date:20140222


I ran across these units
http://www.conwin.com/time-frequency_references-gps_disciplined-gps_references.html

and I found some references from a few years ago in the time-nuts 
archives, but I can't find any data on phase noise, etc. for the 
disciplined output.


The data sheet/user manual/etc just say NCO, but there's no specs on 
the performance.


Has anyone measured one of these?

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Re: [time-nuts] New WWVB modulation format receivers

Carrier extraction by squareing does not work well at all in a high noise
environment. The BPSK limits the narowness of the IF BW.

If you rule out modelling the data stream, and phase switching the signal
before the IF, you have to go w/ something like a Costas Loop.

-John

=


 Hi Paul,

 Without digging through the archives, I'll rely on your memory of that
 past thread!

 The scheme of using the doubler relied on the 100 kHz carrier recovery
 relied on the fact that the 200 kHz bandpass filters, being based on
 quartz crystals, was extremely narrow - on the order of fractions of
 Hz.  This effectively made them frequency-selective integrators (not the
 right word, but you get the idea...) and they were effectively immune to
 noise pulses as they simply could not react quickly.

 IIRC - and I'll have to review my old notes - I used the first 200 kHz
 crystal as a series element and then passed it to a source-follower and
 then a bipolar amplifier with ridiculous gain (e.g. grounded emitter,
 high collector resistance) to form a limiter - and then ran it through
 another 200 kHz crystal and JFET/limiter. It took a couple of seconds
 for the outputs of the two limiters to saturate due to the narrow
 bandwidth and it was extremely tolerant of amplitude variations.  There
 was a phase shift with different amplitude levels, but since, on an FM
 microwave link the amplitude wasn't going to change much, that - and the
 phase shift related to temperature - was inconsequential.

 On this simple recover scheme you could remove the input carrier for
 nearly a second (or blot it out with noise) and there would be almost no
 measurable effect on the output, aside from a phase shift of a few 10's
 of degrees which quickly rectified itself once the signal was returned.
 Had added some better tuning of the resonators I could have likely
 minimized this.  (I happened to have these 200 kHz HC-6 style units in
 my semi-large collection of 40-80's vintage crystals.)

 The trick to replicating such a filter would be to find a suitable
 bandpass filter for the doubled frequency - in this case, a 120.005 kHz
 crystal (or thereabouts) - but it should be practical to convert the
 previously-filtered 60 kHz signal to a frequency for which a suitable
 crystal could be located.

 The 60.003 kHz crystal to which I referred was a bandpass filter rather
 than an oscillator:  The TRF units found in WWVB clocks use these since
 most standard 60.000 kHz units end up being low in frequency when used
 in this sort of mode and they are a bit tricky to pull this far.

 Rather than try to find such a crystal I would probably throw together a
 Tayloe commutating mixer with RC lowpass filtering with a time
 constant of a hundred milliseconds or so - this, filter/mixer being
 clocked at the nominal 60 kHz receive signal.

 I would then follow it with another commutating mixer to translate the
 quadrature signal to any convenient frequency (say, audio - no doubt
 available from the 4060 or 4040 counter I'd be using!) where I would
 then do my frequency doubling and then follow it by yet another
 extremely narrow filter - this time, using an 8-capacitor SCF where I
 could set the detection bandwidth to a tiny fraction of 1 Hz just using
 a bunch of electrolytics!  It should be easy to set the carrier
 detection bandwidth to be a fraction of the information bandwidth so
 that reliable carrier recovery can be maintained under any conditions
 under which the BPSK data could be recovered.

 (An example of an 8-capacitor Roanoake type SCF may be seen here:
 http://ka7oei.com/emm2a_scf.html  )

 This recovered (and slightly filtered) signal, divided-by-two, could
 then be used to synchronously demodulate the original
 frequency-converted signal, at which point one should have a reasonable
 representation of the phase (and amplitude) of the transmitted signal -
 albeit, delayed by a fairly consistent amount.

 Of course, all of this could be done by throwing a 16 bit A/D and DSP
 chip at it, but sometimes there's a simple pleasure in doing it with a
 bunch of 4000 CMOS and a few op-amps, handing the recovered baseband off
 to a PIC or Arduino only at the very end!

 * * *

 Many years ago I built a WWVB carrier recovery circuit using just a
 single-stage LC bandpass filter (to get rid of the VLF powerhouses) and
 an NE565 phase detector along with a 6 MHz VCXO divided down to 60 kHz
 as the comparison.  What amazed me was that even with the practically
 nonexistant filtering in front of the '565 (you really couldn't see the
 60 kHz carrier with the oscilloscope) that '565 would always find its
 way into lock over time - and then it would stay firmly there owing to
 that effect that occurs in which the effective loop bandwidth seems to
 decrease once lock has been achieved.  (WWVB's 45 degree phase shift
 ID would always throw it for a loop, though - pun intended!)

 73,

 Clint
 KA7OEI


 Date: Thu, 20 Feb 2014 22:10:26 -0500
 From:

Re: [time-nuts] software-defined WWVB receivers

I was monitoring WWVB against a good local standard and evaluating 60kHz
'seeing' 30 years ago. Sometimes it is beautifully quiet, after a storm
front went through as I remember, at other times it's absolute hash...  to
the point that the HP 117A would not even hold lock.

-John

=


 The randomness of WWVB propagation require incredibly long measurements
 to get an interesting degree of accuracy compared to a GPS driven
 solution.

 The WWVB signal does respond nicely to solar flares if measurements are
 integrated
 over one minute.  Check out the VLF monitoring stuff on my web page.

 On 02/21/2014 12:06 PM, John Seamons wrote:
 As a starting point: Here's an extension of the SAQrx PC sound card
 receiver that supports 192 KHz sample-rate sound cards. Enough to get
 you WWVB.
 https://sites.google.com/site/swljo30tb

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 Developer of Industrial ZMODEM(Tm) for Embedded Applications
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 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430

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Re: [time-nuts] ID this filter

2014-02-22 Thread Lester Veenstra

Or just put it on a VNA and characterize it
I would be happy to.


Lester B Veenstra  MØYCM K1YCM W8YCM
les...@veenstras.com

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[time-nuts] comparing two clocks

2014-02-22 Thread Jimmy Burrell

I need some help with a 'noob' question regarding some practical examples in 
some of the NIST literature. When attempting to compare two clocks, I'm a bit 
confused on the subject of exactly how to use my counter to compare a delayed 
clock relative to another. Or perhaps I should just say 'comparing two clocks'. 
Let's take some concrete examples. 

Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. 
Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the counter's 
input 'A'. Obviously, I can feed in a second, external reference clock at 10MHz 
into input 'B'.  Suppose, however, I didn't have an external reference clock. 
Can I compare against the counter's internal time base by hooking a line from 
the rear jack time base output to channel 'B' input? Or am I making it too 
complicated? Do I simply plug into input 'A' and go?

