[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[ed breya]

On 4/7/22 3:09 PM, Joseph Gwinn wrote:
>
> This BTULN OCXO looks very good.  While they do mention that it
> contains its own regulator, no numbers are given, so it's hard to
> know what to make of that claim.
>

As far as I know, every OCXO and most everything else has its own 
internal supply and further regulation of some sort, running from the 
crude real world sources applied. As long as the supply you give it 
meets the specs and other characteristics, stated, it should be just 
fine. Making the outside supply part better may or may not make the 
thing work better, but maybe it's worth a shot.



>> I wouldn't assume battery power - but this is where a phone call helps -
>> they'll be happy to tell you.
> I must say that I've run into the battery-power (or *really* good lab
> power supply) approach, neither which is applicable in non-lab
> applications.  I suppose if Wenzel does the packaging, they will
> ensure that full OCXO performance is achieved when powered from the
> usual lab AC power.  The box would also shield the power wiring and
> frequency-control input (if any) and associated wiring from passing
> EMI.


Relating to power supply filter capacitance multipliers from the 
concurrent 1/f noise discussion, are you talking about this kind of deal 
maybe?


http://www.wenzel.com/documents/finesse.html

Ed
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[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[John Ackermann N8UR]

On 4/7/22 18:46, Lux, Jim wrote:

Wenzel is not some giant WalMart of oscillators, with forklifts going 
hither and yon full of palletized ULNs - there are probably 50-60 people 
there total, so odds are, you'll be talking to someone who actually has 
touched (with gloves) your oscillator.


This is true.  Wenzel is a small shop that really tries to be helpful. 
For example, I've asked them for details on surplus oscillators that 
have a custom part number.  They won't give you data for that exact 
part, but they'll nudge you to something that's very similar.


And while they're by no means cheap, a lot of their 
multiplier/divider/buffer/PLL/etc. modules are not out of the reach of a 
serious experimenter.  They actually have things in their parts list 
that are priced in three figures.


They're just good people.

John
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[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[Lux, Jim]

On 4/7/22 3:09 PM, Joseph Gwinn wrote:


This BTULN OCXO looks very good.  While they do mention that it
contains its own regulator, no numbers are given, so it's hard to
know what to make of that claim.

  

I wouldn't assume battery power - but this is where a phone call helps -
they'll be happy to tell you.

I must say that I've run into the battery-power (or *really* good lab
power supply) approach, neither which is applicable in non-lab
applications.  I suppose if Wenzel does the packaging, they will
ensure that full OCXO performance is achieved when powered from the
usual lab AC power.  The box would also shield the power wiring and
frequency-control input (if any) and associated wiring from passing
EMI.

Joe Gwinn





That's a "call Wenzel and ask"  - They can answer your questions, and 
all we can do is speculate.  Even if I had a Wenzel box here in front of 
me with test data, that doesn't mean YOUR Wenzel box would be the 
same.   And when it comes to "in the catalog, but really we have a 
subset of stuff on the shelf" that's where calling is best.  Who knows 
what work they've been doing.  They might have had a job to build half a 
dozen sources, and they built 8, so that they'd have 6 guaranteed to 
meet the requirements, and now they happen to have a spare, or a spare 
that didn't quite hit -180, but only got -179.  And you'd be happy with 
that.


Wenzel is not some giant WalMart of oscillators, with forklifts going 
hither and yon full of palletized ULNs - there are probably 50-60 people 
there total, so odds are, you'll be talking to someone who actually has 
touched (with gloves) your oscillator.

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[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[Bob kb8tq]

Hi

Since this is Time Nuts … crazy isn’t always ruled out :)

> ……….
> “TSP #162   Tutorial   on   Theory,   Characterization  & Measurement
> Techniques of Phase Noise"
> 
>  https://www.youtube.com/watch?v=SOHjFtw0sgo
> 
> each 5db  of improvement requires an order of magnitude  increase in
> the number of correlations.
> 
> dB  5   10  15  20  25  30  35  40
> N   10  100 10001E4 1E5 1E6 1e7 1e8
> 
> So going from -180dBc/Hz to 220dBc/Hz would require 1e8 correlations.
> 
> 6. Nobody would wait that long. But how many correlations do you need?
> ……..

