Re: [time-nuts] 4046 replacement

[John Miles]

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> donald collie
> Sent: Wednesday, April 18, 2018 2:40 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] 4046 replacement
> 
> Thankyou Attila. I remember reading a book on PLL theory, recently,writen
> by a very knowledgable fellow, but I didn`t think to make a copy of his
> critique of the 4046. I recall that the nub of it was that the 4046 isn`t
> suitable for some applications because of a design flaw. Perhaps somebody
> in this group could explain further.
> Thankyou Bill, for the datasheet on the 74HCT9046, and your comments
> Cheers!..Don
> jnr ZL4GX

The tristate phase/freq comparator in the original 4046 had a dead-band problem 
that caused its gain to vary widely as it approached its normal operating point 
in a stable loop.  This wasn't so much a 'bug' as it was a consequence of the 
fact that there's effectively no gain when there's no phase error to correct.  

Ulrich Rohde's book indicates that this problem was first documented in 1978 in 
an EDN article by some authors named Egan and Clark.  Newer PFDs implement the 
'antibacklash' logic that Rohde mentions.  If you really must use a 4046, I'd 
look for a newer version whose data sheet explicitly addresses this problem.  
Better still, use a newer part.

Another workaround is to force the PFD to stay out of its dead zone by loading 
the output lightly, e.g. with a 1M resistor.  You can never compensate for this 
effect perfectly, though.  You can probably expect some downsides like worse 
reference suppression.  

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[John Miles]

> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John
> Ackermann N8UR
>
> Reviving the conversation about superb voltage regulators, I am looking
> for one to run the analog and PLL bits of a high performance frequency
> synthesizer chip.
> 
> The current drain looks to be about 160-180 mA at 1.8 V, which is
> uncomfortably close to the limit for the LT3042 (200 mA).  The
> manufacturer's evaluation board uses a MAX8869, which appears to be
> nowhere in the LT3042's league, but will source 1 A.
> 
> Any recommendations for a 1.8 V regulator a little beefier than the
> LT3042, but with similar noise performance?

These days, the best RF synthesizer and clock generator chips include dedicated 
low-noise LDOs inside the package.  It's rarely worthwhile to use a quieter 
regulator than the manufacturer recommends, or one that's quieter than whatever 
is on their own demo board. 

One very nifty example is the LMK61E2, which I X-rayed a while back:
http://www.ke5fx.com/LMK61E2_30kVp_20s.png

The overall package is only about 1 cm square.  The synthesizer has its own 
die, while the input regulators and (presumably) their bypass caps are mounted 
directly above the Vdd input pad.  According to TI, the PSRR of the internal 
LDO that runs the analog section is better than 70 dB at offsets below 1 MHz.  
So you could even power it directly from a switcher, assuming you keep a leash 
on its harmonics. 

-- john, KE5FX
Miles Design LLC


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[time-nuts] Assorted replies, and request for info

[John Miles]

Request for data from an off-list friend who is looking for info on an Ovenaire 
OCXO and/or the instrument it was used in:

> Could you send a post on my behalf asking if anyone else has an 
> Ovenaire 42-15 or if not, a Spectracom 8131 Frequency Standard Oscillator. 

This is from Dennis Tillman, who can be reached directly at dennis (at) 
ridesoft.com.

> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What
> do you think that is? On a hunch I opened the front panel and reset the
> blinking amber battery alarm lamp, and voila, that noise went away. Makes
> sense when you think of the power variations associated with a blinking
> incandescent lamp.

I hadn't heard of that one, but some other examples include 1-pps crosstalk on 
the 10 MHz output of some of the HP GPSDOs (which I've run into myself), and 
the inadvertent ~5 MHz comb generator that drives the indicator LED on the HP 
5370's reference clock interface PCB that Bruce Griffiths noticed several years 
ago.  Presumably neither of these faux pas were bad enough to be noticed by the 
original designers or their paying customers, but they probably would have been 
fixed if they had come to the attention of the people involved.  Goes to show 
how improved instrumentation can be a curse as well as a blessing.

Poul-Henning's observation on the 5065A integrator cap highlights the risk of 
erring too far in the opposite direction:

> When I experimented, I could hardly find *any* property that mattered
> for that capacitor, not even the exact capacitance, because the
> adjustment procedue handles that.

I have a feeling this is true of most of the components in that circuit.  The 
nice thing about an integrator is that it's also a low-pass filter.  And the 
nice thing about a closed loop is that it's, well, closed.

Before spending too much time arguing about whether the opamp should be 
replaced with an LT1012 or an AD797 or a cryocooled tunnel diode or whatever, 
I'd suggest replacing it with a 741 and seeing how much *worse* the performance 
gets.  It is easier to measure the effect of that kind of change.  If there is 
little or no harm in using the crappiest opamp you can find, that means that 
you can safely stop worrying about what the best one might be.  

> One of the TimePods that I had access to in the past was particularly good
> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a
> lot which instrument the power transformer was in. For some weird 
> reason it was a good magnetometer at line frequencies. I never bothered to 
> send it back for analysis. Simply moving it onto the bench top (rather than 
> stacked on top of this or that) would take care of the issue.
> 
> As far as I could tell, it was just the one unit that had the issue. None of 
> the
> others in the fleet of TimePods seemed to behave this way. Given that they
> normally are very good at rejecting all sorts of crud and ground loops, it was
> somewhat odd to see.

I've seen similar behavior here, not only with respect to units responding 
differently to 60/120 Hz magnetic interference, but also at higher offsets in 
the absence of an obvious coupling mechanism.  There was one case where a 
TimePod I was working with picked up an unstable low-level spur near 25 kHz 
from an LED aquarium light fixture several meters away.  Other units swapped 
into the same position did not show the spur at all, and I was never able to 
narrow down the cause with any certainty.  I don't have a good explanation for 
any of the above, unfortunately.

That being said, Phil Hobbs posted something on sci.electronics.design the 
other day that I thought was subtly insightful, even though he was just stating 
an obvious point.  Namely, ground loops are inherently very low impedance 
phenomena, often occurring in the milliohm range.  Especially when dealing with 
anodized aluminum hardware like the TimePod's enclosure, the difference between 
a test setup where all the coax shields act as a near-perfect shorted 
transformer turn versus one with significant loss might come down to small 
differences in fastener torque, or perhaps a missing star washer.  So it's 
possible to envision a scenario where tightening up all the proverbial loose 
screws actually makes a magnetically-coupled spur worse.  

Lifting a coax shield is usually not the best solution to ground loops, but 
Phil's offhand comment made me wonder about the effects of deliberately adding 
just a few ohms of series R.  It's on my list of things to look into when I 
have time.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Selling Time and Frequency Equipment

[John Miles]

> To echo Attila, just sayin.

$4000 is up there, but not outrageous IMO.  If you have a $4000 budget and 
don't actually need a primary standard, a well-kept 5065A is a good way to go.  
At taus less than a few hours they can outperform the best 5071As, even before 
Corby's mod is applied.  And they can be left powered on full time.

You can't do any better for the same money, put it that way.  5065As with the 
optical-filter mod are more appropriately compared to passive H-masers than to 
cesium standards.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Curious, how many t-nuts have 5065A

[John Miles]

> Hi
> 
> Well, if anybody else is “giving away” 5065’s I’d certainly be willing to
> “accept”
> one :)
> 
> Bob

Be careful what you wish for. :) The unit Pete is talking about is a 1969-era 
model, in nice overall shape but with the usual bad capacitors on the oven 
controller board.  The lamp oven winding should be about 50 ohms cold, but is 
closer to a dead short.  It will take a LOT of work to restore to working 
condition. 

The failed controller ran long enough to smoke a 1.5-ohm 1W resistor, 
1N400-something diode, and eventually the 1A line fuse ( 
http://www.ke5fx.com/5065A_A11_sm.jpg ).  Needless to say the lamp PCB looks 
like something out of Fukushima.  It'll need to be rebuilt from scratch after 
rewinding the heater.

Seriously -- anyone with a 5065A who hasn't checked/replaced the caps on A11, 
don't let this happen to you.  They aren't making any more of these puppies.  
If the caps on that board are original, don't bother to check them, just 
replace them, as Luciano suggests at http://www.timeok.it/hp5065a-corner-3/.  
No need for exotic parts, just put in whatever you have that is somewhere close 
to the original values.  

Not a bad idea to verify the ESR of the new parts you're installing as well.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] More on SiLabs 5340

[John Miles]

> -Original Message-
> There is a small detail that puzzles me: the ADEV for the internal
> reference 10MHz and 30MHz bends upwards at tau greater than 0.1s.
> Shouldn't that be visible by a change in slope in the phase noise
> plot at ~10Hz as well?
> 
>   Attila Kinali


Linear drift (which is what's happening here) has a bigger effect on the 
overall gestalt of an ADEV plot than it will on a phase noise plot.  This is 
because long-term drift looks similar to DC offset or noise at extremely low 
frequencies, both of which are attenuated by an HPF stage prior to each FFT 
segment.  But ADEV doesn't benefit from DC removal, and since it doesn't 
converge in the presence of drift, you get the usual upturn in the trace at 
increasing taus. 

When you see a highly-elevated noise trace at low offset frequencies, it's also 
a good idea to check for glitches in the 'f' measurement view, although in this 
case the L(f) spectrum is very typical of these sorts of parts. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Microsemi 3120A sold on eBay

[John Miles]

They're essentially the same as the original TimePod 5330A specs  ( 
http://www.miles.io/TimePod_5330A_user_manual.pdf page 11).  The 3120A doesn't 
display noise at offsets below 1 Hz, though, while the 5330A went down to 0.01 
Hz.  Also, some of the TimePod features are "added-value" software options in 
the 3120A, but it's not clear if this unit came with any of the license keys.  

The final selling price seems fairly reasonable considering the sparse details 
provided by the seller.  If someone on the list bought it and it doesn't have 
the software CD, drop me a note offline and I'll hook you up.

-- john, KE5FX
Miles Design LLC

> What are the specs ? 73 de N1UL
> 
> Sent from my iPhone
> 
> > On Jan 27, 2018, at 5:38 PM, John Miles <j...@miles.io> wrote:
> >
> > So, who's the lucky winner?  Anyone on here?  That's the first one of these
> > I've seen in the "secondary market," so to speak.
> >
> >
> >
> > https://www.ebay.com/itm/332531180078
> >

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[time-nuts] Microsemi 3120A sold on eBay

[John Miles]

So, who's the lucky winner?  Anyone on here?  That's the first one of these
I've seen in the "secondary market," so to speak.

 

https://www.ebay.com/itm/332531180078

 

-- john

Miles Design LLC

 

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Re: [time-nuts] Wenzel VHF PLO Oscillators Off Frequency

[John Miles]

> Yes, exactly those. With no input, would they be expected to be 4 kHz off?
> The spec for the standard part wants the input to be within 1e-7. I would
> not expect them to be so far off free running.

That does seem like a lot.  I'd expect a few hundred Hz of error at the most.
 
> I saw 13 MHz on the 500-14273 and stayed away from those.
> 
> Do you know of any part numbers that use 10 MHz in? Wenzel would not tell
> me the exact specs of the 500 series parts available on ebay and only sent
> me the specs for the standard 501-14057 that takes 10 MHz.

Most of the 100 and 200 MHz bricks I've seen work with either 5 or 10 MHz .  I 
don't know if I've seen any 80 MHz units that do.  All of the ones I've bought 
on eBay have been from the customer-proprietary 500- series with unusual input 
frequencies.

> Do you know what the pll lock output does when the input frequency is off?
> These toggle high for any frequencies I have put in.

Not offhand.  If there's a PFD inside it should be easy to zero in on the right 
frequency, but if there's only a phase detector you may need to set up a sweep 
and watch the tuning-voltage output on a scope.  I don't remember it taking 
very long to find the correct input frequencies for the ones I bought, though.  
 

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Wenzel VHF PLO Oscillators Off Frequency

[John Miles]

Sounds like he's talking about the small 'bricks' that Wenzel sells with 
internal PLL-disciplined OCXOs.  Some of these expect oddball input 
frequencies.  Just looking at the 80 MHz parts on the shelf around here, 
500-14273 wants a 13 MHz input, 500-25010 uses 24.576 MHz, and 500-25009  uses 
19.2 MHz.   So that's probably the issue, if two of them seem to be failing the 
same way.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
> Camp
> Sent: Sunday, November 12, 2017 2:03 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Wenzel VHF PLO Oscillators Off Frequency
> 
> Hi
> 
> I guess my point was more that there is not a VCO / PLL combo in an OCXO.
> 
> If dropping the supply gets you on frequency, then you have moved things a
> lot
> with that voltage change. 50 PPM is a lot of delta T on any normal OCXO
> crystal.
> That strongly suggests there is something wrong in the control circuit.
> 
> Bob
> 
> > On Nov 12, 2017, at 2:52 PM, Mark Goldberg 
> wrote:
> >
> > The standard oscillator, 501-14057 (
> > www.wenzel.com/wp-content/parts/501-14057.pdf) will lock to an
> external 10
> > MHz reference and this one is marked "80 MHz" and "15V on the label.
> Maybe
> > someone swapped the labels. I did try lowering the supply voltage. It got
> > to 80 MHz at about 11V and still did not lock to the reference. This
> > oscillator is specified at 1e-6/year aging. That is way less than it is off
> > now.
> >

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Re: [time-nuts] Phase noise measurement experiment by Andrew Holme

[John Miles]

> But be aware, that measurements close to the limit of thermal noise
> will make your measurement go sour. There the noise of your splitter
> will cause an anti-correlation effect and the measured noise will
> suddenly drop way below thermal noise. Craig Nelson and Archita Hati
> from NIST, Enrico Rubiola from FEMTO, Magnus from time-nuts and several
> others have been discussing this for a couple of years now at PTTI,
> IFCS and EFTF.
> (e.g. https://www.nist.gov/publications/cross-spectral-collapse-anti-
> correlated-thermal-noise-power-splitters )

Cross-spectral collapse due to thermal noise is basically Mother Nature 
complaining that we're trying to do something that's physically ill-advised, by 
trying to measure the noise in a system at levels near the thermal floor of the 
termination resistance that's necessary to define such a system in the first 
place.  Unfortunately the issue can affect measurements at levels several dB 
higher than the thermal floor, making it a genuine occupational hazard.