In a somewhat related question, in this article 
(http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
 where two clocks, both divided to 1PPS, were compared, W.Riley makes the 
following statement, The two 1 PPS outputs were connected to a Racal Dana 1992 
time internal counter having 1 nanosecond resolution, and the start and stop 
signals were separated sufficiently in time for the counter to function 
properly.  I wonder what exactly is meant by separated sufficiently in time 
for the counter to function properly and how one would go about doing this? 
For example, is inverting one of the signals sufficient separation? If not, how 
is this typically done? Delay line?

Thank you,

Jim...
N5SPE
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Re: [time-nuts] comparing two clocks


On 2/22/14 5:17 AM, Jimmy Burrell wrote:

I need some help with a 'noob' question regarding some practical
examples in some of the NIST literature. When attempting to compare
two clocks, I'm a bit confused on the subject of exactly how to use
my counter to compare a delayed clock relative to another. Or perhaps
I should just say 'comparing two clocks'. Let's take some concrete
examples.

Let's say I want to characterize my Morion MV89 ocxo using my
HP5335a. Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed
it to the counter's input 'A'. Obviously, I can feed in a second,
external reference clock at 10MHz into input 'B'.  Suppose, however,
I didn't have an external reference clock. Can I compare against the
counter's internal time base by hooking a line from the rear jack
time base output to channel 'B' input? Or am I making it too
complicated? Do I simply plug into input 'A' and go?



Just plug it into A and go..  Fire up TIMELAB and see the curves 
revealed..  Just remember that what you're seeing is

 sqrt( ADEV(unknown)^2 + ADEV(counter osc)^2)

If your counter is worse than your Unit Under Test, then you're really 
measuring the counter's performance (which is actually quite fun..if you 
have something you know is high quality)




In a somewhat related question, in this article
(http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
where two clocks, both divided to 1PPS, were compared, W.Riley makes
the following statement, The two 1 PPS outputs were connected to a
Racal Dana 1992 time internal counter having 1 nanosecond resolution,
and the start and stop signals were separated sufficiently in time
for the counter to function properly.  I wonder what exactly is
meant by separated sufficiently in time for the counter to function
properly and how one would go about doing this? For example, is
inverting one of the signals sufficient separation? If not, how is
this typically done? Delay line?


Inverting would work..

Generally, in this sort of thing, you want to make sure that A always 
occurs before B, so you're counting the right thing, and that you're 
getting small changes in, say, 0.25 seconds, as opposed to getting 0.01 
seconds on one measurement, and then 0.99 seconds on the next.


A lot of 1pps systems (e.g. those not synchronized to an outside source) 
have a starting phase that is arbitrary.  You have a 10 MHz crystal 
running to a divide by 1E7.  Turn it on, and you start getting 1pps 
pulses out.

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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Bob Camp

Hi

On some counters, if both inputs arrive at exactly the same time, they get very 
confused. The normal approach is to offset one by a few hundred ns or so. The 
exact offset is fairly non-critical. It’s real value depends entirely on the 
amount of drift you expect to see over the time period you are checking. 

If your oscillators are off by 1 ppm, they will slip by 1 us per second. If you 
want to check them for 12 days or more you will need an offset of more than one 
second. If they are off by 1 ppb, then your offset could be a bit over one 
millisecond to handle a 12 day run.  (12 days is roughly 1 million seconds). 

Bob

On Feb 22, 2014, at 8:17 AM, Jimmy Burrell jimmydb...@gmail.com wrote:

 I need some help with a 'noob' question regarding some practical examples in 
 some of the NIST literature. When attempting to compare two clocks, I'm a bit 
 confused on the subject of exactly how to use my counter to compare a delayed 
 clock relative to another. Or perhaps I should just say 'comparing two 
 clocks'. Let's take some concrete examples. 
 
 Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. 
 Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the 
 counter's input 'A'. Obviously, I can feed in a second, external reference 
 clock at 10MHz into input 'B'.  Suppose, however, I didn't have an external 
 reference clock. Can I compare against the counter's internal time base by 
 hooking a line from the rear jack time base output to channel 'B' input? Or 
 am I making it too complicated? Do I simply plug into input 'A' and go?
 
 In a somewhat related question, in this article 
 (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
  where two clocks, both divided to 1PPS, were compared, W.Riley makes the 
 following statement, The two 1 PPS outputs were connected to a Racal Dana 
 1992 time internal counter having 1 nanosecond resolution, and the start and 
 stop signals were separated sufficiently in time for the counter to function 
 properly.  I wonder what exactly is meant by separated sufficiently in time 
 for the counter to function properly and how one would go about doing this? 
 For example, is inverting one of the signals sufficient separation? If not, 
 how is this typically done? Delay line?
 
 Thank you,
 
 Jim...
 N5SPE
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Re: [time-nuts] WWVB antennas

2014-02-22 Thread JIM FARLEY

Google 'fractal antenna'.  Fractal Antennas are a relatively recent (late 
1980's to mid-1990's) discovery/invention.  I have read that they are 
approximately 20% more efficient than normal antennas.

 Jim, KG4FXV

 From: d0ct0r t...@patoka.org
To: Discussion of precise time and frequency measurement time-nuts@febo.com 
Sent: Saturday, February 22, 2014 12:54 AM
Subject: Re: [time-nuts] WWVB antennas

I am impressed by Casio engineers who created tiny antenna for my wrist watch. 
I don't know how, but that Pathfinder able to catch and decode 60 khz wwvb in 
noisy city environment. And it did even better when i was 500 km north !

:40, Alexander Pummer wrote:
 here are the other 60kHz transmitters:
 http://www.ka7oei.com/wwvb_antenna.html

 U.S. based WWVB transmitter.  As described, it
           could also be used for theUK-based 60 kHz MSF
 http://en.wikipedia.org/wiki/Time_from_NPL    MSF signal  formerly
 the Rugby clock*    *and the
 Japanese 60 kHz JJY  http://en.wikipedia.org/wiki/JJY_
 _our fiend in Australia most likely*_  _*receive the JapaneseWWVB
 73
 KJ6HUN
 Alex
 _*//*_

 On 2/21/2014 12:21 PM, Robert Roehrig wrote:
 John Forster said:

 WWVB is hard to detect w/ a 3-foot diameter HP shielded loop w/ integral
 preamp  2 stages of mechanical filters. (HP 117A). The other half of the
 time it was undetectable. Paul S uses a loop that is much larger.

 I am near Chicago and I have 2 60 kHz antennas. One is a ferrite
 rod type and the other a 5  foot diameter loop. Both are tuned
 and feed identical 2 transistor preamp. The loop does work better.
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-- WBW,

V.P.
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Re: [time-nuts] New WWVB modulation format receivers (NOT)



On 2/20/14, 8:51 PM, Bob Camp wrote:
 Hi
 
 You can get parts in the 18 bit and up range for not a whole lot of money 
 with rational sample rates for a WWVB receiver. Analog Devices and Linear 
 Tech both make some interesting looking parts. They get you into the =100 db 
  dynamic range area. 

Yes. 192ksps is considered audio and is now available as a common part
for consumer devices. Or go with a 1-bit part and then decimate the hell
out of the result.

 Even with a lower bit count part, you pick up some bits in the downsampling 
 process. As long as you have enough noise to keep things moving, you can 
 track pretty far down into the crud. GPS receivers do that sort of thing all 
 the time. 
 
