Re: [time-nuts] Commercial software defined radio for clockmetrology

[Kevin Rosenberg]

Hi Mangus,

No apologies necessary. Your music festival sounds more like it was more fun 
than the process review and implementation direction conference that I just 
returned from!

It is very kind of you to share your detailed knowledge on this subject. It is 
extremely relevant to what I am working on and is a great resource.

Much appreciated!

Kevin

> On Jul 31, 2016, at 10:41 PM, Magnus Danielson  
> wrote:
> 
> Hi Kevin,
> 
> Sorry for jumping into the thread somewhat late, but I am away on a music 
> festival, spending my vacation working.
> 
> I think some of what I would like to point out has already been covered, 
> somewhat indirectly.
> 
> When you measure ADEV, white phase modulation and flicker phase modulation 
> both depend on the bandwidth of the input channel. This is known already from 
> David Allan's article in Feb 1966. One peculiarity in there, that I discussed 
> with him as I met him at the IFCS 2016, is that the white phase modulation is 
> assumed to be a block filter, and he said that it reflects the counters that 
> they had at that time.
> Anyway, any averaging you will do will affect the white and flicker phase 
> modulations, but not white and flicker frequency modulations.
> When you filter, you will inflict a bias in the values, but the bandwidth is 
> the main cause of bias for white and flicker phase modulation. It turns out 
> that also the frequency modulations is affected by filtering, which comes as 
> no surprise. This makes ADEV a tricky business as you get biases to "true 
> ADEV".
> 
> What is "true ADEV"? Well, ADEV is a method to estimate noise amplitudes 
> using counters, simply because at the time, phase noise systems simply did 
> not have enough frequency resolution to be useful for atomic clocks. The 
> definition gives the relationship between the noise level and the ADEV value 
> for that particular noise-type.
> Any number of reasons to deviate from the ADEV values cause biases, and this 
> in itself is not a problem if the bias can be characterized and compensated 
> for, which is what the bias functions do. The pre-filtering that MDEV does is 
> just a tau-long phase sample average prior to the ADEV step, and this causes 
> a bias between the MDEV and ADEV functions, different between the different 
> noise-types, but the bias functions is known. The use of bias functions is 
> usually where most people fail.
> 
> Now, it was known in the beginning that ADEV values should always be given 
> with the channel bandwidth, and the assumed assumption there is that it is a 
> brick-wall filter as expected from time interval counters, delivering phase 
> samples, or possibly frequency samples which is just a post-processing of the 
> phase samples. The annotation of bandwidth got lost over time, and we can 
> assume that it is f_h=1/(2T) due to Nyquist.
> 
> Let's now consider two averaging methods, one where we average all samples 
> over a second and another when we use a classic one-pole low-pass filter and 
> sample the output. The average will have the assumed brick-wall property, as 
> if the counter measured at 1 s tau, but obviously the white phase modulation 
> noise is being averaged down and so will flicker phase modulation noise be to 
> some degree, which is already in their formulas. For the low-pass filter, you 
> will get the bandwidth aspect, which will behave similar, but as the slope 
> behaves, it will sum up the noise differently as you integrate over 
> frequency, so it will provide a different answer, in fact, the ADEV response 
> and hence bias function has not been established in published work, and as I 
> have asked around fellow researchers, only one has made some scrap note 
> calculations during the PhD thesis time and David Allan knows that Fred Walls 
> was working on it, as they had their offices next to each other at NBS/NIST 
> in Boulder,
  but it is not known if the notes every survived.
> 
> What we do know is what was hinted before, if you produce samples at high 
> enough rate compared to your lowest analysis tau, then the bias will be small 
> enough to not be a practical matter. For telecom measurements for instance, 
> the highest sample tau is 1/30 of the lowest analysis tau in order to avoid 
> this bias. The standard is very well-written in this regard, as it then 
> provides a practical solution while allowing for many different types of 
> implementation of the measurement, while keeping the implementation type from 
> coloring the result too much, as the comparability of results is important.
> 
> Another aspect of box-car averaging or any form of averaging is also that 
> sub-sampling can suffer from aliasing problems, and neither box-car averaging 
> or single-pole filters have very good anti-aliasing properties, so higher 
> degree filters is needed, it's just that well, we don't have their bias 
> functions.
> 
> A fascinating set of additional biases can be found in counters using various 
> averaging t

Re: [time-nuts] Commercial software defined radio for clockmetrology

[Kevin Rosenberg]

Hi Tom,

Thanks for your thoughts. I had looked at your helpful page when I started 
researching the effects of averaging. Currently, I’m experimenting with the 
dual receivers in the SDR using cross-correlation to reduce the noise floor.

Kevin
 
> On Jul 30, 2016, at 5:08 PM, Tom Van Baak  wrote:
> 
>> SDRs sample at high rates. The slowest the USRP N2x0 can sample is just 
>> under 200Ksps.
> 
> Hi Kevin,
> 
> I don't have an easy answer for you. BobC / BruceG / MagnusD / JohnM / 
> EnricoR can shed light on this. But I support your effort to figure out how 
> to obtain real truth from a massive oversampled data set.
> 
> If you feel uneasy that ADEV statistics might lie, see: 
> http://leapsecond.com/pages/adev-avg/
> 
> ADEV is always a tricky, since the measurement bandwidth is not always 
> specified, or how that bandwidth is implemented. Both the front-end h/w 
> design and any embedded s/w manipulation of raw data will distort (bias) the 
> statistics. Distortion itself is not a show-stopper, as long as you can 
> properly model it and back it out. But it seems the challenge is knowing how 
> valid the model is, and if model itself depends on the noise type.
> 
> /tvb
> 
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Re: [time-nuts] Commercial software defined radio for clock metrology

[Kevin Rosenberg]

Hmm, I might have answered my own question: filter to the fast samples to the 
equivalent noise bandwidth (ENBW) of the lower desired sampling rate and then 
decimate.

> On Jul 29, 2016, at 9:44 PM, Kevin Rosenberg  wrote:
> 
> Hi Bob,
> 
> You have a good point. That leads to the question is what is the “best” 
> measurement technique when you are sampling at a more smaller interval than 
> the desired tau?
> 
> SDRs sample at high rates. The slowest the USRP N2x0 can sample is just under 
> 200Ksps. For easy math, let’s assume we sample at 1Msps but we want to record 
> only 1sps for a long-term measurement. What’s best way to handle the 1e6 to 1 
> ratio of available samples to desired samples? One method is to discard 
> 999,999 samples and just record the phase difference with a true tau of 1 
> sec. The other is to take a window of 1e6 samples and output the average 
> phase difference over that 1 second window. Is your point that averaging 
> samples that are more frequent than the tau will overestimate stability at 
> the tau? If using averaged data, would it be “less lying” to multiply the 
> ADEV by the sqrt of the length of the averaging window?
> 
> I’d appreciate your thoughts on the subject,
> 
> Kevin
> 
>> On Jul 29, 2016, at 6:51 PM, Bob Camp  wrote:
>> 
>> HI
>> 
>> Keep in mind that if you apply pre-filtering, an ADEV plot is lying to you ….
>> 
>> Bob
>> 
>>> On Jul 29, 2016, at 6:58 PM, Kevin Rosenberg  wrote:
>>> 
>>> Jeff,
>>> 
>>> Thanks for your very useful paper Oscillator Metrology with SDRs[1]. I
>>> created a C++ program and checked residuals using a 10 MHz clock split
>>> to the A and B channels of a LFRX and BasicRX boards and sampled at 1
>>> Mhz. Using boxcar averaging of 1000 samples at 1 kHz, I was impressed
>>> by the low noise floor approaching that of my Timepod which was
>>> several times the cost. I included the Allan Deviation without
>>> averaging showing the sqrt(1000) increase in noise floor without the
>>> averaging[2].
>>> 
>>> I had a question about your experience. You mentioned using a input
>>> signal near the maximum of the USRP’s ADC to get the best SNR. I
>>> reviewed the schematics and application notes. I found a maximum Vpp
>>> mentioned of 3.3V. I was wondering what voltage you were using to
>>> drive the USRPs. When I go above 1.5-2 Vpp, I start getting signal
>>> distortions and not much increase in the amplitude.
>>> 
>>> Many thanks for publishing your work in this area.
>>> 
>>> Kevin
>>> 
>>> [1]
>>> https://arxiv.org/abs/1605.03505
>>> 
>>> [2]
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>> 
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> 
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Re: [time-nuts] Commercial software defined radio for clock metrology

[Kevin Rosenberg]

Hi Bob,

You have a good point. That leads to the question is what is the “best” 
measurement technique when you are sampling at a more smaller interval than the 
desired tau?

SDRs sample at high rates. The slowest the USRP N2x0 can sample is just under 
200Ksps. For easy math, let’s assume we sample at 1Msps but we want to record 
only 1sps for a long-term measurement. What’s best way to handle the 1e6 to 1 
ratio of available samples to desired samples? One method is to discard 999,999 
samples and just record the phase difference with a true tau of 1 sec. The 
other is to take a window of 1e6 samples and output the average phase 
difference over that 1 second window. Is your point that averaging samples that 
are more frequent than the tau will overestimate stability at the tau? If using 
averaged data, would it be “less lying” to multiply the ADEV by the sqrt of the 
length of the averaging window?

I’d appreciate your thoughts on the subject,

Kevin

> On Jul 29, 2016, at 6:51 PM, Bob Camp  wrote:
> 
> HI
> 
> Keep in mind that if you apply pre-filtering, an ADEV plot is lying to you ….
> 
> Bob
> 
>> On Jul 29, 2016, at 6:58 PM, Kevin Rosenberg  wrote:
>> 
>> Jeff,
>> 
>> Thanks for your very useful paper Oscillator Metrology with SDRs[1]. I
>> created a C++ program and checked residuals using a 10 MHz clock split
>> to the A and B channels of a LFRX and BasicRX boards and sampled at 1
>> Mhz. Using boxcar averaging of 1000 samples at 1 kHz, I was impressed
>> by the low noise floor approaching that of my Timepod which was
>> several times the cost. I included the Allan Deviation without
>> averaging showing the sqrt(1000) increase in noise floor without the
>> averaging[2].
>> 
>> I had a question about your experience. You mentioned using a input
>> signal near the maximum of the USRP’s ADC to get the best SNR. I
>> reviewed the schematics and application notes. I found a maximum Vpp
>> mentioned of 3.3V. I was wondering what voltage you were using to
>> drive the USRPs. When I go above 1.5-2 Vpp, I start getting signal
>> distortions and not much increase in the amplitude.
>> 
>> Many thanks for publishing your work in this area.
>> 
>> Kevin
>> 
>> [1]
>> https://arxiv.org/abs/1605.03505
>> 
>> [2]
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> 
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Re: [time-nuts] Commercial software defined radio for clock metrology

[Kevin Rosenberg]

Jeff,

Thanks for your very useful paper Oscillator Metrology with SDRs[1]. I created 
a C++ program and checked residuals using a 10 MHz clock split to the A and B 
channels of a LFRX and BasicRX boards and sampled at 1 Mhz. Using boxcar 
averaging of 1000 samples at 1 kHz, I was impressed by the low noise floor 
approaching that of my Timepod which was several times the cost. I included the 
Allan Deviation without averaging showing the sqrt(1000) increase in noise 
floor without the averaging[2].

I had a question about your experience. You mentioned using a input signal near 
the maximum of the USRP’s ADC to get the best SNR. I reviewed the schematics 
and application notes. I found a maximum Vpp mentioned of 3.3V. I was wondering 
what voltage you were using to drive the USRPs. When I go above 1.5-2 Vpp, I 
start getting signal distortions and not much increase in the amplitude. 

Many thanks for publishing your work in this area.

Kevin

[1]
https://arxiv.org/abs/1605.03505

[2]
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[time-nuts] SRS CG635 Schematic

[Kevin Rosenberg]

Hello,

I purchased a used Stanford Research System CG365 clock generator that is 
without a printed manual. As SRS's online manuals do not include schematics, 
does someone have a link to, or a copy of, the CG635 schematics that they would 
share with me?

Thanks!