On the bright side, splitter topologies that use a single resistive load with 
no differential-mode termination have little or no vulnerability to this 
phenomenon.  Of course the common-mode termination imposes its own noise floor, 
but that's life in this particular universe.   

That being said, it's still a bit of an awkward situation for designers of 
future test sets.  We can't use Wilkinson splitters anymore -- or at least we 
shouldn't, given what's been learned over the past couple of years.  As a 
result, some customers' best devices may suddenly start looking noisier than 
they did when measured on earlier instruments, or (worse) when measured on 
competing ones.  Those customers may not respond agreeably when advised to dunk 
the termination in liquid helium...

> > Since the cross correlation could reduce noise a lot, I am wondering what
> > the differences between 14 bits and 16 bits ADC are.

None to speak of.  The original TSC 5120A used 14-bit parts while the later 
test sets have used 16-bit parts, and the performance limits are essentially 
identical.  Once you go below a certain point, generally well below -170 
dBc/Hz, you tend to run into a correlation floor that arises from one or more 
different causes unrelated to the quantization precision itself.  These effects 
seem to arise in and near the S/H stage and aren't improved by going beyond 
14-bit precision. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] HP 3048 question: how to export graphs?

[John Miles]

I don't believe there's a way to save images from within HTBasic, although 
there certainly should be.  I use the "Snipping Tool" accessory in Windows 7 
for that sort of thing.  It probably exists in all versions of WIndows 
including 10, but who knows what they call it these days.  

 If you create a shortcut key for the tool, it's easy to invoke whenever 
needed.   Hit ctrl-shift-C (in my case), wait for the tool to come up, and drag 
a box around the graph or other content to be cropped and saved.  The image can 
then be saved as a .PNG, .GIF, or .JPG, or pasted directly into a document.

The RESU files saved by 3048A.BAS are similar to the .res files saved by 
PN3048, and PN3048 can load them directly if you select 'All files' in the 
file-open dialog.   You can then save the graph or the entire window as a .PNG 
file.  TimeLab ( http://www.miles.io/timelab/beta.htm ) can also import them 
(File->Import .RES or .PNP noise data) and save images (File->Save image or 
.TIM file or File->Copy image to clipboard).  But if all you want is a .PNG, 
the snipping tool is much easier than dealing with any of this stuff.

-- john, KE5FX

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Richard (Rick) Karlquist
> Sent: Sunday, October 15, 2017 12:03 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] HP 3048 question: how to export graphs?
> 
> I am running an HP 3048 under HTBasic and I
> have a nice looking phase noise graph on the
> screen.  I want to export the graph to the
> world outside of RMB...

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Re: [time-nuts] 5071A Reference Oscillator ?

[John Miles]

> One of the few things I dont have a manual for
> 
> Can anyone tell me if there is an HP model number for the Reference
> Oscillator Assembly (A19) in the 5071A? Might be a  a 10544A ?
> 

The OCXO was 05071-60219.  As Rick says, it was a modified 10811.  The 10544 
was long gone by the 5071A's time.

See the Mejia-Norton document in the ko4bb.com Manuals section for the exact 
specs...

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] sine to square wave circuits - performance data?

[John Miles]

> Do you recall what the amplitude of the input signal to the Wenzel shaper
> was?
> 
> Since I used a 1:2 (3dB) terminated splitter for my measurements the input
> to the splitter is the same as the Timepod reference signal amplitude
> 

I was using a similar setup, so the shaper input would have been +4 to +5 dBm.  
My intention at the time was probably to feed it a signal comparable to the 
lowest levels commonly seen from typical 10 MHz sources.  It may or may not do 
better at higher input levels, but it'll obviously get worse once the level 
goes below a certain point.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] sine to square wave circuits - performance data?

[John Miles]

> I have measured the PN of the LTC6957-4 at 10MHz.
> 
> I could measure the PN of the TAPR variant of the Wenzel circuit as well as
> the PN of the comparator based circuit (with CMOS output buffer).
> 

These plots came from the Wenzel diff-amp shaper:
http://www.ke5fx.com/wenzel_resid_PN.png
http://www.ke5fx.com/wenzel_resid_ADEV.png

I don't recall many details of the test setup, or how faithful my 
implementation of the shaper was to Charles W.'s app note, but this is 
representative of several plots I have lying around. Not bad performance at all 
for the cost/complexity involved. 

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] PN on internal/external references and Cross correlation

[John Miles]

> Thanks for clarifying this issue! I may use references with close-in PN
> (1Hz-1kHz) 10 dB noisier than the DUT, however as you said it may
> require an overnight run for 1 Hz offset, which isn't the nice part... I
> assume then that speeding up the measurement process can only be
> obtained using references sources at least quieter than the DUT.

A 10-dB deficit may not be too bad, since the performance improvement isn't 
linear with time.  If your instrument takes 8 hours to drop the measurement 
floor by 20 dB, for instance, it will only take 4 hours to achieve 18.5 dB of 
improvement, or 2 hours for 17 dB.   So if each of the references is 10 dB 
noisier than the DUT, their effect will be mostly gone after 2 hours.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] PN on internal/external references and Cross correlation

[John Miles]

> In a PN measurement system with a dual channel cross correlation is there a
> simple rule of thumb for how low should be the PN of the (external)
> references compared to the DUT? (even with a 20 dB noise floor
> improvement with 1 cross correlations)

If you have two references, then it's OK for them to be somewhat noisier than 
the DUT.  Their contribution will average out of the cross spectrum over time 
just like the rest of the instrument noise.  There is no penalty in accuracy, 
only in measurement time.

Given a choice, you're better off using references with good close-in noise 
performance rather than good broadband performance, since it takes longer for 
those FFT segments to converge.  You can achieve 20 dB of noise floor 
improvement at offsets >10 kHz within a few minutes, but a 20-dB improvement at 
1 Hz might require running overnight or even longer.

> In the case of the references
> have an equal noise contribution compared to the DUT will the results suffer
> from loss of accuracy?

With two references it's not a problem.  If you have only one reference source 
-- or if your measurement setup doesn't do cross correlation at all -- then the 
reference needs to be at least 10 dB quieter than the expected DUT performance 
to keep its contribution below 0.5 dB.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] HP 5065 Meter readings after restoration and adjustments: 2nd Harmonic Problems ?

[John Miles]

> My intention is to leave the instrument on for severalweeks in order to see
> if it is stable. Right nowmy concern is wether the 2nd harmonic
> readingindicates a wear out of the photo cell.
> When repairing the RFV Cavity, all components weretaken out and carefully
> examined. There wereno dimmed or darkened glass surfaces
> whatsoever.Apart from repairing the TX heater, the only other thingwas
> replacing the 1K something resistor in the TXassembly.

You've checked the ESR of all the axial electrolytic caps, right?  If not, it's 
quite unlikely that they're all good.  

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] HP 3048 NI GP-IB cards help requested

[John Miles]

I'd recommend a GPIB-USB-HS adapter.  There are tons of them on eBay, e.g.

http://www.ebay.com/itm/322360711342 
http://www.ebay.com/itm/321957086926 

These will work well with both PN3048 and HTBasic.  I've purchased them from 
both of those sellers in the past.  They appear to be genuine, unlike the 
counterfeit Agilent 82357Bs that are commonly sold out of China.

Re: the card selection option, PN3048 lets you choose between "Adapter 1" and 
"Adapter 2."  This only comes into play if you have more than one NI adapter on 
your PC.  In your case, you'll use the default Adapter 1 setting with it.

You can also use a NI PCI-GPIB board with either PN3048 or HTBasic.  I'd go 
with the GPIB-USB-HS even though it may be a bit more expensive.  It will be 
more future-proof than a plug-in card.

-- john, KE5FX
Miles Design LLC


> HOWEVER, I don't have a GP-IB card.  According to
> KE5FX, both the bus card and USB dongle types work.
> It looks like current NI driver supports many
> legacy cards.  I am curious about whether this
> means that all of these cards will be OK, or if I
> have to buy the latest card/dongle?  I would like
> to be able to run both programs.  The HT Basic
> site says that certain bus chips are incompatible
> with its software, and I should call them for suggestions.
> 

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Re: [time-nuts] Three-cornered hat on timelab?

[John Miles]

Longer runs would be better to the extent that they give you smaller error bars 
in your tau range of interest, certainly.  But any effects that influence one 
of your runs but not the others will render the 3-cornered hat solution 
questionable, if not outright invalid.  Only through many repeated runs can you 
learn to tell the bogus data from the good stuff.  So I'd make shorter runs at 
first, until you're sure you know what you're looking at.

 

It doesn't matter which source is applied to the start versus stop channel, as 
long as the assignments are consistent with the source labels you apply.  I 
would use frequency-count mode to simplify things, at least at first.  This is 
already a very challenging measurement for all the reasons mentioned. 

 

-- john, KE5FX

Miles Design LLC

 

 

From: Bob Stewart [mailto:b...@evoria.net] 
Sent: Thursday, April 13, 2017 8:41 AM
To: Discussion of precise time and frequency measurement; John Miles
Subject: Re: [time-nuts] Three-cornered hat on timelab?

 

Hi John,

 

Thanks!  With lesser equipment, such as the 5370A, would longer runs be better? 
 I used a set of 1 hr runs and the result wasn't quite what I had expected.  
However, it may be that I had mislabeled the files, and thus got the sources 
confused.  Of course, it may be that the ionospheric effect was grossly 
different between the three tests.  So, with a 5370, Source A would be the 
START input and Source B would be the STOP input, right?  For my testing, the 
sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a 
GPSDO.



 

Bob 

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Re: [time-nuts] Three-cornered hat on timelab?

[John Miles]

> It was mentioned that Timelab can do a three-cornered hat.  I can't find it.  
> Is
> this something that can only be done with multiple Timepods connected, or
> is there an option that I'm missing?  Or is there some other tool that needs
> to be used?  For the record, I want to create the 3c-hat from data that was
> run at different times, and I understand (at least somewhat) the
> shortcomings of doing that.  But, it would be interesting to see what would
> result.  And, not having three 5370s in good condition, it's the best I can 
> do.

Hi, Bob --

N-cornered hat measurement is a beta feature, not in the docs yet.  A single 
TimePod can generate the required three plots simultaneously, but you can use 
individual plots from TICs and frequency counters as long as you start with 
highly-reproducible measurements and are careful with your interpretation of 
the results.  If your setup returns inconsistent results from one run to the 
next, then any attempt at a separated-variance plot will be GIGO.

You can see some examples at http://www.ke5fx.com/gpscomp.htm .   Various 
finicky conditions need to be met before the 3-cornered hat display will become 
available; check out 
https://www.febo.com/pipermail/time-nuts/2015-September/094039.html for some 
tips.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] HP5061B Peak to Valley Ratios

[John Miles]

> We are having trouble getting beam current on our #2 HP5061B.  Ion
> current has gone down in a week from 10 to zero. It looks like the rf
> chain is working normally.  Both HV power supplies had to repaired.
> Beam current is all the way up and which gives 2 on the meter. We are
> preparing to do the Low Frequency Coil test mentioned on page 5-22
> section 5-175.
> 
> I got this idea from that procedure.  On our good #1 instrument we set
> the beam current at 20 with normal lock.  The middle coax J2 which
> carries 12.631 mc to the harmonic generator was removed next.  The
> beam current instantly dropped to 2.  We set the beam current with the
> front panel control at 10 to 30 and all three settings dropped about
> 10 to one when the cable was pulled.  This ratio seems to be a good
> indicator of beam tube quality.  

Other useful cues are the effect on the beam current when you turn the 
modulation off -- it should rise a bit -- and the stability of the meter needle 
in the beam-current position as an indicator of tube noise.  In that regard, 
excess noise from A13CR1 could potentially be mistaken for noise in the tube 
itself.  It could stand a bit more bypassing IMHO.

> I don't see it in the manual, but the
> fine five turn pot oscillator control works much better than the
> course adjustment for setting peak beam current.  It also works better
> for setting the control voltage to zero.  The push to turn course
> frequency control slot has been chewed up by the previous owner.

It's a good idea to remove that contraption altogether.  You don't want 
anything poking into the 10811's trimmer access hole or otherwise touching it.  
Drill a hole in the panel that will let you reach the 10811's trimmer directly 
with an alignment tool.   It will then be easy to follow the guidelines in the 
manual -- i.e., set the OCXO trimmer to the central peak with the pot at 250.  