 Since this is slow audio after the CIC decimator, things like ARM chips 
 probably have enough DSP horsepower to do what you need to do. The decimator 
 it’s self is not terribly taxing if you don’t go too crazy with the rate 
 change. 

This all makes more sense to me than hacking a bunch of op amps and
filter hardware. Use a low bit-depth but fast part then decimate. If it
is fast enough you can get by with very simple anti-alias filtering.
Like you said, if you have enough noise to randomize the LSB you are
good to go. I bet that the AMBCB provides more than enough randomization
power. And if it doesn't, just inject enough broadband noise to
randomize the LSB. The rest is just SMOP.

Just for giggles I took a look at the output of the ADC on my Hermes
board. The input is my Pixelsat loop which is broadband from 50kHz to
30MHz. (It has significant output down to below 20kHz.) The ADC of my
Hermes HPSDR board is being fed with the raw output of the antenna with
no filtering so the ADC is seeing everything from DC to 60MHz that comes
out of the antenna. Peak ADC level at my location is -40dBFS. I live
about 35km N of San Antonio so my location is neither particularly RF
quiet nor noisy. Seems like the 16-bit ADC has plenty of headroom. I
hear WWVB very handily on this setup and I am seeing -83dBm out of my
antenna for WWVB on peaks. (Actually the S:N is pretty good at over 16dB
in a 300Hz bandwidth.) This is near noon local time.

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
br...@lloyd.com
+1.916.877.5067
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Re: [time-nuts] WWVB antennas

I doubt that a 'fractal antenna' is going to do very well at 60 kHz in a
size small enough to fit in a wrist watch.

YMMV,

-John

==


 Google 'fractal antenna'.  Fractal Antennas are a relatively recent (late
 1980's to mid-1990's) discovery/invention.  I have read that they are
 approximately 20% more efficient than normal antennas.

  Jim, KG4FXV



 From: d0ct0r t...@patoka.org
To: Discussion of precise time and frequency measurement
 time-nuts@febo.com
Sent: Saturday, February 22, 2014 12:54 AM
Subject: Re: [time-nuts] WWVB antennas


I am impressed by Casio engineers who created tiny antenna for my wrist
 watch. I don't know how, but that Pathfinder able to catch and decode 60
 khz wwvb in noisy city environment. And it did even better when i was 500
 km north !

:40, Alexander Pummer wrote:
 here are the other 60kHz transmitters:
 http://www.ka7oei.com/wwvb_antenna.html

 U.S. based WWVB transmitter.  As described, it
           could also be used for theUK-based 60 kHz MSF
 http://en.wikipedia.org/wiki/Time_from_NPL    MSF signal  formerly
 the Rugby clock*    *and the
 Japanese 60 kHz JJY  http://en.wikipedia.org/wiki/JJY_
 _our fiend in Australia most likely*_  _*receive the JapaneseWWVB
 73
 KJ6HUN
 Alex
 _*//*_






 On 2/21/2014 12:21 PM, Robert Roehrig wrote:
 John Forster said:

 WWVB is hard to detect w/ a 3-foot diameter HP shielded loop w/
 integral
 preamp  2 stages of mechanical filters. (HP 117A). The other half of
 the
 time it was undetectable. Paul S uses a loop that is much larger.

 I am near Chicago and I have 2 60 kHz antennas. One is a ferrite
 rod type and the other a 5  foot diameter loop. Both are tuned
 and feed identical 2 transistor preamp. The loop does work better.
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-- WBW,

V.P.
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Re: [time-nuts] New WWVB modulation format receivers (NOT)



On 2/20/14, 10:35 PM, Graeme Zimmer wrote:
 I have a Kenwood TS-940S transceiver that can receive 60 kHz but I
 have never heard anything
 
 Where are you? It must be deaf as a post.

Most ham receivers that purport to have coverage down there really
don't. I thought my Flex 5000 should hear that handily but all it ever
heard were images of the AM-BCB. The HPSDR Hermes board in my ANAN-10
hears WWVB a treat. Direct Down Conversion (DDC) is your friend and
anyone considering playing with this stuff really needs to be thinking
about a DDC receiver.

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
br...@lloyd.com
+1.916.877.5067
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Re: [time-nuts] New WWVB modulation format receivers (NOT)



On 2/20/14, 11:08 PM, John Marvin wrote:
 I have an OpenHPSDR Hermes and it has no problem receiving WWVB;
 however, since I live in Fort Collins - Colorado, part of the success
 might just be the strong signal. I wonder if I could just stick a piece
 of wire into one of the channel inputs of a 192Khz sample rate audio
 interface (especially if it had a good low noise mic preamp) and decode
 WWVB from baseband audio!

Yes, presuming that the mic preamp doesn't cut off near 20kHz. Some do.
192kHz sampling ADCs are not all equal in their performance up there.
Just because they sample that fast doesn't mean they are flat out to the
Nyquist frequency. Just remember it is a spec game with the audio ADC
people. Sure they may sample at 192kHz but many (most?) really are no
better than those that sample at 48kHz or even those that sample at 44.1kHz.

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
br...@lloyd.com
+1.916.877.5067
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Re: [time-nuts] New WWVB modulation format receivers (NOT)

2014-02-22 Thread Poul-Henning Kamp


Sorry for comming late to the party...

This may be relevant:

http://phk.freebsd.dk/loran-c/CW/

The basic idea is that you use a high-rate ADC, something like 1MS/s
and then you average into for instance a 1msec = 1.000 samples circular
buffer.

That gives you a very narrow comb filter for all frequencies which
are a multiple of 1 kHz, and extracting the phase from, for instance
the 60 kHz WWVB carrier will be trivial.

In the example above, the buffer were w full second long, 1.000.000
samples, this reveals the per-second modulation of the carrier, and
allows you to extract any (averaged) signal on an integral Hz carrier
frequency.

There are Arm chips out there now with 1MSPS*12bit ADCs that's
plenty for this kind of stuff. (see also: http://phk.freebsd.dk/AducLoran/)


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

2014-02-22 Thread Alan Melia

Claims on antenna efficiency at these frequencies are fairly meaningless (as 
always) in that a normal antenna efficiency would be less than 1% !!

Alan
G3NYK

- Original Message - 
From: JIM FARLEY jimfar...@att.net
To: t...@patoka.org; Discussion of precise time and frequency 
measurement time-nuts@febo.com

Sent: Saturday, February 22, 2014 4:28 PM
Subject: Re: [time-nuts] WWVB antennas

Google 'fractal antenna'. Fractal Antennas are a relatively recent (late 
1980's to mid-1990's) discovery/invention. I have read that they are 
approximately 20% more efficient than normal antennas.

Jim, KG4FXV

From: d0ct0r t...@patoka.org
To: Discussion of precise time and frequency measurement 
time-nuts@febo.com

Sent: Saturday, February 22, 2014 12:54 AM
Subject: Re: [time-nuts] WWVB antennas

I am impressed by Casio engineers who created tiny antenna for my wrist 
watch. I don't know how, but that Pathfinder able to catch and decode 60 
khz wwvb in noisy city environment. And it did even better when i was 500 
km north !