Kevin

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Re: [time-nuts] Some videos from the recent Symmetricom 3120A webinar

[Kevin Rosenberg]

On Jun 26, 2013, at 10:13 PM, John Miles  wrote:
> Here are some short demo videos that we used in our webinar recently
> (http://www.symmetricom.com/resources/downloads/webcasts/#Government%20Solut
> ions ).  They're focused on the Symmetricom 3120A test set (née TimePod
> 5330A) but they illustrate some basic stability/noise measurement concepts
> that apply to other instruments as well.  They're worth checking out if you
> use TimeLab, even with a counter, since the software is almost the same.  

Thanks for creating and posting the videos, John. I really enjoyed them!

Thanks also for extremely useful TimePod and TimeLab. Your videos well 
demonstrate the versatility, precision, and ease of use of the tools you've 
created.

Kevin

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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

Thanks to all for the very helpful discussion. 

Appreciatively, Kevin

On Apr 25, 2013, at 9:26 AM, Chris Albertson  wrote:

> The problem with analog 10MHz is the non-linear parts at each end of
> the fiber optic.  It would be hard to get a nice sine wave at the
> output.
> 
> I think if you have a requirement for very clean sine wave at the far
> end you'd best try to phase lock a local XO.  Send a 10 MHz square
> wave down the fiber and use that to phase lock a local XO.I think
> almost all fiber systems use a PLL for clock recovery.
> 
> Problem is the parts built into the jacks.
> 
> On Thu, Apr 25, 2013 at 12:08 AM, Attila Kinali  wrote:
> 
>> Sorry, i was a bit unclear. What i meant with modulation was to
>> use an analog scheme that never saturates the transmitter or receiver
>> both in the max (fully on) or min (fully off) direction.
>> Ie do not send 1's and 0's as it is common in the digital domain of
>> networking, but an "analog" 10MHz sine. With that you get around
>> of the non-idealities that come with on-off transmissions.
> 
> --
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

On Apr 24, 2013, at 2:50 AM, Attila Kinali  wrote:
> [...]
> low jitter (sub 1ns rise/fall times). For the transmitters, if possible
> go for those with laser diodes and modulate them (ie no on-off switching).
> This will give you jitter way below 1ns (sorry, don't know any hard numbers).

For < 1ns jitter, do you have a recommendation of 
modulation (ASK/PSK?) and carrier frequency?
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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

On Apr 23, 2013, at 4:16 PM, Bob Camp  wrote:
> There are optical links that are better than your typical opto coupler. I 
> have not seen many that are good to -170 dbc. 

Rather than for a 10 MHz signal, I might prefer an optical link rather than 
differential for a PPS signal. Could you recommend any optical links with 
jitter of about 1 ns?

Kevin

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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

On Apr 23, 2013, at 4:04 PM, Bob Camp  wrote:
> If you are "only" worried into 1 Hz or even 0.1 Hz, temperature on the coax 
> will not be a big issue. If you are trying to maintain 170 dbc at the far end 
> of the wire, shielding and isolation will be a *big* issue. You may need some 
> pretty fancy cable and magnetics to make that work….

Sounds like your original suggestion of a balanced twinax and magnetics would 
be a better start than LMR240 for this goal. Thanks!

Kevin

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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

On Apr 23, 2013, at 2:24 AM, WB6BNQ  wrote:
> I had to buy the three components at three different places.  The TOSLINK 
> receiver came from Mouse (p/n 757-TORX177F,T) and cost $1.31.  The TOSLINK 
> transmitter came from DIGIKEY (p/n 1080-1428-ND)
> and cost $0.866.  At the time, for whatever reason each supplier had the one 
> end but not the other.  
> [...]

Thanks, I did consider optical isolation, but wasn't sure of what parts to use. 
Looks like the receiver isn't stocked by Mouser anymore, but I could look for 
it.

I saw the transmitter's max jitter is specified at 20 ns. I wonder if there is 
a reasonably-priced substitution with < 1 ns jitter.

Thanks for your thoughts,

Kevin


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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

On Apr 23, 2013, at 4:43 AM, Bob Camp  wrote:
> Like any design, the first question is - what's the goal?

My favorite first question, too. Move my most stable OXCO in
the 1 Hz to 10 KHz range to the more stable environment,
and maintain its phase noise of -100 dBc/Hz @ 1 Hz and
-170 dBc/Hz at 10 kHz.

Since the cable will be inside the structure, passive insulation 
should help keep the temperature change rate < 1 degK / hr. 
Though, the HVAC does cycle the lab ambient temperature a few degrees 
K per hour.

Twinax is an interesting idea, thanks.

Kevin

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Re: [time-nuts] ngTADD-1

[Kevin Rosenberg]

On Apr 22, 2013, at 7:13 PM, Bob Camp  wrote:
> U, e. Even with all the mods, a 4501 is a fairly low resolution 
> device. It's an amazing little box and I have several of them. Some (but not 
> all) with the mods actually done correctly. 

Ummm, apologies for the errant posting that should have been a private message 
to N8UR.
The 4501 was directed about a previous post to John.

The question for John about his new distribution amplifier was so that I could 
place my 
RF and thermally-shielded 10811-60109 in the corner of my concrete basement. 
Then,
run 100 ft of galvanically-isolated coax to my lab.

Now that's its public, do you have suggestions for the coax? I was thinking 
about LMR-240
for its double-shielding and low tempco at 10 MHz.

Thanks,

Kevin




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[time-nuts] ngTADD-1

[Kevin Rosenberg]

I hope all is going well with your next-generation TADD-1. I'm thinking just 
thinking about putting 
a T-bolt disciplining a PRS-10 discipling a Soekris 4501. I was thinking a 
TADD-1 one would be nice for driving 10 MHz line to another room with the 
TADD-1 also providing galvanic isolation. 

If you need help testing, I have a TimePod along with some 10811s and PRS-10s 
for testing. Though, I know that you have more stable sources than I and I've 
appreciated looking at your published phase noise plots of the years.

Kevin

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Re: [time-nuts] Don't use cheap cables -- a cautionary tale

[Kevin Rosenberg]

On Mar 3, 2013, at 7:59 AM, John Ackermann  wrote:
> Lesson learned -- use only double-shielded cable in the oscillator rack (and 
> in any RF measurement path) from now on.

I've learned that lesson as well. John Miles said that RG-58 is occasionally 
referred to as 'soaker hose'.

Kevin

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Re: [time-nuts] Brooks Shera

[Kevin Rosenberg]

If needed, I can provide some local help. Karen's address is a
short drive from my home.

Kevin

On Dec 21, 2012, at 7:15 AM, paul swed  wrote:

> Bert
> A thought has crossed my mind here.
> His wife can not access his computer.
> If its windows XP or earlier the password is recoverable. I use a boot cd
> that exposes all. Its been helpful.
> Is there a way to reach out and offer help aside from snail mail?
> Would she be open to that help?
> Regards
> Paul
> 
> On Wed, Dec 19, 2012 at 4:03 PM,  wrote:
> 
>> Some how time nuts combined two lines  it is
>> Karen Stoll46 Crazy Rabbit  Rd  Santa Fee,  NM   87508
>> 
>> 
>> In a message dated 12/19/2012 3:55:33 P.M. Eastern Standard Time,
>> ewkeh...@aol.com writes:
>> 
>> 
>> Brooks Shera has been a major contributor with his GPSDO.   Before Tbolts
>> where affordable his QST article for the first time opened  the  door for
>> many
>> amateurs to precision frequency at an affordable  price. Over the  years I
>> build many units. For a year I have tried to  buy his latest version  4.02.
>> I
>> did not get a response, so last week  I wrote a hardcopy  letter.
>> Yesterday I got an answer from his wife  Karen Stoll. She  is not able to
>> access his emails.
>> Brooks is in  a Memory Care  Unit in a local senior residence, suffering
>> from  dementia.
>> I think it is appropriate  that those of us that appreciate  his
>> contribution take the time to write a  personal note to his wife,  I am
>> sure it will
>> help her in these difficult times  and maybe seeing  the letters will help
>> him
>> to.
>> Bert  Kehren
>> Karen   Stoll46 Crazy Rabbit Rd.
>> Santa Fe, NM   87508
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Re: [time-nuts] 3120A Phase Noise Test Probe

[Kevin Rosenberg]

Magnus Danielson wrote:
> Congratulation John! Good work!

Truly well-deserved, John!

Kevin

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Re: [time-nuts] Warning if buying from directly from Agilent via eBay with Paypal.

[Kevin Rosenberg]

On Nov 17, 2012, at 4:37 PM, Don Latham  wrote:
> I'm wondering if agilentused is really part of the Agilent corp or
> whatever it's called? or an "independent" company entirely? My only and
> last $.02!

I reviewed my email archive. Emails regarding my purchase from "agilentused" 
came from, and went to, the SMTP address of "e...@agilent.com". 

It took almost 12 weeks to get my scope with the software options I ordered. In 
compensation for the delay, e...@agilent.com sent me two additional software 
license keys via email.

Kevin



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Re: [time-nuts] Warning if buying from directly from Agilent via eBay with Paypal.

[Kevin Rosenberg]

On Nov 17, 2012, at 5:29 PM, David Kirkby  wrote:
> It is Agilent - at least to the extent I can determine. Some reported
> [...]

Also to the extent that I could determine.

> All emails after the sales were from the UK offices of Agilent. Any
> emails sent to contactcenter...@agilent.com about this are answered.
> So as far as I'm concerned, this is Agilent.

My email and phone calls went to Germany, perhaps because I was buying an 
oscilloscope rather than a VNA.

agilentused also wanted me to use PayPal. I used two transactions. The first 
for the item and the second for software options. I would have also preferred 
credit card for the cash back, but agilentused wanted PayPal.

Kevin


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Re: [time-nuts] Best counter setting for ADEV?

[Kevin Rosenberg]

On Oct 3, 2012, at 6:52 PM, Kevin Rosenberg  wrote:
> Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 seconds.

Sorry, 1E-14 at 1E5.


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Re: [time-nuts] Best counter setting for ADEV?

[Kevin Rosenberg]

On Oct 3, 2012, at 11:15 AM, saidj...@aol.com wrote:
> The CSAC is cheap compared to the  reference you need to measure  it...
> 
> http://www.leapsecond.com/pages/csac/log96872v.gif

Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 seconds.

Kevin


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Re: [time-nuts] Best counter setting for ADEV?

[Kevin Rosenberg]

On Oct 2, 2012, at 1:39 PM, saidj...@aol.com wrote:
> 1) calibrate the internal 100MHz vectron OCXO using a small screwdriver,  
> this is not really critical though as the unit does not really function as a  
> frequency counter.
> 
> 2) Calibrate the power supplies for proper voltages if necessary with same  
> screwdriver, I found that is really not necessary usually

Thanks for those two steps. I've found a copy of the user and GPIB manuals, but 
not a service manual. Do you have a service manual that you could forward to me.

Also, I was interested in the VISI software, but talking with Wavecrest a few 
years ago they said that it was no longer supported. Do you know to get an 
orphaned copy?

Many thanks and for all of your help thoughts over the years. I'll look forward 
to the day and I can afford a GPS disciplined CSAC.

Best,

Kevin


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Re: [time-nuts] Automatic switching of a µC osc. to external 10MHz reference as clock?

[Kevin Rosenberg]

On Sep 11, 2012, at 4:42 PM, Peter Krengel  wrote:
> I'm looking for a possibility to make an automatic switching
> between the internal µC oscillator (Atmel µC) to the 10MHz output
> of my thunderbolt to use it as a precise µC clock. Has anybody an idea how to 
> do best
> without disturbing the accuracy of the ref. signal?

Hi Peter,

I'm likely misinterpreting what you want to do. From my reading your question, 
the answer is: no, you can't the change the source of an AVR's system clock bus 
at runtime. You can only change the CLKSEL fuses only during programming. 
CLKSEL sets your AVR to get its system CLK bus from a number of difference 
sourceson either its internal oscillator or an external clock or crystal, While 
modern AVR's can read fuse settings at runtime, the values of those fuses can't 
be modified. I set the fuses on my AVR timers to use the external clock source 
and feed CLKIN from whatever reference clock I want to use.
 
However, the new XMEGA's do allow more change of clocks during runtime compared 
to AVRs. Perhaps they may be able to programmatically change the input of its 
CLK bus.