The intent was probably to achieve a consistent operating point at a linear 
spot in the EFC curve, while discouraging technicians from setting the 5-turn 
pot near either extreme.  By specifying a midscale setting for the pot, they 
were able to maintain a consistent damping factor between units while 
incidentally making it easier to return to the central peak after any temporary 
adjustments.   The 10811-60109s are all labeled with a factory-selected 
resistor value for the same reason.  Overkill, but that's how HP rolled.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Timelab, GPIB-USB-B in a VM

[John Miles]

Try running the 32-bit version (timelab.exe) instead of timelab64.exe, even if 
the VM supports 64-bit execution.  That can sometimes help with compatibility.

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
> Bownes
> Sent: Monday, March 27, 2017 2:49 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Timelab, GPIB-USB-B in a VM
> 
> So I'm trying to run timelab in a windows 7 VM with a GPIB-USB-B interface.
> 
> Anyone ever tried such a thing?
> 
> The NI explorer sees the interface but nothing else does.
> 
> Pointers welcome!
> 
> Data on a bunch of oscillators as soon as I get it to work...:)
> 
> Thanks,
> Bob
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Re: [time-nuts] Fwd: Fwd: HP5061B Ion Current

[John Miles]

Yeah, I wouldn't worry about the oven, but the ionizer filament is a different 
story.  Those can definitely open up.

-- john,  KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Donald E. Pauly
> Sent: Wednesday, March 22, 2017 11:32 AM
> To: time-nuts; rwa...@aol.com; Donald E. Pauly
> Subject: [time-nuts] Fwd: Fwd: HP5061B Ion Current
> 
> https://www.febo.com/pipermail/time-nuts/2017-March/104374.html
> 
> I have posted two HP patents on the cesium beam tube at
> http://gonascent.com/papers/hp/US3323008.pdf and
> http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic
> interest. The first claims that the cesium oven operates at 60°-70° C.
> This is a tiny heating compared to a 1,000° filament on a power
> transmitting tube.  I say that it can be cycled a million times with
> no problem of thermal cracking.
> 
> πθ°μΩω±√·Γλ
> WB0KVV
> 

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Re: [time-nuts] Fwd: HP5061B Ion Current

[John Miles]

That's some very nice work, Donald.  Looking back, I have junked one or two Cs 
tubes that might have been usable if I'd thought through the problem of high 
ion pump current as you and KB7APQ seem to have done. 

Another good reason to raise the lockout threshold would be to cut down on the 
repetitive ionizer filament cycling that the tube will otherwise undergo when 
you first fire up the oven.  That phenomenon always makes me rally nervous.

-- john, KE5FX
Miles Design LLC

> -snip-
> When we overrode the cesium lockout at 29 μA or so of ion current, we
> needed only minor front panel adjustments for beam current of 20 μA.
> (We shorted across A15 R-4.) Our last ion current before power supply
> modifications at risen to 39 uA.  Beam current has been stable.
> 

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Re: [time-nuts] Timelab question

[John Miles]

> John,
> I apologize.  I was mistaken in my question.  Under wine it behaves poorly,
> but that's to be expected.  Under XP in a Virtual box, it works as you say.  
> The
> same in a real Win 10 box.  The problem is actually that I was expecting the
> "No" box to be checked, and to require the user to change it to "Yes" if he
> really wanted to exit.  So, if I press the Enter key to get rid of the dialog 
> box,
> the program exits.

I see what you mean.  I've got a couple of other minor tweak requests lined up 
for the next beta, so I'll add MB_DEFBUTTON2 to those prompts to keep that from 
happening.

If Wine is interpreting a second Escape keypress as 'Yes', then that's 
definitely a bug on their part.  Worth reporting to them if it still happens in 
the current version.

-- john
Miles Design LLC

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Re: [time-nuts] Timelab question

[John Miles]

> Is there a way to change the escape key in Timelab so that it doesn't default
> to "yes"?  I love Timelab, but this is driving me nuts.  I hit the escape key 
> and
> it asks me if I really want to exit.  No, I don't!  So, I hit the escape key 
> and
> yes, it does exit.
> Bob

Hmm.  I can't repro this on Win7 x64 -- what version of Windows are you running?

If I hit Escape followed by Enter, it does exit, since 'Yes' is the default 
choice.  But hitting Escape twice doesn't do anything (and shouldn't).

-- john
Miles Design LLC

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Re: [time-nuts] Vintage Frequency Measurement

[John Miles]

Agreed, it's probably reasonable to say that a real absorption  wavemeter would 
(a) have to have a meter or some other visual indicator; and (b) likely be 
powered exclusively by the energy its tank circuit "absorbs."  The BC221/LM 
boxes fall a little short of both requirements.  

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
> Camp
> Sent: Monday, February 13, 2017 3:47 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Vintage Frequency Measurement
> 
> Hi
> 
> With a VFO running, you have a heterodyne frequency meter. That is (at
> least to me)
> a very different device than an absorption wave meter. I know way to put
> power into
> a BC-221 and use it as an absorption device.
> 
> I’m not in any way saying that the LM or the 221 are less useful. They are 
> still
> to this day
> great little boxes. The just aren’t (by my understanding) wave meters. That
> term describes
> a different device that works a different way.
> 
> Bob

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Re: [time-nuts] Vintage Frequency Measurement

[John Miles]

You could use it as an absorption wavemeter, in its broadest sense of a passive 
tuned circuit with an indicating load.  The headphone jack was normally used to 
calibrate the VFO against a harmonic of the internal crystal oscillator, but it 
could zero beat an external source as well.  It stretches the nomenclature but 
the job still gets done.

Even as late as the 1980s a BC-221 (or LM-10 in my case) was a useful piece of 
gear.  As Bill suggests, all the qualities needed for indulgence in 
time/frequency nuttery were present.  They were incredibly expensive to build, 
being engineered to survive bombs that hadn't even been invented yet, and they 
could perform at levels beyond any reasonable requirement.  I used one for 
frequency spotting on my even-older Philco console.  

Just the other day, I visited the Spark Museum in Bellingham, WA, and was 
amused to see one over by the 'Titanic' exhibit.  Not a curation mistake on 
their part, just a consequence of having more cool stuff than exhibit space.  I 
had to restrain myself from reaching down and giving the dial a tweak.

-- john, KE5FX
Miles Design LLC

> Hi Bob:
> 
> The BC-221 is usually referred to as either a Frequency Meter or a
> Heterodyne Frequency Meter.
> 

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Re: [time-nuts] HP 5061A Cesium Beam Std

[John Miles]

> Search the list for what Paul and I did. There is a web page where someone
> did the same forced pump down. If all the voltage s are good you have
> nothing to loose. You are going to need a "real" high voltage source.

That may have been my page here: http://www.ke5fx.com/cs.htm 

Bertan HV supplies are reasonably common on eBay for less than $50.  Worth a 
try before giving up on the tube.

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] distribution amp question + hp 59309A

[John Miles]

> What is the general feeling here about this issue?  I confess that if the amp
> output is transformer coupled, I see exactly zero benefit in a grounded
> connector as the feed from the amplifier.

This question comes up every so often.  It comes down to whether you want your 
test setup to look like a loop antenna or a dipole antenna.  Usually the loop 
is better if you're forced to accept one condition or the other.   You 
shouldn't break, lift, or otherwise mess with coax shields without a very good 
reason.  If you need a balanced connection, use a balanced medium.

Obviously if you're setting up a commercial 10base2 installation the rules are 
different. :)  But for sensitive work with low signal levels in coax, you will 
most often be better off if all of your gear looks like a series of monolithic 
metal bricks.   Ground loops are not the worst thing that can happen to a 
precision T measurement.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] PN/AM and 1.5Hz spur from frequency doubling?

[John Miles]

You may find that the behavior varies quite a bit depending on what you put 
between the maser output and the doubler.  I've seen one case in particular 
that generates a ton of PM spurs, specifically an HP 11721A doubler driven by 
the 5 MHz output of a 5061A Cs standard.  The 5 MHz output uses a narrowband 
transformer with a parallel-tuned primary, so it looks highly reactive at 
frequencies other than 5 MHz.  I'm not sure what's really going on, but the 
11721A (which is being run below its frequency spec in this case) doesn't seem 
happy at all ( http://www.ke5fx.com/11721a.png ).  Adding an SLP-5 lowpass 
filter in front of the 11721A makes the spurs go away, as does an isolation amp.

The 1.5 Hz spur in your plot looks like leakage from a nearby 10 MHz source, 
presumably a free-running OCXO that's a bit off frequency.  The rest of it 
looks like an open coax shield or something.  (If you're using a coaxial balun, 
try removing it.)  It's possible to get 2-3 dB of excess noise from a 
multiplier beyond the expected 20*log(N), depending on source and load 
characteristics, but I haven't seen anything that bad in the absence of other 
problems.

-- john, KE5FX
Miles Design LLC

> >> I'm seeing +20-30 dBc/Hz of excess AM/PN, as well as a strong 1.5 Hz spur
> >> created by frequency doubling from 5 MHz to 10 MHz.
> >> https://goo.gl/photos/GFx9tQoxrSmyzUQo8
> >> The input amplitude to the doubler should be just above the
> recommended 11
> >> dBm.
> >> What's going on??
> >>
> >> thanks!
> >> Anders

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Re: [time-nuts] EFOS Maser turns 34!

[John Miles]

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John
> Ponsonby
> ... It turns out that the resonant frequency of the cavity is much more
> critically dependent on its diameter than on its length. So it would be best
> to be able to mount the bulb in the cavity and to measure the resonant
> frequency with the cavity still in the lathe... 

This reminds me of an anecdote about the construction of the first NH3 maser in 
Charles Townes's book ("How the Laser Happened.")   They were having trouble 
with the irregularities in the cavity associated with the entrance and exit 
apertures for the ammonia gas.  They found it was better to get rid of the gas 
ports altogether and open the cavity completely at the ends, essentially 
replacing it with a long pipe relative to the resonant frequency at K band.  

Is that an option at 1420 MHz?  Or would the cavity pipe and storage cylinder 
have to be so long that it would be even more expensive to build (and to 
shield)?

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] EFOS 3 online

[John Miles]

> Inspired by Corbys post, I thought I'd follow up with putting the
> telemetry-data from EFOS 3 on the web, for those with any interest in these
> things. There is also a small picture gallery. Can be found on
> www.efos3.com.
> If I got the scheduling right, weekly plots should update every 5 minutes..

1E-13 at t=1s in your plot at http://www.efos3.com/efos3.html is looking great. 
 I think you have it working as well as it possibly can, at least in the short 
term.  You just need two more of them to be sure. :)

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Lady Heather 5.0 and COFS/Jupiter-T Receiver

[John Miles]

Sorry about that. :)  Send me a new zipfile and I'll update the distribution...

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark
> Sims
> Sent: Monday, December 26, 2016 10:12 AM
> To: time-nuts@febo.com
> Subject: [time-nuts] Lady Heather 5.0 and COFS/Jupiter-T Receiver
> 
> Yes,  John added  the "N" keyboard command to let you bring up Notepad to
> edit heather.cfg.  The way he did it broke any two letter keyboard command
> that ends in "N".   I've since fixed that and added the ability to specify the
> file to edit.  I also added a command to let you run any program from within
> Heather.
> 
> The "S3" keyboard command should do the same thing as "SN"...
> 

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Re: [time-nuts] Lady Heather Ver 5 Problem

[John Miles]

The error message in question came from the IPCONN::connect() method in 
ipconn.cpp.  That particular code (11004) is returned by gethostbyname() when 
it fails to resolve a DNS name.  Normally, when Heather tries to connect to the 
test server, gethostbyname() is used to turn "ke5fx.dyndns.org" into a numeric 
address that can be passed to connect().  If it returns 11004, it means that 
the client's DNS provider was able to find a record, but couldn't actually 
resolve it.  

Should just be a temporary glitch in the Matrix.  Nothing specific can be done 
about it AFAIK.

-- john, KE5FX
Miles Design LLC

> I grep'd all the source code and there is no 11004 anywhere in the program...
> 

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Re: [time-nuts] Lady Heather Ver 5 Problem

[John Miles]

Hmm, no, that shouldn't affect anything.  Sounds like a DNS issue of some kind, 
presumably (but not necessarily) at your end.  Try again?

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Richard W. Solomon
> Sent: Monday, December 12, 2016 11:45 AM
> To: time-nuts@febo.com
> Subject: [time-nuts] Lady Heather Ver 5 Problem
> 
> I installed LH Ver 5 and when I try to open it I get an error message:
> 
> 
> 
> ke5fx.dyndns.org not found (code 11004)
> 
> 
> 
> Was I supposed to install it in the old LH Folder ?
> 
> 
> 
> Thanks, Dick, W1KSZ
> 
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Re: [time-nuts] Lady Heather Version 5 is now available

[John Miles]

> As said, if I put the .cfg file in the system32 directory I can set eg.
> the new time zone.
> Strange, if I enable eg. the esc esc command to shut off LH, it does the
> job well, but with the exception for the time zone setting, this and all
> the other commands once set are not anymore to be disabled ... ?
> I think this is in better hands with the experts.
> 
> Unfortunately I am not at home so I am not in the position to run LH
> with my Thunderbolt, but one can start at least with the time display
> functions :-)
> 
> Yes, I forgot to thank as well John for the great program, sorry John!

You're welcome -- I'm really just the Web host here, all the good stuff is 
Mark's. :)

It's true that there is a copy of heather.cfg in the installation directory, 
but it's only stored there to make the installation a complete copy of my 
development directory.  (In other words, if you have Inno Setup installed on 
your machine, you should be able to create your own distribution of LH by 
running the same batch file I do to create a release.)  This copy of 
heather.cfg is not read by the program under normal conditions.   For the most 
part you should only be working with the .cfg file in your Documents folder.

