob 
Camp's explanation of close enough.

Tom Holmes, N8ZM

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Artek Manuals
Sent: Tuesday, March 01, 2016 4:50 AM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] Effect of the Antenna Delay in setting in Z380!A

On 2/29/2016 11:36 PM, Andy wrote:
> Dave wrote:
>
> For those of who might care I would assume that actually taking the coax
>> and measuring the delay at 1.5GHZ would be better than relying on the
>> manufactures published specs for velocity factor.  I was going to set up
>> and measure the delay with a signal generator and  good oscilloscope (I
>> have a 7104 1GHZ scope which still shows decent signal at 1.5 GHZ)
>>
>
> Technically I think what you would want to measure is the group delay, not
> the phase delay.
>
> Andy
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>

If by group delay you mean the additional delays inside the Z3801A I 
would think HP/Semetricom would have taken that into account in the 
firmware and that only delay external to the Z3801A is "compensated" for ...

Dave
NR1DX

-- 
Dave
manu...@artekmanuals.com
www.ArtekManuals.com

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Re: [time-nuts] Inside a CTS 1960017 OCXO

[Alex Pummer]

sometimes high frequency oscillators could get in certain mode of 
operation the "blocking oscillation" see here: 
https://en.wikipedia.org/wiki/Blocking_oscillator, also it could happen, 
that the high frequency oscillation does not stops entirely, just 
undergoes an amplitude fluctuation, that could cause side bands on both 
side of the carrier. Blocking oscillation could happen because of to 
strong positive feedback -- due to design error or component error. The 
dumping of that product on e-Bay also could be a sign of a to late 
recognized error

73
KJ6UHN

On 2/29/2016 2:04 PM, Gregory Muir wrote:

Not sure if I am missing something here or not but an early mention was made 
regarding synching the test equipment used to the 60 Hz line to see if the 
purported 60 Hz anomaly is actually synchronous or asynchronous.  I haven't 
heard anything regarding this since then.

Greg
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Re: [time-nuts] WWVB format change in 2012

[paul swed]

As Tom mentioned I am familiar with the chips. But the bottom line is there
are no chips either old style or new around anymore from what I have seen.
If you can find the consumer atomic clocks that are pretty rare these days
you can get the AM clock receiver from those. The new chips (Literally the
die, not even an soic) was supposed to show up in clocks around the new
year. They never did or at least its totally not apparent. The intent was
not for consumer but embedded in things like stop lights.
But this thread shifted from the original request I believe for something
that could be used in Singapore.
Regards
Paul
WB8TSL

On Tue, Mar 1, 2016 at 7:39 AM, Bob Camp  wrote:

> Hi
>
> > On Mar 1, 2016, at 2:44 AM, Sanjeev Gupta  wrote:
> >
> > On Sun, Feb 28, 2016 at 3:09 PM, Sanjeev Gupta  wrote:
> >
> >> Are there commercially (or widely-used) receivers for professional use
> >> which listen to the WWVB signal?
> >
> >
> > Folks, I am trying to trace down xtendwave.  They seem to have released a
> > Everset IC, and then renamed themselves to Everset in 2013 or 2014.
> >
> > Is there *any* commercial gear available for WWVB at all, today?  Price
> is
> > not an issue, just a public product page will do.
>
> GPS has become so cheap and it’s so accurate under normal conditions that
> you rarely see anything else considered for this stuff. That’s not to say
> that a
> monoculture is a good idea (it isn’t).
>
> Bob
>
>
> >
> >
> > --
> > Sanjeev Gupta
> > +65 98551208 http://www.linkedin.com/in/ghane
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Re: [time-nuts] WWVB format change in 2012

[Bob Camp]

Hi

> On Mar 1, 2016, at 2:44 AM, Sanjeev Gupta  wrote:
> 
> On Sun, Feb 28, 2016 at 3:09 PM, Sanjeev Gupta  wrote:
> 
>> Are there commercially (or widely-used) receivers for professional use
>> which listen to the WWVB signal?
> 
> 
> Folks, I am trying to trace down xtendwave.  They seem to have released a
> Everset IC, and then renamed themselves to Everset in 2013 or 2014.
> 
> Is there *any* commercial gear available for WWVB at all, today?  Price is
> not an issue, just a public product page will do.