To have an AVR automatically switch input clock sources, I'd use a supervisory 
internal (RC) oscillator as CLKSEL. The supervisor can monitor error signal 
quality as also query for an error conditions for multiple clocks inputs. That 
supervisory AVR can then control a switch to route the desired clock into the 
CLKIN of the timing AVRs. A one-time phase offset can be expected during the 
switch to the new clock input line.

Kevin


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Re: [time-nuts] ublox chip sets - what GPS device should I buy?

[Kevin Rosenberg]

On Aug 31, 2012, at 4:05 PM, David Kirkby  wrote:
> I don't have it yet, but bought it on eBay today from the seller
> "agilentused" which is Agilent, and sells used/ex-demo units which
> have been reconditioned, and have a fully warranty. Since I have not
> [...]

I bought my MSO7104B oscilloscope from the same seller and was overall very 
pleased. It did take a long time to get the scope with the software options 
that I requested (6 weeks). But, they apologized and offered to include another 
$3K of options of my choice to compensate for the delay. The 3-year Agilent 
warranty was also important to me.

Kevin


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Re: [time-nuts] Tidbit for Soekris 4501 NTP users

[Kevin Rosenberg]

On Aug 19, 2012, at 12:15 PM, John Ackermann N8UR  wrote:
> This is probably something that very, very few other people are going to 
> encounter, but thought I would note it here for posterity.

Thanks! You've already helped one person. I ran up against that problem when 
testing one of my 4501's with only a PPS signal.

Kevin


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Re: [time-nuts] TimePod, cross-correlation fun and measurements

[Kevin Rosenberg]

On Jun 17, 2012, at 9:32 PM, Joseph Gray  wrote:
> I was recently reading the manual for the TimePod. It looks quite
> nice. I'm curious as to the price. Or is this a case of "if you have
> to ask, you can't afford one"?

The price is right on the TimePod web site: http://www.miles.io.
I couldn't be happier with the TimePod that I got back in December.
Highly recommended.

Kevin


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Re: [time-nuts] NTGS50AA 1pps

[Kevin Rosenberg]

On May 3, 2012, at 11:27 PM, Murray Greenman wrote:
> No, I've not found a 1PPS output. Not that I've looked, and I don't have the 
> official pinouts for the big connector on the back. It would be easy enough 
> to synthesize one, for example using a divider on one of the other products, 
> resetting it if necessary with the 1PPS2 (2 sec) pulse.

Appreciate the info, Murray. Good point, the TADD-3 sync input for work well 
for that.

Kevin


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Re: [time-nuts] NTGS50AA, better than Thunderbolt

[Kevin Rosenberg]

On May 3, 2012, at 7:21 PM, Sam wrote:
> Kevin, you asked if there was a PPS output. There isn't a 1PPS output at all, 
> but there is a Even Second output with a negative pulse, 40-60 ns wide.
> This is available via the font mounted SMB connector or via the rear 110-pin 
> "AMP Z-pack" connector.

Thanks for that bit and all the other NTGS50AA information.

Kevin


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Re: [time-nuts] NTGS50AA, better than Thunderbolt

[Kevin Rosenberg]

On May 3, 2012, at 2:08 PM, Steve wrote:
> Did the seller double the shipping cost today? I could have sworn it was $30 
> the 
> last time I looked at the listing. 

I paid $30 shipping early today.

Kevin


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Re: [time-nuts] NTGS50AA, better than Thunderbolt

[Kevin Rosenberg]

On May 3, 2012, at 1:18 PM, Murray Greenman wrote:
> I agree with you. I've been using an NTGS50AA here for some time, and it is 
> an excellent unit with none of the thermal problems of the Tbolt. Easily as 
> good as the old Z3801A, and much lower power consumption. I use the NTGS50AA 
> with the Thunderbolt software in TSIP mode, although not all the messages 
> work.


Hi Murray,

Were you able to find an PPS output? As I understand it, the unit has a 
connector for a pulse every 2 seconds.

Kevin


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Re: [time-nuts] WWVB phase-modulation test

[Kevin Rosenberg]

On Apr 14, 2012, at 10:45 PM, Shaun Merrigan wrote:
> Just wondering if anyone on the list is monitoring their WWVB gear at the
> moment?  I got in a bit late, but I have been recording my 8170 since about
> 0300 and it has remained locked.  QTH here is about 1500km north of Ft.
> Collins.

Spectracom 8182 relocked at 1403Z today.

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Re: [time-nuts] WWVB phase-modulation test

[Kevin Rosenberg]

On Apr 14, 2012, at 10:45 PM, Shaun Merrigan wrote:
> Just wondering if anyone on the list is monitoring their WWVB gear at the
> moment?  I got in a bit late, but I have been recording my 8170 since about
> 0300 and it has remained locked.  QTH here is about 1500km north of Ft.
> Collins.

I've been monitoring my Spectracom 8182. It's been unlocked since 0100,
about 1000km south of Ft. Collins.

Kevin


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Re: [time-nuts] 1 pps correction

[Kevin Rosenberg]

On Mar 31, 2012, at 12:33 PM, Brooke Clarke wrote:
> But for the general first case the hardware solution with the delay line is 
> the only way.  I think there may be an exception specifically for the PRS10 
> in that it may accept a sawtooth correction on the RS-232 input (I seem to 
> remember that).

Your memory is correct, though it requires a later PRS10
firmware that permits setting the 'TO' parameter.
I wrote a C program for Darwin/Cygwin that reads the sawtooth 
correction from an iLotus M12 and sets the 'TO' on the PRS10.

Ultimate goal was to target a microcontroller to drive the
software correction. But, with the PRS10's prefilter, I'm
not sure (and didn't measure) how important the sawtooth correction
was for the PRS10's PPS output.

Kevin


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Re: [time-nuts] Agilent 53230A Counter

[Kevin Rosenberg]

On Mar 10, 2012, at 7:12 AM, Adrian wrote:
> just wondering if anyone has tried the new Agilent 53230A counter?

I like it quite a bit. The YouTube videos by Agilent 
do a fair job showing the instrument and are worth a 
few minutes if you are interested. Using TimeLab with 
John's new TCP/IP support  for the 53230A makes some 
of the built-in logging and statistical functions less 
important  unless you want to use some of the 53230A's 
advanced features such as its zero dead-time modes.

I measured a residual of 3E-11 ADEV @ 1sec using a 
non-optimum setup of TimeLab in the frequency measurement 
mode measuring a 10 MHz Thunderbolt signal from a TSC 
distribution amp as input 1 with another output from the 
TSC supplying the Ext Ref. I get a STDDEV of 8 ps measuring
delay through 3 feet of RG-223 cable.
 
Kevin


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Kevin Rosenberg]

On Jan 7, 2012, at 10:39 AM, Chris Albertson wrote:
> I think this is exactly what you want.  An RF distribution amp using
> video amplifier chips. The kit is no longer available but the
> schematic is.  Look near the end of the user manual and you can get
> that here.  This design is well tested and people way it works well.
> http://www.tapr.org/kits_tadd-1.html
> The transformers in the above are not available but I bet you could
> take some using toroid cores.

TAPR told me last year that the kit discontinuance was due to the Maxim RF 
amplifiers becoming unavailable. I believe the T1-X65 transformers [1]
I just bought from Mini-circuits are similar or identical to the 
transformer mentioned in the schematic.

Kevin

[1] 
http://www.minicircuits.com/MCLStore/ModelPriceDisplay?13259623730480.6126895864089323


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[time-nuts] Temporal cloaking in Nature journal

[Kevin Rosenberg]

The abstract and a two graphics are online at
http://www.nature.com/nature/journal/v481/n7379/full/nature10695.html


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Re: [time-nuts] Another Trimble Thunderbolt-like GPS?

[Kevin Rosenberg]

On Dec 19, 2011, at 11:59 AM, Chris Albertson wrote:
> Where is the source code for Lady Heather?

It's included with the binary distribution.

Kevin


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Re: [time-nuts] DG535 triggering problem

[Kevin Rosenberg]

On Dec 16, 2011, at 11:25 AM, Brooke Clarke wrote:
> Just a guess.  If line triggering does that there may be a problem with the 
> power transformer.
> Use an Ohm meter to locate the transformer terminals for the AC line and then 
> check from one of those to all the other terminals.
> I suspect there's a short in the transformer.
> Look at U502 to see of it's burned up.

Actually, I'm more confused what U502 actually is.
The revision M manual calls it both a LM2901
quad comparator (parts list and two sections)
as well as a MC12040 phase comparator.
The little PCB soldered into U502 has MC12040
silk-screened on it.

Kevin


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Re: [time-nuts] DG535 triggering problem

[Kevin Rosenberg]

On Dec 16, 2011, at 11:25 AM, Brooke Clarke wrote:
> Just a guess.  If line triggering does that there may be a problem with the 
> power transformer.
> Use an Ohm meter to locate the transformer terminals for the AC line and then 
> check from one of those to all the other terminals.
> I suspect there's a short in the transformer.
> Look at U502 to see of it's burned up.

Thanks for the thoughts. U502 is interesting. It's a small
PCB with an 8-pin SOIC and an SMD cap on one side soldered
into with a two rows of 0.1" pins into the main PCB. Since
it's only a 8-pin IC on top, and U502 is supposed to be
a quad comparator, likely there's another 8-pin IC on
the bottom on the adapter board. I'd need to desolder the
14-pins to check that. I suspect that SOIC to DIP board is
there because the original U502, a MC12040, became unavailable.

I'll need to do some more disassembly to check resistance
between the primary and the secondary taps. I was wondering
about the transformer or other power rails as well. That's why 
I checked the 6 regulated outputs. 

While the sonic noise with 'line' triggering is an important clue, 
I was thinking it was probably more in the logic circuitry since 
the other 4 trigger modes won't trigger. Unfortunately, I don't
have a schematic.

Anyway, thanks again for the information on trimming C512.

Kevin


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[time-nuts] DG535 triggering problem

[Kevin Rosenberg]

Hello,

Thanks to Brooke's excellent web page [1] on getting the DG535
80 MHz clock working, I was able to fix the "Ext Clk Err" on
a DG535. Everything on the front panel seems to work.

However, triggering does not work. I can't get a trigger to
occur in any triggering mode. Setting the triggering mode to 
'Line' causes a loud 120 Hz vibration from the rear of the device.

I've checked voltages from all of regulators mentioned in
the manual, and they seem fine.

I wonder if someone has an idea about helping the DG535
trigger.

Thanks,

Kevin

[1] http://www.prc68.com/I/TandFTE.shtml#DG535

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Re: [time-nuts] Using GPS 1PPS for accurate period measurement

[Kevin Rosenberg]

On Dec 2, 2011, at 4:12 PM, Azelio Boriani wrote:
> Man, what should we follow if not the manufacturer datasheet? Everyone can
> [...]

Oh, I have an active imagination and tried a 1/2 dozen different ideas. 
But, lesson learned!

Kevin


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Re: [time-nuts] Using GPS 1PPS for accurate period measurement

[Kevin Rosenberg]

On Dec 2, 2011, at 10:59 AM, Hal Murray wrote:
> I've been playing with one of the Dallas DS32KHZ parts.  I'm guessing you are 
> [...]
> Another possibility is that I didn't ground the NC pins.  (I didn't notice 
> that in the data sheet until I read it again looking for crap like that.)

Using a DS1306, I found the ground plane was essential for a stable 32768 Hz 
signal. I tried a number of ground planes in a proto board I was building. Who 
would have predicted that the best results came from the ground plane that was 
described in the 1306 datasheet. Lesson: before using a DS32KHz, I'll 
definitely 
connect the "NC pins" (sic) to ground as specified in the datasheet.

> You might try a pair of tvb's picPETs.

+1E3 on tvb's picPETs! Thanks, Tom!

Kevin


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Re: [time-nuts] Symmetricom TimeSource 2700

[Kevin Rosenberg]

Hi Charles,

Thanks very much for the information on the pinout of the TOD connector
on the TS2700.

I verified the PPS signal between pins 6 and 1. It's duration and voltage
matches your report. I compared the timing of the PPS signal with the PPS
of two synchronized thunderbolts.

