Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bruce Griffiths]

On Thursday, September 22, 2016 01:37:02 AM Gerhard Hoffmann wrote:
> Am 22.09.2016 um 00:24 schrieb Bruce Griffiths:
> > Another issue is the requirement to trim the current sink for low 
output
> > offset.
> 
> And _that_ FET is made from Unobtainium.
> 
> > If one takes advantage of the fact that the PLL imposes a low
> > frequency cutoff to the PN measurements, the amplifier input   can be 
AC
> > coupled, allowing dc bias feedback to be applied to the input device 
gate.
> > Use a parallel dc coupled JFET input opamp for the PLL
> 
> That's what I did. Original Burr-Brown opa2134, time to use them up..
> 
> > Paralleled BF862's can be substituted for the input JFET.
> 
> Yep!
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One still has to deal with the negative R in series with negative C input 
impedance component which will cause peaking with source resistance 
greater than a few ohms (typically 1k source resistance shows significant 
gain peaking at high frequencies near the upper end of the amplifiers 
bandwidth).

Bruce
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Gerhard Hoffmann]

Am 22.09.2016 um 00:24 schrieb Bruce Griffiths:

Another issue is the requirement to trim the current sink for low output
offset.


And _that_ FET is made from Unobtainium.

If one takes advantage of the fact that the PLL imposes a low
frequency cutoff to the PN measurements, the amplifier input   can be AC
coupled, allowing dc bias feedback to be applied to the input device gate.
Use a parallel dc coupled JFET input opamp for the PLL

That's what I did. Original Burr-Brown opa2134, time to use them up..

Paralleled BF862's can be substituted for the input JFET.


Yep!
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Gerhard Hoffmann]

Am 22.09.2016 um 00:24 schrieb Bruce Griffiths:

For the later, Bruce commented that an jFET input stage would

probably be more quiet. Gerhard Hoffman has designed a similar

I must insist in my second "n" Hoffmann   :-)

system[3] that uses a couple of paralel low noise opamps instead
of a jfet stage and claims a noise floor of 220pV/sqrt(Hz). All of
these would need to be adapted to imporve thier frequency response
up to 10MHz (or actually a bit higher), but then the input stage
gets also a bit simpler as you don't need the huge capacitors anymore.


The ADA4898 has ft= 50 MHz, so that will be hard. It already takes some 
cascoding

to get to 2 MHz with the new FET amp.

Another issue is the requirement to trim the current sink for low output
offset. If one takes advantage of the fact that the PLL imposes a low
frequency cutoff to the PN measurements, the amplifier input   can be AC
coupled, allowing dc bias feedback to be applied to the input device gate.
Use a parallel dc coupled JFET input opamp for the PLL

Using a single ended input stage is significantly quieter than using a
differential pair.

Paralleled BF862's can be substituted for the input JFET.


Hi, Bruce and Attila (and ...),

the JFET version of my preamp is making progress. It supports either upto 16
BF862 or 2 pairs of Interfet IF3602. Upper bandwidth limit will be 2 MHz if
it runs like the simulation. There is also a low gain DC output for the PLL.

< 
https://www.flickr.com/photos/137684711@N07/29193737144/in/dateposted-public/ 
>


One is populated with BF862, the other with Interfet. The 3rd will be 
populated

according to the outcome of the first tests, so that I have 2 equal ones for
X correlation. There will be some leftover boards available, but not to 
put them

into the drawer.

Soldered them last weekend, debug them on the next :-)
I expect 170 pV/rt Hz at least for the Interfet version. That is 
probably pearls before

swine after a ring mixer, but then we are nuts.

Attila, you are just half an hour of driving away, at least during the 
weekend!


regards, Gerhard




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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bruce Griffiths]

On Wednesday, September 21, 2016 08:59:18 PM Attila Kinali wrote:
> On Wed, 21 Sep 2016 09:16:18 -0700
> 
> Dan Rae  wrote:
> > On 9/21/2016 9:01 AM, David C. Partridge wrote:
> > > Yes,  I fear a timepod is a bit out of my budget (I can dream tho'). 
> > > Over here in the UK PN measurement kit is a bit thin on the ground 
too.
> > > 
> > > So I looked at 