Say you did go the brute force approach. We’re talking far removed
phase noise for stuff like -220 dbc/Hz so each sample set could be pretty 
short. 
Just to toss out a number, let’s go with 1 ms. Yes, this would be quite far 
from carrier.

We now are at 1x10^5 seconds of data. That’s “only” a bit over a day. That’s 
not 
an insane run time for an R environment. An “over the weekend” run of 
three days would get you all the way out to 3 ms sample sets. 

Want longer samples? 

How many samplers / correlation processors do you have? How much 
does each one add to the mix? If it was linear, you are out to a whopping
300 ms with “only” 100 processors. Yes that sounds insane. This isn’t quite
as simple as a video graphics card or four being plugged into a PC. Still, 
it could cut down the time. 

So maybe not quite so crazy after all …..

Bob
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[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[Joseph Gwinn]

On Sun, 03 Apr 2022 03:30:27 -0400, time-nuts-requ...@lists.febo.com 
wrote:
time-nuts Digest, Vol 216, Issue 4

Multiple responses interspersed below.

> 
> --
> 
> Message: 5
> Date: Sat, 2 Apr 2022 07:13:32 -0700
> From: "Lux, Jim" 
> Subject: [time-nuts] Re: Low Phase Noise 10 MHz bench signal source
>   sought
> To: time-nuts@lists.febo.com
> Message-ID: 
> Content-Type: text/plain; charset=UTF-8; format=flowed
> 
> On 4/1/22 2:12 PM, Joseph Gwinn wrote:
>> I'm looking for suggestions for AC-powered 10 MHz sinewave laboratory
>> signal sources with very low phase noise, having a noise floor below
>> -170 dBc/Hz.  Rubidium is desired, but not essential.  Reliability
>> and durability in lab use is essential.
>> 
>> Which makes and models should I consider purchasing?
>> 
>> I like the SRS model FS725, but its noise floor is too high at -150
>> dBm/Hz, 20 dB noisier than many things I may wish to measure.
>> 
>> 
>> Thanks,
> 
> Ultimately, what you're looking for is a "oscillator and distribution 
> amp in a box with a power supply" - you can build it yourself, or you 
> can contract it out to a variety of places, or you can go to an 
> oscillator manufacturer.
> 
> Call Wenzel Associates (https://www.wenzel.com/) - they'll put some of 
> their low noise sources/distribution amps into a box with a power 
> supply. For a price. Their website is broken for these kinds of 
> products, but it's something they do all the time.

Yes.

> --
> 
> 
> Message: 16
> Date: Sat, 2 Apr 2022 18:13:42 -0700
> From: "Lux, Jim" 
> Subject: [time-nuts] Re: Low Phase Noise 10 MHz bench signal source
>   sought
> To: time-nuts@lists.febo.com
> Message-ID: <08b0df36-9358-8950-9c1e-54b02c04a...@luxfamily.com>
> Content-Type: multipart/mixed;
>   boundary="75rdw5reGZnT1q5be5m0JRMp"
> 
> On 4/2/22 4:47 PM, Joseph Gwinn wrote:
>> On Sat, 02 Apr 2022 03:27:06 -0400, time-nuts-requ...@lists.febo.com
>> wrote:
>> time-nuts Digest, Vol 216, Issue 3
>> 
>>>11. Re: Low Phase Noise70 10 MHz bench signal source sought
>>>(Richard (Rick) Karlquist)
>>> 
>>> Date: Fri, 1 Apr 2022 19:12:07 -0700
>>> From: "Richard (Rick) Karlquist" 
>>> Subject: [time-nuts] Re: Low Phase Noise70 10 MHz bench signal source
>>> sought
>>> To: Discussion of precise time and frequency measurement
>>> ,Bob kb8tq 
>>> Message-ID: <0f524fb8-2220-635e-3f62-28f7f0816...@karlquist.com>
>>> Content-Type: text/plain; charset=UTF-8; format=flowed
>>> 
>>> He [Joe] should be looking at Wenzel Associates and NEL.
>>> Wenzel specs -170 dBc at 100 Hz offset.
>> I know of Wenzel, but they don't make bench-top lab instruments.
>> Rack-mount is available, but as a custom part.
> 
> Wenzel will be happy (for a price) to put it in any size or shape box 
> you want. Most people want rack mounts, but it's mostly a matter of 
> sheet metal work and they can certainly do that.