Interesting, the PPS signal from the TS2700 is delayed a rather constant
280ms compared to the two TBolts over about a minute of observation.

One reason why I'm interested in the PPS output is to provide a varied
NTP source for my Soekris 4501s. I have TBolts, M12M, Netclock/2 WWVB,
and Garmin 18x. I thought it's be nice to have a CDMA clock as well.

If of the PPS offset remains a constant, then I could use the TS2700 as 
an NTP reference clock. (I realize I'd have to write an NTP driver for
the device). But, the fact that the TS2700 is a 1/4 sec off of GPS
PPS makes me suspicious that the device was never interested to provide
a precise PPS -- just a reference frequency source as advertised.

Anyway, many thanks for all your help in understanding the device.
I'll report more if I learn anything interesting.

Kevin


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Re: [time-nuts] Clocking a PIC16F628A from a Rubidium Standard

[Kevin Rosenberg]

On Nov 26, 2011, at 10:36 AM, Don Latham wrote:
> Come on, folks. never hook anything directly to the power line. The
> source is just too stiff. Use an opto. I used fiber optic isolation with
> my big DC power supply.

I don't disagree on isolation. I will say that Atmel's (and presumably 
Microchip's) app notes don't give much information on safe construction.

Tom wrote a nice page showing a safer-than-average construction for sipping
AC main voltage through high resistance:

   http://www.leapsecond.com/pages/ac-detect/

Kevin


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Re: [time-nuts] Thunderbolt Monitoring for Pocket PC

[Kevin Rosenberg]

On Nov 25, 2011, at 3:55 PM, Justin Pinnix wrote:
> A while back, I scored an old Compaq iPaq Pocket PC for cheap at an
> auction.  Recently, I wrote a program for it that reads the time and health
> information from a Thunderbolt and displays it in real-time.  More info
> available here:  http://www.fuzzythinking.com/projects/thunderhead/

Nice project. Could you recommend some model numbers of iPaqs
that would be compatible with the hardware and software?

Thanks!

Kevin


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Re: [time-nuts] Clocking a PIC16F628A from a Rubidium Standard

[Kevin Rosenberg]

On Nov 25, 2011, at 1:17 AM, Attila Kinali wrote:
> Using the protection diodes as part of the circuit is bad design practice.

In general, I agree completely, Further, I think of operating outside
of the datasheet may result in any manner of unspecified behavior. Basically,
results while operating outside the datasheet specifications are unspecified.

In this case, the use of the protection diode and the 1 ma limit
comes directly from the manufacturer Atmel's App Note AVR182 [1].
That said, I'm cautious even when the manufacturer in an App Note
says it's okay, but the use falls outside of the datasheet 
specifications.

Thanks for the thoughts on an alternative circuit that doesn't rely
on internal device knowledge that may, or may not, be okay.

Kevin

[1] http://www.atmel.com/dyn/resources/prod_documents/doc2508.pdf


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Re: [time-nuts] Low noise power supplies for time nuts circuitry

[Kevin Rosenberg]

On Nov 24, 2011, at 4:46 PM, Bob Camp wrote:
> The Linear LT1764 is reasonably quiet / high current / low dropout. Don't 
> count on getting all three at once.

Thanks, Bob!

Kevin


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Re: [time-nuts] Symmetricom TimeSource 2700

[Kevin Rosenberg]

On Nov 24, 2011, at 2:43 PM, Charles P. Steinmetz wrote:
> I just did this, and the TS2700 has been silent for 30 minutes (it has not 
> had an Alarm or Event since its last power cycle, about 6 months ago, 
> according to its log).  I did not want to disturb it by creating an Alarm or 
> Event.  However, I tested the terminal emulator by switching the COM port to 
> a TBolt, and confirmed that the TBolt is very chatty.  So:  I conclude that 
> the TS2700 sends time and date information to the Craft output only as 
> parameters in Alarm and Event messages, not as independent events (at least 
> not more frequently than once in 1/2 hour).


Thanks for the report on that, Charles. 

I use the Craft connector for monitoring with BTMon rather than the RS-232 port.
It appears the Craft output, while spontaneously emitting alarm/events, does 
respond 
to queries from BTMon on the Craft input.

Do you happen to have a RS-422/485 interface? I don't, but I'm interested to 
see 
if any spontaneous output occurs on the TOD port.

Best,

Kevin


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Re: [time-nuts] Clocking a PIC16F628A from a Rubidium Standard

[Kevin Rosenberg]

On Nov 24, 2011, at 7:50 AM, Attila Kinali wrote:
> Have a look at the PIC 16F628 data sheet, it will tell you the requirements
> for the clock input and there should be circuit for external clock signal
> listed. If it's not in the datasheet, it should be in an appnote.
> 
> Usually, chips accept sinusoidal and rectangular inputs up to 0V-VDD swing.
> If i'm reading the schematic correctly and the PIC runs with 5V, then
> you should be able to just feed the Efratom output directly to the PIC.
> Maybe, a ceramic 100n capacitor in this line should be used to do
> a DC isolation (1u cermaic should do as well).

Tom's picPET page http://www.leapsecond.com/pic/picpet.htm describes
using a TBolt sine directly as a clock source. I'm going something
similar with AVRs for an external clock.

Since frequency reference sine wave can exceed Vdd, you want to current 
limit the external clock. For example, an unterminated TBolt puts out 0-7V
Pk-Pk. Atmel, in an app note where they hook up the pins of an AVR
to 220V mains, states the over/under voltage protection diodes should
not carry more than 1 milliamp of current. But, you should both read
the datasheet for the output voltage of the Efratom and measure Pk-Pk
voltage output at the point of your PIC.

To limit to 1 ma for an AVR with a TBolt, you'd want to use a 2K
series resistor to drop that extra 2V (7V Pk vs. 5V Vdd) to a 
milliamp of current.

Kevin


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Re: [time-nuts] Clock Correction Algorithm

[Kevin Rosenberg]

On Nov 24, 2011, at 9:35 AM, Miguel Gonçalves wrote:
> The software way is probably the best idea as it would account for small 
> differences in different oscillators. I have 3 Arduino boards and will make 3 
> time displays. 


For precision timing with a microcontroller, I've been using
the 10 MHz from either a TBolt or PRS10 to be the external clock
rather than compensating for the frequency offset of a crystal.

The disadvantage of this is you need either a GPSDO or a Rb nearby,
or cabling to your frequency reference limiting its placement and
mobility.

Kevin
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Re: [time-nuts] Low noise power supplies for time nuts circuitry

[Kevin Rosenberg]

On Nov 23, 2011, at 5:50 AM, Chuck Forsberg WA7KGX N2469R wrote:
> How sensitive are each of a Thunderbolt's 3 supplies to noise?

This doesn't break down the sensitivities to noise, but Tom shows
a range of TBolt output noise for different 3 voltage power supplies:
http://www.leapsecond.com/pages/tbolt/noise.htm

My suspicion is the -12V is the least sensitive as I heard that it
is only used for the RS-232 port. I think either the the +5V which
controls the electronics (including things like comparators) and
the +12V (which controls the heater to the OXCO) are both noise
sensitive. I think the +5V will be the most sensitive.

For the PRS10 Rb, two 24V inputs are provided. A higher current
for the heater and a lower current for the electronics. To my
mind, that makes it likely the electronics (+5V on the TBolt)
are the most sensitive.

Maybe someone will actually have data to show.

Kevin


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Re: [time-nuts] Low noise power supplies for time nuts circuitry

[Kevin Rosenberg]

> 78xx Regulators are quite noisy. You can use them to filter the
> noise of a cheap DC/DC converter, but i wouldnt use them feed
> high precision electronics. There are a lot better designs these days.

Hi Attila,

Would you mind recommending some low-noise regulators? Perhaps for
both low and high current applications? I'm looking for 12V to power 
some OXCOs to be used a reference oscillator for a phase noise tester.
On the higher current side, maybe to power a rubidium (or at least
filter the switcher).

Thanks very much,

Kevin


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Re: [time-nuts] Symmetricom TimeSource 2700

[Kevin Rosenberg]

On Nov 24, 2011, at 9:25 AM, Charles P. Steinmetz wrote:
> I did a little investigating, and it turns out that the TOD displayed in the 
> BTMon windows is the local system time, NOT time received from the TS2700.  
> Apparently, the TS2700 does not send TOD on the Craft output.

Hi Charles,

When I first used BTMon, I wondered if that was the case.
However, reading more about the TL1 messages from the Craft
output, there are messages for date and time:

date: 
This parameter is the current date in the 8-digit form -mm-dd, where  
is year, mm is month (01–12), and dd is day (01–31).

time:
This parameter is the current time in the 6-digit form hh-mm-ss where hh is 
hours (0–23), mm is minutes (0–59), and ss is seconds (0–59). The factory 
setting is GMT for local time.

Assuming your investigation is connect, then system time is used in BTMon 
windows, but it's also
documented to be present on the Craft output.

For my next investigation, I need to read a bit on RS-422/485 pinouts on a DE-9 
connector. I think
I have a Maxim sample RS-485 transceiver I can use to look at data on the TOD 
output.
Also, once I know the pinout, I'll know where ground is and can look for a PPS 
on one of the other
pins.

If I don't get far there, then I was thinking about looking at the 2 Hz test 
point and seeing if
that's synchronized to a GPS PPS signal.

Thanks for information!

Kevin


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Re: [time-nuts] Symmetricom TimeSource 2700

[Kevin Rosenberg]

On Nov 21, 2011, at 10:33 PM, Charles P. Steinmetz wrote:
> The TS2500 was a very similar unit that received its timing signals from GPS. 
>  I assume they were built on the same case, hence the spare chassis hole (and 
> perhaps also some features in BTMon that are not used by the TS2700).

I appreciate that information. It makes such observations less mysterious.

> Yes, please report your findings on the TOD connector.  That connector, and 
> the corresponding feature in the BTMon software, could apply only to versions 
> of the TS2700 with an optional TOD function, or, more likely, to the TS2500 
> or other model built on the same chassis/motherboard.  It will be interesting 
> to see if there is any data there in a TS2700.

I took apart the 3 boards of the TS2700. It's really a very beautifully 
constructed device.
Pins on the TOD connector are connected to two MAX490Es (RS-422/485 
transceivers). Likely some
TOD data is present on TOD connector. 

I reassembled the TS2700 enough it turn it back on with the Rb. 
Using BTMon and selecting NTP or Cisco for the TOD, the actual error 
message affirms your assumption. The message is "Incompatible Target Revision,
Cannot Configure TOD". I hadn't realized that BTMon was used for other
devices. 

I found labelled test points for 200 Hz, 4 Hz, and 2 Hz on the logic board.
I didn't find any pins labelled 1 Hz or PPS.

Kevin


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Re: [time-nuts] Symmetricom TimeSource 2700

[Kevin Rosenberg]

On Nov 21, 2011, at 4:13 PM, Charles P. Steinmetz wrote:
> The whole point of the TS2700 is to be a Stratum 1 time source.  See the 
> TS2700 manual at pp. 14 and 113.  The TS2700 clearly sends TOD information -- 
> pretty much every BTMon window contains a TOD display.

Hi Charles,

Thanks very much for the information and your insights. Much appreciated.
Your point above is dead-on. I think the TS2700 is an excellent tool and its
"whole point" is clearly stated and very well executed.

Reading your post, I realize I had misspoke in a previous message using
the term 'dismayed'. The TS2700 gave me exactly what I was seeking, a spare
PRS10. There was a time when I would have also appreciated the T1 input and 
output 1.544 MHz references. I think I rather surprised the local RBOC's 
engineer in our town of 40,000 when I ordered a T1 and 30 voice circuits for
my bedroom back in 1994. As there was no internet service in that town when 
I moved there, I went about changing that.

I regret intimating that the TS2700 is anything less that it purports to be.
The reason for my posts about its internals is to see if it can do more that
what it advertises. Things like a unused cutout in the case with the label 
"GPS" on the inside and a BTMon error message about "PPS too high" makes me
wonder what the TS2700 can do beyond what's documented.

I do wonder about its TOD capabilities. Yes, the time of day is clear in the 
BTmon. Thanks for the explanation of the term "Craft". I see your point
that some time of day information is coming though the RS-232 and Craft outputs.