> > > but that seemed a little thin on details.  Or were you referring to
> > > something else?> 
> > The Wenzel note is at: http://www.wenzel.com/documents/circuits1.htm
> > 
> > as a pdf under link: "Low noise amplifier for Phase Noise 
measurements"
> > or try:  www.wenzel.com/wp-content/uploads/lowamp.pdf
> > 
> > Pretty much all there, but the FET is hard to find now.
> 
> If you want to build such an amplifier, then the first stage (aka the
> jFET input and the first opamp) is the critical component. There are
> other, more modern descriptions for this kind of application, in case
> you don't want to just replace the jFET by one if its modern cousins.
> 
> One well known is AN124[1] and it's more current cousin AN159[2].
> For the later, Bruce commented that an jFET input stage would
> probably be more quiet. Gerhard Hoffman has designed a similar
> system[3] that uses a couple of paralel low noise opamps instead
> of a jfet stage and claims a noise floor of 220pV/sqrt(Hz). All of
> these would need to be adapted to imporve thier frequency response
> up to 10MHz (or actually a bit higher), but then the input stage
> gets also a bit simpler as you don't need the huge capacitors anymore.
> 
> I also recommend a look at [4] which lists a couple of issues with jFET
> input stages for opamps and how to get around them.
> 
>   Attila Kinali
> 
> 
> [1] "775 Nanovolt Noise Measurement for A Low Noise Voltage 
Reference",
> by Jim Williams, Linear AN124, 2009
> 
> [2] "Measuring 2nV/sqrt(Hz) Noise and 120dB Supply Rejection
> on Linear Regulators", by Todd Owen and Amit Patel, Linear AN159, 2016
> 
> [3] "A 220 pV/sqrt(Hz) low noise preamplifier", by Gerhard Hoffman, 2014
> http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf
> 
> [4] "Some Tips on Making a FETching Discrete Amplifier", by George
> Alexandrov and Nathan Carter, Analog Dialog 47-10, 2013
> 
http://www.analog.com/library/analogdialogue/archives/47-10/discrete_ampl
ifi
> er.html

2sk369BL are still available from:
http://www.ampslab.com/trans_2sk369.htm

I obtained some from them, they met the noise specs so are probably not 
counterfeit.

One issue with the Wenzel preamp is that it has poor PSRR.
This can easily be improved substantially by redesigning the bias circuitry 
for the opamp noninverting input.

Another issue is the requirement to trim the current sink for low output 
offset. If one takes advantage of the fact that the PLL imposes a low 
frequency cutoff to the PN measurements, the amplifier input   can be AC 
coupled, allowing dc bias feedback to be applied to the input device gate.
Use a parallel dc coupled JFET input opamp for the PLL

Using a single ended input stage is significantly quieter than using a 
differential pair.

Paralleled BF862's can be substituted for the input JFET.

Bruce
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Chris Caudle]

On Wed, September 21, 2016 1:59 pm, Attila Kinali wrote:
> On Wed, 21 Sep 2016 09:16:18 -0700
  > Dan Rae  wrote:
  >> Pretty much all there, but the FET is hard to find now.
>
> If you want to build such an amplifier, then the first stage (aka the
> jFET input and the first opamp) is the critical component. There are
> other, more modern descriptions for this kind of application, in case
> you don't want to just replace the jFET by one if its modern cousins.

If you do want to just substitute newer parts into the same style design,
you should be able to get Linear Systems jfets.  They are not as quiet,
but much lower capacitance, so you could put more in parallel to get
reduced noise.

http://linearsystems.com/products_details.php?pr=jfet-amplifiers--duals_id=65

-- 
Chris Caudle


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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Attila Kinali]

On Wed, 21 Sep 2016 09:16:18 -0700
Dan Rae  wrote:

> On 9/21/2016 9:01 AM, David C. Partridge wrote:
> > Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over 
> > here in the UK PN measurement kit is a bit thin on the ground too.
> >
> > So I looked at  
> > but that seemed a little thin on details.  Or were you referring to 
> > something else?
> >
> The Wenzel note is at: http://www.wenzel.com/documents/circuits1.htm
> 
> as a pdf under link: "Low noise amplifier for Phase Noise measurements"
> or try:  www.wenzel.com/wp-content/uploads/lowamp.pdf
> 
> Pretty much all there, but the FET is hard to find now.

If you want to build such an amplifier, then the first stage (aka the
jFET input and the first opamp) is the critical component. There are
other, more modern descriptions for this kind of application, in case
you don't want to just replace the jFET by one if its modern cousins.

One well known is AN124[1] and it's more current cousin AN159[2].
For the later, Bruce commented that an jFET input stage would
probably be more quiet. Gerhard Hoffman has designed a similar
system[3] that uses a couple of paralel low noise opamps instead
of a jfet stage and claims a noise floor of 220pV/sqrt(Hz). All of
these would need to be adapted to imporve thier frequency response
up to 10MHz (or actually a bit higher), but then the input stage
gets also a bit simpler as you don't need the huge capacitors anymore.