Yes.

> Depending on your frequency and performance, you *might* find a "in 
> stock"  oscillator.  A 10 MHz Onyx or something like that might be 
> basically stock.
> 
...
> 
>> 
>> What is also needed is a very quiet source of DC power for the Rb,
>> OCXO, et al.  None of the vendors seem to specify their PSRR (power
>> supply rejection ratio), and I assume that all published curves are
>> obtained using a battery-powered unit under test.
> 
> No, that's a "call them and ask", but most have pretty good PSRR 
> (although what are you looking for?) - the guy or gal on the phone will 
> tell you what it is in a "not guaranteed on the data sheet" sort of way. 
> Unless you want them to hit a spec, but you'll pay for it.

The basic requirement intent is simply to not undermine the 
performance of the OCXO being powered.


> https://wenzel.com/model/btuln/ mentions that they have an internal low 
> noise regulator - it's about 5dB shy of your -170 at 100Hz requirement.

This BTULN OCXO looks very good.  While they do mention that it 
contains its own regulator, no numbers are given, so it's hard to 
know what to make of that claim.

 
> I wouldn't assume battery power - but this is where a phone call helps - 
> they'll be happy to tell you.

I must say that I've run into the battery-power (or *really* good lab 
power supply) approach, neither which is applicable in non-lab 
applications.  I suppose if Wenzel does the packaging, they will 
ensure that full OCXO performance is achieved when powered from the 
usual lab AC power.  The box would also shield the power wiring and 
frequency-control input (if any) and associated wiring from passing 
EMI.

Joe Gwinn







> --
> 
> Message: 17
> Date: Sat, 02 Apr 2022 18:16:50 -0700
> From: Hal Murray 
> Subject: [time-nuts] Re: Low Phase Noise70 10 MHz bench signal source
>   sought
> To: Discussion of precise time and frequency measurement
>   
> Cc: Hal Murray 
> Message-ID: 

[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[Mike Monett]

Hello Time-Nuts fans,

>From "Phase  Noise   Measurements   and   its  Limitations", Synergy
Microwave Corporation:

  https://synergymwave.com/articles/2013/04/full_article.pdf

"There is an optimum condition and some of the  measurements showing
-190dBc/Hz do  not seem to match the  theoretical  calculations. The
correlation allows  us to look below KT, but the  noise contribution
below KT is as useful as finding one gold atom in your body's blood.
This gold atom has no contribution to your system."

This is not accurate or complete.

1. The  human body is composed of many elements. One  of  the lesser
know elements is actually Gold. An average person's body weighing 70
kilograms would contain a total mass of 0.2 milligrams of gold.

Gold plays  a  vital role in health and maintenance  of  the joints.
Also, being  a good conductor of electricity, it  actually  helps in
transmitting electrical signals throughout the body.  (including the
brain - MRM)

 
https://www.indiatoday.in/education-today/gk-current-affairs/story/gold-body-345917-2016-10-10

2. The Atomic weight of the Gold (Au) is = 196.97 (197g apprx.)

The Avogadro's number in one mole are = 6.022X10^23

That means 6.022X10^23 atoms weigh 196.97 g.

1.0 g/ 196.97 g = 0.0051 mol

So the number of atoms in one gram of gold are:

0.0051 x 6.022X10^23 = 3.057318373 x 10^21

  https://brainly.in/question/6453418

3. 0.2 milligrams of gold is

3.05e21 * 0.0002 = 6.1e+17 atoms

This is  a  very large number, but we can break it  down  to  a more
manageable number.