:40, Alexander Pummer wrote:

here are the other 60kHz transmitters:
http://www.ka7oei.com/wwvb_antenna.html

U.S. based WWVB transmitter. As described, it
  could also be used for theUK-based 60 kHz MSF
http://en.wikipedia.org/wiki/Time_from_NPL MSF signal formerly
the Rugby clock* *and the
Japanese 60 kHz JJY http://en.wikipedia.org/wiki/JJY_
_our fiend in Australia most likely*_ _*receive the JapaneseWWVB
73
KJ6HUN
Alex
_*//*_

On 2/21/2014 12:21 PM, Robert Roehrig wrote:

John Forster said:

WWVB is hard to detect w/ a 3-foot diameter HP shielded loop w/ 
integral
preamp  2 stages of mechanical filters. (HP 117A). The other half of 
the

time it was undetectable. Paul S uses a loop that is much larger.

I am near Chicago and I have 2 60 kHz antennas. One is a ferrite
rod type and the other a 5 foot diameter loop. Both are tuned
and feed identical 2 transistor preamp. The loop does work better.
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Re: [time-nuts] New WWVB modulation format receivers (NOT)

On 2/20/14, 11:35 PM, Hal Murray wrote:

 Can somebody give me a lesson in the tradeoffs between number of bits and 
 sampling rate?

Sure, the Shannon-Hartley Theorem. See:

http://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
br...@lloyd.com
+1.916.877.5067
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Re: [time-nuts] WWVB antennas



On 2/21/14, 2:21 PM, Robert Roehrig wrote:
 John Forster said: 
 
 WWVB is hard to detect w/ a 3-foot diameter HP shielded loop w/ integral
 preamp  2 stages of mechanical filters. (HP 117A). The other half of the
 time it was undetectable. Paul S uses a loop that is much larger.
 
 I am near Chicago and I have 2 60 kHz antennas. One is a ferrite
 rod type and the other a 5  foot diameter loop. Both are tuned 
 and feed identical 2 transistor preamp. The loop does work better.

I am in San Antonio, TX, and I use a Pixelsat untuned loop. It receives
WWVB just fine. It also receives pretty much everything from DC-20MHz
just fine.

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
br...@lloyd.com
+1.916.877.5067
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[time-nuts] Question about DDMTD deglitching

2014-02-22 Thread Robert Darby

In August 2011 there was a brief mention on Time-Nuts of DDMTD's which 
led me to The P. Moreira  and I. Darwazeh  paper Digital femtosecond 
time difference circuit for CERN’s timing system.  I'm hoping that 
someone can explain one item mentioned in this paper for me.   For those 
not familiar with this work, it is part of a sub-nanosecond network 
synchronization scheme know as White Rabbit.


One of the elements of the DDMTD is a deglitching system and the authors 
describe three possible deglitching strategies.  The first two are quite 
straightforward but the third method  described as Zero Count – counts 
the numbers of “1” and “0” and selects as the best edge the time 
position where the number of zeros is the same as the number of ones. 
seems totally ambiguous.  If I take the statement quite literally, there 
must be dozens or hundreds of times when the number of 1's and 0's in a 
glitch are equal.   Can anyone familiar with this work explain what I am 
missing? I realize that the answer to my question is probably at hand in 
the FPGA code but that's well beyond my pay grade.


This paper is available at:
http://www.ee.ucl.ac.uk/lcs/previous/LCS2011/LCS1136.pdf
A list of White Rabbit papers is available at:
http://www.ohwr.org/projects/white-rabbit/wiki/WRpublications

Thanks,
Bob Darby

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Re: [time-nuts] WWVB antennas

You are about 1/4 the distance away. Inverse square law.

-John

===




 On 2/21/14, 2:21 PM, Robert Roehrig wrote:
 John Forster said:

 WWVB is hard to detect w/ a 3-foot diameter HP shielded loop w/
 integral
 preamp  2 stages of mechanical filters. (HP 117A). The other half of
 the
 time it was undetectable. Paul S uses a loop that is much larger.

 I am near Chicago and I have 2 60 kHz antennas. One is a ferrite
 rod type and the other a 5  foot diameter loop. Both are tuned
 and feed identical 2 transistor preamp. The loop does work better.

 I am in San Antonio, TX, and I use a Pixelsat untuned loop. It receives
 WWVB just fine. It also receives pretty much everything from DC-20MHz
 just fine.

 --
 Brian Lloyd, WB6RQN/J79BPL
 706 Flightline Drive
 Spring Branch, TX 78070
 br...@lloyd.com
 +1.916.877.5067
 ___
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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Said Jackson

Jim, Bob,

we just had the pleasure of doing exactly this aligned-1PPS measurement two 
days ago. I had to measure the difference (noise) of two units that were locked 
to the same source. To jump ahead, the difference was 0ns +/- about 500ps noise 
range.

We used an HP 5335, no problem, it jumped back and forth by +/-1ns steps. If I 
had done very long averages, it may be useful.

Next came an HP 5370A. A bit tedious to set up, but the noise floor of about 
40ps was helpful, but the unit had about 200ps offset when in COM-A test mode 
so needs some adjustment.

Then moved to a DTS-2070, once we found space for it and the correct 
attenuators to not damage the inputs it was quit funny to see single 
femtosecond resolution on a ~500ps pulse to pulse noise.

Lastly we used the HP 53132A. This was the easiest to set up. It works fine as 
long as you stay within about -6ns, if you go earlier then the counter will 
measure an entire second, adding one second of error from its internal time 
base, and showing numbers like 0.999,999,997s. Since we were within a 1ns 
window, the numbers looked almost identical to the DTS-2070 so we know we have 
a good measurement.

I took the output of the 53132A and ran it through Excel and got a standard 
deviation of 220ps. Not bad considering some of that was probably counter noise 
and the counter has 'only' 150ps resolution if I remember correctly.

The 53132A it will be for future 1PPS to 1PPS measurements for me.

Bye,
Said

Sent From iPhone

On Feb 22, 2014, at 7:25, Bob Camp li...@rtty.us wrote:

 Hi
 
 On some counters, if both inputs arrive at exactly the same time, they get 
 very confused. The normal approach is to offset one by a few hundred ns or 
 so. The exact offset is fairly non-critical. It’s real value depends entirely 
 on the amount of drift you expect to see over the time period you are 
 checking. 
 
 If your oscillators are off by 1 ppm, they will slip by 1 us per second. If 
 you want to check them for 12 days or more you will need an offset of more 
 than one second. If they are off by 1 ppb, then your offset could be a bit 
 over one millisecond to handle a 12 day run.  (12 days is roughly 1 million 
 seconds). 
 
 Bob
 
 On Feb 22, 2014, at 8:17 AM, Jimmy Burrell jimmydb...@gmail.com wrote:
 
 I need some help with a 'noob' question regarding some practical examples in 
 some of the NIST literature. When attempting to compare two clocks, I'm a 
 bit confused on the subject of exactly how to use my counter to compare a 
 delayed clock relative to another. Or perhaps I should just say 'comparing 
 two clocks'. Let's take some concrete examples. 
 
 Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. 
 Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the 
 counter's input 'A'. Obviously, I can feed in a second, external reference 
 clock at 10MHz into input 'B'.  Suppose, however, I didn't have an external 
 reference clock. Can I compare against the counter's internal time base by 
 hooking a line from the rear jack time base output to channel 'B' input? Or 
 am I making it too complicated? Do I simply plug into input 'A' and go?
 
 In a somewhat related question, in this article 
 (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
  where two clocks, both divided to 1PPS, were compared, W.Riley makes the 
 following statement, The two 1 PPS outputs were connected to a Racal Dana 
 1992 time internal counter having 1 nanosecond resolution, and the start and 
 stop signals were separated sufficiently in time for the counter to function 
 properly.  I wonder what exactly is meant by separated sufficiently in 
 time for the counter to function properly and how one would go about doing 
 this? For example, is inverting one of the signals sufficient separation? If 
 not, how is this typically done? Delay line?
 
 Thank you,
 
 Jim...
 N5SPE
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Re: [time-nuts] Question about DDMTD deglitching

2014-02-22 Thread Bob Camp

Hi

When you do any of these delay line based gizmos, you get some very strange 
outputs. Flip flops go metastable, edges don’t quite arrive in the right 
sequence. If all you do is look for solid ones or solid zeros you don’t get a 
lot of data. Counting the ones and counting zeros is another approach. 

They calibrate the devices by random pulses and then categorizing the result. 
By deciding that all buckets with the same number of 1’s and 0’s in them (plus 
some other stuff) are equal, they get more hits per bucket. That gives more 
data in less time. 

The implicit assumption is that buckets with equal 0’s and 1’s (and what ever 
else) are equal to each other time wise. Another related assumption is that 
buckets with fewer 0’s and more 1’s are slower (or faster depending on the 
structure) than ones with more 0’s. 

There apparently is some strong data somewhere suggesting that this is all true.

Bob

On Feb 22, 2014, at 12:30 PM, Robert Darby bobda...@triad.rr.com wrote:

 In August 2011 there was a brief mention on Time-Nuts of DDMTD's which led me 
 to The P. Moreira  and I. Darwazeh  paper Digital femtosecond time 
 difference circuit for CERN’s timing system.  I'm hoping that someone can 
 explain one item mentioned in this paper for me.   For those not familiar 
 with this work, it is part of a sub-nanosecond network synchronization scheme 
 know as White Rabbit.
 
 One of the elements of the DDMTD is a deglitching system and the authors 
 describe three possible deglitching strategies.  The first two are quite 
 straightforward but the third method  described as Zero Count – counts the 
 numbers of “1” and “0” and selects as the best edge the time position where 
 the number of zeros is the same as the number of ones. seems totally 
 ambiguous.  If I take the statement quite literally, there must be dozens or 
 hundreds of times when the number of 1's and 0's in a glitch are equal.   Can 
 anyone familiar with this work explain what I am missing? I realize that the 
 answer to my question is probably at hand in the FPGA code but that's well 
 beyond my pay grade.
 
 This paper is available at:
 http://www.ee.ucl.ac.uk/lcs/previous/LCS2011/LCS1136.pdf
 A list of White Rabbit papers is available at:
 http://www.ohwr.org/projects/white-rabbit/wiki/WRpublications
 
 Thanks,
 Bob Darby
 
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Re: [time-nuts] connor winfield GPSDO module phase noise

2014-02-22 Thread Said Jackson

Jim,

Check the archives, I am pretty sure I reported on one of them, I think it was 
on the FTS-250.. Or FTS-125.

My recollection: Not that bad for the price, but phase noise and spurs on my 
sample unit were significantly worse than what they show in their plots no 
matter what I tried, and quite large phase/frequency jumps when 
disconnecting/re-aquiring GPS.

Drawbacks of NCOs versus GPSDOs I guess.

Bye,
Said

Sent From iPhone

On Feb 22, 2014, at 5:33, Jim Lux jim...@earthlink.net wrote:

 I ran across these units
 http://www.conwin.com/time-frequency_references-gps_disciplined-gps_references.html
 
 and I found some references from a few years ago in the time-nuts archives, 
 but I can't find any data on phase noise, etc. for the disciplined output.
 
 The data sheet/user manual/etc just say NCO, but there's no specs on the 
 performance.
 
 Has anyone measured one of these?
 
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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Volker Esper

Jim,

If I get you right, you want to compare the 10MHz outputs (not the
1PPS). As Jim and Bob told us so far, the thing is to provide, that
input A _always_ starts before input B (or the other way around).

Connect the signals to an oscilloscope, and check, how much the phase
differs - if the rising slopes occur close together, put some
meters/yards of coaxial cable into one of the two signal paths. 1 meter
is roughly worth 5ns - while the period of 10MHz is 100ns, 1m cable will
phase shift about 18 degrees. I didn't verify, if the coax cable (with
it's microphonic effect) affects the ADEV - does anybody have experience
with this? Otherwise I'd have to fire up my counter and have a
measurement on the run...

Of course, inverting one signal will do as well. If you do it with extra
electronics that definitely will affect the ADEV. I find it much easier
to use some meters of cable.

Ok, my counter is heating up by now...

Volker


Am 22.02.2014 14:17, schrieb Jimmy Burrell:
 I need some help with a 'noob' question regarding some practical examples in 
 some of the NIST literature. When attempting to compare two clocks, I'm a bit 
 confused on the subject of exactly how to use my counter to compare a delayed 
 clock relative to another. Or perhaps I should just say 'comparing two 
 clocks'. Let's take some concrete examples. 

 Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. 
 Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the 
 counter's input 'A'. Obviously, I can feed in a second, external reference 
 clock at 10MHz into input 'B'.  Suppose, however, I didn't have an external 
 reference clock. Can I compare against the counter's internal time base by 
 hooking a line from the rear jack time base output to channel 'B' input? Or 
 am I making it too complicated? Do I simply plug into input 'A' and go?

 In a somewhat related question, in this article 
 (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
  where two clocks, both divided to 1PPS, were compared, W.Riley makes the 
 following statement, The two 1 PPS outputs were connected to a Racal Dana 
 1992 time internal counter having 1 nanosecond resolution, and the start and 
 stop signals were separated sufficiently in time for the counter to function 
 properly.  I wonder what exactly is meant by separated sufficiently in time 
 for the counter to function properly and how one would go about doing this? 
 For example, is inverting one of the signals sufficient separation? If not, 
 how is this typically done? Delay line?

 Thank you,

 Jim...
 N5SPE
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Re: [time-nuts] WWVB antennas

On Sat, Feb 22, 2014 at 11:56 AM, J. Forster j...@quikus.com wrote:

 You are about 1/4 the distance away. Inverse square law.


