[time-nuts] Baseline measurement with different standard. (same timebase for clock and DUT)

[Taka Kamiya via time-nuts]

I hear a term equipment noise, base line noise, and noise floor of the 
equipment all the time. I had a few concerning and unexpected result with 
recent tests so I've conducted tests of testing methods.  I'd like to verify, 
my understanding of the situation is correct.  I basically did baseline test of 
the same interval counter with different time standards.

I took an adev measurement of my time-interval counter using standard-A for 
both clock and input.I took another adev measurement using the same 
time-interval counter using standard-B for both clock and input.I repeated the 
same test with standard-C.Run time was 1 hour and interval was 1 second.  

Method of measurement was, time stamping interval measurement (OK, it was a 
TICC), clock was 10MHz and input A was fed with 1 pps from the same source.
Each represents Cesium, Rubidium, and GPSD.
My expectation was, I will get an over-lapping (right on top of each other) 
with very minor variations.  Since clock and the DUT was the same, why would 
there be any different
Surprising result (to me) was that they all started with different Adev value 
(origin) and sloped downwards at the slope -a (same value).  They were EXACTLY 
parallel from 1 second all the way to the end (which was 900 seconds but run 
time was 1 hour).  

What did I just do?  How can I make use of this graph?  Why are they all the 
same slope?  Why are they not overlapping?
I can assume one of the answers to be, clock and the TICC form an "equipment" 
and that line represents the base line FOR THAT standard.  That's as far as I 
can get.  If I can get a better explanations, I would very much like to hear 
it.  I also wonder if this would be the same situation for every counter and 
every method, but I can do that test later.
Thank you.


--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
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Re: [time-nuts] potential low-RFI power supply

[ed breya]

Trying to look at the junk on the output voltage won't tell the story 
you need. Just connect a scope (1 meg) input to the DC output ground, 
and you'll begin to see the common-mode current situation. The actual LF 
and HF ripple on the DC out can be dealt with by sufficient filtering or 
post-regulation, and hardly matter compared to the common-mode currents, 
which will pervade everything connected.


First, put only a scope probe tip or direct input connection on the DC 
out ground or plus - shouldn't matter too much either way if the output 
floats. Do not connect the scope's ground to the PS yet - let its ground 
return to earth via its mains cord. This will likely indicate a very 
large signal, including the noises of the power supply and the scope and 
other local ground loop sources, against the high measuring impedance. 
This is the gross (in size and disgusting-ness) available CM driving 
voltage in your measurement setup, including line leakage, especially if 
the PS is fed by a two-wire cord.


With this setup, you should be able to see a pretty good representation 
of the actual signal on the main switching device in the PS. This is 
usually by far the biggest, fastest signal inside, and the cause of most 
EMC grief. Set up the scope triggering for LF Reject, and speed up the 
sweep to observe where the SMPS runs, say 20 kHz to maybe 300 kHz for 
newer type products, then play with the trigger level and hold-off. 
There should be plenty of crap available to trigger on - the trick is to 
get the right part. A dual timebase may help, but shouldn't be necessary.


You'll be able to tell if the PS runs in burst mode at no load, 
evidenced by chirping at low frequency, on the scope and maybe audibly. 
Now add some load, say 10 percent, and it will likely leave burst mode, 
and go to regular PWM at the proper frequency, which you now can 
measure. This frequency is the fundamental, for figuring out 
interference issues.


With a small load, depending on the topology, the PS may be running in 
discontinuous mode, evident on the switch waveform when the device shuts 
off, and a large ringing voltage appears, higher than the fundamental 
frequency. This represents energy in the tank circuit - transformer L 
and device and parasitic C all over the place. The resonant frequency 
and decay can change dramatically with conditions, and is not dependent 
on the fundamental, but is triggered by it, so imagine all the mixing 
products involved. This, plus line harmonics mixed in, tends to make 
what appears to be broadband noise, but a lot of it is actually finely 
spaced spurs that may move around with different loads and other 
conditions - what a mess..