>From what I can see, it looks like the .cfg file will always be created in 
>\users\\documents as intended, and accessed there as well.  As 
>things stand, Mark's current code appears to do the right thing even if you 
>don't install to the Program Files subtree, as long as you launch it from the 
>shortcut and not the command prompt.  So most users should be OK with the 
>current behavior.  

My main point is, if the program is doing anything at all in the 
\windows\system32 folder, something has gone very wrong somewhere.  I've never 
seen that before, and I'm afraid I don't have any ideas to offer.  It should 
certainly not be looking there for the .cfg file, unless you somehow managed to 
install the program itself there... and even then, it still shouldn't. :-P  
We'll need to see if anyone else reports similar behavior.

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Lady Heather Version 5 is now available

[John Miles]

Yeah, that's probably something we should fix.  Installation programs don't 
normally set that field at all.  But when Heather's initial working directory 
isn't in the usual Program Files hierarchy, it tries to load the .cfg file from 
the same directory as the executable.  This is something I do to make life 
easier during development.  It's not a problem in applications where the user 
doesn't access the .cfg or.ini file directly, but in this case different parts 
of the program are probably looking for the file in different places.
 
For now, I'd recommend installing LH under the default Program Files or Program 
Files (x86) subtree, just to minimize confusion.  I probably won't have a 
chance to tweak this behavior today, but will try to get to it this week. 

-- john, KE5FX
Miles Design LLC

> Look at this screen capture :
> 
> https://dl.dropboxusercontent.com/u/15089947/lh.gif
> 
> When properly set, the error disappeared. My suggestion would be to
> modify the installer so that
> also that field is correctly set.
> 

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Re: [time-nuts] Lady Heather Version 5 is now available

[John Miles]

Hmm, that doesn't make any sense at all.  Nothing should be written to 
\windows\system32 by the installer under any conditions.  

-- john, KE5FX
Miles Design LLC

> Many thanks Brian!
> 
> I found it!
> In Windows 7 (10?) this file must be copied into the system32 directory
> of windows in order to be read and enable the instructions to be executed.
> 
> 73
> Arnold DK2WT

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Re: [time-nuts] Lady Heather Version 5 is now available

[John Miles]

> It seems during the install at least on Windows 10 that it does not give the
> full permissions to the files. I just gave the folder the correct permissions
> after the isntall. If you go to help, at the bottom of the screen  it tells 
> you
> where during the install another copy of the heather.cfg was installed. You
> should be able to read/write this copy. At least that was my experience
> during installing.

I'm not sure what might be going on here, but one thing that tripped me up 
personally was that some options I was using in both my old heather.cfg file 
and my command-line shortcut were changed between V3 (which is what I was 
running before) and V5.  If you somehow get into a situation where LH V5 is 
trying to load an older config file, you may need to track down that file and 
modify or delete it.

In general, make sure you run the LH setup program while logged in as the same 
user that will run the app.  Currently the installer always writes heather.cfg 
to the current user's documents folder (e.g., c:\Users\johnm\Documents).  If 
you have a separate admin user on your system and you launch the installer 
under that account, heather.cfg may end up in a different directory.   That, in 
turn, may leave an older copy of heather.cfg  lying around for the program to 
find.

Still another thing to watch out for, now that heather.cfg is an 
officially-installed file, is that subsequent reinstallations of LH will 
overwrite any changes you've made to heather.cfg.  So you may want to make a 
backup if you need to reinstall for any reason after making extensive changes 
to heather.cfg.  

Future builds will solve both of these problems by having the program itself 
create heather.cfg the first time it's run, if the file isn't already present 
in {userdocs}.  That's really the only right way to install .cfg/.ini files in 
Windows-land, but neither of us got around to implementing that for the initial 
V5.00 release.

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Prologix USB-GPIB Controller

[John Miles]

> thanks for the offer, Geo
> We've already found a new Prologix unit at much less than retail.  I'm not
> familiar with the NI units, and have seen postings that they are
> tempermental with some instruments. 

I've mentioned before that NI adapters are the _least_ temperamental of all of 
them.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] COTS cesium standard physics package life

[John Miles]

If I remember correctly, the oven power supply runs off of the same bus that 
powers the rest of the unit, in the 5062C's case.   It took a fair bit of 
hacking to install the switch and make it do what I wanted.  Not much besides 
the ion pump and the OCXO remains active with the switch in the 'off' position. 
  

I'd expect the Datum unit to be pretty different in terms  of its schematic and 
power distribution scheme, but I'd shoot for the same functionality if I were 
installing a switch in one.

-- john, KE5FX
Miles Design LLC

> I have a Datum FTS-5060 unit. Did you just open up the heater line to the
> beam tube? I like the idea of conserving the Cs when pumping down the
> tube
> for maintenance.
> 
> Regards,
> Tom
> 

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Re: [time-nuts] COTS cesium standard physics package life

[John Miles]

> 1.  Cesium depletion, which only occurs when the tube is operating with
> cesium oven on, and high voltage at the other end; and

The Cs atoms need to be electrically neutral, so their depletion rate shouldn't 
depend on the presence of HV, just the oven heater.  State selection wouldn't 
work on ionized atoms, and you also wouldn't want them to be accelerated 
towards the electron multiplier until after they've reached the ionizer 
filament at the end of the cavity.  (The longer they spend hanging out with 
Schroedinger's cat in the Ramsey cavity, the narrower the line width.)

> 2.  Tube vacuum and other physical aspects that may deteriorate over
> time, whether or not the tube is operating.  The routine ion pumping
> helps keep the vacuum up in storage, but is not as effective as the
> continuous pumping that occurs during operation.

Some of the HP standards (5060, 5061, 5071) have a CS OFF setting that enables 
the ion pump by itself.  Those tubes should last indefinitely in that mode of 
operation.  Unfortunately the 5062C didn't have a way to disable the Cs oven 
while leaving the ion pump active, which is probably why there are so few 
operational 5062C tubes left.  By now, most are either out of cesium or too 
gassy for the ion pump to recover.  

I added a switch to  my 5062C to allow the vacuum to be maintained without 
running  the Cs oven.  It gets turned on every so often, maybe a couple of 
times per year, when I want a noisy signal source with known ADEV 
characteristics.  Even though the ion pump runs 24/7/365, there are always a 
few overcurrent cycles on initial powerup for some reason, where the beam 
current exceeds the trip point and shuts down the power supplies.  Something 
inside the tube is apparently outgassing during warmup -- whether it's the Cs 
oven or the hot-wire ionizer ribbon, I don't know.  But the condition always 
clears itself within a few  seconds.  The same thing happens when I turn my 
5061s on after a long period in CS OFF.

- john, KE5FX
Miles Design LLC


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Re: [time-nuts] ke5fx.com - something's up

[John Miles]

Yep.  It should be all good now (once the DNS records propagate.)

-- john, KE5FX

> Domain name expired on September 8th - needs renewing!
> 
> On 11/09/2016, at 10:48 AM, Nick Sayer via time-nuts wrote:
> 
> > I tried to look for Lady Heather docs today, but it appears like the ke5fx
> domain is… funky.
> >
> > The name servers are NS1.PENDINGRENEWALDELETION.COM and there are
> other indications that maybe the domain lapsed…?
> 

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Re: [time-nuts] ke5fx.com - something's up

[John Miles]

Hmm.  Gotta be some kind of DNS glitch, it's not due for renewal as far as I 
can see.  I'll look into it, thanks.

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Nick Sayer
> via time-nuts
> Sent: Saturday, September 10, 2016 3:48 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] ke5fx.com - something's up
> 
> I tried to look for Lady Heather docs today, but it appears like the ke5fx 
> domain
> is… funky.
> 
> The name servers are NS1.PENDINGRENEWALDELETION.COM and there are
> other indications that maybe the domain lapsed…?
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Re: [time-nuts] timelab question

[John Miles]

> That's a pretty scary problem to have.  Are these frequency counts or TI
> readings?  You wouldn't normally see two identical TI readings in a row,

Actually, that's not even safe to assume for TI readings, depending on how your 
triggering works.  It would make sense to do whatever it takes to fix this at 
the source. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] timelab question

[John Miles]

> I've got a file with counter values that are latched once per second,
> with the count read from the latch every half second.  So, generally,
> there are two identical values, then two different identical values,
> etc.  But, of course, the routine that does the every half second
> reading isn't perfect.. it could run fast or slow.
> 
> I want to process the count values in timelab, and I was wondering if it
> knows to eliminate the duplicates, or if I write some code to strip the
> dupes.

That's a pretty scary problem to have.  Are these frequency counts or TI 
readings?  You wouldn't normally see two identical TI readings in a row, but if 
they're frequency counts, how do you know for sure you're eliminating a 
duplicate reading, as opposed to one that just happened to be the same as the 
last?

There's nothing that TimeLab can do to help with this scenario, I'm afraid.  
Stable32 may be able to remove duplicate TI readings, but otherwise, yes, you'd 
need to write some kind of script to preprocess the sample file.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Lady Heather

[John Miles]

> I am just starting out using Lady Heather.
> 
> I am trying to create a .cfg file to set the program to COM 3 at startup.
> 
> I created the file and saw the instructions to put it in my “Documents” 
> folder.
> The only documents folder in Windows is “My Documents.”
> 
> I created a text file and called it “Heather.cfg” and put it in the My 
> Documents
> folder, but it does not work.  I just put “/3” to change the COM port to COM 
> 3.
> 
> I also tried putting in the “Heather” program folder.

It works OK at this end.  But having just checked, I've noticed that things can 
get complicated if you want to use a config filename other than HEATHER.CFG, or 
if you want to put it in a directory other than the one Heather suggests in the 
'?' help dialog.  Heather allows you to specify a .cfg filename other than the 
default HEATHER.CFG with the /h= option, but if I run a command like:

"c:\program files (x86)\heather\heather" /h="my config file.cfg"

... it doesn't treat the quoted string as a valid pathname, even though it 
ought to.  So, there are at least two things to check if you're still having 
problems:

1) If you use a filename other than HEATHER.CFG, make sure your /h= argument 
doesn't contain any spaces.  Just use the filename itself, with no directory 
prefix.

2) Make sure the .cfg file goes in the directory that Heather suggests in the 
'?' help screen.  Again, it doesn't have to be called HEATHER.CFG (if you use 
the /h= option) but it does need to go into the directory where the program 
expects to find it, because there's currently no robust way to force it to read 
the file from another directory.

> Also, I have read and re-read the list of commands and don’t see any to change
> the display to show the “sky” view of the satellites, as is shown on the Lady
> Heather web page.

I see the line that turns it on "plot_signals = 4", but I'll be darned if I can 
see how the code gets there.  Mark?

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] State of the art of crystal oscillator measurements

[John Miles]

> If the oscillator output is thru the resonator, then at large offsets,
> the source impedance is reactive.  It can easily have an effective
> temperature less than room temperature.  If this "source" is then
> used with a low noise temperature preamp, it is entirely possible
> to go beyond these supposed theoretical limits that are based
> on T=300K.

Sure, until you try to measure it with a Zo=50R instrument, or otherwise do 
something that involves putting real power into a load.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] State of the art of crystal oscillator measurements

[John Miles]

-177 = the -174 dBm/Hz SSB thermal noise floor at 25C, less 3 dB to account for 
the usual assumption that half of it is AM, half PM.   

dBm/Hz is obviously equivalent to dBc/Hz for a 0 dBm carrier.  

Anyone who claims to measure noise in a 1 Hz bandwidth below -177 dBm/Hz at 
room temperature is either doing something wrong somewhere, or doing something 
amazing somewhere.

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike
> Feher
> Sent: Thursday, August 11, 2016 4:15 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> That is why I asked what the Po was. Where did the 177 come from? L(f) is
> single sided. This is not my first "rodeo" in these matters. 73 - Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
> 

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Re: [time-nuts] State of the art of crystal oscillator measurements

[John Miles]

Good point, the 'milliwatt' part of 'dBm' takes the E^2/R part out of the math. 
 If we were speaking of dBv/Hz, the system Zo would need to be considered to 
determine the power.  

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Thursday, August 11, 2016 3:01 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> Zo doesn't matter for these purposes.
> dBm works just as well for 75 ohm systems.
> 

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Re: [time-nuts] State of the art of crystal oscillator measurements

[John Miles]

Right, I'm speaking specifically of L(f).  The device being driven by the 
oscillator doesn't care about the NF of the driver stage, only what a PN 
analyzer would measure at the output jack.

For any 50-ohm source, the practical L(f) floor is -177 dBm/Hz - the carrier 
power in dBm.  No oscillator with an output of 0 dBm can be quieter than -177 
dBc/Hz at any offset, but an oscillator that puts out +20 dBm could approach 
-197 dBc/Hz.

Given a proverbial black box containing a +17 dBm oscillator that measures -195 
dBc/Hz at 100 kHz, the interesting question is, "What's in the box?"  There 
could be a passive resonator that's shaving off the broadband noise after the 
last active stage without contributing additive noise of its own.  Another 
possibility might be cross-spectral collapse due to correlated thermal noise 
from the splitter.   