When I get the Rb back inside the TS2700, I look to see if any signals are 
coming
out of the DE-9F connector labelled as "TOD" on the case. The PDF manual labels
that connector as "Not used." As the BTMon software has a "TOD" option where
one can choose "Cisco" or "NTP" makes me think that there is a precision PPS
signal somewhere on the circuit board. With the error message of "Not 
implemented"
when one chooses "Cisco" or "NTP", my suspicion is output on the TOD connector
wasn't completed in firmware. But, perhaps a precision PPS will even be present
on one of the TOD connector's 9 pins. I look forward to further investigation.

Thanks again for your very informative post.

Kevin




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Re: [time-nuts] Symmetricom 2700 Time Source

[Kevin Rosenberg]

On Nov 20, 2011, at 3:29 PM, Frederick Bray wrote:
> There appears to be a 1pps function.  The test documentation that came with 
> mine showed that step # 22 of the "TS2700 PANEL TEST" was a 1 PPS output test.
> 
> As I recall from prior reading, there appears to be such an output on the 
> PRS10.  It would be interesting to figure out where this was accessed for the 
> TS2700 panel test.

Hi Fred,

The PPS in/out of the PRS10 do not appear to connected to the TS2700
logic board.

I'll look back the the documentation for step #22. I'm not looking for a 
PPS that's just a frequency/period reference, but instead places the PPS
at the GPS PPS position. Perhaps the TS2700 is already do it, but so far,
I've only seed evidence that it's a frequency reference. I was a bit
dismayed that selecting the TOD output as either NTP or Cisco results
in an "unimplemented" error message.

As for the connections between the PRS10 in the TS2700, here's a pinout:

PRS10 Connector  Wire Color  PRS10 function
Pin  4   White   TXD or PHOTO I/V OUT
Pin  6   Green   +24V Heater/Lamp
Pin  7   Red RXD or EFC OUT
Pin  9   Orange  +24V Electronics
Pin 10   Yellow  Ground

The center coaxial 10 MHz output is connected to
the logic board via a white coaxial (RG-178 ?)
cable.

Pin 1 (PPS out) and Pin 5 (PPS in) are not connected.

After I re-install the PRS10 in the TS2700, I'll add wires
to log the RS-232 communication between the TS2700 and the PRS10.

Thanks for sharing your investigation.

Kevin



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Re: [time-nuts] Symmetricom 2700 Time Source

[Kevin Rosenberg]

On Nov 20, 2011, at 2:44 PM, Frederick Bray wrote:
> Looks like the time of day function is not implemented in the 2700.

I hadn't been able to activate it, either. Even with a TOD feature,
the unit would be much more useful to me if it had a PPS output. Perhaps
there is one hidden within.
Kevin


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[time-nuts] Unused/Old stock PRS10's available via Timesource 2700

[Kevin Rosenberg]

Hello Time Nuts,

I was interested in acquiring a second PRS10 Rb/OXCO oscillator. I purchased
one of the "Brand New" Symmetricom Timesource 2700 from the popular auction
site. From the time-nuts archive, there is a single message that the TS 2700
contain a PRS10 unit.

The Timesource 2700 purchase @ $650 yielded what appeared to be a boxed 
Timesource 
2700 unit from 2001. Opening the 2700, there wasn't a speck a dust present in 
the ]
10 year old unit. Indeed, a PRS10 was inside with a manufacture date in 2001 
and a 
firmware of version 3.15 (too old for the TO setting option).

The PRS10 appears to do as well as my 2008 manufactured PRS10 based on the DS 
error
and resonance levels. While the firmware can't set TO to offset sawtooth nsec
from M12M GPS units, it can synchronize to an external PPS signal.

I hope this report helps those interested in acquiring a PRS10.

Kevin, KR5F



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Re: [time-nuts] T-Bolt Companion

[Kevin Rosenberg]

On Nov 5, 2011, at 7:44 PM, Kevin Rosenberg wrote:
> Hi David,
> I got it, thanks!

Heh, wrong reply address. Sorry!

Kevin


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Re: [time-nuts] T-Bolt Companion

[Kevin Rosenberg]

On Oct 27, 2011, at 10:09 AM, David C. Partridge wrote:
> Run, don't walk to: 

Hi David,

I got it, thanks!

Kevin



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Re: [time-nuts] [Solved] Looking simple temperature logging

[Kevin Rosenberg]

Hi List,

Thanks for all the suggestions on monitoring temperature at the location
of the XO. A lot of fine ideas. I found a solution, not inexpensive,
at the same time tvb recommended it to me. It can be placed near
the XO, no construction needed, and continuously outputs data.

Some of the USB monitors with an external probe would work, but I
ended selecting Sparkfun's Weather Station: 
http://www.sparkfun.com/products/10586

So, for my son's project, he can also test whether relative humidity,
air pressure, or ambient light are correlated with XO frequency.

Lastly, it's nice that it's setup to optionally use a XBee ZB radio. 
So, I bought a second one for a sheltered location outside
and will use the radio for monitoring.

Thanks to all,

Kevin



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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp loggi ng

[Kevin Rosenberg]

On Oct 6, 2011, at 3:21 AM, David J Taylor wrote:
>> http://www.g4jnt.com/SerialLogger_ShortForm.pdf
> 
> I couldn't find what sampling rates the device supported, but otherwise I'm 
> keen to acquire one!

Looks like a nice device. I do like continuous monitoring!

>From the datasheet:
  "The interval between measurements can be configured by
   link selection to be in the range 80ms to 5 minutes."

Kevin


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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

On Oct 5, 2011, at 7:49 PM, Jim Lux wrote:
> There's also the Labjack product... http://www.labjack.com/  USB interface 
> for events, ADC, etc.  In the $100 range depending on the model.
> 
> A few years ago when it first came out, it was a pain because it was Windows 
> only, with limited protocol doc.  But now they've got Linux, Mac, Windows, 
> with bindings for just about every language

Cool gadgets. Thanks for the link!

Kevin


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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

On Oct 4, 2011, at 9:10 AM, Bob Bownes wrote:
> If you need a simple/cheap pollable ADC, there is a Velleman kit
> available with USB. Can sample ADC, and a number of discrete inputs as
> well.
> 
> And it can now be found on the wall at Radio Shack, strangely enough.

Hi Bob,

That's nice that it's available down the street, but for reading the LM35
at 0.20 to 0.28 V, the kit's 8-bit resolution will be lower than I'd like.
Thanks for the idea -- I wasn't aware that RS was carrying Velleman kits.

Kevin


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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

On Oct 4, 2011, at 10:16 AM, Tijd Dingen wrote:
> You mentioned wanting to use the parallel port under linux for pps purposes, 
> right?

Hi Fred, I consider it, but tvb's picPET's will work much better for the 
project.

> So if some parallel port programming is acceptable, then you can do the 
> following:
> - get an adc with SPI bus (which means plenty of choice)
> - connect the 3 SPI wires to parallel port
> - bitbang spi (just google "bitbang spi" and you'll find example code. it's 
> pretty simple to do yourself and a fairly forgiving protocol (timing wise))

I like SPI as well and have done a fair bit of AVR bit banging. Doing it though 
the parallel port is intriguing.

> Alternatively you could use a microcontroller with both spi and uart 
> (microchip and atmel have plenty), and use that to serve as uart <--> spi 
> bridge. Or for something like a 10 bit ADC you can use the internal adc of 
> the MCU. 

I'm leaning toward an ATMega168 which has a USART and a TWI interface, 
so simplify programming and work at the byte rather than bit level.

> - get an ADS1258EVM board for about $50
> - bring your own supply voltage
> - bitbang spi on the parallel port
> - bitbang i2c on the parallel port (this is optional for this board, not 
> strictly needed)

That's a nice board. I ended up ordering the PDK version which comes with a some
other features including a USB interface so can skip worrying about having a 
parallel
port on whatever system I'll be using the ADS1258EVM with. Creating a fpga 
interface
like you did is a fine idea, but I'll end up trading some dollars for time with 
the PDK
version.

Kevin



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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

Hi Jim,

Thanks for the thought. I forgot about my Dataq DI-720 which can do 
14-bit ADC. However, I'll need to spend more time looking at their
acquisition software.

I haven't seen a way to have WinDaq/Pro output an ASCII log file, though
the software sheet talks about streaming disk files, it appears to be
their proprietary format. BTW, I have an open-source program called
wdq2wav to convert WinDaq files to .wav files @ http://wdq2wav.b9.com/

I haven't found a simple C API for the unit to allow me to write my 
own logging program for the DI-720.

But, you have a good idea. I should give Dataq a call and find out
what options I have for simple, continuous ASCII logging output.

Kevin

On Oct 4, 2011, at 9:40 AM, Jim Lux wrote:

> On 10/4/11 8:03 AM, Kevin Rosenberg wrote:
> 
>> So, if you know of any simple ADC to UART firmwares available, that'd
>> be great so he can just reference someone else's code. The picPET
>> is a perfect device at the perfect time. But, we can't rely on tvb
>> to come up with a 'picADC' at a similarly serendipitous time.
>> 
> 
> DATAQ
> 
> http://www.dataq.com/products/startkit/di145.html
> 
> $29, 4 channel 10 bit ADC with USB  interface
> 
> You'll need to cobble up a sensor, of course, and I don't know if the 
> resolution of the di145 is good enough (20mV/LSB as I recall) for a LM335 
> (10mV/Kelvin?).  One thing you get with cheap is a +/- 10V full scale range.
> 
> A thermistor and resistor into the DATAQ might work better.
> 
> Maxim/Dallas One-Wire devices are another possibility  There's tons of PIC 
> code out there to interface to them.  The sensors are cheap (few bucks, 
> depending on whether you buy raw device, or you get one potted with a cable)  
> Sparkfun.com has them, among other places.
> 
> 
> There's also a whole raft of USB temperature loggers out there from Onset 
> (HOBO) or DataQ or a variety of other companies.  They tend to run in the $80 
> range  (if someone knows about a battery powered temperature logger in the 
> under $25 range, I'd love to hear about it)
> 
> And, of course, a DMM with a RS-232 interface is another possibility
> 
> 
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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

Hi Didier,

Thanks for the idea. I haven't done any 8051 programming, but the price is 
great and you
list other advantages on your web site. I appreciate the recommendation.

Kevin

> A cheap way to measure temperature that will also be a good learning exercise 
> would be to use a Silabs Toolstick. Most of their chips have a built in 
> temperature sensor and a demo ADC program that spits out the temperature over 
> the serial port emulated USB interface.
> 
> The toolsticks are all about $10 and you need a Base Adapter that is $15 I 
> believe. The tools are free (demo, size limited Keil compiler, or the free 
> unlimited SDCC)
> 
> More info on my web site in the Wiki
> 
> http://www.ko4bb.com
> 
> Alternately, you can buy a USB temperature sensor on eBay for about $10 I 
> believe, but you won't learn much by using it...
> 
> Didier KO4BB
> 
> Sent from my BlackBerry Wireless thingy while I do other things...
> 
> -Original Message-
> From: Kevin Rosenberg 
> Sender: time-nuts-boun...@febo.com
> Date: Tue, 4 Oct 2011 09:03:56 
> To: Discussion of precise time and frequency measurement
> Reply-To: Discussion of precise time and frequency measurement
>   
> Subject: Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging
> 
> On Oct 4, 2011, at 4:36 AM, Hal Murray wrote:
>> In California, the diurnal temperature swings are big enough to be useful. :)
> 
> Here in New Mexico as well, useful or ruinous depending upon your application.
> Hence, I believe, your smiley face above ;)
> 
>> The swing would be much bigger outside, especially with an open sky.
> 
> We thought about an outdoor light and temperature sensor when my son
> considered measuring the stability of the PPS signal from a NetClock/2
> WWVB receiver. But, we'll be measuring the temperature near the indoor XO.
> 
>> I was thinking of keeping track of when you expected each pulse to arrive 
>> next and sleeping until a little before you expected the soonest one.  
>> (Adjust "a little" by trial and error.)
> 
> Sure, and the solution becomes more interesting the more pulse lines that
> are being polled.
> 
>> I agree that Tom's picPET will be a fine way to do it.  I was just playing 
>> with how to do it with the parallel port.
> 
> I lot of fine ideas come from thought experiments.
> 
>> It's still an interesting question of how accurate you need to measure the 
>> time.  That's probably a good one to work through with your son on the back 
>> of an envelope.
> 
> I think so, too. So, my son will be learning more about stability, Allan
> deviations, modified Allan deviations (which should be more useful for 
> the number of averaging points over a month), and improving his exponent
> skills.
> 
> Another statistic he'll be learning is the Pearson correlation coefficient
> to compare temperature (probably in Kelvin) to the XO frequency. The more
> precisely those are measured, the more likely the Pearson will reflect the
> true correlation.
> 
>> How are you measuring temperature?
> 
> Good question, because we haven't completely solved that. We'll be using
> a LM35CAH mounted next to the 32768 crystal and measuring the
> voltage once a second.
> 
> What I haven't decided is whether to have my son use the 34401A and GPIB
> polling via a Prologix adapter versus a simple MCU firmware using a 2.5V
> reference voltage and a 10-12 bit ADC and outputs the ADC result either
> once a second, or in response to a pulse (probably from the PPS of the XO).
> The first has merits of accuracy and simplicity, but I prefer he use
> more affordable devices than the 34401A in his experiment to even his 
> project compared with other students. The latter has the advantage of 
> price, but the disadvantage of me writing the firmware (though, the 
> firmware is almost trivial). But again, I'd like him to be as 
> independent as possible.
> 
> So, if you know of any simple ADC to UART firmwares available, that'd
> be great so he can just reference someone else's code. The picPET
> is a perfect device at the perfect time. But, we can't rely on tvb
> to come up with a 'picADC' at a similarly serendipitous time.
> 
> Kevin
> 
> 
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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