I also recommend a look at [4] which lists a couple of issues with jFET
input stages for opamps and how to get around them.

Attila Kinali


[1] "775 Nanovolt Noise Measurement for A Low Noise Voltage Reference",
by Jim Williams, Linear AN124, 2009

[2] "Measuring 2nV/sqrt(Hz) Noise and 120dB Supply Rejection
on Linear Regulators", by Todd Owen and Amit Patel, Linear AN159, 2016

[3] "A 220 pV/sqrt(Hz) low noise preamplifier", by Gerhard Hoffman, 2014
http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf

[4] "Some Tips on Making a FETching Discrete Amplifier", by George Alexandrov
and Nathan Carter, Analog Dialog 47-10, 2013
http://www.analog.com/library/analogdialogue/archives/47-10/discrete_amplifier.html


-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Dan Rae]

On 9/21/2016 9:01 AM, David C. Partridge wrote:

Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over here 
in the UK PN measurement kit is a bit thin on the ground too.

So I looked at  but 
that seemed a little thin on details.  Or were you referring to something else?


The Wenzel note is at: http://www.wenzel.com/documents/circuits1.htm

as a pdf under link: "Low noise amplifier for Phase Noise measurements"
or try:  www.wenzel.com/wp-content/uploads/lowamp.pdf

Pretty much all there, but the FET is hard to find now.

Dan
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Dan Rae]

On 9/21/2016 8:01 AM, David C. Partridge wrote:

Looks like all I've managed to do is measure the baseline noise of the 
analyser.  Ho-hum looks like I need something a *lot* quieter to do these 
measurements.

Indeed Dave, yes.  I made the same mistake a few years ago when I tried 
to compare the results of three different DDS clocks on the output of my 
homebrew transceiver DDS LO using a 3585A spectrum analyser and John's 
program.  It took me a while to figure out why they were identical and 
then the penny dropped that I was just measuring the 3585A...


The plot of the three thunderbolts I sent before using my -hp- phase 
noise system is interesting in that the white plot was from the Tbolt I 
keep on the bench to run all the stuff there, and it uses the switch 
mode power supply that came with the TAPR ones, built into an Extron 
distribution amp case.  All the spurs that are shown with dotted lines 
aren't all spurious, most are probably real.  The other two are from 
units with linear supplies and are significantly improved.


Most older phase noise systems use some kind of low noise oscillator for 
reference, mixing the signal under test down to AF and going from there 
with low noise amps and then the actual measurement. Wenzel has a very 
good application note describing a system that can be copied in the home 
lab.


I attach a plot of my -hp- 3048A system noise floor showing what levels 
can be achieved with twenty year old technology.  The spurs the system 
shows dotted may not be real.  The modern system John Miles designed can 
no doubt do better and in about one hundredth of the volume, but is a 
little more expensive :^)


Dan





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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over here 
in the UK PN measurement kit is a bit thin on the ground too.

So I looked at  but 
that seemed a little thin on details.  Or were you referring to something else?

Dave


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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Looks like all I've managed to do is measure the baseline noise of the 
analyser.  Ho-hum looks like I need something a *lot* quieter to do these 
measurements.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 18 September 2016 13:43
To: 'Bruce Griffiths'; 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load 
> on the capacitor after the rectifier creates an inverse sawtooth wave 
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
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>>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David]

Worn out aluminum electrolytic capacitors usually improve in
performance lowering ripple and noise as they warm up.

On Sun, 18 Sep 2016 12:27:38 +0100, you wrote:

>Now that's interesting I just re-ran the measurement, and got a quite 
>different result which is attached.  The spurs have GONE.
>
>My only guess right now is that the E4406A power supply is getting quieter as 
>it has been on for longer (I've only had it powered for short periods before 
>now).
>
>Dave
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bob Camp]

Hi

If you are measuring the OCXO, you should be getting around -155 to -160 dbc / 
Hz at 100 Hz offset. 
Depending on the particular board you have, and how it is powered, the numbers 
out of the TBolt
can be quite a bit worse than this. With a good supply, you should get within 5 
db. There are a lot of
spurs, so you do need a pretty good (narrow bandwidth) analyzer to sort them 
out from the noise floor. 