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU--
> - via time-nuts
> Sent: Thursday, August 11, 2016 2:37 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> NO, the maximum  possible noise dynamic range is ( 177 +  Pout)  [dBm]  -
> Transistor large signal NF ( dB),
>  the signal to noise ration is dimensionless 
> 

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Re: [time-nuts] State of the art of crystal oscillator measurements

[John Miles]

Or rather -(177+DUT output power in dBm).  The minus sign makes the difference 
between the thermal floor and a nuclear war!

-- john, KE5FX
Miles Design LLC

> Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz,
> then kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the DUT's
> output power in dBm.


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Re: [time-nuts] State of the art of crystal oscillator measurements

[John Miles]

Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz, then 
kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the DUT's 
output power in dBm.  

Assuming a 50 ohm system, of course.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike
> Feher
> Sent: Thursday, August 11, 2016 12:51 PM
> To: 'Discussion of precise time and frequency measurement';
> ka2...@aol.com; t...@leapsecond.com
> Cc: enrico.rubi...@gmail.com
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> kT is indeed relevant for a physical implementation. - Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell

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Re: [time-nuts] Oscillator Phase Noise: A 50-Year Review

[John Miles]

> 
> Very selected and incomplete references and the equally  important
> question
> of measurements strangely not covered
> 
> 73 de N 1  UL
> 

I suppose he could write an equally-lengthy article on measurements alone, but 
leaving out the post-1970s history entirely was a little disappointing.  It was 
strange to hit "ctrl-f Rohde" and see only one reference in the bibliography.  
Same for "Hewlett."  "Rubiola" brings up one hit (but no citations) and "Stein" 
brings up none at all.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] OCXO noise as they retrace

[John Miles]

> I've had a specific GPSDO running for some time now, and I notice that the
> noise at tau 1s has gotten worse as the retrace flattens out.  In this case,
> the  ADEV was about 3.6E-11 a month or so ago, and has now gone up to about
> 8.5E-11.  (Measurements performed by a 5370A against a PRS-45A Cs
> standard.)  Is this normal as the startup drift settles out?  It's been on 
> the same
> power supply module during this time, but I have been using it to test new
> code, so the DAC has been cycled from midpoint to lock numerous
> times.  Another unit that's been running for some time has done essentially 
> the
> same thing.
> Weather?  Environment?  GPS demons?
> 

Are you sure it's not the PRS-45A?  Cs standards get noisy as the tube ages, 
typically becoming much noisier before failing entirely.  This is usually 
pretty easy to diagnose by watching the beam current fluctuate.

You're also bumping up against the limits of what your counter can do.  
Readings in the 4E-11 to 8E-11 range at t=1s are common with 5370s, depending 
on any number of factors.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] 82357b and TimeLab?

[John Miles]

> But TimeLab doesn´t list any GPIB interfaces.
> 
> Did anyone have success with this combination? Any insights
> highly appreciated...

Agilent's NI488.2 compatibility layer seems to work only with 32-bit apps, not 
64-bit ones, so you may be able to get it running by modifying your Windows 
shortcut to run timelab.exe instead of timelab64.exe.  The 64-bit version of 
TimeLab isn't usually needed when working with standard TICs and frequency 
counters.

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] 3120A issues

[John Miles]

> On 6/18/16 6:17 PM, Tom Knox wrote:
> > Does anyone have any insight as to why Microsemi has stopped shipping
> 3120A Phase Noise test sets  beside that they are not to spec?
> >
> They're shipping them.. I got quoted a 12 week delivery in April, $9k
> for the box, about $12k-15k for the software, although I find that the
> Microsemi site doesn't really explain what the various software options are.
> 

Briefly --

'Signal Statistics' = you can display the non-ADEV deviation types (MDEV, HDEV, 
TDEV) and enable the various integrated noise/jitter options for display in the 
legend table below the plot 

'AM Noise' = you can enable AM noise measurements in the acquisition dialog

'Frequency Counter' = you can display the high-precision frequency-count chart 
alongside a Frequency Difference plot

'Mask Test' = you can display pass/fail status and margin values in the legend 
table below the plot.  Mask limit lines can be displayed on the plot without 
this option, but the program won't evaluate them (or allow automated test 
scripts to access them) without it. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] 3120A issues

[John Miles]

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Knox
> Sent: Saturday, June 18, 2016 6:17 PM
> To: Time-Nuts
> Subject: [time-nuts] 3120A issues
> 
> Does anyone have any insight as to why Microsemi has stopped shipping 3120A
> Phase Noise test sets  beside that they are not to spec?
> 

It looks like they're still advertising the 3120A on their site.  I'm pretty 
far out of the loop at this point, but if they're having production-test 
problems, I haven't heard anything about them at all -- and I normally would, 
if they're having problems passing the factory tests.  Is that what you meant 
by "to spec?"

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[John Miles]

> I note your software works with the HP 7 too. As I say, I already have
> one of them, but was thinking the E4406A would be a worthwhile addition.
> But perhaps not in that case. Although maybe it will outperform my 7
> system for phase noise measurements. I expect you will know the answer to
> that.

The E4406A will let you measure all the way down to 1 Hz from the carrier, and 
is quieter past 100 kHz.  And it's faster, being FFT-based.  Overall, though, 
their LO noise floors aren't that different.  They both need a lot of help to 
perform serious PN measurements.

> BTW, the link to the  "Wenzel Associates, BluePhase 1000 Phase Noise Test
> System Operations Manual
>  (30
> pages, 1.3 MB)" PDF is broken.

Thanks -- coincidentally, someone else just reported that one a few days ago.  
I've fixed it but haven't updated it on the server yet.  It's safe to say there 
are plenty of other broken links on my site, as some of those pages are over 10 
years old now.  

> OK, I will give this idea a miss. I was actually looking to compare 116 MHz
> oscillators. but I guess the same principles apply.

Sadly, there are few good answers there other than "build a quadrature PLL."

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[John Miles]

> and looked at what was used to make the phase noise measurements. It was an
> Agilent E4406A. The noise floor is nowhere near as low as the more
> expensive instruments, but the E4406A is available for under $500, which is
> more than two orders of magnitudes cheaper than an E5052B.

It appears that Leo's using a notch filter to remove the carrier before 
measuring it with the E4406A, so it's not quite a plug-and-play sort of 
measurement.  But yes, the E4406A is a really cool piece of gear given the 
prices they sell for.  It's not meant to be a general-purpose spectrum analyzer 
-- and Agilent went well out of their way to make sure of that -- but it can 
still handle many common SA measurement tasks including SSB noise.

The plot on that page came from my freeware phase noise app from 
http://www.ke5fx.com/gpib/pn.htm , which is a (very) distant ancestor of 
TimeLab.  The last two FAQ entries at http://www.ke5fx.com/gpib/faq.htm offer 
some hints for suppressed-carrier measurements that can be used with the E4406A 
and other analyzers.  There's nothing special about the E4406A with respect to 
this type of measurement, except that it's an unusually cost-effective way to 
get the job done.  

I've also heard of people opening up the E4406A and feeding HF signals directly 
to the ADC, eliminating the LO noise contribution but not the ADC's white 
noise, 1/f noise, or clock jitter.
 
> I'm wondering if there are other more suitable commercial instruments
> around that don't cost a fortune, yet would allow lower levels of phase
> noise to be measured. I tend to preference HP/Agilent kit, as it is better
> supported, both by the manufacturer and places like the HP/Agilent Yahoo
> group.

The E5052A/B's most immediate predecessor was probably the HP 4352A/B.  They 
were made specifically for VCO and PLL transient analysis and noise 
measurement, and they've been selling in the $1K-$3K neighborhood for several 
years.  Their measurement floor is better than a conventional spectrum 
analyzer, but still not adequate for "time nuts"-class measurements on 10 MHz 
sources. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] windows for FFT measurements of phase noise

[John Miles]

> I was thinking more of the sidelobes: if you're looking at a quiet
> oscillator (e.g. -140dBc @ 100Hz) , with a 1 second epoch, and you want
> to measure the noise at, say, 100Hz out, the window function needs to be
> down 140 dB at that bin.
> 
> WIndows like uniform and Hamming are probably only down 50 dB that far out.

The segmented FFT helps with that.  Ideally you have enough segments that 
there's rarely more than 30-40 dB of flatness variation within any one of them, 
which is why HFT95 works well and Hann is still usable.  

Except in the presence of very strong spurs, most of the energy in the 
narrowband segments is going to reside in the first few bins.  It's the HPF 
prior to each FFT stage that keeps that close-in noise from spreading, more 
than the choice of window function.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] windows for FFT measurements of phase noise

[John Miles]

> What sort of windows do folks use for making FFT measurements of phase
> noise.
> 
> Say you have 1 second of sampled data (so the FFT resolution is 1 Hz).
> If you're interested in the noise power at, say, 10 Hz away, a
> rectangular window isn't going to be very far down, unless you have a
> LOT of points in the FFT.
> 
> Grove's paper from 2004 doesn't mention this detail.

As Bob suggests, a multisegment FFT chain is the usual approach.  By the time 
you're displaying noise down to 10 Hz, you should have quite a bit more than 1 
second worth of data to draw from. 

For measuring noise the choice of window function doesn't matter very much as 
long as you correct for the noise bandwidth of the function you use.  However, 
for spur detection there are major window-dependent differences that need to be 
considered.  There is only one reference that's worth looking at, and that's 
the paper by Heinzel, Ruediger, and Schilling.  (Google the authors' names and 
it'll come up.)  

The TimePod and 3120A allow the user to choose between the HFT95 function from 
the Heinzel paper -- which was essentially reverse-engineered from the HP 
35670A -- as well as the usual (von) Hann(ning) window.  HFT95 is the default, 
with good sidelobe rejection and high amplitude accuracy for spurs regardless 
of where they fall in their FFT bin.  The Hann window can be selected when 
frequency offset accuracy and/or resolution of closely-spaced spurs is more 
important, but it can underreport their amplitude due to scalloping loss.  

I would suggest using one of the HFT windows unless/until you have a specific 
reason not to.  Heinzel also describes several flattop variants with higher 
sidelobe rejection than HFT95, in the unlikely event you need them.  In my 
experience it's better to stick with flattop windows and increase your bin 
density if you need better frequency resolution, rather than put up with 
scalloping loss.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Timelab and the 53220A - getting best results

[John Miles]

One workaround for the 1-million point limitation on imported data is to use 
"Acquire->Acquire from live ASCII file" instead of "File->Import ASCII 
phase/frequency data."  Most of the same code is used for both cases, but 
unlike the static file-import version of the dialog, the live data importer 
will let you specify the expected duration yourself.  So you can give it a 
duration value that you know will be long enough to cover the whole data set.  

I'm not too familiar with the 532x0A counters myself, but 8.9E-11 at t=1s 
doesn't sound too unrealistic.  When in doubt, look at the 'f'requency and/or 
'p'hase trends and residuals to sanity-check your data, rather than trying to 
puzzle out what's going wrong with the ADEV plot as many users seem to do.  
First you should satisfy yourself that the data makes sense, is unwrapped and 
scaled properly, and doesn't contain glitches, large crystal jumps, obvious 
beatnotes or other interference, or unexpected amounts of drift.  

-- john, KE5FX
Miles Design LLC

> I’ve gotten a little further with this. If I capture 60 seconds worth of time
> interval measurements (between two FE-5680As that are GPS disciplined, but
> with a long enough time constant that they’re basically free-running), I get
> 60,000 of them. So I imported at a sample interval of 1e-3 and got the right
> duration. There are a couple of problems, however. 1 is that even if I 
> attempt to
> log to a USB stick, it appears I can only log 1e6 samples before it stops. 
> That’s
> 16:40 or so, which isn’t very long. I haven’t figured out how to change the
> sample gate for time intervals (I’m assuming that a million samples is a hard
> limit). Also, importing the interval samples into TimeLab still shows me a 
> graph
> that’s still much steeper than I would expect. The graph is linear, with 
> points at
> tau 1s = 8.9E-11, 10s = 9.47E-12, 100s = 1.5E-12 (by then, the ADEV graph is
> starting to flatten out a bit, which probably indicates the noise floor of the
> 53220A near 1E-12), but the FEI datasheet shows a spec with points more like
> tau 1s = 1.5E-11, 10s = 4.5E-12 and 100s = 1.5E-12.
> 

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Re: [time-nuts] Get together at IMS?

[John Miles]

> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark
> Kahrs
> 
> Anyone else going to IMS in SFO this coming week?
> 
> 
> I would propose meeting during the "industry Reception" Wednesday
> afternoon...

I'm there from Monday night through Thursday, and that sounds like a good idea 
to me!  Maybe get together someplace conspicuous like the NI or Keysight booth 
on the main corridor through the show floor?

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] GENIUS by Stephen Hawking (PBS TV), with 5071A cesium clocks

[John Miles]

Public service announcement: I just tried to stream this episode on Amazon 
Prime Video, and it seems they have some sort of indexing snafu going on.  They 
offer episode 1 ("Can We Time-Travel?") and episode 2 ("Are We Alone?") for 
viewing, but what actually played when I selected them were two completely 
unrelated/unannounced episodes.  The first episode is on the size of the Earth, 
solar system and Universe, and the second one discusses abiogenesis and 
evolution.

Both episodes are worth the $2.99 price of entry IMO, but there are a grand 
total of zero 5071As in either of them. 

-- john, KE5FX
Miles Design LLC
 
> Anyway, I'll see if the videos appear somewhere on the internet some
> time. ;-)
> 
> Martin

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Re: [time-nuts] Lady Heather Ver 4.0 beta test available (has Linux support)

[John Miles]

I've updated my existing LH download page with Mark's new beta version in both 
.zip and (Windows) setup.exe formats:
http://www.ke5fx.com/heather/readme.htm

There's also a link to his readme.txt file with Linux build instructions.  
(Mark is the best point of contact for anyone with questions on that, as I'm 
just the Windows guy.)