Hi Chris,

select is a great idea, but I think I'll be using cygwin which doesn't
appear to have an emulation of select on Windows.

Kevin

On Oct 4, 2011, at 10:23 AM, Chris Albertson wrote:

> On Tue, Oct 4, 2011 at 3:36 AM, Hal Murray  wrote:
>>> The temperature swings won't be large, just the usual diuneral indoor 
>>> cycles.
>> 
>> In California, the diurnal temperature swings are big enough to be useful. :)
>> 
>> This is what ntp sees the main/CPU crystal doing in a non airconditioned
>> room.  Each color is a different day.
>>  http://www.megapathdsl.net/~hmurray/ntp/slope.gif
>> 
>> The swing would be much bigger outside, especially with an open sky.
>> 
>> 
>>> Since we'd be measuring 4 PPS signals that won't be in phase, I wasn't
>>> planning on sleeping for long. But, I some 10 usec sleeps with usleep(1)
>>> after reading a pulse would be reasonable. But, with the system not doing
>>> anything  but polling and writing to the disk, I wasn't expecting much
>>> interruptions from other processes.
>> 
>> I was thinking of keeping track of when you expected each pulse to arrive
>> next and sleeping until a little before you expected the soonest one.
>> (Adjust "a little" by trial and error.)
> 
> This is a UNIX-like system?  If so use a "select" on the file
> descriptor(s).This system call allows you to sleep until there is
> data available on one of a set of files.   See "man 2 select"
> 
> The code right after the select() has to poll all the files to see
> which one has data, your read/process it then go back an wait/sleep.
> If you do poll after a fixed length sleep you will on average to 1/2
> of a polling cycle late reading the data and also you waste time
> checking when nothing is there.
> 
> Chris Albertson
> Redondo Beach, California
> 
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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

On Oct 4, 2011, at 11:42 AM, Mark Sims wrote:
> Use an LM34 sensor,  not the LM35.  It has twice the resolution per volt 
> since it outputs in degrees F,  not degrees C.

That's a good idea. That's one issue that I have with a 10-bit ADC common to 
many MCUs, is the
low voltage of 0.20 to 0.28 mV in the office.

> Better yet,  use the DS1620 (old revision) that is used on the Tbolt.  It has 
> a digital interface.  It will give you around 0.01C res without any ADC 
> conversion noise, etc.

That's a good idea. In fact, I saw that I have some DS1631 samples on the shelf.
I like that idea as that can be bit-banged by a simple, small MCU on same
board as the XO.

Thanks for the thoughts, Mark!

Kevin


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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

On Oct 4, 2011, at 4:36 AM, Hal Murray wrote:
> In California, the diurnal temperature swings are big enough to be useful. :)

Here in New Mexico as well, useful or ruinous depending upon your application.
Hence, I believe, your smiley face above ;)

> The swing would be much bigger outside, especially with an open sky.

We thought about an outdoor light and temperature sensor when my son
considered measuring the stability of the PPS signal from a NetClock/2
WWVB receiver. But, we'll be measuring the temperature near the indoor XO.

> I was thinking of keeping track of when you expected each pulse to arrive 
> next and sleeping until a little before you expected the soonest one.  
> (Adjust "a little" by trial and error.)

Sure, and the solution becomes more interesting the more pulse lines that
are being polled.

> I agree that Tom's picPET will be a fine way to do it.  I was just playing 
> with how to do it with the parallel port.

I lot of fine ideas come from thought experiments.

> It's still an interesting question of how accurate you need to measure the 
> time.  That's probably a good one to work through with your son on the back 
> of an envelope.

I think so, too. So, my son will be learning more about stability, Allan
deviations, modified Allan deviations (which should be more useful for 
the number of averaging points over a month), and improving his exponent
skills.

Another statistic he'll be learning is the Pearson correlation coefficient
to compare temperature (probably in Kelvin) to the XO frequency. The more
precisely those are measured, the more likely the Pearson will reflect the
true correlation.

> How are you measuring temperature?

Good question, because we haven't completely solved that. We'll be using
a LM35CAH mounted next to the 32768 crystal and measuring the
voltage once a second.

What I haven't decided is whether to have my son use the 34401A and GPIB
polling via a Prologix adapter versus a simple MCU firmware using a 2.5V
reference voltage and a 10-12 bit ADC and outputs the ADC result either
once a second, or in response to a pulse (probably from the PPS of the XO).
The first has merits of accuracy and simplicity, but I prefer he use
more affordable devices than the 34401A in his experiment to even his 
project compared with other students. The latter has the advantage of 
price, but the disadvantage of me writing the firmware (though, the 
firmware is almost trivial). But again, I'd like him to be as 
independent as possible.

So, if you know of any simple ADC to UART firmwares available, that'd
be great so he can just reference someone else's code. The picPET
is a perfect device at the perfect time. But, we can't rely on tvb
to come up with a 'picADC' at a similarly serendipitous time.

Kevin


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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

On Oct 3, 2011, at 12:59 PM, Hal Murray wrote:
> Why do you need microsecond resolution?
> 
> A junk XO will drift ballpark of 1 PPM per C.  That's 86 ms per day or 3.6 ms 
> per hour.

The temperature swings won't be large, just the usual diuneral indoor cycles.
He wants to use compute much much of the frequency change can be explained
by temperature alone, we were going to measure temperature and frequency
as precisely as is reasonable cost. So, it would be nice to measure a
microsecond difference in a second if the temperature very suddenly changed
by 1 degree C.

> What sort of resolution do you think you can get from a parallel port?

I think the point it moot now that tvb has the very useful picPET for
this application. I think resolution will depend upon the load of
the OS. I was going to use an old PC running linux and no graphics
mode. I think sub-millisecond stability is a reasonable expectation.
So, probably need to use fatPPS for the 10 usec PRS10 PPS.

> It might be fun to see how far you can push the parallel port.
> How about a loop like this: [...]

Yes, that about the flow that I was contemplating. I also planned
to use optoisolators on the input pins from the readings I did
on interfacings with a parallel port.

> For extra credit...  Suppose  you are expecting PPS type signals and you know 
> roughly where they are located within a second.  There is no point is 
> spinning when you aren't expecting something to happen.  So you can sleep 
> until a bit before the next event.   That will let the scheduler run other 
> jobs.  Hopefully it will be nicer to you when you do want to run.

Since we'd be measuring 4 PPS signals that won't be in phase, I wasn't planning
on sleeping for long. But, I some 10 usec sleeps with usleep(1) after
reading a pulse would be reasonable. But, with the system not doing anything 
but polling and writing to the disk, I wasn't expecting much interruptions from
other processes.

But, I really like Tom's picPET, not just for this project, but after my son's
project, I'm going to use 4 picPETs to measure stability across my group of 
Thunderbolts of varying vintage as well as comparing long-term drift across
some Rb oscillators.

Thanks again for the excellent parallel polling idea. I was going to go
with that plan before Tom letting me know about his picPETs.

Kevin


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Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging

[Kevin Rosenberg]

Thank you to everyone for their thought answers and insights, they gave
me some great ideas. I was thinking about the parallel port polling idea,
but then my son wanted to measure the relation between temperature and XO
frequency, so we needed microsecond resolution.

tvb came up with just the perfect solution:
  - Cheap, $5 per part
  - Easy for my son to construct, an 8-pin PIC and a bypass capacitor for
each PPS line
  - Easy to analyze results, one ASCII text line for each input pulse
  - Continuously counting indefinitely
  - sub-microsecond resolution (useful for measuring tempc for an XO)

Thanks again to everyone for their good thoughts and valuable time
spent considering my question.

Kevin



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Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs

[Kevin Rosenberg]

On Sep 28, 2011, at 5:46 PM, Chris Albertson wrote:
> Counters will not log the time of a pulse but they will continuously
> measure time intervals.And the interval might be "time from the
> last tick ofthe second."  So you 'd use the  Rb's PPS to trigger the
> "start" channel and the device under test to trigger the "stop"
> channel.  the counter measures the time difference.  You don't care
> what the difference is but only how it changes over time. If the
> pulses are going at different rates you will see the times get longer
> and long and then very short.   later you figure out the "beat
> frequency" and then you have the rate of the DUT.

Thanks, Chris, that makes sense. I considered recommending my DTS-2077 
using a phase difference method like that. But, one of the goals is 
to count all PPS cycles, not just the rate of the DUT, especially if one 
of the oscillators is less stable than expected.

> A Thunderbolt will do as well as Rb.

For timing purposes, sure. In the thread, also talked about the benefits 
of NTP. Nonetheless, my son wants to use the Rb and (more importantly) 
understand some of the physics of the Rb. So, while the Rb as a long-term
reference isn't as good as NTP +/- Thunderbolt, it intrigues him. 
That's good enough for me to help him with his goal.

Kevin


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Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs

[Kevin Rosenberg]

Hi Bob,

That's a fine solution that wins on re-use of old PC's and scalability of 
inputs. 
Obviously over the course of days, NTP is superior to an Rb clock, but my son
really wants to use the Rb for reference time. I suppose we could read the PPS
from the Rb to compare to the other two PPS lines, though. Could be a winner.
In fact, if don't use NTP to discipline the local clock, we can use the local 
clock
as a measurement of a the stability of a quartz oscillator for his project.

Not having used counters much, I'm a little surprised they can't do continuous
logging. I suppose their strengths, though, are in triggering and gating.