If we were in free space I might concur on the inverse square law. We
aren't and propagation certainly has an effect on path loss. I posted
signal levels coming from my Pixelsat loop for WWVB at my location right
now (-82dBm at 1800Z) which might be a useful datum for someone
contemplating building or fielding a WWVB receiver and considering this
particular antenna. (More data, the S:N is 36dB based on an 11Hz bin-width
for the FFT I am running right now.)

BTW, the distance from WWV in Ft. Collins, Colorado, to my antenna is
1,346.75km, great circle ground route.

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
br...@lloyd.com
+1.916.877.5067
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[time-nuts] new gps sat prn30 svn64

2014-02-22 Thread tom jones

svn64 alive and well

Using sirfdemo pc software coupled with sirf iv gps receiver I picked up the 
first signal from svn64 (now assigned prn30).
The sat was launched from cape canavral (airforce station) florida last 
thursday evening 2-20-14 about 17:55pdt.
The gps control people seem to be turning on the satellites transmitter 
intermittantly.
The new satellite will not be in its final orbit for approximately 30 days and 
not usable till about 36 days from its launch 

date.

My first reception was at 23:32:22pdt

gps time error  freq-drift date  time pdt

4.4716290517e-010,-1.1166002510e-014@ 02/21/2014 23:32:22
2.7434175598e-010,-5.1373205549e-014@ 02/22/2014 00:57:22
2.7264644019e-010,-5.1373205549e-014@ 02/22/2014 00:57:52
2.7202887741e-010,-5.2401886405e-014@ 02/22/2014 00:58:22
2.7003760573e-010,-5.2401886405e-014@ 02/22/2014 00:58:52
2.6877996045e-010,-5.2401886405e-014@ 02/22/2014 00:59:22
2.6416859445e-010,-5.2401886405e-014@ 02/22/2014 01:00:52
2.5693992947e-010,-5.3422655975e-014@ 02/22/2014 01:02:52
2.5624543494e-010,-5.3422655975e-014@ 02/22/2014 01:03:22
2.5421537401e-010,-5.3422655975e-014@ 02/22/2014 01:03:52
2.4365104104e-010,-5.4384875238e-014@ 02/22/2014 01:06:52
2.4196987886e-010,-5.5335398671e-014@ 02/22/2014 01:07:22
2.3208415713e-010,-5.6217685129e-014@ 02/22/2014 01:10:22
2.3084736806e-010,-5.6217685129e-014@ 02/22/2014 01:10:52
2.1308972996e-010,-5.7062414147e-014@ 02/22/2014 01:15:52
2.1229085616e-010,-5.7062414147e-014@ 02/22/2014 01:16:22
2.1024898532e-010,-5.7873397372e-014@ 02/22/2014 01:16:52
1.7422816710e-010,-6.0095673013e-014@ 02/22/2014 01:26:52
1.4985197051e-010,-6.1364392842e-014@ 02/22/2014 01:33:52
-8.2096225744e-011,-6.4458299267e-014   @ 02/22/2014 02:33:22
-8.7252889686e-011,-6.4458299267e-014   @ 02/22/2014 02:34:52
-8.8348680774e-011,-6.4458299267e-014   @ 02/22/2014 02:35:22
-1.0635115866e-010,-6.3795634899e-014   @ 02/22/2014 02:39:52
-1.0947714477e-010,-6.3795634899e-014   @ 02/22/2014 02:40:52
-1.2733387921e-010,-6.2957112939e-014   @ 02/22/2014 02:45:22

This is a complete list of all that was received from the new prn30 satellite 
(so far). perhaps there saving power till solar 

pannel deployment? or are saving power to charge batterys after just deploying 
solar pannels?

The numbers were cut an pasted from message id 30 (nl sv state data) from the 
sirfdemo pc software logging feature.
I've been monitoring this information for the last 8 weeks logging many days of 
satellite data.

It appears that gps time error gets updated from the satellite broadcast 
navagation message at least daily.
I believe that the gps receiver then computes the satellite frequency drift 
(including doppler shift) and computes gps time 

error till the next satellite navagation broadcast message updates the 
accumulated time error.

Atomic clocks in gps orbit run 45us fast perday due to less gravity but loose 8 
us per day do to 
there high velocity. the net result is 37us per daily. 
 
It looks like the new satellite clock is keeping excellant time for not being 
in orbit yet.. perhaps it is allready high 

enough above earth to not experience the slower time of earths gravity?

The old Prn30 has been flagged unusable for years. but data was still received 
and logged with sirfdemo. 

This is the last data from the old satellite prn30 (norad number 34661) whose 
transmissions became intermittant the last week 

(control operators turning it off and on).

gps time error frequency drift
6.7348954278e-004,2.8731554896e-012 @ 02/21/2014 11:21:28 = last 
intermittant message from the old prn30 satellite.

My gps receiver is a bu-353s4 (sirf-4) usb dongle that is available on ebay for 
about $40 dollars. My old sirfIII worked a 

little better (globalsat holux gr-213u). the new sirf IV spitts unwanted data 
randomly into log file. random data labeled 

unk:hexadecimal strings no help on internet but many complaints.. sirfdemo 
software is still downloadable from the internet.

Nothing else has been received sense 02:45. I dont know if the sat is still 
visable to the usa right now or if the 

transmissions have been disabled .. 
There isn't any information on the internet yet.. No norad satellite numbers 
(svn64) published for tracking it yet.

Enjoy. hope my tabs and spaces keep data aligned..

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Re: [time-nuts] connor winfield GPSDO module phase noise


On 2/22/14 10:01 AM, Said Jackson wrote:

Jim,

Check the archives, I am pretty sure I reported on one of them, I think it was 
on the FTS-250.. Or FTS-125.



Found it.. thanks.. the key was to put your name in the search



My recollection: Not that bad for the price, but phase noise and spurs on my 
sample unit were significantly worse than what they show in their plots no 
matter what I tried, and quite large phase/frequency jumps when 
disconnecting/re-aquiring GPS.

Drawbacks of NCOs versus GPSDOs I guess.

Bye,
Said

Sent From iPhone

On Feb 22, 2014, at 5:33, Jim Lux jim...@earthlink.net wrote:


I ran across these units
http://www.conwin.com/time-frequency_references-gps_disciplined-gps_references.html

and I found some references from a few years ago in the time-nuts archives, but 
I can't find any data on phase noise, etc. for the disciplined output.

The data sheet/user manual/etc just say NCO, but there's no specs on the 
performance.

Has anyone measured one of these?

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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Bob Stewart

Hi Jimmy,

Someone touched on the idea of using a scope.  Go to the Agilent site and 
download a copy of the 10811 manual, 10811-90002.pdf.  Section 3 describes how 
to adjust the 10811 and gives info on how to time the phase drift to calculate 
the frequency error.  You can pull the time base out of the back of the counter 
and use it as one of the inputs to the scope for this measurement.  


For that matter, you should be able to send the time base back into the counter 
for a Time Interval measurement against your other oscillator.  However, that 
won't give you much value unless you have a GPIB adapter and can capture the 
time interval value over some period and make pretty phase plots and do ADEV 
plots.  You can get useful values a lot quicker using the method in the 10811 
manual.  