-- john, KE5FX
Miles Design LLC



> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark
> Sims
> Sent: Tuesday, April 26, 2016 5:50 PM
> To: time-nuts@febo.com
> Subject: [time-nuts] Lady Heather Ver 4.0 beta test available (has Linux
> support)
> 
> I have uploaded a ZIP file to tinyupload.com with the source and a Windoze
> .EXE file for the beta test version of Lady Heather.  For Windows users, copy
> the heather.exe to your current Lady Heather directory (might want to first
> rename or copy your old heather.exe as a backup.
> For Linux users,  unzip the archive into a new directory,  read the readme.txt
> file.  You will need libx11-dev and g++ installed to build it.
> http://s000.tinyupload.com/index.php?file_id=28617692862395218928
> PLEASE direct comments and questions off-list... no need to clutter up the
> list.
> 
> 
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Re: [time-nuts] Rpair of an 8662 HP Generator

[John Miles]

> My  signal generator has a poor, intermittent power  supply.  The RF
> section is ok. Who can please tell me which company can and  will fix these
> older
> but excellent  generators?
> 
> Thanks, Ulrich

Have a look at the capacitors in the voltage divider that drives the bases of 
the switching transistors.  There's a good chance that's your problem, and they 
probably need to be replaced even if not.  75-TVA1607 (Mouser p/n for Sprague 
TVA1607) works well.  

It would be nice to use 105C parts if you can find some, but the 85C TVA1607s 
have worked well for me in multiple 8662As over several years. 

The other likely suspect is one of the large screw-terminal electrolytics on 
the motherboard.  The power supply can almost-but-not-quite start up when one 
of those is completely open.  High ESR is very likely to cause intermittent 
operation. 

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Timelab bug (was: Framework for simulation of oscillators)

[John Miles]

> Here it takes slightly less 3 minutes, but stops at 10M samples.

> Memory consumption of Timelab stays below 350MB the whole time

> and drops to 98MB after it finished.

> 

> OS is windows XP pro

> 

> How many samples did you get? It should have been 14926518 (ie slightly

> less than 15M) 

 

D'oh, sorry, I misunderstood -- I thought you were saying it locked up.
Yes, the normal file-import process stops at 10M samples because that's the
arbitrary maximum value allowed for the Trace Duration property in the
file-import dialog.  I'll go ahead and raise the limit to 100M points for
the 64-bit version.

 

For now, you can work around the 10M-point import limit by using
Acquire->Acquire from live ASCII file instead of File->Import
phase/frequency data.  Most of the same code is used for both cases, but
unlike the static file-import version of the dialog, the live data importer
will let you specify the expected duration yourself.  So you can give it a
duration value that you know will be long enough to cover the whole data set
(10 days in this case.)  

 

To use the live-ASCII acquisition option on a static file, uncheck "Auto"
and check "Include existing file contents" before hitting the Start
Measurement button.  When the file finishes loading, it will sit there
waiting for more data to be appended to the file.  At that point you can hit
the space bar to stop the acquisition, and it will readjust the duration to
correspond to the actual number of points it read.

 



 

 

-- john, KE5FX

Miles Design LLC

 

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Re: [time-nuts] Framework for simulation of oscillators

[John Miles]

> > BTW: I discovered that Timelab stops processing after 10'000'000 datapoints,
> > which is kind inconvenient when doing a long term measurment...
> 
> I didn't know that. Good to know.

Attila, wasn't this related to an invalid ':' character in the filename coming 
through from VirtualBox?  Or is this issue different from the one we discussed 
in email last month?

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Framework for simulation of oscillators

[John Miles]

> BTW: I discovered that Timelab stops processing after 10'000'000 datapoints,
> which is kind inconvenient when doing a long term measurment...

It had better not! :)  Any steps to reproduce?

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] high rev isolation amps

[John Miles]

> I'm looking for off the shelf connectorized amplifiers with very good
> reverse isolation for doing things like intermod measurements (e.g. 2
> signal generators followed by amps/pads into a combiner) and phase noise
> measurements for a digital receiver.
> 
> 1-100 MHz kind of frequency range..
> 
> I've used ZFL-500LN (30dB gain, 27 dB directivity in the data sheet,
> which I interpret as 57dB reverse) , ZX60-4016 (really more of a
> microwave amp, and not so hot reverse wise.. 25 dB)
> 
> I'm not particularly cost constrained, so a higher power amp (which also
> reduces distortion products from the amp) followed by pads is always an
> alternative.

Lots of options at http://www.spectradynamics.com, also see the LNDA series at 
http://www.wenzel.com.  

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] BG7TBL GPS Disciplined Source

[John Miles]

My understanding from someone who has purchased one recently is that the 
frequency offset error was indeed just a bug, and that it's now fixed.  I've 
added a note to the end of my page at http://www.ke5fx.com/gpscomp.htm to that 
effect.

If the bug has been fixed (or the algorithm replaced), and if you get one with 
a good MV89A OCXO, the BG7TBL GPSDO has the potential for decent performance.  
In principle all of the right ingredients are there... it's just a question of 
whether the software is making the most of them.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Lars
> Walenius
> Sent: Monday, March 14, 2016 12:41 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] BG7TBL GPS Disciplined Source
> 
> Hi
> 
> If you are lucky the MV89 might be a very good OCXO and U-Blox makes very
> good GPS modules. The NEO-6M is not the best as it isn´t a timing module. But
> in your GPSDO the GPS module with an external antenna is not the limiting
> factor but more the controller and it´s limited resolution on the time
> measurement that is larger than the ripple from the GPS module. Also the
> software with FLL seems to limit the performance a lot. But with the long time
> constant the frequency accuracy, even with the offset due to the FLL, will be
> quite good.
> 
> U-blox own software uCenter have worked well for me.
> 
> Lars

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Re: [time-nuts] Agilent 53220A and TimeLab

[John Miles]

Hi, Timothy --
 
> I've had an Agilent 53220A for some time, and recently discovered the
> wonderful TimeLab software, but I've hit a bit of a snag trying to run some
> ADEV measurements on a Rb clock.  The problem is that the graph doesn't
> line up with the amount of data TimeLab says is collected. I ran an
> acquisition for 100 seconds, but according to the chart it only shows data
> collected for 20 seconds

See page 31-32 of the manual 
(http://www.miles.io/TimePod_5330A_user_manual.pdf).  I think you'll find it 
anticipates that very same question. :)

> On a side note, I was disappointed to find out that I missed the boat on
> the semi-affordable TimePod. Is there anything remotely in the price rang
> (sub 5K) that can do stability AND phase noise measurements? It seems like
> the Wavecrest DST "might" be able to, but from what I read in the time-nuts
> archive I wasn't able to get a clear picture there's an app note
> floating around about making phase noise measurements with it, but
> nothing
> solid.

The Microsemi 3120A's price has come down a bit over time, so I'd suggest 
checking with them to see what the current pricing is like.  (Obligatory 
disclaimer: I have no current financial/professional involvement with the 
3120A.)  I suspect it's still well north of $5K, depending on options, but I 
know they've stepped back from the initial prices they were quoting.

I'd encourage you to build something, though, given that you're not doing this 
stuff for your day job.  There's a reasonable amount of literature out there on 
both quadrature PLLs for PN measurement and the related tight-PLL topology 
that's well-suited to stability measurement.  They can both return very 
high-quality results for very little money, if you're willing to put in the 
necessary "sweat equity."  This approach is much more educational than simply 
throwing money at hardware, and (speaking from experience) more fun as well.

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Timelab, two SR620s and losing samples

[John Miles]

> Therefore, talk-only mode is a big advantage in terms of decoupling
> on RS-232 and makes almost no difference on GPIB.

That's not the case when it comes to counters.  By timing issues, I wasn't 
referring to layer-1 handshaking, but rather the interplay between the GPIB 
software application, the network or bus connectivity between the app and GPIB 
controller, the controller itself and its firmware, and an addressable counter 
that returns each measurement only in response to a command from the app.  The 
difference in performance between a talk-only connection and a two-way 
conversation can be substantial.  Yes, everything runs in lockstep, but the sum 
of the delays and latencies in each of those stages can easily exceed 0.1 
second.  In Attila's case there are also VM crossings in both directions to 
worry about.

The counter, unlike any of the other participants in the conversation, is 
working on a deadline.  Everything in a counter tends to happen in the 
"foreground," so to speak.  If the counter takes too long to interpret and 
execute a GPIB command, it may fail to rearm itself in time for the next 
trigger.  That's never a problem in talk-only mode, at least not at rates we're 
concerned with here, because the counter never has to do anything but send out 
data.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Timelab, two SR620s and losing samples

[John Miles]

Agreed with Magnus that there are a lot of possible variables in your setup 
that need to be ruled out.  

Are you using the SR620 driver in TimeLab, or did you find a way to get it to 
emit data continuously via the RS232 port for use with the talk-only driver?  
I've seen occasional instances where a counter has ignored every other trigger 
when used in addressable mode by TimeLab.  It's not always readily 
reproducible, but the counter drivers in the current beta at 
http://www.miles.io/timelab/beta.htm seem to be a bit less prone to that 
behavior.  If you aren't already using the beta, try that.

It's always safest to use counters in talk-only mode when possible, since that 
rules out any timing problems that might arise in a two-way GPIB or serial 
conversation where each individual reading is requested by the software as done 
by the 5313xA, Philips, DTS2070-series, and SR620 drivers.  Some of those 
counters can be used in both talk-only and addressable modes, but I don't 
believe that's true of the SR620, unfortunately.  All of the programming 
examples in the SR620 manual work by requesting each reading individually. 

-- john, KE5FX
Miles Design LLC

> > I have here a setup with four (FPGA) nodes that produce synchronized pulses
> > with a 20kHz rate. I have two SR620s two measure those pulses.
> >

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Re: [time-nuts] Lady Heather Server On Raspberry Pi 2 Model B?

[John Miles]

The server is a console app that uses plain Winsock calls derived from the BSD 
sockets API, so it could run on anything down to and including an Arduino 
without too much work.  Porting the GUI client to anything else would be a fair 
bit of work, though.

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris
> Caudle
> Sent: Saturday, January 09, 2016 1:32 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Lady Heather Server On Raspberry Pi 2 Model B?
> 
> On Sat, January 9, 2016 8:36 am, Chuck Harris wrote:
> > Unfortunately, LH uses a graphics toolkit that was written by
> > John Miles, and it, and he, is windows only.
> 
> Even compiling as just the server only still compiles and links the
> graphics toolkit?
> 
> --
> Chris Caudle
> 
> 

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Re: [time-nuts] SMD TADD-1 distribution amplifier

[John Miles]

> Amp (now Tyco) did introduce them.  Called "Decoupled Connectors''  Info at
> http://www.te.com/usa-
> en/search.html?q=Decoupled%2BConnectors=header
> 
> Tyco parts 413476-2 and 5413476-2 are available from Mouser, maybe Digikey
> as well
> 

And you might notice that the TimePod itself doesn't use them.  Neither does 
the 5120A, the E5052B, the 11848A, or any other high-performance PN/stability 
test equipment I can think of.

Don't lift, fold, spindle, mutilate, isolate, or otherwise mess with coax 
shields.  If you have ground loop problems, find another way to fix them... or 
better yet, ignore them.  There are worse monsters under this particular bed 
than ground loops.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

[John Miles]

Those spurs are reminiscent of what happens when you lift the ground of a coax 
cable at one end and turn it into an antenna, in my experience.  It is almost 
always a bad idea to do this.  Try shorting out the capacitor(s) at your input 
and output jacks. 

-- john, KE5FX
Miles Design LLC
 
> My 'ultra-low-noise DC-supply' in the form of a lead-acid battery improves
> things somewhat, but some spurs still remain:
> http://www.anderswallin.net/wp-content/uploads/2015/12/2015-12-
> 17_fda_spurs_and_comments.png
> interpretations and explanations are welcome!
> The board was not enclosed in a metal can for these tests.
> 

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Re: [time-nuts] Data collection from 5115A phase noise test set?

[John Miles]

> It seems there is no way to estimate frequency from looking at the phase

> data then?

 

Not to my knowledge.  The frequency count chart on the instrument itself is 
always correct, since it can take the internal baseband offset out of the 
incoming data.  Because TimeLab doesn't have access to that offset, its 
frequency count chart won't be accurate when acquiring data from the 51xx.

 

> Does TimeLab have automated collection for the frequency-counter data on

> the control port?

 

TimeLab doesn't, but I have another collection of quick-and-dirty utilities 
that includes a way to do it (http://www.ke5fx.com/gpib/readme.htm).   The 
tsccmd.bat file can be run without any arguments to get command help; this 
option in particular will pull the frequency count entries across as ASCII text:

 



   C:\Program Files (x86)\KE5FX\GPIB>tsccmd 192.168.1.225 "show fcounter"

   Using Windows Sockets V2.2 (WinSock 2.0)

   Initializing host JMCORE64, address 192.168.1.200

   Attempting to connect to server 192.168.1.225:1299 . . .