Kevin

Sent from my iPad

On Sep 28, 2011, at 3:28 PM, "Bob Camp"  wrote:

> Hi
> 
> For milliseconds, route the signals into a hard wired parallel port (not
> USB) and sample the data. Looking at it 1K times a second is pretty easy.
> All software running on a tired old PC. Sync the thing up with NTP or what
> ever to keep it stable long term.
> 
> Bob
> 
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Kevin Rosenberg
> Sent: Wednesday, September 28, 2011 3:56 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Looking for off-the-shelf device to
> timestampmultiple PPS inputs
> 
> On Sep 28, 2011, at 1:21 PM, Chris Albertson wrote:
>> Milliseconds?  So why are we talking about HP counters and PicTic and
>> so on.  A basic low end Linux system that is controlled by NTP and a
>> GPS receiver is maybe about 100X better than your requirements.
>> (I figure you are looking for about 1000 parts per million, NTP is way
>> better then that if you have a local GPS)
> 
> 
> Heh! I suppose milliseconds don't really belong on time nuts, they're in
> the range of polling! But, for his needs, that's sufficient resolution. 
> What would be nice is if the PPS times would just "show up" log file for
> him. Hence, the request about off-the-shelf hardware.
> 
> But, as long as I'll be looking at buying some new hardware, I'd be glad to
> get 
> resolution of nanoseconds or better. Probably best sigma for the price will
> be 
> the XMega with 32 MHz input from Clockbox with a sigma of 31ns. I've written
> more
> than my share of microcontroller firmwares. But, I feel strongly that he
> should do 
> as much of the project as he can himself. So, I'll be teaching him some more
> C, 
> but I'd like that at around the level of GPIB programming and fprintf rather
> than 
> low-level XMega or other micro-controller programming.
> 
> So, if there was a way for the 53230A to do this, it sure would have a
> pretty
> display that he'd like (and a 20 ps single-shot resolution that I'd like).
> 
> Yes, I have some thunderbolts that I've used with some Soekris
> net4501's+nonoBSD
> and they're great. But, he's keen on using an the PRS-10 for his reference
> clock. Something about the term "atomic", I'm sure. And, since we're just
> talking 
> milliseconds(!) over a month or so, then the PRS-10 will do well without any
> GPS disciplining.
> 
> Kevin
> 
> 
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Re: [time-nuts] Looking for off-the-shelf device to timestamp multiple PPS in...

[Kevin Rosenberg]

On Sep 28, 2011, at 1:05 PM, ewkeh...@aol.com wrote:
> It takes less than an hour to assemble I do one in twenty minutes,  
> programming the PICs takes me the longest, because I am not good at it.

Thanks for the time estimate, Bert. As long as we're building
the opto-isolated, divide-by-120 ZCD, what's a few more minutes?
Plus, it's nice the firmware is already written. I have some PIC
programmers, but haven't spent as much time with them as AVR JTAG.
But, like you, they get the job done eventually.

Kevin


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Re: [time-nuts] Looking for off-the-shelf device to timestamp multiple PPS inputs

[Kevin Rosenberg]

On Sep 28, 2011, at 1:21 PM, Chris Albertson wrote:
> Milliseconds?  So why are we talking about HP counters and PicTic and
> so on.  A basic low end Linux system that is controlled by NTP and a
> GPS receiver is maybe about 100X better than your requirements.
> (I figure you are looking for about 1000 parts per million, NTP is way
> better then that if you have a local GPS)


Heh! I suppose milliseconds don't really belong on time nuts, they're in
the range of polling! But, for his needs, that's sufficient resolution. 
What would be nice is if the PPS times would just "show up" log file for
him. Hence, the request about off-the-shelf hardware.

But, as long as I'll be looking at buying some new hardware, I'd be glad to get 
resolution of nanoseconds or better. Probably best sigma for the price will be 
the XMega with 32 MHz input from Clockbox with a sigma of 31ns. I've written 
more
than my share of microcontroller firmwares. But, I feel strongly that he should 
do 
as much of the project as he can himself. So, I'll be teaching him some more C, 
but I'd like that at around the level of GPIB programming and fprintf rather 
than 
low-level XMega or other micro-controller programming.

So, if there was a way for the 53230A to do this, it sure would have a pretty
display that he'd like (and a 20 ps single-shot resolution that I'd like).

Yes, I have some thunderbolts that I've used with some Soekris net4501's+nonoBSD
and they're great. But, he's keen on using an the PRS-10 for his reference
clock. Something about the term "atomic", I'm sure. And, since we're just 
talking 
milliseconds(!) over a month or so, then the PRS-10 will do well without any
GPS disciplining.

Kevin


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Re: [time-nuts] Looking for off-the-shelf device to timestamp multiple PPS in...

[Kevin Rosenberg]

On Sep 28, 2011, at 12:21 PM, ewkeh...@aol.com wrote:
> look at the attached description of the 5 channel counter system that I use 
> on my Dual Mixer it does what I call pseudo time stamp. Counters are 
> always  counting. Code and write up courtesy of Richard McCorkle.

Thanks, Bert -- looks interesting! I'm enjoying read it. But, I'd like
to find something not requiring much construction so that my son can
do the project on his own.

Kevin


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Re: [time-nuts] Looking for off-the-shelf device to timestamp multiple PPS in...

[Kevin Rosenberg]

On Sep 28, 2011, at 12:34 PM, Chris Albertson wrote:
> There are much cheaper counters on eBay the HP5328 goes for $100 more or less.

That's a nice price. I hadn't looked at that unit, just the PM8660/B (since 
I own one) and the 53230A (since I want one).

I'll be glad to read the manual for the HP5328, but for the above two
counters, I couldn't find a way to have the unit continuously counting
which report the period of every PPS pulse. There'd be some delay while
the gate re-arms it. Is there something I'm  missing? I'd love to use an 
off-the-shelf counter so my son can do all the work himself. Though, 
perhaps I'll need to help him with his hardware skills.

>> 5) ... I haven't
>> enough experience running FreeBSD  or Linux on ARM to know how well
>> this will work for me.
> 
> All those billions of Android phones and tablets are all Linux on Arm
> if you look inside.

Sure, I meant I didn't know how much work it'd take for me to get the
PPS API kernel feature working an ARM platform or if I'd have to
try a few difference development boards to get PPS working on the board.

> One other option.  What about a PicTic II?  It is basically you micro
> processor option but it's less work because someone else has already
> written the uP software and made a PCB..  But they cost $50 to build
> and the HP5328 counter is in that same price range.

PicTic II is an interesting idea, I haven't look at it's features
in close to two years, so I should revisit it!

Thanks for your ideas, Chris!

Kevin


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Re: [time-nuts] Looking for off-the-shelf device to timestamp multiple PPS inputs

[Kevin Rosenberg]

On Sep 28, 2011, at 12:19 PM, Hal Murray wrote:
> What sort of accuracy and/or resolution do you want/need?

Whoops, left out that critical piece of information!
It's for my son's project, he'll be looking at deviations probably
no shorter than one 1 sec, so milliseconds will be plenty for him.

>> 7) Use a box like in #5, and capture the PPS from the PRS-10 as well and
>> using that to scale the other PPS inputs that arrive around the same time. 
> 
> If you have a Linux box handy, that one is easy to try.

I agree. That idea was listed last because I came up with it while describing
the other options that I considered. I do have a linux box with a 4-port PCI
serial port that seems to be supported by the kernel's PPSAPI.

> After the 60Hz grab-every-cycle experiment, I started collecting every-cycle 
> data for PPS signals.  I have a box  with 3 PPS signals: one from a Z3801A 
> and 2 from low cost GPS units.
> 
> I can send you some files if you want to investigate.  (5-6 megabytes per day)

Thanks, I would be interested. One of the PPS signals will be 60 Hz mains, but 
probably will use two ICs to divide it by 60 to simplify the analysis for him
and keep all his signals nominally 1 Hz.

> I'll have to make some graphs.  The ballpark is several microseconds of 
> noise, but that's on top of your system clock offset.  I think it would be 
> easy to see 10 microseconds of offset.  You would have to work harder to see 
> smaller numbers.

That'd be more than enough resolution for him. The main thing I was hoping for 
was something simple to use, without much construction, so that he can do the 
project himself.

> Reminder: Your system may have troubles catching 10 microsecond PPS signals.  
> TAPR says "no longer available" for the FatPPS.  I poked John.  He was going 
> to see if they could build another batch.

Your quite right about the PRS-10 PPS pulse, 10 us was obviously too fast for 
the
Soekris with a kernel timing frequency of 1000 Hz. I wasn't aware that FatPPS
had gone "no longer available". Makes me glad that I got mine last year along
with a TADD-1 which was also discontinued. That was considerate of you to 
mention
it to John to assist others who have such brief PPS pulses.

Thanks the great thoughts, Hal!

Kevin


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[time-nuts] Looking for off-the-shelf device to timestamp multiple PPS inputs

[Kevin Rosenberg]

Hello esteemed time nuts,

I'm looking for device with an external clock input as well as inputs
for multiple PPS signals that outputs timestamped messages for each
input pulse via RS232. The initial need will be for two PPS inputs.
I've considered a number of options, but I wonder if there a more
prepackaged solution available since the device will for someone less
technical than myself.

A bit more about the device. It needs to be clocked with an external
reference. Ideally, taking 10 Mhz sine from the PRS-10, but I can
easily enough convert the sine wave that to a square wave.  Also, I
can use a TAPR ClockBox to convert to other reference frequencies.

The purpose of the device will be to measure PPS periods for at least
two oscillators over a course of a few months, sending the data via
RS-232 to a logging computer for each input PPS input. The minimum the
serial record will need to have is a time stamp of seconds.nanosecons
and a label of which PPS signal triggered.

About options I've considered,

1) A Soekris 4501 clocked by the PRS-10 to a ClockBox, and then using
the TMR1IN and a GPIO input to time stamp the PPS signal. However,
that'll require one 4501 for each PPS signal, so scaling effort is
moderate.

2) Writing a firmware for an AVR XMEGA that is clocked from the PRS-10
and uses external interrupts and timers to output RS-232
messages. Certainly less expensive than #1 option, but takes more
time programming.

3) Using some other micro-controller with external clock and times,
perhaps an ARM.

4) Using a dedicated time counter for each PPS. However, reading the
manual for my PM6680/B as well as a Agilent 53230A, that won't work
because in standard gating mode, some time would be missed between PPS
signals. While the 53230A has a continuous mode, that would require
the polling computer to accurately keep time of the requests unless
the 53230A is collecting data under its 1,000,000 sample limit (only
~11 days at a PPS). Also, at $3500 per PPS input, a 53230A is the
most expensive to scale..

5) Using a FreeBSD or Linux box with multiple RS-232 inputs and using
their PPS API.  However, outside of some ARM boards, I haven't found
any boxes that can be clocked by a external reference. And, I haven't
enough experience running FreeBSD or Linux on ARM to know how well
this will work for me.

6) I'm quite familar with using something like a Thunderbolt and its
PPS to make a stable clock with NTP which could be used with an Intel
FreeBSD or Linux box in #5. However, rather than NTP, the device
should be clocked only by the external reference clock. The goal is to
see how the input PPS signals deviate from the reference clock.

7) Use a box like in #5, and capture the PPS from the PRS-10 as well
and using that to scale the other PPS inputs that arrive around the
same time.

I've done web searches, found some data loggers, but I haven't found
something that can run continuously for months collecting data and
meet the other needs. I'd really like to find a more prepacked
solution for the user of this device. I'm surprised by my inability
find such a device for this seemingly straightforward task.

Thanks for considering the issues. I feel I'm overlooking some perfect
device that exists outside of just my imagination.

Kevin

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Re: [time-nuts] Distribution amp

[Kevin Rosenberg]

On May 11, 2011, at 8:25 AM, John Ackermann N8UR wrote:
> Yes, unfortunately the MAX477 line driver chip that we used in the TADD-1 has 
> become unobtanium, and there's no drop-in replacement.
> 
> I'm (very slowly) working on a new distribution amp that will replace the 
> TADD-1 and have significantly better specs, but I'm hesitant to give an ETA 
> yet.

Will the new design also be based on a high-speed op amp, or have
you come up with a different amplification/isolation design to 
achieve the better specs?

Thanks for the TADD-[123], I've been pleased with all of them.

Kevin


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[time-nuts] IEEE 1588 PTP transceiver chip announced by NatSemi

[Kevin Rosenberg]

For those interested, from http://www.national.com/pf/DP/DP83630.html

The DP83630 Precision PHYTER® device delivers the highest level of precision 
clock synchronization for real time industrial connectivity based on the IEEE 
1588 standard. The DP83630 has deterministic, low latency and allows choice of 
microcontroller with no hardware customization required. The integrated 1588 
functionality allows system designers the flexibility and precision of a close 
to the wire timestamp. The three key 1588 features supported by the device are:

— Packet time stamps for clock synchronization

— Integrated IEEE 1588 synchronized low jitter clock generation

— Synchronized event triggering and time stamping through GPIO

DP83630 offers innovative diagnostic features unique to National Semiconductor, 
including dynamic monitoring of link quality during standard operation for 
fault prediction. These advanced features allow the system designer to 
implement a fault prediction mechanism to detect and warn of deteriorating and 
changing link conditions. This single port fast Ethernet transceiver can 
support both copper and fiber media.