Regardless of which method you use, you will quickly wonder which clock is 
being measured.  Once you ask that question, a GPSDO is in your future.  Been 
There, Done That.  Still doing it.


Bob - AE6RV





 From: Jimmy Burrell jimmydb...@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com 
Sent: Saturday, February 22, 2014 7:17 AM
Subject: [time-nuts] comparing two clocks
 

I need some help with a 'noob' question regarding some practical examples in 
some of the NIST literature. When attempting to compare two clocks, I'm a bit 
confused on the subject of exactly how to use my counter to compare a delayed 
clock relative to another. Or perhaps I should just say 'comparing two 
clocks'. Let's take some concrete examples. 

Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. 
Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the counter's 
input 'A'. Obviously, I can feed in a second, external reference clock at 
10MHz into input 'B'.  Suppose, however, I didn't have an external reference 
clock. Can I compare against the counter's internal time base by hooking a 
line from the rear jack time base output to channel 'B' input? Or am I making 
it too complicated? Do I simply plug into input 'A' and go?

In a somewhat related question, in this article 
(http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
 where two clocks, both divided to 1PPS, were compared, W.Riley makes the 
following statement, The two 1 PPS outputs were connected to a Racal Dana 
1992 time internal counter having 1 nanosecond resolution, and the start and 
stop signals were separated sufficiently in time for the counter to function 
properly.  I wonder what exactly is meant by separated sufficiently in time 
for the counter to function properly and how one would go about doing this? 
For example, is inverting one of the signals sufficient separation? If not, 
how is this typically done? Delay line?

Thank you,

Jim...
N5SPE
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Re: [time-nuts] Question about DDMTD deglitching

2014-02-22 Thread Robert Darby

Thanks Bob,

Found several papers that describe the process after getting your info.

Bob Darby

On 2/22/2014 1:00 PM, Bob Camp wrote:

When you do any of these delay line based gizmos, you get some very strange
outputs. Flip flops go metastable, edges don’t quite arrive in the right
sequence. If all you do is look for solid ones or solid zeros you don’t get a
lot of data. Counting the ones and counting zeros is another approach.

They calibrate the devices by random pulses and then categorizing the result.
By deciding that all buckets with the same number of 1’s and 0’s in them (plus
some other stuff) are equal, they get more hits per bucket. That gives more
data in less time.

The implicit assumption is that buckets with equal 0’s and 1’s (and what ever
else) are equal to each other time wise. Another related assumption is that
buckets with fewer 0’s and more 1’s are slower (or faster depending on the
structure) than ones with more 0’s.

There apparently is some strong data somewhere suggesting that this is all true.

Bob

On Feb 22, 2014, at 12:30 PM, Robert Darby bobda...@triad.rr.com wrote:

In August 2011 there was a brief mention on Time-Nuts of DDMTD's which led me to The P.
Moreira and I. Darwazeh paper Digital femtosecond time difference circuit for
CERN’s timing system. I'm hoping that someone can explain one item mentioned in
this paper for me. For those not familiar with this work, it is part of a
sub-nanosecond network synchronization scheme know as White Rabbit.

One of the elements of the DDMTD is a deglitching system and the authors describe three
possible deglitching strategies. The first two are quite straightforward but the third
method described as Zero Count – counts the numbers of “1” and “0” and selects as
the best edge the time position where the number of zeros is the same as the number of
ones. seems totally ambiguous. If I take the statement quite literally, there must
be dozens or hundreds of times when the number of 1's and 0's in a glitch are equal.
Can anyone familiar with this work explain what I am missing? I realize that the answer
to my question is probably at hand in the FPGA code but that's well beyond my pay grade.

This paper is available at:
http://www.ee.ucl.ac.uk/lcs/previous/LCS2011/LCS1136.pdf
A list of White Rabbit papers is available at:
http://www.ohwr.org/projects/white-rabbit/wiki/WRpublications

Thanks,
Bob Darby

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[time-nuts] new gps

2014-02-22 Thread tom jones


I picked up prn30 signal for the second time around 11:30pdt but did not get 
any data till 12:11pdt
All though my sirf receiver is advertised to track some rediculous amount of 
sat's at once (something 32 or is it 48 

sats) the sirfdemo software only allows 12 sat's to be tracked at once..

The sirfdemo had 11 channels tracking strong high altitude sats, the 12th 
channel was toggling between two low horizon 

sats and prn30 and couldn't lock on either.
Prn30 had good signal strength about 20db out of 35db (sirf receiver is 
indoors) the software saw it as unuseable and 

kept trying to aquire other low horizion sats.  Around 12pdt the low horizon 
sats fell below the horizon freeing up two 

more channels.
This is about the time I received the good prn30 data.

The gps clock timing received looks very similar to last nights clock data 
except the rate doesn't go negitive.
It looks to me like mission control shut power off to the sat between last 
nights and todays data? or they tested a 

second  new ribidum clock today? 

Anyway todays clock data looks a little more stable than last nights clock / 
data.
I've cut and pasted only todays (noon time) first reception and todays last 
reception.

4.1019065602e-010,-2.6931360042e-014 @ 02/22/2014 12:11:52

2.8165598456e-010,-5.0887679487e-014 @ 02/22/2014 13:04:22

I'm expecting the negative drift to stabilize as the spacecraft gets further 
from earth.

I did find the norad satellite tracking numbers;
prn30 svn64 39533
delta 4 r/b 39534

but I haven't put the norad numbers into sat tracking program yet.

Having fun Tom...



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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Magnus Danielson

Hi Jim,

On 22/02/14 14:17, Jimmy Burrell wrote:

I need some help with a 'noob' question regarding some practical examples in
some of the NIST literature. When attempting to compare two clocks, I'm a bit
confused on the subject of exactly how to use my counter to compare a delayed
clock relative to another. Or perhaps I should just say 'comparing two clocks'.
Let's take some concrete examples.

Let's say I want to characterize my Morion MV89 ocxo using my HP5335a.
Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the counter's
input 'A'. Obviously, I can feed in a second, external reference clock at 10MHz
into input 'B'. Suppose, however, I didn't have an external reference clock.
Can I compare against the counter's internal time base by hooking a line from
the rear jack time base output to channel 'B' input? Or am I making it too
complicated? Do I simply plug into input 'A' and go?

In a somewhat related question, in this article
(http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf) where two clocks,
both divided to 1PPS, were compared, W.Riley makes the following statement, The two 1 PPS
outputs were connected to a Racal Dana 1992 time internal counter having 1 nanosecond resolution,
and the start and stop signals were separated sufficiently in time for the counter to function
properly. I wonder what exactly is meant by separated sufficiently in time for the
counter to function properly and how one would go about doing this? For example, is inverting
one of the signals sufficient separation? If not, how is this typically done? Delay line?

The problem is that the start trigger (Channel A) will arm the
measurement on the stop channel (Channel B). For this process to operate
properly, allow 5 ns. If you look into the 1992 spec-sheet it says that
TI interval is from 5 ns.

If you have a 10 MHz or 5 MHz signal, you only have 100 ns or 200 ns
periods to play with. Dividing them down to say 10 Hz gives you plenty
of time such that you can boot-strap one of the dividers such that you
don't go through zero within the measurement period.