   Connected to server 192.168.1.225:1299

   Transmitting "show fcounter" ...

   show fcounter

   Welcome to the Symmetricom 5125A

 

   =192.168.1.225 > Reference Frequency: 100.0 MHz (auto)

 

   Avg Time (s)Frequency (MHz)

   1   9.999627589

   10  9.9996274766

   100 9.99962746890

 

   Done, 8 line(s) received

   Average rate = 11.0/sec



 

 

There's probably a way (wget?) to do something similar in most other OSes -- 
you basically need to send "show fcounter" to port 1299 with an appropriate 
timeout interval.  Then you can pipe the response to something that parses the 
text that comes back, if desired.

 

-- john, KE5FX

Miles Design LLC

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Re: [time-nuts] Data collection from 5115A phase noise test set?

[John Miles]

> Hi all,
> 
> A 5115A phase noise test set landed in our lab and I am wondering about the
> data collection.
> It has two telnet ports one for commands and one for phase data.
> When issuing "start" on the command-port it starts spitting out
> phase-difference values on the data port.
> 
> However it seems to me that the phase data alone (REF-DUT phase, in units
> of the REF period) is almost useless without knowing the internal workings
> of the device.
> The phase values are clearly not the true phase difference, which would
> quickly accumulate to a huge number with e.g. REF=10MHz and DUT=11MHz.
> My
> understanding is that digital downconversion (DDC) is performed on both REF
> and DUT signals, and without knowing the LO frequencies for the DDC the raw
> phase data alone is almost useless.
> 
> The command prompt does have commands for displaying the internally
> calculated ADEV, L(f), frequency-counter readings, etc. and these seem to
> show correct and OK values, but there seems to be no way to reproduce e.g.
> the ADEV or frequency-counter values/statistics from the raw phase values
> on the data port??
> Is this correct? Any other experiences with the 5115A or higher end 5120A?

The shorter-term ADEV values on the 5120A/5125A test sets are mathematically 
backed out of the phase noise data.  They will never perfectly match the ADEV 
values you get from plotting the phase data stream in my experience.  

I don't actually know what they do on the 5115A, though -- since it doesn't do 
cross-correlated PN, there's presumably no reason to derive the short-term ADEV 
plot from the PN data pipeline.  I'd expect the plots to match in that case, 
apart from any errors due to different measurement bandwidths and ADEV bin 
distributions.

It's also true that there will always be an arbitrary phase slope error due to 
the mismatch between the frequency estimate used to tune the internal DDCs and 
the "real" frequency of the incoming data.  Knowledge of the actual DDC core 
frequencies would not be enough to correct for this behavior, because you would 
also need to know how far off they are.  The true frequency offset can't be 
measured ahead of time with perfect certainty, so it has to be estimated, and 
the resulting error will often dominate the slope of the phase-difference graph.

The TimePod and 3120A test sets allow you to specify the input and reference 
frequencies explicitly to obtain a valid phase slope in residual measurements 
and other cases where the exact frequencies are known by the user.  But this is 
something you have to remember to do prior to the measurement, and you still 
don't get a calibrated absolute offset. 

(Also, note that TimeLab can read both phase and PN data from 51xx test sets 
without the need to use a Telnet client.  Not that it helps with this 
particular issue, of course.)

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] HP 5065A Start-Up

[John Miles]

> Microphonics.
> 
> What's the norm here?  I see it in the 2nd harmonic level on the panel
> meter.  It runs about 20 normally, but a pretty light tap (with my
> fingernail) anywhere on the instrument can peg the meter for a few
> seconds.  While I had the scope on A8 TP2 / TP3 (showing the off-resonance
> phase shift peak it manifested as bursts of noise) It's hard to localize -
> but I think the RVFR and Synthesizer are the most sensitive.

If your 5065A is like most of the older ones I've seen, it has been upgraded 
with a 10811-60109 OCXO.  If so, there is a spring-loaded shaft extension that 
allows you to access the 10811's calibration trimmer from the panel behind the 
hinged door.  It can be a good idea to remove that hardware, since it can 
otherwise transfer external vibrations to the OCXO.  That probably isn't enough 
to pin the meter but it's still worth checking.

(Be sure to check the ESR of all of the axial tantalum electrolytics on the 
RVFR oven control board, if you haven't already.  A failed oven controller can 
really hose the RVFR.)

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] Einstein Special on PBS

[John Miles]

It's not exactly a rigorous explanation, but I think it's a good memory aid.  
Once you realize that c is a 4D constant rather than a scalar speed, you can 
work out for yourself which way clock measurements are skewed from various 
points of view.

-- john, KE5FX

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Didier
> Juges
> Sent: Sunday, November 29, 2015 11:20 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Einstein Special on PBS
> 
> Wow. So elegantly simple explanation, thanks John!
> 
> On November 27, 2015 2:54:51 PM CST, John Miles <j...@miles.io> wrote:
> >So, here's how I finally grokked this stuff.  c, the speed of light in
> >a vacuum, is often spoken of as a "speed limit" that nothing can ever
> >exceed.  That's a bad way to put it, and people who have expressed it
> >that way in popular science writing for 100 years should feel bad.
> 


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Re: [time-nuts] Einstein Special on PBS

[John Miles]

The reference was probably a bit too obscure for an international audience. :)  
https://www.youtube.com/watch?v=VPJqIT7a3qA

-- john, KE5FX
Miles Design LLC


> Hi John,
> 
> Thank you very much for this explanation, I found it very "explicative".
> What I am not able to grasp is the sense of the phrase " That second
> part was what really baked peoples' noodles".  I think that is some
> colloquial but not being English my native language I can't figure out
> its meaning.
> 
> Thank you,
> Ignacio
> 

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Re: [time-nuts] Einstein Special on PBS

[John Miles]

So, here's how I finally grokked this stuff.  c, the speed of light in a 
vacuum, is often spoken of as a "speed limit" that nothing can ever exceed.  
That's a bad way to put it, and people who have expressed it that way in 
popular science writing for 100 years should feel bad.  

Instead, the way to visualize relativity is to realize that c is the *only* 
speed at which anything can travel.  You are always moving at 300,000,000 
meters per second, whether you want to or not.  But you're doing it through all 
four dimensions including time.  If you choose to remain stationary in (x,y,z), 
then all of your velocity is in the t direction.  If you move through space at 
100,000,000 meters per second in space, then your velocity in the t direction 
is 283,000,000 meters per second (because sqrt(100E6^2 + 283E6^2) = 300E6.)   

It doesn't make sense to speak of moving a certain number of "meters" through 
time, so your location in time itself is what has to change.  You won't 
perceive any drift in your personal timebase when you move in space, any more 
than you will perceive a change in your location relative to yourself.  ("No 
matter where you go, there you are.")  But an independent observer will see a 
person who's moving at 100,000,000 meters per second in x,y,z and 283,000,000 
meters per second in t.   They see you moving in space, in the form of a 
location change, and they also see you moving in time, in the form of a 
disagreement between their perception of elapsed time and your own.   

Likewise, if you spend all of your velocity allowance in (x,y,z), your t 
component is necessarily zero.  Among other inconvenient effects that occur at 
dt/dt=0, you won't get any closer to your destination, even though your own 
watch is still ticking normally.  Particles moving near c experience this 
effect from their point of view, even while we watch them smash into their 
targets at unimaginable speeds.

This is special relativity in action.  The insight behind general relativity is 
twofold:  1) movement caused by the acceleration of gravity is 
indistinguishable from movement caused by anything else; and 2) you don't even 
have to move, just feel the acceleration.  That second part was what really 
baked peoples' noodles.  It is what's responsible for the disagreement between 
the two 5071As.

-- john, KE5FX
Miles Design LLC

> Hi Mike,
> 
> The time rate does remain the same - at the device.  The problem is the idea
> that it is the hyperfine transitions that determine the time...

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Re: [time-nuts] Timelab Query (likely noob error)

[John Miles]

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jason Ball
> Sent: Friday, October 23, 2015 10:38 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Timelab Query (likely noob error)
> 
> Hi all,
> 
> I'm afraid this may be a noob question as I've undoubtedly done something
> wrong, either that or I have some phenominal time sources... more likely
> I've made an error in an assumption or two.   This should to my mind be
> within the capabilities of the counter I have, but right now I'm starting
> to wonder.
> 
> The problem is I'm seeing a 10s tau of 9.29E-18 which to my limited
> understanding is highly doubtful.
> 
> So what have I done wrong ?
> 

Hi, Jason --

Let's take a look at the .tim file (email it to j...@miles.io) -- probably just 
a missing/inappropriate scale factor.

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] SRS FS710 spurs at 50Hz and harmonics?

[John Miles]

SRS likes to isolate their RF connectors from ground, it seems.  This is almost 
never a good idea.  When measuring PRS10 Rb standards, I've seen similar line 
spurs that went away when I grounded one side of the balanced 10 MHz output at 
the point where the DC supply was connected to the unit.   

Looking at the schematic that Orin posted earlier, it seems they've done the 
same thing with the FS710.  Try bonding the insulated BNC input jack to ground 
at the point where it enters the chassis, and I'll bet those spurs get a lot 
better.  (That is, unless you actually do have a bad filter capacitor.)

-- john, KE5FX
Miles Design LLC

> > I seem to get very strong spurs at 50Hz and harmonics with an old
> > second-hand SRS FS710:
> > http://www.anderswallin.net/2015/09/srs-fs710-noise-measurement/
> > feature or bug? Anyone looked at the powersupply and figured out what parts
> > to change?
> 
> If you live in a country with 50 Hz mains network then this sounds like
> a dead capacitor in the power supply...

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Re: [time-nuts] TimeLab and the N cornered hat...?

[John Miles]

If you're only loading two files, that's definitely not going to work since a 
3-cornered hat requires 3 plots.  In your example, there must be a third plot 
representing A-C, so that each of the three sources will contribute to two 
different plots.  

Apart from that, check for mismatched file parameters.  The way it's currently 
set up, all of the following conditions have to be met before Trace->Show 
separated variances (Ctrl-h) will work:

- A deviation measurement must be selected (ADEV, MDEV, TDEV, HDEV)
- Overlay mode must be enabled with Display->Overlay (o)
- At least three plots must be loaded
- All participating plots need to have visibility turned on (Display->Toggle 
visibility (v))
- All participating plots must have valid Source A and Source B labels
- The source labels must be spelled consistently between all of the 
participating plots
- All participating plots need to have trace history set to 1 (Edit->Trace 
properties (e)->Trace History)
- All participating plots need to have been acquired with the same xDEV bin 
density
- All participating plots need to have exactly the same sample interval (tau 
zero)

The last condition is especially easy to miss if your plots came from a counter 
with "Use incoming data to configure measurement" checked.  It may have 
measured the sampling interval a bit differently in one or more of the plots. 

If you've already checked these points and it still isn't rendering the hat 
traces, zip up the .tim files and send them to john (at) miles.io, and I'll 
have a look.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Nick Sayer
> via time-nuts
> Sent: Sunday, September 27, 2015 8:25 AM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] TimeLab and the N cornered hat...?
> 
> I’m running the latest beta, and I’ve found the spot in Edit > Trace details 
> where
> you tell it the two sources that contribute to a particular dataset. I’d 
> expect that
> having done that and loaded two traces A-B and B-C that I’d be able to elect 
> to
> show the N cornered hat and see something different in the ADEV window, but
> it’s not doing anything. What am I missing?
> ___
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Re: [time-nuts] HP 3048A Alternative to HP3561A?

[John Miles]

> Hello all - I have always wanted an HP 3048A system.  I have acquired a
> 11848A, but need an HP 3561A or equivalent.
> 
> Is there any substitute to the 3561A?

Nope.  It's the 3561A or nothing.

> Also, are their other spectrum analyzers that are acceptable other than the
> ones listed here?
> 
> http://www.geocities.jp/etm_llc/pub/HP3048A/3048A.html

No, it needs to be one of those.  The 3585A (or 3585B) is the best option but 
the others will work too.

You can get by without any RF spectrum analyzer at all, but the 3561A is 
mandatory.

-- john, KE5FX


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Re: [time-nuts] HP5065A C-field current voltage mod

[John Miles]

One idea would be to leave the existing C-field circuit in place with a switch 
to disable it.  That'd preserve your ability to carry out the second harmonic 
adjustment procedure, while allowing you to switch back to a stable current for 
normal operation.

For that matter, it's not clear what "aging process in the A12 RVFR assembly" 
accounts for the presence of that adjustment procedure in the manual.  Given 
the absence of any other aging mechanisms other than (very) gradual lamp 
darkening, I have to wonder if the Implementers mistakenly blamed the RVFR for 
drift in some other component.  I suppose they could be referring to partial 
diffusion of the buffer gas through the cell walls... but after 40 years, is 
there any indication that this is actually an issue?

Has anyone looked into the oven temperature stability to make sure that further 
optimization of C-field stability is worthwhile?  I'm a bit behind on my email 
so this may have already come up.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-
> Henning Kamp
> Sent: Friday, September 04, 2015 2:38 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] HP5065A C-field current voltage mod
> 
> 
> In message <89828.1441376...@critter.freebsd.dk>, "Poul-Henning Kamp"
> writes:
> 
> >I actually have some calculations relevant to this, I'll write them
> >up on my homepage when I have a second.
> 
> Here:
> 
>   http://phk.freebsd.dk/hacks/HP5065A/20150904_math
> 
> I'd be very pleased if somebody would double-check the calculations.
> 
> --
> 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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> and follow the instructions there.

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Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat

[John Miles]

 The is a publication by the NPL that talks about a similar technique, but
 comes to a somewhat different conclusion.
 
 http://publications.npl.co.uk/npl_web/pdf/mgpg68.pdf
 
 Bottom line: it holds that the phase noise of all three sources can be
 determined if they are taken two at a time; one as ref and the other as
 the DUT.