Bob

> On Sep 18, 2016, at 8:42 AM, David C. Partridge 
>  wrote:
> 
> I've just redone the measurement without the external attenuator and with 
> 10dB attenuation set internally to the analyser.
> 
> The results are attached.
> 
> Dave
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce 
> Griffiths
> Sent: 18 September 2016 12:52
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
> 
> The signal level is also very low.
> Brue 
> 
>On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
>  wrote:
> 
> 
> The phase-noise still looks fairly high. How do you measure this?
> 
> Cheers,
> Magnus
> 
> On 09/18/2016 01:27 PM, David C. Partridge wrote:
>> Now that's interesting I just re-ran the measurement, and got a quite 
>> different result which is attached.  The spurs have GONE.
>> 
>> My only guess right now is that the E4406A power supply is getting quieter 
>> as it has been on for longer (I've only had it powered for short periods 
>> before now).
>> 
>> Dave
>> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
>> Magnus Danielson
>> Sent: 18 September 2016 11:56
>> To: time-nuts@febo.com
>> Cc: mag...@rubidium.se
>> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 
>> 200Hz from signal.
>> 
>> Hi,
>> 
>> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>>> just BAU harmonics?
>> 
>> Consider full-wave rectification of 50 Hz, the power consumption load 
>> on the capacitor after the rectifier creates an inverse sawtooth wave 
>> of
>> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>> 
>> While much of this is regulated out in the next step, some of it makes it 
>> though.
>> 
>> Cheers,
>> Magnus
>> 
>>> 
>>> 
>>> Thanks
>>> 
>>> Dave
>>> 
>>> 
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
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>> 
>> 
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Dan Rae]

On 9/18/2016 5:42 AM, David C. Partridge wrote:

I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

I suspect that you are measuring the analyser phase noise, but it's 
rather early in the morning...


I attach, if I can get it to work, a plot of three different Tbolts on 
my 3048A system.


Dan
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Peter Marczinowski]

Assuming a nonlinearity, a distortion or partly clipping of only one
halfwave, would result in a massive even harmonic, as the 200Hz in the
example. From this point of view "as expected", but a different distortion
could as well result in any other even harmonic.

Peter


Am Sonntag, 18. September 2016 schrieb David C. Partridge :

> Thanks, that makes sense.  Is the PN plot much as expected, or is it
> "could do better"?
>
> Thanks again
> Dave
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com ] On
> Behalf Of Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com 
> Cc: mag...@rubidium.se 
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and
> 200Hz from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
> > The local power is 50Hz, so I can understand the 100Hz spurs, but I
> > don't quite "get" where the 200Hz spurs are coming from.  Or is that
> > just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load on
> the capacitor after the rectifier creates an inverse sawtooth wave of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it
> though.
>
> Cheers,
> Magnus
>
> >
> >
> > Thanks
> >
> > Dave
> >
> >
> >
> > ___
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> unsubscribe, go to
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Peter Marczinowski]

Even harmonics are caused by asymmetrical nonlinearities, odd harmonics by
symmetrical nonlinearities.

Peter


Am Sonntag, 18. September 2016 schrieb Magnus Danielson :

> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I don't
>> quite "get" where the 200Hz spurs are coming from.  Or is that just BAU
>> harmonics?
>>
>
> Consider full-wave rectification of 50 Hz, the power consumption load on
> the capacitor after the rectifier creates an inverse sawtooth wave of 100
> Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it
> though.
>
> Cheers,
> Magnus
>
>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
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>> ailman/listinfo/time-nuts
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bruce Griffiths]

Still way above what it should be.Whats the noise floor of the measurement 
system?
Bruce 

On Monday, 19 September 2016 12:43 AM, David C. Partridge 
 wrote:
 

 I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

    On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load 
> on the capacitor after the rectifier creates an inverse sawtooth wave 
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Lars Walenius]

What is the specification for the Spectrum analyzer? They don´t tend to be 
useful for OCXO measurments so is this especially good? Or is it only the 
Analyzer phase noise we see?



Lars



Från: David C. Partridge
Skickat: den 18 september 2016 14:43
Till: 'Bruce Griffiths'; 'Discussion of 
precise time and frequency measurement'
Ämne: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from 
signal.



I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:


 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load
> on the capacitor after the rectifier creates an inverse sawtooth wave
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load 
> on the capacitor after the rectifier creates an inverse sawtooth wave 
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Yes, it's through a 20dB attenuator. I'll redo the measurement w/o the 
attenuator.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Using John Miles PN.exe and Agilent E4406A

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 12:47
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Magnus Danielson]

Indeed, now I see it. As we expect around +10 dBm, the noise-floor might 
be raised by about 20 dB.