The average  human has a mass of about 62 kg, or 62,000  grams. That
means the  average  volume of a human is  62,000  cubic centimeters,
ignoring the weight of bones. So each cubic centimeter contains

62e3/6.1e17 = 1.016e-13 atoms of gold

This is 10,160,000,000,000 atoms per cubic centimeter. So you have a
very good chance of finding an atom of gold in your body. And  it is
vital to your health.

4. Here is a brief explanation of how cross-correlation works:
"Understanding Phase Noise - the Cross Correlation Method"

  https://www.youtube.com/watch?v=Sf7qiysPFbQ   

5. The  benefit  of cross-correlation depends on  how  long  you are
willing to wait. My recent quote of -220dBc/Hz was unrealistic. I do
not know  where  I found that figure, but I will now  set  the story
straight. From

"TSP #162   Tutorial   on   Theory,   Characterization  & Measurement
Techniques of Phase Noise"

  https://www.youtube.com/watch?v=SOHjFtw0sgo

each 5db  of improvement requires an order of magnitude  increase in
the number of correlations.

dB  5   10  15  20  25  30  35  40
N   10  100 10001E4 1E5 1E6 1e7 1e8

So going from -180dBc/Hz to 220dBc/Hz would require 1e8 correlations.

6. Nobody would wait that long. But how many correlations do you need?

A commonly accepted figure is your measurement noise floor has to be
at least  10 dB below the noise you are trying to measure.  We could
pad that by 5 db, which would require

15 / 5 = 3
1e3 = 1000 correlations. That is not too bad.

7. It  is  interesting  to note the  Holsworth  HA7062C  Phase Noise
Analyzer goes  to   a   maximum   of   1024  cross-correlations. 100
correlations (-10dB) takes 7 min, 9s at 10 MHz.

  https://holzworth.com/Portals/0/HA7062C_Web_Datasheet.pdf

8. Finally, "Frequency Signal Source's PN (Phase Noise) Measurements
Challenges and  Uncertainty",  by  Ulrich L.  Rohde,  has  some very
important information on cross-correlation errors. This file is at

  https://www.mrmonett.com/pdfs/2015-IFCS-Rohde-Oscillator-noise.pdf
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[time-nuts] Re: +1/f of transistors

[Joseph Gwinn]

On Thu, 07 Apr 2022 03:30:40 -0400, time-nuts-requ...@lists.febo.com 
wrote:
time-nuts Digest, Vol 216, Issue 11

> Message: 11
> Date: Thu, 07 Apr 2022 04:04:37 +0200
> From: g...@hoffmann-hochfrequenz.de
> Subject: [time-nuts] Re: +1/f of transistors
> To: Discussion of precise time and frequency measurement
>   
> Cc: Joseph Gwinn 
> Message-ID:
>   
> Content-Type: multipart/mixed;
>   boundary="=_d7d66c5dc46758f967fd363190701e4d"
> 
> Am 2022-04-07 1:37, schrieb Joseph Gwinn:
> 
>>> Lately, I've been seeing papers using various microwave pHEMTs but, by
>>> the time you find and read the paper, the part is no longer available.
>>> And, of course, just like low noise MMICs (PGA-103, GALI-74) you have 
>>> to
>>> measure them yourself to find out - because the mfr only measures from
>>> 50 MHz and up.
>> 
>> It's a big problem.  Nor do they specify DC parameters all that well.
>> 
>> 
>>> A good example is the 2018 paper by Chen, et al. which references the
>>> ATF54143 - a 3 year old paper, and the part isn't available any more.
>>> The 2SK117 shows up a lot in some older articles and app notes (e.g.
>>> from Wenzel) - it's discontinued, but potentially available from some
>>> surplus/obsolete dealers.
> 
>>> There is a list in The Art of Electronics, but some of them won't be
>>> available.   Some datasheets do have the curve - the JFE150 from TI 
>>> has
>>> its voltage noise curve right on the front page.
>> 
>> What those folk are currently using for capacitance multipliers and
>> the like (where low 1/f noise is also essential) are SiGe transistors
>> like the following:  BFP640H (Infineon), BFP780, SAV541
>> (MiniCircuits), and 2S2114K (NPN, beta 1200) for high current
> 
> and 2SD2704 from ROHM, even more beta

Interesting.  I would not have thought of this one.  It's big and 
slow, and made from modern very clean silicon, so it could have low 
1/f noise.  Its transition frequency (*= gain-BW product?) is 35 MHz, 
so it ought to work on switcher noise.