Yes, that's the three-cornered hat technique.  The document is a bit dated in 
that respect -- it was published in 2004, just as Timing Solutions was starting 
to work on cross-correlated direct digital measurements.  

The dual-reference method always converges on the DUT noise if set up properly, 
but it doesn't give you any insight into the two independent sources being used 
as references.  You have to swap the DUT with each of the references and repeat 
the measurement if you want to characterize all three sources, while the 
N-cornered hat returns separated variances for all sources at once (at least 
ideally.)

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat

[John Miles]

 On that note, did you look more closely on the NIST analysis of
 cross-correlation and a possible cancellation and thus overly optimistic
 results? Did it have any consequence on your code? What did you take
 away from it?

Yes, you can definitely get divots in the PN trace, especially in multiple-hour 
runs needed to reach very low noise levels.  I've seen that on occasion when 
making measurements with independent downconverters.  If the DUT signal 
experiences significant phase shift in one downconverter path relative to the 
other, I imagine that's a good way to provoke this behavior.  

Fortunately I haven't run into any instances of the worst-case scenario 
described in the Nelson paper, where the whole noise floor collapses without 
any exhibiting any other weird artifacts.  The phenomenon is certainly worth 
keeping in mind but most people are not going to run into it, especially with 
the Ch0 and Ch2 jumpers in place.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] 3 corner hat

[John Miles]

 Thank you for the answers.
 
 I've already posted my formulas that work for phase noise.
 
 But John, I will now try your method with the Timepod and see how they
 compare.
 
 I did get the N corner to work with the Timepod, but as you say, that's for
 ADEV.

You're welcome -- I haven't seen that done for PN, but on the surface I don't 
see why it wouldn't work.  You'll always get the best data with the dual-source 
technique, though.  It would be good to hear how your results from the two 
different methods compare to each other.

Re: the spurs, any uncorrelated spurs on the Ch0 and Ch2 sources should average 
out just like the noise.  But for high-level spurs close to the carrier, this 
process may take too long to be useful, and it won't be helpful for removing 
common-mode interference like ground loops.  Frequency drift between Ch0 and 
Ch2 will also tend to keep the spurs from cancelling, and will also make it 
hard for the software to remove them.  It's a good idea to use clean, stable 
sources for these types of measurements whenever possible.

 Just a personal note.  The Timepod is the worlds best bit of electronics
 ever, and if John Miles was English, I would recommend him for a knighthood.
 
 John, hope you're blushing now.
 

Heh, I'm afraid I'd have to politely decline the title.  Too many people 
already mistake me for Rowan Atkinson, and that would only make matters worse! 

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] 3 corner hat for phase noise

[John Miles]

Actually, after typing all that, it occurred to me that you might have actually 
meant to ask about N-cornered stability measurements.  They aren't supported by 
the current official release of TImeLab; you need to use the beta version from 
http://www.miles.io/timelab/beta.htm .  

For instructions, hit 'e' to bring up the Trace Properties dialog box and move 
your mouse cursor over the 'Source A/Source B' fields.  These allow you to add 
channel labels to existing .tim files.  For TimePod acquisitions, it's easier 
to name the sources at acquisition time.  Hover over the 'Ch 0/Ch 1/Ch 2' and 
'Stability' fields on the Advanced tab of the acquisition dialog to see how to 
do that.  

Contrary to what the help text says, the TimeLab manual hasn't yet been 
updated, so the help text is all there is, as far as documentation goes.

-- john, KE5FX
Miles Design LLC

 One nice thing about phase noise is that it's computable with complex FFTs,
 rather than the one-dimensional phase or frequency differences that ADEV
 uses...

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Re: [time-nuts] 3 corner hat for phase noise

[John Miles]

One nice thing about phase noise is that it's computable with complex FFTs, 
rather than the one-dimensional phase or frequency differences that ADEV uses.  
Another nice thing is that it's stationary -- meaning its probability 
distribution can (usually) be treated as unchanging from one measurement to the 
next.  These two properties allow PN measurements to be performed with vector 
averaging over time, resulting in a single correct value at each bin.  Unlike 
a stability measurement, the expectation with PN is that repeated measurements 
will always yield the same plot.

So you don't need to use statistical hacks like N-corner hats to measure phase 
noise with a TimePod or other multichannel instrument.  Pull the SMA jumpers 
off of the Ch0 and Ch2 jacks and feed two independent references to them.  Over 
time, the measurement will converge to the phase noise of the source at the REF 
IN jack, even if it is quieter than either of the two sources at the input 
jacks.  

The TimePod/3120A firmware can't compensate for frequency offsets between Ch0 
and Ch2, so the two independent sources need to be very close in frequency and 
they need to stay that way over the course of the measurement.  A pair of 
good-quality rubidium or GPS clocks can be a good way to go.  

-- john, KE5FX
Miles Design LLC


 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
 Baak
 Sent: Tuesday, August 25, 2015 11:11 AM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] 3 corner hat for phase noise
 
 This is from 3hat.c -- C code, but you get the idea:
 
 A[i] = sqrt( (0 + SQUARE(AB[i]) - SQUARE(BC[i]) + SQUARE(AC[i])) / 
 2.0 );
 B[i] = sqrt( (0 + SQUARE(AB[i]) + SQUARE(BC[i]) - SQUARE(AC[i])) / 
 2.0 );
 C[i] = sqrt( (0 - SQUARE(AB[i]) + SQUARE(BC[i]) + SQUARE(AC[i])) / 
 2.0 );
 
 And watch out for negative square roots.
 
 /tvb
 
 - Original Message -
 From: Martyn Smith mar...@ptsyst.com
 To: time-nuts@febo.com
 Sent: Tuesday, August 25, 2015 9:36 AM
 Subject: [time-nuts] 3 corner hat for phase noise
 
 
 
  Hello,
 
  Does anyone have an EXCEL spreadsheet that calculates the individual phase
  noise of  3 oscillators when they are compared against each other, e.g  A vs
  B, A vs C, B vs C.
 
  I.e the 3 corner hat technique.
 
  I do have a Timepod and I thought Timelab could do that, have haven't found
  how to do that.
 
  Regards
 
  Martyn

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Re: [time-nuts] ADEV measurement question

[John Miles]

I think the simplest way to explain the evils of TI averaging is that white 
noise doesn't alias in a conventional sense.  If a value is perfectly random, 
then it doesn't matter how you sample it.  Your sampling bandwidth -- and 
nothing else -- determines how much energy you get.  You can legitimately 
change that bandwidth after the fact by resampling or averaging the data.  
(Another way to say this is that components of the white noise spectrum above 
the Nyquist frequency don't have a net effect on the observed spectrum.)  But 
this is only true for white noise; with any other variety of signal or noise 
energy, once it's sampled, it's there for good.  

So, postprocessing a sampled stream with averaging has the effect of reducing 
the white-noise component of the data to a greater extent than the rest.  This 
is why you see tend to see 'better' results from an MDEV plot than an ADEV 
plot.  MDEV has some built-in averaging properties, while ADEV does not.  
Energy in a given part of the spectrum will influence an ADEV plot to a greater 
extent than with MDEV.  

ADEV isn't particularly frequency-selective.  If you've ever seen 1-pps or 
50/60 Hz interference in an ADEV plot, you've noticed that its influence can 
corrupt the plot for the next decade or two.   So if you must use your 
counter's averaging feature to get good ADEV plots, it's important to carry out 
that averaging at a very small fraction of the tau-zero interval.  The more 
1/f^n noise is present in your measurement, the more important that becomes.  
Otherwise you end up with a transfer function that isn't really ADEV, even 
though that's what the label on the plot says it is.  

This gets more complicated with counters that dither their sampling clock, 
and/or apply other filter functions in their averaging process.  Some appear to 
be give better ADEV fidelity than others.  If nothing else, I would expect that 
averaging at sub-t0 intervals would introduce a dead-time effect in the portion 
of t0 over which the data is not contributing to the average.  It is always 
going to be better to avoid TI averaging whenever possible, and use great care 
in interpreting the data.

-- john, KE5FX
Miles Design LLC


 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Matthias
 Jelen
 Sent: Wednesday, August 19, 2015 9:40 AM
 To: Discussion of precise time and frequency measurement
 Subject: [time-nuts] ADEV measurement question
 
 Hello,
 
 I´ve got a question concerning ADEV-measurements.
 
 I´m measuring the 15 MHz output of a KS-24361 with my SR-620
 with it´s internal (Wenzel) OCXO using Timelab. For the
 first shot I used the counters frequency mode with 1s
 gatetime. ADEV at tau=1s turned out to be arounf 2E-11,
 which fits the 20 ps single shot resolution of the SR-620
 nicely.
 
 To overcome this limitation without setting up a DMTD
 system, I used the counter as TIC, feeding 1 kHz (derived
 from the counter´s reference) to the start channel, the 15
 MHz to the stop channel and put the counter into average
 mode / 1k samples. This gives me one averaged result per second.
 
 The idea was that this shouldn´t change the measurement
 itself, because like in frequency mode with 1s gate time I
 get the averaged value over one second, but I expected
 trigger noise etc. to be averaged out to a certain amount. I
 have to watch out for phase wraps, but as the two frequencys
 are quite equal, this is not a big issue here.
 
 As expected, ADEV at tau=1s got much better, it is now in
 the 4E-12 area, which sound reasonable.
 
 What makes me wonder is the fact that result are
 significantly better now at longer taus (10..100s) also,
 despite of the fact that also in frequency mode these result
 were well aboce the noise floor (2E-12 @ 10s and so on...).
 
 So, is it a good idea to use this kind of averaging, or am I
 overlooking something which turns the numbers better than
 they really are? I´m pretty sure I am not the first one to
 try this...
 
 I´m looking forward to your comments.
 
 Best regards,
 
 Matthias
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Re: [time-nuts] HP10811 vs 00105 OCXO

[John Miles]

 Hi
 
 If that data is correct, then the 10811 you have is defective.
 Bob

Well... some of the data is reasonable for a scenario where a counter is being 
used to measure OCXOs.  

Looking at the ADEV plot, I'd say the blue trace (HP105B vs 5065A) is the most 
questionable one if it came from a standalone TIC or frequency counter, because 
7E-12 @ t=1s isn't achievable with most counters under most circumstances.  A 
Wavecrest box can measure at that level if it's set up _perfectly_ to take 
bursts of 100+ wrap-free averages within a small fraction of the t0 interval.  
It might also be doable with an HP 5370A/B under similar conditions, but I'd 
have less confidence that the averaging isn't distorting the measurement.  So 
while It looks like a valid measurement of an OCXO with some minor crosstalk or 
other external interference, that may just be a coincidence.  

Luciano, how was the blue trace taken?  Is this from your DMTD project?  If so, 
it's looking promising.

The green and magenta traces are definitely in the right ballpark for 
measurements on a 5370-class counter.  At 3E-11 @ t=12s the magenta trace is 
optimistic but not outrageously so, while the green trace looks exactly like 
I'd expect for a typical 10811 measured on a 5370.  The observed noise is due 
entirely to the counter until about t=200s.  We see a glimpse of the 10811's 
typical  ADEV at about 250 seconds, just before either drift or ADEV 
uncertainty causes the trace to turn upwards.  A longer run would be needed to 
distinguish between these two situations.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Modified Allan Deviation and counter averaging

[John Miles]

 Apart from the delayed measurement point, I have not been able
 to identify any issues.
 
 The frequency spectrum filtered out by the averaging is wy to
 the left of our minimum Tau.
 
 Phase wrap-around inside bursts can be detected and unfolded
 in the processing.
 
 Am I overlooking anything ?

I think this is basically a valid thing to do, under specific conditions.  It 
works well with the Wavecrest DTS boxes, which can take several thousand 
samples per second and distill them down to a single TI reading.  I've observed 
good agreement between ADEV plots taken with the DTS2070 and direct-digital 
analyzers down to the ~2E-12 level at t=1s. 

The main caveat is that the burst of averaged readings needs to take up a very 
small portion of the tau-zero interval, as you point out, to keep the averaging 
effects out of the visible portion of the plot.  This might not be a very big 
problem with MDEV but it is definitely an issue with ADEV.

The second thing to watch for is even more important: while the host software 
(TimeLab, Stable32, etc.) can handle phase wraps that occur between counter 
readings, the sub-reading averaging algorithm in the counter will not.  Phase 
wraps in the middle of a burst will corrupt the data badly, and I don't see any 
reliable way to detect and unfold them after the fact.  

So if John's firmware can handle intra-burst phase wraps before returning each 
averaged reading to the software, it could be a big win.  Otherwise this 
technique should be confined to cases where two extremely stable sources are 
being compared with no possibility of phase wraps.  It would be a good way to 
keep an eye on the short-term behavior of a pair of Cs or GPS clocks, for 
instance.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] how to find low noise transistors

[John Miles]

  The BFG540 is amongst the best Oscillators  oscillators
 
 http://www.nxp.com/documents/data_sheet/BFG540_X_XR_N.pdf
 
 Now you outperform most colleagues
 
 73 de Ulrich N1UL

Last time buy 31-Dec-15. :(   Have you heard of any good substitutes?  

I've built a lot of amps with BFG591s, and they also got the axe recently.
Small-signal RF bipolars seem to be an endangered species.

-- john, KE5FX
Miles Design LLC

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