As you increase the load, the PS may transition to continuous mode, and 
the big rings will disappear, since current through the energy storage 
inductance never goes to zero. Always present, are the very fast, 
smaller rings on all the sharp edges, due to leakage inductances and 
other device parasitics. These make up the very high frequency harmonic 
content, and easily escape into the environment.


As you can imagine, the EMC/spectral content can change a lot under 
different conditions. It's good to know as much as you can about what 
it's doing inside. Then it may be possible to avoid certain problems by 
operating in conditions where it's least offensive to your situation.


It's pretty slick to be able to see somewhat inside a black box, if you 
know what to look for. There's no guarantee this will work in any 
particular situation, but I'd say there's a very good chance of getting 
lots of details - or at least to see a lot of ugly waveforms that won't 
trigger properly. If you hardly see anything, then that means the device 
and you ambient environment are extremely clean - or more likely that 
your setup or scope have a problem.


The next step is to see some of your measurement limits. Now connect the 
scope ground (via BNC outer) or probe's ground clip to the signal point, 
which ideally results in no apparent signal, even with the sensitivity 
cranked way up. If this happens, then you're in great shape, 
ground-loop-wise. However, I'd guess or predict that you'll see plenty, 
because there is no true ground. The minimum signal is with the input 
shorted, and no connection to anything. When you hook it up, everything 
changes. Remember also, that a lot of noise will be around that's not 
from the DUT, so you need to determine what's what and where.


There are more measurements that can be made, of course, especially when 
you can think inside as well as outside the box. I'll have a bit more to 
say next time.


Ed



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Re: [time-nuts] potential low-RFI power supply

[Dana Whitlow]

IIRC the HP3561A goes to 100 kHz.  It's a well-built FFT analyzer at heart.

Dana


On Sun, May 17, 2020 at 4:12 PM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> I have an HP audio FFT that starts from sub 1Hz so I can do that when I
> get mine.  What kind of load shall I use for this?  Purely resistive load?
> What kind of power?  Near 100%, 50% or??  I don't know off the top of head
> what the available RBW is.  It's HP3561A
>
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>
>
> On Sunday, May 17, 2020, 4:12:03 PM EDT, jimlux 
> wrote:
>
>  On 5/17/20 11:53 AM, Eric Scace wrote:
> > Pro Audio Engineering announced a sale (through Friday) on its nominal
> 14 Vdc 4A switching supply <
> https://proaudioeng.com/products/pae-kx33-low-rfi-ac-power-supply/>. The
> test results <
> https://proaudioeng.com/products/pae-kx33-low-rfi-ac-power-supply/>
> webpage compares noise on the DC output and noise frequency spectrum under
> a variety of conditions with a lead-acid battery, an Astron linear supply,
> and a variety of switching supplies from other manufacturers.
> >
> > I have not used this and can’t vouch for its performance. Given recent
> discussions here on supplies, the analysis might be interesting. At least
> the supplier has attempted to quantify the performance of its power supply
> and make that information available to the prospective purchaser.
> >
> > It would be interesting to see comparable (or more suitable)
> measurements made by others posted here.
> > ___
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> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
>
>
> Interesting.. It would have been nice to see spectrum analyzer plots
> from, say, 0 to 1 MHz with a much narrower resolution BW.  1 MHz/div
> with 300 kHz RBW isn't going to show the "row of discrete spurs" that
> the switchers put out.
>
> 4mV ripple isn't bad, or at least, it's better than most of the other
> switchers.  The Astron linear is given as 5mV, but the scope photo
> doesn't seem to show anything. At 5ms for the whole screen, you should
> see some variation for over the 8.33 ms ripple period.
>
>
> I get that they're demonstrating the performance with a specific
> transceiver load - but I'd be interested in seeing measurements at zero,
> 50%, and 100% load on a switcher.
>
>
>
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Re: [time-nuts] potential low-RFI power supply