> Those SiGe transistors have wonderful low Rbb of just a few Ohms,
> which results in nice low voltage noise, but some have 1/f corners
> of 50 MHz or more; that kills my application completely.

While these chips are small, they are made from very clean material, 
so one wonders why so high. The circuit should be physically designed 
as if it were to be handling GHz signals, because it could be 
oscillating far above the capability of available instruments to 
detect.

High input path resistance in the GHz won't affect or cause 1/f noise 
near DC.

I would try a lossy ferrite bead on the input.  


> My application was a base band low noise amplifier and I wanted
> a C-multiplier to suppress the noise on Vcc that is fed into
> the input Cascode. That noise comes from a LT3042 regulator:
> 2nV/rtHz in the flat part, but it rises worse than 1/f until
> you get the full broadside of Rset = 13K7 here. Increasing the capacitor
> over Rset to 47uF or even 100 uF tantalum removed that for
> my requirements. The amplifier stays below 1nV/rtHz until
> at least <5 Hz.

Regulators are pretty complicated, with many active devices, many in 
loops, and so are always noisier than a one-transistor capacitance 
multiplier with film capacitor.


> The amplifier has 16 CPH3910 FETs in parallel (On Semi), the purple
> line is the noise of a 60 Ohm resistor or 1 nV/rtHz. The horizontal
> part of the purple line should be at -180 dBV, gain was not yet tuned
> when the picture was made.
> 
> The line with the input shorted is 10 dB lower, so the amplifier's
> own voltage noise is abt. 320 pV/rtHz. I don't think that JFETs
> can do much better, including the overpriced JFE150.
> 
> Having large organic electrolytics across Vcc (Panasonic SEPF 1000u/16)
> seems to worsen things at low frequencies. (orange trace)
> I had that result also with other amplifiers. I think that from time
> to time, a bunch of electrons defects through the capacitor, creating
> some popcorn/telegraph noise.

Try film capacitors.  The LIGO crowd did a study of 1/f noise of 
capacitors, and found the best.


> With a capacitance multiplier, one can use only film capacitors.

True.


> Seeing the effect of a 60 Ohm resistor at the input of a low noise
> amplifier also makes it clear why 17 dBm+ mixers give bad results
> when used as phase detectors. The mixer literature shows that most
> 17 dBm+ mixers have a resistor in series to each diode to produce
> back bias for the other branch, only bypassed for RF.
> Probably an array of low level mixers with power dividers and the
> outputs summed up fares better as low noise phase detector.
> 
> The NIST 2N ring mixer does not have these resistors, contrarily
> the transistors are used as switches and not as real diodes, which
> keeps their impedance low. Ok, the diode noise is only half-thermal.
> But the resistor noise is not.
> 
> I think I'll have to set up a series of 1/f noise measurements for AF
> and RF parts. The pre-amp puts 

[time-nuts] Steering UK time station MSF

[Steven Sommars]

NIST steers the WWV/WWVB/WWVH radio stations using GPS common view.

Recent youtube piece on MSF
https://www.youtube.com/watch?v=yqciKS_N0K8
I was surprised that NPL (Teddington) steers MSF (Anthorn) based on the
signals received at NPL.   While  this steering seems less accurate than
GPS common view it does not require satellites.
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[time-nuts] HP5065A fs

[timeok]

   Fs an HP5065A, the best ribidium ever produced on the market. In perfect 
condition with digital clock, complete with power cord. Xtal 00105.

   Electrolytic capacitors replaced, otherwise in original condition.