Kevin, KR5F



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Re: [time-nuts] advice: frequency calibration to 1 ppm possible without GPSDO?

[Kevin Rosenberg]

On Feb 18, 2011, at 3:25 PM, Mike S wrote:
> I'd think one of these should work, for a buck plus shipping:
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=S9009E-05-ND
> 
> I used one similar to that, soldered on the appropriate wires, then used some 
> corona dope to insulate and reinforce the connections.

I bought one of these: 
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SAM8219-ND
These aren't cheap at $11. But, you can get two assemblies by cutting the cable 
in the midpoint.
Each half has 6" of free cable. 

Kevin
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Re: [time-nuts] Thunderbolt Supply

[Kevin Rosenberg]

On Feb 12, 2011, at 8:16 PM, Mark J. Blair wrote:
> my setup eventually, when I feel a surge of time-nuttiness coming on. :) Even 
> in its current configuration, it far exceeds my needs for a frequency 
> reference.

Exceeding your needs? Doesn't seen like that surge of time-nuttiness has hit 
yet ;)

Kevin
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Re: [time-nuts] Thunderbolt Supply

[Kevin Rosenberg]

On Feb 12, 2011, at 3:12 PM, Bruce Griffiths wrote:
>  Cuk switching regulator

Thanks for the tip!

Kevin


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Re: [time-nuts] Thunderbolt Supply

[Kevin Rosenberg]

On Feb 11, 2011, at 9:44 PM, Neville Michie wrote:
> [...]For the minus 12v I used a ICL7662, these are rare, so a cmos gate 
> oscillator and diode pump negative generator could be used. I am told the 
> -12V is quite uncritical.[...]

Thanks for the thoughts. I'm thinking about redoing the power supplies for my 
T-bolts.
So, your comments are helpful.

May I ask where is the ICL7662 rare? Digikey has over 20K in various forms.

I've also heard that the 5V supply is not noise critical. For your minimum 
power goal,
I imagine that's why you used a switcher rather than lose up to 0.4A x 7V 
(2.8W) using
a linear 5V regular off the +12V line.

Kevin


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Re: [time-nuts] cheap antenna

[Kevin Rosenberg]

On Jan 21, 2011, at 4:52 PM, Jerry wrote:
> I would like to thank everyone on the list who helped me get through
> the problems with my 58503 and the suggestions that resulted in my
> []
> getting a Trimble Tbolt which is now up and working.  Someone a bit
> back was looking for a cheap antenna and while waiting for my used HP
> antenna to come from China I happened across a good cheap antenna at
> Frys Electronics for $29.99.  It is a Gilsson Technologies FME
> universal GPS antenna.  It works well with my Tbolt getting up to 8
> [...]

Jerry, I'm glad that it worked well on your Tbolt. I tried using
a Gilsson FME1S09B090 Universal High Performance GPS Antenna with
a SyncServer S200, but I got current overload (IIRC, that'd be 80ma+).

I'm glad to hear that I'll be able to use mine with one of my tbolts!

Kevin


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Re: [time-nuts] Achievable temperature stability for Thunderboltenvironment

[Kevin Rosenberg]

On Jan 16, 2011, at 9:00 PM, Mark Sims wrote:
> There is some info on implementing the temperature controller in the comments 
> at the start of the file heather.cpp

Hi Mark,

Thanks very much for the information. I wasn't actually aware that Heather was 
open-source.
That's great as I can read the source for all the details I need. Your comments 
will help me 
move more quickly towards optimal results.

I like the idea of the DC relay to control the cooling fan.

Thanks for your input!

Kevin


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Re: [time-nuts] Achievable temperature stability for Thunderboltenvironment?

[Kevin Rosenberg]

On Jan 16, 2011, at 4:46 PM, WarrenS wrote:
> I don't know if this low resolution picture will post correctly.
> If anyone wants a high resolution view of the H/W,
> or an expanded plot showing the results over a 2 week period, 
> I can provide them, if someone will send me the name of a site to post them 
> at.

The photo and schematic were clear, thanks for posting! I see that you have
the fan controlled by pin 4 of the RS-232. Is there a mechanism in Lady Heather
to control pin 4 (DTR) based on temperature readings? Or, maybe you monitor the
temperature and control pin 4 with some other monitor/control program using an
output different that the RS-232 port controlled by Lady Heather?

Anyway, that's a great looking temperature plot, and the implementation is 
nicely
simple. Lots of bang for that buck!

Kevin


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[time-nuts] PRS-10 / GPS PPS discipline program

[Kevin Rosenberg]

Hello,

I was inspiring by PHK's post of his open-source GPIB monitoring system to 
mention
that I'm working on remote monitoring and control of my newly acquired PRS-10.
I've read the posts in the lists archive about how the discipline against a
GPS external PPS is not optimal.

I've been working on a C program to display the parameters from my PRS-10 and 
present its state 
in logical blocks with conversion of raw values to real-world voltages and 
frequencies. 
That's inspired by Brooke's screenshots of his LabView program. However, since 
I want to
do remote monitoring, I'm using ncurses to layout the full-screen display so I 
can monitor
with ssh to my monitoring system. When I get done with that, I'll post it as 
open-source
to my git repository at http://git.b9.com. 

However, the monitoring is only a portion of what I want the program to do.
I'd also want to add reading from a M12+T's sawtooth correction to get
better short-term stability of the PRS-10's PPS signal. 

Does anyone have a code sample or general thoughts about what to monitor on the 
PRS-10
and the GPS PPS signal and how to get better short-term stability out of the 
PRS-10's
PPS signal that using the PRS-10's firmware alone?

Thanks,

Kevin
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Re: [time-nuts] "PYLT" Python LabTools

[Kevin Rosenberg]

On Jan 16, 2011, at 3:00 AM, Poul-Henning Kamp wrote:
> I have created a Github project for the Python Labtools I'm using
> to deal with my instruments.

Looks nice. While GUI tools like LabView have their role, I'm more often 
interested in remote
monitoring and control.

Probably the next thing I'd add to your system is the ability to select my 
Prologix ethernet
controller, rather than the USB controller.
I'll send you a patch when that is done (unless I just buy a Prologix USB for 
simplicity sake).

Thanks for sharing your work!

Kevin


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Re: [time-nuts] Yes, Virginia, $200 5370B's do happen

[Kevin Rosenberg]

On Jan 6, 2011, at 4:38 PM, Bob Bownes wrote:
> After the discussion a few weeks ago, I started looking for a 5370. In
> [...]
> Only a full checkout will tell, but so far, I'm pretty optimistic.

Wow, Bob -- great story and great price. Nice pickup on finding photo
evidence of the PS voltage switch being incorrectly set.

I was looking at 5370's last week. I ended up with a buying a Wavecrest
DTS 2075-2. But, heck, getting a 5370 for 0.1x the cost of the DTS, I'd 
take that deal anyday!

Thanks for sharing,

Kevin, KR5F


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Re: [time-nuts] My Garmin 18x, Ver 3.50, currently 1 second slow to UTC

[Kevin Rosenberg]

On Jan 5, 2011, at 4:08 AM, Kiwi Geoff wrote:
> I have "reverted" quite a number of times now Kevin - trying to
> understand why the 18x can be 1 second slow. I have never had an issue
> putting in an older version into the 18x, the updater software does
> know what your doing, it says:

Hi Geoff (of Kiwiland),

Thanks for the information and testing. Having had my 3.50 18x and 
NTP report that NMEA time is -1.00 seconds compared to PPS time, 
I'll give 3.20 a whirl.

I've certainly bricked my share of devices by attempting to 
"reverse the timeline" of firmware images. Manufacturer's have 
cavalierly deemed  such attempts to install an older firmware image 
as being "unsupported". I tend to think of it more of as programmers, 
for reasons as diverse as lack of time, talent, technology, or 
imagination, who create insufficiently robust installers.

It's very nice of you to actually test going from 3.50 to 3.20 for
the rest of us.

Kevin (of New Mexicoland)



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Re: [time-nuts] My Garmin 18x, Ver 3.50, currently 1 second slow to UTC

[Kevin Rosenberg]

On Jan 5, 2011, at 1:15 AM, David J Taylor wrote:
> [...]
> The Garmin rep who wrote to me suggested that Garmin were unaware of the 
> problem, but would investigate it.  Could I urge you all to report this 
> problem to Garmin, please, so that we have a greater chance of getting a fix 
> in the next firmware upgrade?

David, that's a fine idea. Do you have an email address (or other contact info)
where our reports of this issue have a greater chance of getting to the firmware
group compared to being forwarded to a write-once, read-never file?

Kevin



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Re: [time-nuts] My Garmin 18x, Ver 3.50, currently 1 second slow to UTC

[Kevin Rosenberg]

I agree, very helpful, thanks Joseph!

I recently got two 18x that I upgraded to 3.50. (I'm starting to work on
integrating some M12+T modules to supplement/replace the 18x's).

Has anyone had trouble with reverting firmware upgrades on Garmin products? 
Of course, feedback on going back from 3.50 to 3.20 on an 18x would be most 
specific to my situation.

Thanks in advance!

Kevin Rosenberg
KR5F

On Jan 4, 2011, at 9:29 PM, Joseph Gray wrote:

> Geoff,
> 
> Thanks a lot for comparing firmwares. That hard information helps 
> tremendously.
> 
> Joe Gray
> W5JG
> 
> On Tue, Jan 4, 2011 at 8:46 PM, Kiwi Geoff  wrote:
>> Joseph Gray wrote:
>>> If I am using the NMEA data (as in the Garmin is the only time
>>> source), what firmware is recommended by all those using a GPS18x-LVC?
>> 
>> I thought I would run some tests for you Joe, using Version 3.0 and 3.2
>> 
>> Although I myself have run version 3.0 for a number of months (when it
>> first came out in 2009) without issues, I take note of what Kasper
>> Pedersen wrote about his experience  - so I have now loaded version
>> 3.2 into my 18x, rather than any newer version (until Garmin fix the
>> NMEA latency issue).
>> 
>> I ran my tests for 2 hours each (7,200 one second samples) with GPS
>> sitting on an inside window sill with a very limited view of the sky,
>> so my readings should be taken as perhaps worse case rather than from
>> a perfect view of the sky. The GPS was using 9 - 10 satellites for the
>> fix solution during the test.
>> 
>> The RF sensitivity of the 18x is much better than the Garmin 18.
>> 
>> I measured the time of the "START" character ($) of the $GPRMC
>> sentence and  the "LAST" 0x10 (Linefeed) character, GPS 18x set to
>> 4800 Baud.
>> 
>> Following times are in milliseconds from the leading edge of the 1PPS marker.
>> 
>> Version 3.00 firmware for Garmin 18x
>> START Min =  365
>> START Avg =  427 (N = 7200)
>> START Max =  499
>> LAST Min =   513
>> LAST Avg =   576 (N = 7200)
>> LAST Max =   648
>> 
>> Version 3.20 firmware for Garmin 18x
>> START Min =  370
>> START Avg =  433  (N = 7200)
>> START Max =  518
>> LAST Min =  519
>> LAST Avg =  582  (N = 7200)
>> LAST Max=  667
>> 
>> So if you use Version 3.20 firmware for the 18x, at 4800 baud the NMEA
>> RMC sentence will give the time of the current UTC second and will be
>> received by an average of 582 ms after the leading edge of the 1PPS
>> transition (with a maximum jitter of plus 85 ms / minus 63 ms).
>> 
>> From what I have said earlier in the thread, and from tests that
>> Kasper Pedersen has done, I think we can say that currently version
>> 3.2 is the "best" version if you want to use the 18x NMEA timestamps
>> to be given early in the second (rather than much later as per version
>> 3.3 and 3.5).
>> 
>> Joe, you can downloadGPS18xPC_LVC_320.exe from here:
>> 
>> http://www.gawisp.com/perry/oem_sensor/
>> 
>> The above file is identical to the one I downloaded in 2009 from Garmin.
>> 
>> Hope that helps.
>> 
>> Regards, Geoff (Christchurch, New Zealand).
>> 
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>> 
> 
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