GPS has become so cheap and it’s so accurate under normal conditions that
you rarely see anything else considered for this stuff. That’s not to say that a
monoculture is a good idea (it isn’t). 

Bob


> 
> 
> -- 
> Sanjeev Gupta
> +65 98551208 http://www.linkedin.com/in/ghane
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

Hi

As you do the tweaks, the frequency changes should go from parts in 10^8 to 
10^9 to 10^10
per turn. A lot depends on the pot setup and the crystal in terms of how high 
it starts. The flip
side to that is your counter and local reference standard need to be able to 
measure at least 
parts in 10^10 to get it set.

Is it worth getting it super close? Probably not without a temperature test 
setup.

Bob

> On Feb 29, 2016, at 11:14 PM, Nigel Vander Houwen 
>  wrote:
> 
> Howdy All,
> 
> This thread has split into a couple, but I’ll try to respond here to the 
> various things.
> 
> Based on how this crystal warms up, it does appear that it is a BT type 
> crystal, as it warms up frequency goes up, and as it gets hotter eventually 
> turns around and heads downhill again.
> 
> I’ve managed to tune the oven to where the peak seems to be. It’s a many turn 
> potentiometer (something like 21 turns), that plays a small portion on the 
> resistance, so +/- about a quarter turn at the peak didn’t seem to really 
> impact the frequency. I left it in the middle of that range.
> 
> My replacement thermistor has a lower beta than what it seems the original 
> had. The original thermistor being specified at 9.93K @ 80C, and the 
> calculator shows mine at about 12K @ 80C. Since the circuit for this crystal 
> has a 10K + 9K & the 2K POT on one side of an op-amp comparator, and a 10K + 
> the thermistor on the other side, I added a 2.2K resistor to the POT leg of 
> that voltage divider to bring the tuning range about to where it was stock, 
> as I found that unaltered, with the new thermistor I couldn’t set the oven 
> temperature low enough, every frequency was on the downhill slope past the 
> peak.
> 
> I appreciate Frank’s offer for a close to original thermistor, however I’m 
> not in the netherlands (despite my name), and I’ve already got a reasonably 
> close replacement epoxied into the oven like the original was.
> 
> Now I’ll leave it run for a while and see about tuning the frequency. I’ve 
> got it pretty close at the moment, but the coming days/weeks will show their 
> own colors.
> 
> I would like to thank everyone for the insight around getting this thing 
> tuned up. It’s sincerely appreciated.
> 
> I’ll probably start designing a DAC + Phase comparator board to GPS 
> discipline this old crystal. Have to see how that ends up comparing to my 
> thunderbolt.
> 
> Nigel
> 
>> On Feb 28, 2016, at 15:03, Bob Camp  wrote:
>> 
>> Hi
>> 
>> Ok a bit more of the story. 
>> 
>> It’s easy to simply turn on the device and see how it warms up. Back when it 
>> was made, the 
>> SC did not yet exist. The only thing it could be was a BT. With an X-ray 
>> setup you can absolutely 
>> tell it’s a BT. With the blank and a pair of calipers you can make a darn 
>> good guess it’s a BT. 
>> 
>> Since HP did not make their own blanks, the “competition” was the source of 
>> their blanks. No need
>> for those guys to guess about anything. 
>> 
>> Despite all of this logical and rational thinking, the BT remained a “top 
>> secret” sort of thing as far
>> as (at least certain people at) HP were concerned. Those who were concerned 
>> also had the route
>> to the HP PR machine so that’s the story that went out to the world. 
>> 
>> Those involved left HP long ago. The whole thing became a non-issue once the 
>> 10811 came out. 
>> What is the most amazing thing to me is that 30 years after it became a 
>> non-issue there still is 
>> confusion about the topic. 
>> 
>> Bob
>> 
>>> On Feb 28, 2016, at 11:48 AM, jimlux  wrote:
>>> 
>>> On 2/28/16 6:23 AM, Bob Camp wrote:
 Hi
 