   1450.oo € shipping included Central Europe, for other countries to check the 
costs. Guaranteed excellent packaging.

   Luciano P. S. Paramithiotti
   tim...@timok.it
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[time-nuts] Re: Ublox LEA-4T mentioned here. Have fired one up

[paul swed]

John
I suspect we may be the only ones interested in these units. Can we connect
offline?
I am at paulsw...@gmail.com.

With respect to Murphey Surplus they have been around for 30+ years. I
think if you reach out to them they will take care of the issue of
wrong/bad units. I have one damaged top connector. No real need to fix that.

USB you need a USB driver to use it. Will reach out to Ublox to see if a
32/64 bit may be available.

With respect to wire on the next unit for TX1/RX1 plan to use 34 gauge wire
nice and flexible. This particular stuff is supposed to be solderable. Will
see.
Regards
Paul
Regards
Paul

On Wed, Apr 6, 2022 at 7:08 PM paul swed  wrote:

> John your pins are correct. I am thinking about 3 and 1 for ttl rs 232
> from tx1/rx1.
> Though I really need to try usb, maybe no need to screw with tacking wires
> on.
> I have found the chip by the top connector. Its a L-band switch. Doesn't
> make sense but what can I say. Also removed the 3.5V glob board this
> afternoon.
> As far as the connector goes I acquired connectors and cables at hamfests
> years ago.
> So that made it easy.
> Regards
> Paul
>
>
>
> On Wed, Apr 6, 2022 at 6:15 PM John Miller via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
>> Paul,
>> Thanks again for the addition info - very helpful. Mine came in this
>> afternoon
>> and unfortunately only three of them are LEA-4Ts, the other two are
>> Leadtek
>> LR9548S SiRF StarIII based modules, one of which has a sticker that reads
>> "short" on it. I could request a partial refund but the seller probably
>> just had
>> no idea.
>>
>> From my own continuity testing (I haven't powered them up yet) I have
>> determined the following pinout. With the boards in "vertical"
>> orientation,
>> pin 1 is the leftmost pin. It's also the square pin on the footprint.
>>
>> 1 - NC
>> 2 - Vcc/VDDUSB (3v)
>> 3 - NC or 3v for LNA power if sub-board is present
>> 4 - USB DM
>> 5 - USB DP
>> 6 - PPS
>> 7 - GND
>> 8 - NC
>>
>> My next step is to find my 30AWG wire-wrap wire and tack wires straight to
>> the module, then figure out how to get an antenna connected. I don't
>> think I
>> have any adapters this small.
>>
>> John
>>
>>
>>
>>
>> > On Apr 6, 2022, at 1:09 PM, paul swed  wrote:
>> >
>> > John indeed on the 3V. I have lots of 3.3V regs. Not sure I have a 3.
>> But
>> > like you I am thinking the same only maybe simpler. Simply solder it to
>> a
>> > piece of copper board thats larger so I can mount interface chips drill
>> > holes for screws and such. Also some standoffs for 1pps, ext in/out,
>> rs232
>> > tx1/rx1. Smaller wires are the way to go on connecting to the pins. At
>> 3V
>> > startup is 65ma settles to 57ma. The input is a bit odd. Like you I
>> spotted
>> > the mcl combiner/splitter. The side port is 4-5 db hotter than the top
>> > port. But both work. So its a bit odd as if it was intended for 2
>> antennas.
>> > Kind of doesn't really matter as its totally working on the TX1/RX1
>> port. I
>> > set it to 115200 baud. It comes up 9600. That change is sort of silly.
>> > Thinking about mounting the board on the copper board component side
>> down.
>> > Easy to solder copper support wires then. No screw holes kind of a pain.
>> > While soldering I have a small tip iron and found it really needs to be
>> at
>> > 700 F or so to do good job.
>> > On one of my units and in the ebay pix there is a spot of tape that
>> holds
>> > down I assume a small regulator and TCXO. But it really doesn't seem to
>> do
>> > anything. Four of my units do not have that mod. So have not really
>> figured
>> > it out yet.
>> > Good luck.
>> > Paul
>> >
>> > On Wed, Apr 6, 2022 at 12:51 PM John Miller via time-nuts <
>> > time-nuts@lists.febo.com> wrote:
>> >
>> >> Hi Paul,
>> >> Thanks for sharing this info! I ordered one of these lots as well, and
>> it
>> >> should arrive today, actually. My intention is to re-mount the modules
>> on
>> >> more sensible breakout boards, maybe a Pi Hat.
>> >>
>> >> The 8 pin chip on the board is an MCL BP2G. RF power combiner/splitter
>> >> https://www.minicircuits.com/pdfs/BP2G+.pdf <
>> >> https://www.minicircuits.com/pdfs/BP2G+.pdf>
>> >>
>> >> If I am reading the datasheet and board layout right, the top
>> connector is
>> >> connected to PORT1, the GPS is PORT2, and the side connector is SUM. I
>> >> would imagine that the GPS would be on SUM if the idea was to feed in
>> >1 RF
>> >> signal, but maybe I am misunderstanding it?
>> >>
>> >> I was surprised by your note that the USB voltage input is 3v, but
>> after
>> >> checking the LEA-4x datasheet, sure enough, 3.6v max. I thought all
>> USB had
>> >> to be 5v?
>> >>
>> >> Finally, it looks like the PCB is ceramic, rather than normal
>> >> epoxy/fiberglass. Hopefully that doesn't make removing the modules any
>> more
>> >> difficult...
>> >>
>> >> John
>> >>
>> >>> On Apr 5, 2022, at 9:14 PM, paul swed  wrote:
>> >>>
>> >>> Hello to the group.
>> >>> Gregory had mentioned a deal on Ebay for 5 X LEA-4T 