[Taka Kamiya via time-nuts]

I have an HP audio FFT that starts from sub 1Hz so I can do that when I get 
mine.  What kind of load shall I use for this?  Purely resistive load?  What 
kind of power?  Near 100%, 50% or??  I don't know off the top of head what the 
available RBW is.  It's HP3561A

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Sunday, May 17, 2020, 4:12:03 PM EDT, jimlux  
wrote:  
 
 On 5/17/20 11:53 AM, Eric Scace wrote:
> Pro Audio Engineering announced a sale (through Friday) on its nominal 14 Vdc 
> 4A switching supply 
> . The 
> test results 
>  webpage 
> compares noise on the DC output and noise frequency spectrum under a variety 
> of conditions with a lead-acid battery, an Astron linear supply, and a 
> variety of switching supplies from other manufacturers.
> 
> I have not used this and can’t vouch for its performance. Given recent 
> discussions here on supplies, the analysis might be interesting. At least the 
> supplier has attempted to quantify the performance of its power supply and 
> make that information available to the prospective purchaser.
> 
> It would be interesting to see comparable (or more suitable) measurements 
> made by others posted here.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
> 


Interesting.. It would have been nice to see spectrum analyzer plots 
from, say, 0 to 1 MHz with a much narrower resolution BW.  1 MHz/div 
with 300 kHz RBW isn't going to show the "row of discrete spurs" that 
the switchers put out.

4mV ripple isn't bad, or at least, it's better than most of the other 
switchers.  The Astron linear is given as 5mV, but the scope photo 
doesn't seem to show anything. At 5ms for the whole screen, you should 
see some variation for over the 8.33 ms ripple period.


I get that they're demonstrating the performance with a specific 
transceiver load - but I'd be interested in seeing measurements at zero, 
50%, and 100% load on a switcher.



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Re: [time-nuts] Gravity, solid Earth tides

[Steve Allen]

I have taken a much deeper dive through the history of geophysics
and upon coming up for air...

On Fri 2020-05-15T22:02:32-0700 Steve Allen hath writ:
> On Fri 2020-05-15T21:49:43-0700 Tom Van Baak hath writ:
> > Also, some of the very best pendulum clocks ever made were good enough that
> > their timekeeping was affected by lunar/solar tides. One is the English
> > Shortt-Synchronome and another is the Russian Fedchenko.
>
> Those are not measuring solid earth tides per se.  They are measuring
> the failure of the earth to deform as much as, and in phase with, the
> changing potential, so the local acceleration of gravity changes.
>
> I have not found any papers which say that two distant chronometers
> have yet been tied together with a stable enough optical network
> to measure the changing difference in their potentials.

Tom Van Baak is right, there is no question that pendulum clocks were
seeing the effects of solid earth tides by the 1940s.  They were
measuring (semi)diurnal changes in the local acceleration of gravity.
But clocks were not the first measurement of that effect, and not the
best.

The first measurements were from gravimeters which had been developed
and deployed to assist in explorations for oil.  See Truman, 1939
https://ui.adsabs.harvard.edu/abs/1939ApJ89..445T/abstract
Before and after Truman there were other deep investigations of
(semi)diurnal variations in local gravity and their causes.
Those led to estimations of the Love numbers for the amplitude and
phase of the deformation of the solid earth in response to the
lunar and solar tides.

My reaction was prompted by the fact that all of those measurements
were struggling to distinguish the effects of ocean loading at sites
near a shoreline, deformations of the surface due to changes in the
weather, etc.  Getting better numbers needed tying together distant
sites with sufficient accuracy to see the differential ground motions.

I think it is true even now that two distant sites with atomic
chronometers have not yet been tied together with a sufficiently
stable optical fiber network to allow the clocks to measure the
differential changes in gravitational potential due to deformations.
But starting in the 1970s the deformations were measured by VLBI using
the incoming wavefronts from distant quasars as the tie to give the
distance between distant sites.