 The whole “BT Cut” issue was a big top secret in HP. They spent a lot of 
 time obscuring
 the fact that they used BT’s. The belief was that if any of the other 
 outfits figured out that
 was what they were doing, the competition would have better OCXO’s.
 
>>> 
>>> 
>>> Can you tell what the cut is if you have the blank in front of you?
>>> 
>>> Wouldn't the competition just buy an instrument with the oscillator, saw it 
>>> open, and measure it?
>>> 
>>> 
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Re: [time-nuts] GPS Outage

[Bob Camp]

Hi

Take a look at math libraries and things like printf libraries. Each time 
somebody
writes one, there are a group of bugs that come up again and again. Yes, you 
would *think* each group would come up with creative *new* errors … not so 
much. 
There are always obvious assumptions that turn out to be wrong in corner cases.

Bob


> On Mar 1, 2016, at 1:56 AM, Magnus Danielson  
> wrote:
> 
> 
> 
> On 02/29/2016 11:31 AM, Martin Burnicki wrote:
>> Hal,
>> 
>> Hal Murray wrote:
>>> 
>>> martin.burni...@burnicki.net said:
> Strange that at least 3 independant firmware trees/development teams 
> should
> chose the same magic wk860.
>>> 
 I don't find it strange. If the next firmware version is based on the
 previous version and none of the developers has stumbled across this
 potential problem earlier ...
>>> 
>>> That sounds like poor software engineering.  Or poor engineering management.
>>> 
>>> The wk860 is supposed to represent the build time of the software ...
>> 
>> Do you *know* this, or are you just *assuming* this? ;-)
>> 
>>> so it will
>>> work for 20 years from when it was built rather than 20 years from when the
>>> 10 bit week counter last rolled over or 20 years from when the constant was
>>> last updated.
>> 
>> There are also approaches where the proper extension of a week number
>> doesn't just work within a single 1024 week cycle with some hardcoded
>> limit, like this simple example:
>> 
>> if ( wn < 860 )
>>   wn += 1024;
>> 
>> There may always be pieces of code which generate a faulty result under
>> certain conditions, and no stumbles across this even in reviews until it
>> really happens.
>> 
>> I'm not aware of *any* project where each single line of code is checked
>> once again whenever a new release is rolled out.
> 
> Rather, in all projects I've seen there is a tendency to trust existing code 
> and only extend it. Re-validating it is usually regarded as money in the sea. 
> That old code can have incorrect assumptions that you eventually expose as 
> you change its environment is a re-occurring learning experience. Modern 
> approaches to testing helps, and working on the backlog of testing can help 
> to disclose such problems, but only if the test-code writer has the mindset 
> that covers the problem at hand. It's easy to make bold statements, reality 
> is much more humbling experience in the long run. Good test-benches will aid 
> you as you want to make larger clean-ups of old code. Larger clean-ups helps 
> to expose old bugs as you actually look at the code as a designer again. It 
> is also humbling to see what errors a younger yourself did and how you now 
> don't do such design anymore as you have been bitten badly by the bug.
> 
> Cheers,
> Magnus
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Re: [time-nuts] WWVB format change in 2012

[Hal Murray]

gha...@gmail.com said:
> Is there *any* commercial gear available for WWVB at all, today?  Price is
> not an issue, just a public product page will do. 

I don't know of any gear that is currently available in the US.

A few years ago, you used to be able to get a small board and ferrite 
antenna.  I think it was under $20.  I just poked around and they are no 
longer available.
  https://www.sparkfun.com/products/retired/10060
They have a link to the data sheet if you are curious.  It's an old chip that 
only decodes the AM part of the signal so it doesn't get the advantages of 
the new modulation.