[time-nuts] Evaluating counter performance, seeking feedback.

[Erik Kaashoek]

To better understand the performance of a home build counter a 
comparison was done with a Picotest U6200A
The two channel home build counter was setup to measure the frequency of 
the 10MHz output from a Rb on one channel and the 10MHz output from a 
not so good OCXO on the other channel.
The ratio between the two frequencies was measured with a 1 second gate 
time, multiplied by 1e+7 and send to Timelab.
The U6200A had the Rb output as 10MHz reference and the 10MHz from the 
OCXO into channel 1. Gate time was also set to 1 second.
In Timelab the data from the Counter under test and the U6200A where 
recorded simultaneously over a 1000 second period
The recorded data was saved and adjusted for the difference in start 
time of the measurements and loaded back into Timelab.

U6200A TIM file http://athome.kaashoek.com/time-nuts/U6200A.tim
Own counter TIM file http://athome.kaashoek.com/time-nuts/tinyGTC_2.tim
A first performance check was done by plotting the unwrapped linear 
residue of the phase of both measurements. (see: 
http://athome.kaashoek.com/time-nuts/tinyGTCvsU6200A_Phase.png ) . The 
measurements did show some differences in instantaneous  phase but the 
differences where small and even at 980 seconds the two measurements 
agree rather well.
A second performance check was done using the frequency plot. (see 
http://athome.kaashoek.com/time-nuts/tinyGTCvsU6200A_freq.png ). Overall 
the two measured frequencies agreed with sometimes up to 1e-10 
difference. The difference in gate time of the two counters was very 
visible as a gradual shift. As the measurements where aligned in time at 
the end of the measurement the time difference at the start was about 3 
seconds.
A detailed plot of the measured frequencies over the last 100 seconds 
(see 
http://athome.kaashoek.com/time-nuts/tinyGTCvsU6200A_freq_detail.png ) 
showed an occasional difference between the frequency measurements of 
the two counters up to 2e-10

Questions:
1: Is this setup meaningful in assessing performance differences? If 
not, how to improve?
1: How can one compress or expand a TIM file to correct for the 
difference in gate time? A better approach would be to ensure gate times 
where identical.
2: How can one use the two TIM files to calculate the RMS of the 
differences in frequency?  My hope is to use this RMS calculation as a 
single number quality indicator.

Erik.



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