So Tom is right in answering Hal Murray's question, clocks, even
pendulum clocks, were good enough to *detect* solid earth tides.
But without other technologies they are not good enough to give clean
estimates of the magnitude and phase of those tides.

--
Steve Allen  WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street   Voice: +1 831 459 3046 Lng -122.06015
Santa Cruz, CA 95064   https://www.ucolick.org/~sla/  Hgt +250 m

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Re: [time-nuts] potential low-RFI power supply

[jimlux]

On 5/17/20 11:53 AM, Eric Scace wrote:

Pro Audio Engineering announced a sale (through Friday) on its nominal 14 Vdc 4A switching 
supply . The test 
results  webpage 
compares noise on the DC output and noise frequency spectrum under a variety of conditions 
with a lead-acid battery, an Astron linear supply, and a variety of switching supplies from 
other manufacturers.

I have not used this and can’t vouch for its performance. Given recent 
discussions here on supplies, the analysis might be interesting. At least the 
supplier has attempted to quantify the performance of its power supply and make 
that information available to the prospective purchaser.

It would be interesting to see comparable (or more suitable) measurements made 
by others posted here.
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Interesting.. It would have been nice to see spectrum analyzer plots 
from, say, 0 to 1 MHz with a much narrower resolution BW.   1 MHz/div 
with 300 kHz RBW isn't going to show the "row of discrete spurs" that 
the switchers put out.


4mV ripple isn't bad, or at least, it's better than most of the other 
switchers.  The Astron linear is given as 5mV, but the scope photo 
doesn't seem to show anything. At 5ms for the whole screen, you should 
see some variation for over the 8.33 ms ripple period.



I get that they're demonstrating the performance with a specific 
transceiver load - but I'd be interested in seeing measurements at zero, 
50%, and 100% load on a switcher.




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Re: [time-nuts] potential low-RFI power supply

[Taka Kamiya via time-nuts]

Looks promising!  I went ahead and purchased a piece.  With new switching 
supply COMPONENTS targeting audio market from various chip manufacturers, it is 
indeed a hopeful and promising development.  Now I'm wishing someone to make a 
piece one order of noise level less for "time-nuts" market.
A bit off topic but I've been playing with various time-nuts sources with 
internal regulation with various power sources, including bottom of the rung 
switchers.  (100mV +/- noise)  I'm finding perform surprisingly well.

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Sunday, May 17, 2020, 2:54:28 PM EDT, Eric Scace  wrote: 
 
 
 Pro Audio Engineering announced a sale (through Friday) on its nominal 14 Vdc 
4A switching supply 
. The test 
results  
webpage compares noise on the DC output and noise frequency spectrum under a 
variety of conditions with a lead-acid battery, an Astron linear supply, and a 
variety of switching supplies from other manufacturers.

I have not used this and can’t vouch for its performance. Given recent 
discussions here on supplies, the analysis might be interesting. At least the 
supplier has attempted to quantify the performance of its power supply and make 
that information available to the prospective purchaser.

It would be interesting to see comparable (or more suitable) measurements made 
by others posted here.
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[time-nuts] potential low-RFI power supply

[Eric Scace]

Pro Audio Engineering announced a sale (through Friday) on its nominal 14 Vdc 
4A switching supply 
. The test 
results  
webpage compares noise on the DC output and noise frequency spectrum under a 
variety of conditions with a lead-acid battery, an Astron linear supply, and a 
variety of switching supplies from other manufacturers.

I have not used this and can’t vouch for its performance. Given recent 
discussions here on supplies, the analysis might be interesting. At least the 
supplier has attempted to quantify the performance of its power supply and make 
that information available to the prospective purchaser.

It would be interesting to see comparable (or more suitable) measurements made 
by others posted here.
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