Adding a delay doesn't help, as frequency error will get the phase into
through zero condition pretty quick I would guess.

The SR620 counter has a coax delay-line to give trigger look-ahead.

Cheers,
Magnus
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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Jimmy D. Burrell

Hmmm... Magnus thank you for your comments. The 5 ns figure is certainly 
helpful. My 1980 manual from HP just says Time Interval A - B = 0 ns to 10E7 
seconds. Not very helpful.

May I ask where you found your 1992 reference? Perhaps you have a link?

Many thanks,

Jim...
N5SPE

On Feb 22, 2014, at 5:20 PM, Magnus Danielson mag...@rubidium.dyndns.org 
wrote:

 Hi Jim,
 
 On 22/02/14 14:17, Jimmy Burrell wrote:
 I need some help with a 'noob' question regarding some practical examples in 
 some of the NIST literature. When attempting to compare two clocks, I'm a 
 bit confused on the subject of exactly how to use my counter to compare a 
 delayed clock relative to another. Or perhaps I should just say 'comparing 
 two clocks'. Let's take some concrete examples.
 
 Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. 
 Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the 
 counter's input 'A'. Obviously, I can feed in a second, external reference 
 clock at 10MHz into input 'B'.  Suppose, however, I didn't have an external 
 reference clock. Can I compare against the counter's internal time base by 
 hooking a line from the rear jack time base output to channel 'B' input? Or 
 am I making it too complicated? Do I simply plug into input 'A' and go?
 
 In a somewhat related question, in this article 
 (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
  where two clocks, both divided to 1PPS, were compared, W.Riley makes the 
 following statement, The two 1 PPS outputs were connected to a Racal Dana 
 1992 time internal counter having 1 nanosecond resolution, and the start and 
 stop signals were separated sufficiently in time for the counter to function 
 properly.  I wonder what exactly is meant by separated sufficiently in 
 time for the counter to function properly and how one would go about doing 
 this? For example, is inverting one of the signals sufficient separation? If 
 not, how is this typically done? Delay line?
 
 The problem is that the start trigger (Channel A) will arm the measurement on 
 the stop channel (Channel B). For this process to operate properly, allow 5 
 ns. If you look into the 1992 spec-sheet it says that TI interval is from 5 
 ns.
 
 If you have a 10 MHz or 5 MHz signal, you only have 100 ns or 200 ns periods 
 to play with. Dividing them down to say 10 Hz gives you plenty of time such 
 that you can boot-strap one of the dividers such that you don't go through 
 zero within the measurement period.
 
 Adding a delay doesn't help, as frequency error will get the phase into 
 through zero condition pretty quick I would guess.
 
 The SR620 counter has a coax delay-line to give trigger look-ahead.
 
 Cheers,
 Magnus
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Re: [time-nuts] WWVB antennas

2014-02-22 Thread Alex Pummer

Fractal antennas are nice artworks, but as long as their geometry does 
not contain  elements , which are comparable with the wavelength of the 
incoming signal they are more or less not much assets,

73
KJ6UHN
Alex
  On 2/22/2014 8:50 AM, Alan Melia wrote:
Claims on antenna efficiency at these frequencies are fairly 
meaningless (as always) in that a normal antenna efficiency would be 
less than 1% !!

Alan
G3NYK




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Re: [time-nuts] comparing two clocks

2014-02-22 Thread Magnus Danielson


Hi Jim,

On 23/02/14 01:10, Jimmy D. Burrell wrote:

Hmmm... Magnus thank you for your comments. The 5 ns figure is certainly helpful. My 1980 
manual from HP just says Time Interval A - B = 0 ns to 10E7 seconds. Not 
very helpful.

May I ask where you found your 1992 reference? Perhaps you have a link?


I found this manual:
http://www.ko4bb.com/Manuals/Racal/Racal-Dana_1991-1992-UserManual.pdf

I now see that I read of the common mode line.

I don't have one of these. It should be trivial enough to put two 
references at just about near same rate and see how their through-zero 
beat behaves.


Cheers,
Magnus
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Re: [time-nuts] comparing two clocks

2014-02-22 Thread SAIDJACK

Jim,
 
when I did the test on the 53132A, I did the test with the two signals on  
top of each other with a very small cable offset of 400ps, then I added a 
10ns  delay line to the B signal just to see if the counter would behave 
differently.  Here are the results, pretty much looks identical with 0.4ns 
offset 
or 10ns  offset.
 
bye,
Said
 
 
 
 
In a message dated 2/22/2014 10:06:30 Pacific Standard Time,  
ail...@t-online.de writes:

Jim,

If I get you right, you want to compare the 10MHz  outputs (not the
1PPS). As Jim and Bob told us so far, the thing is to  provide, that
input A _always_ starts before input B (or the other way  around).

Connect the signals to an oscilloscope, and check, how much  the phase
differs - if the rising slopes occur close together, put  some
meters/yards of coaxial cable into one of the two signal paths. 1  meter
is roughly worth 5ns - while the period of 10MHz is 100ns, 1m cable  will
phase shift about 18 degrees. I didn't verify, if the coax cable  (with
it's microphonic effect) affects the ADEV - does anybody have  experience
with this? Otherwise I'd have to fire up my counter and have  a
measurement on the run...

Of course, inverting one signal will do  as well. If you do it with extra
electronics that definitely will affect  the ADEV. I find it much easier
to use some meters of cable.

Ok, my  counter is heating up by now...

Volker


Am 22.02.2014 14:17,  schrieb Jimmy Burrell:
 I need some help with a 'noob' question  regarding some practical 
examples in some of the NIST literature. When  attempting to compare two 
clocks, 
I'm a bit confused on the subject of exactly  how to use my counter to compare 
a delayed clock relative to another. Or  perhaps I should just say 
'comparing two clocks'. Let's take some concrete  examples. 

 Let's say I want to characterize my Morion MV89  ocxo using my HP5335a. 
Obviously, I can tune the MV89's 10MHz by +/- 1Hz and  feed it to the 
counter's input 'A'. Obviously, I can feed in a second,  external reference 
clock 
at 10MHz into input 'B'.  Suppose, however, I  didn't have an external 
reference clock. Can I compare against the counter's  internal time base by 
hooking a line from the rear jack time base output to  channel 'B' input? Or am 
I 
making it too complicated? Do I simply plug into  input 'A' and go?

 In a somewhat related question, in this  article  
(http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf)
  where two 
clocks, both divided to 1PPS, were compared, W.Riley makes the  following 
statement, The two 1 PPS outputs were connected to a Racal Dana  1992 time 
internal 
counter having 1 nanosecond resolution, and the start and  stop signals 
were separated sufficiently in time for the counter to function  properly.  I 
wonder what exactly is meant by separated sufficiently in  time for the 
counter to function properly and how one would go about doing  this? For 
example, is inverting one of the signals sufficient separation? If  not, how is 
this typically done? Delay line?

 Thank  you,

 Jim...
 N5SPE
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Re: [time-nuts] connor winfield GPSDO module phase noise