I was more considering what is the reference noise here, is there a 
single oscillator as reference? Can a quieter reference oscillator be 
used? Can a cross-correlation setup be done?


Cheers,
Magnus

On 09/18/2016 01:52 PM, Bruce Griffiths wrote:

The signal level is also very low.
Brue

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:


 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:

Now that's interesting I just re-ran the measurement, and got a quite different 
result which is attached.  The spurs have GONE.

My only guess right now is that the E4406A power supply is getting quieter as 
it has been on for longer (I've only had it powered for short periods before 
now).

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:

The local power is 50Hz, so I can understand the 100Hz spurs, but I
don't quite "get" where the 200Hz spurs are coming from.  Or is that
just BAU harmonics?


Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus




Thanks

Dave



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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Magnus Danielson]

Peter,

Take a peak here (scroll down to the graphs):
http://dsp.stackexchange.com/questions/5959/add-odd-even-harmonics-to-signal

The full-wave rectifier creates a symmetric distortion, which causes 
even harmonics. Each half-cycle has the same output structure, so the 
resulting signal has twice the frequency of the input. The sawtooth 
slope as the capacitor discharge has in itself both even and odd 
overtones, creating the end result of 100 Hz, 200 Hz, 300 Hz etc.
We can expect leakage of the 50 Hz and some harmonics on that, due to 
inbalance between diodes and other paths.


Cheers,
Magnus

On 09/18/2016 01:11 PM, Peter Marczinowski wrote:

Even harmonics are caused by asymmetrical nonlinearities, odd harmonics
by symmetrical nonlinearities.

Peter


Am Sonntag, 18. September 2016 schrieb Magnus Danielson :

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:

The local power is 50Hz, so I can understand the 100Hz spurs,
but I don't
quite "get" where the 200Hz spurs are coming from.  Or is that
just BAU
harmonics?


Consider full-wave rectification of 50 Hz, the power consumption
load on the capacitor after the rectifier creates an inverse
sawtooth wave of 100 Hz, and sawtooth waveshape have both even and
odd harmonics.

While much of this is regulated out in the next step, some of it
makes it though.

Cheers,
Magnus



Thanks

Dave



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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bruce Griffiths]

The signal level is also very low.
Brue 

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
> Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load on the 
> capacitor after the rectifier creates an inverse sawtooth wave of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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> and follow the instructions there.
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>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Magnus Danielson]

The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:

Now that's interesting I just re-ran the measurement, and got a quite different 
result which is attached.  The spurs have GONE.

My only guess right now is that the E4406A power supply is getting quieter as 
it has been on for longer (I've only had it powered for short periods before 
now).

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:

The local power is 50Hz, so I can understand the 100Hz spurs, but I
don't quite "get" where the 200Hz spurs are coming from.  Or is that
just BAU harmonics?


Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus




Thanks

Dave



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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bruce Griffiths]

The PN should be considerably lower than that even with the noisy output buffer 
the PN floor should be considerably lower (>40db lower). The OCXO by itself 
should have somewhat lower PN.
Bruce 

On Sunday, 18 September 2016 11:14 PM, David C. Partridge 
 wrote:
 

 Thanks, that makes sense.  Is the PN plot much as expected, or is it "could do 
better"?

Thanks again
Dave
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:
> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
> just BAU harmonics?

Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus

>
>
> Thanks
>
> Dave
>
>
>
> ___
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Now that's interesting I just re-ran the measurement, and got a quite different 
result which is attached.  The spurs have GONE.

My only guess right now is that the E4406A power supply is getting quieter as 
it has been on for longer (I've only had it powered for short periods before 
now).

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:
> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
> just BAU harmonics?

Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus

>
>
> Thanks
>
> Dave
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Thanks, that makes sense.  Is the PN plot much as expected, or is it "could do 
better"?

Thanks again
Dave
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:
> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
> just BAU harmonics?

Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus

>
>
> Thanks
>
> Dave
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Magnus Danielson]

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:

The local power is 50Hz, so I can understand the 100Hz spurs, but I don't
quite "get" where the 200Hz spurs are coming from.  Or is that just BAU
harmonics?


Consider full-wave rectification of 50 Hz, the power consumption load on 
the capacitor after the rectifier creates an inverse sawtooth wave of 
100 Hz, and sawtooth waveshape have both even and odd harmonics.


While much of this is regulated out in the next step, some of it makes 
it though.


Cheers,
Magnus




Thanks

Dave



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