This might be a lead if you are in the UK:
  http://www.tuxcat.com/benjy/ham/WWVB/

If you are desperate, consider buying a battery powered clock and taking it 
apart to find the antenna and WWVB chip.  The chip will probably be under a 
blob of epoxy.  You will have to hack the board.  ...

-- 
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Re: [time-nuts] Effect of the Antenna Delay in setting in Z380!A

[Artek Manuals]

On 2/29/2016 11:36 PM, Andy wrote:

Dave wrote:

For those of who might care I would assume that actually taking the coax

and measuring the delay at 1.5GHZ would be better than relying on the
manufactures published specs for velocity factor.  I was going to set up
and measure the delay with a signal generator and  good oscilloscope (I
have a 7104 1GHZ scope which still shows decent signal at 1.5 GHZ)



Technically I think what you would want to measure is the group delay, not
the phase delay.

Andy
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If by group delay you mean the additional delays inside the Z3801A I 
would think HP/Semetricom would have taken that into account in the 
firmware and that only delay external to the Z3801A is "compensated" for ...


Dave
NR1DX

--
Dave
manu...@artekmanuals.com
www.ArtekManuals.com

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Re: [time-nuts] WWVB format change in 2012

[Tom Van Baak]

Sanjeev Gupta wrote:
> Folks, I am trying to trace down xtendwave.  They seem to have released a
> Everset IC, and then renamed themselves to Everset in 2013 or 2014.

Contact Paul Swed or me off-list about this.

> Is there *any* commercial gear available for WWVB at all, today?  Price is
> not an issue, just a public product page will do.

Time by radio -- WWVB (and DCF-77, MSF, JJY) -- is still in use. But most of 
the high-end commercial timing companies have long since switched to GPS. Now 
that most everyone on the planet has a mobile phone or WiFi or internet, the 
need for 1-bit-per-second time over LF or SW radio is not as great as it was 20 
years ago.

But you asked for product pages. Try these:

https://www.meinbergglobal.com/english/products/usb-wwvb-clock.htm

https://www.lacrossetechnology.com/clocks/atomic-digital/wall/
https://www.lacrossetechnology.com/clocks/atomic-analog/

http://www.casio.com/products/Watches/wave_ceptor/

http://www.jp-watch.com/product/44

http://www.ebay.com/itm/181283274562

/tvb
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Re: [time-nuts] WWVB format change in 2012

[Majdi S. Abbas]

On Tue, Mar 01, 2016 at 03:44:01PM +0800, Sanjeev Gupta wrote:
> Folks, I am trying to trace down xtendwave.  They seem to have released a
> Everset IC, and then renamed themselves to Everset in 2013 or 2014.

It's not an IC, exactly, it's a bare product intended for 
integration into something else.

> Is there *any* commercial gear available for WWVB at all, today?  Price is
> not an issue, just a public product page will do.

There's plenty of older gear out there that did not phase lock,
and works just fine.  Existing chipsets and receivers work fine for 
those.  Even phase locking receivers can be modified.

They changed the simple carrier to a phase keyed one, but they
did not change the amplitude coding.

I know Meinberg had WWVB modules available for some of their
products, you might see what they are up to.

--msa
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Re: [time-nuts] WWVB format change in 2012

[Sanjeev Gupta]

On Sun, Feb 28, 2016 at 3:09 PM, Sanjeev Gupta  wrote:

> Are there commercially (or widely-used) receivers for professional use
> which listen to the WWVB signal?


Folks, I am trying to trace down xtendwave.  They seem to have released a
Everset IC, and then renamed themselves to Everset in 2013 or 2014.

Is there *any* commercial gear available for WWVB at all, today?  Price is
not an issue, just a public product page will do.


-- 
Sanjeev Gupta
+65 98551208 http://www.linkedin.com/in/ghane
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