Re: [time-nuts] time-nuts Digest, Vol 146, Issue 35

Sun, 18 Sep 2016 12:20:44 -0700

Sometimes rectifiers generating very high harmonics particularly if the rectifier is used close to it's current limits. The reverse recovery time increases, therefore the current is conducted after the polarity change for a very short time --until the now majority charge carriers sweeping out from the junction -- the turn off is very fast [ that effect is used by the step-recovery frequency multipliers] an the result is very high multiplied harmonics with substantial amplitude since that very narrow current pulse is produced by a crowbar across the first charge capacitor's voltage. If there is some wire, which have the proper length for on "output resonator " the high frequency source is perfect and the repetition frequency - which is the double line frequency could be heard with the spectrum analyzer's AM The demodulator. The amplitude of the high frequency pulses is much higher as it displayed on the spectrum analyzer, but the spectrum analyzer will integrate --due to it's limited bandwidth -- and shows the average of the pulses. Why is that important? because these high level pulses could modify an amplifier biasing, and perhaps cause periodically repeating jitters or even kill the input of an amplifier. I run into that problem some forty years ego with output rectifiers of switching mode power supplies. If you look old circuit diagrams of power supplies you could find some small capacitors connected across the rectifiers, these capacitors taking care the "buzz" in the old radios. 

73
KJ6UHN
Alex

On 9/18/2016 7:39 AM, hardy wrote:

Hello
I see that you are using E4406A for direct phasenoise measurement--your results 
are the same as with my E4406A and thunderbolt-but have no spurs.
I think it must be your powersupply for your thunderbolt that made those spurs.
Hardy

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Emne: time-nuts Digest, Vol 146, Issue 35

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Today's Topics:

    1. Re: Thunderbolt spurs on 10MHz output at 100Hz and       200Hz from
       signal. (Lars Walenius)
    2. Re: Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from
       signal. (Bruce Griffiths)
    3. Re: Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from
       signal. (Peter Marczinowski)
    4. Re: Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from
       signal. (Peter Marczinowski)
    5. Re: Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from
       signal. (Dan Rae)


----------------------------------------------------------------------

Message: 1
Date: Sun, 18 Sep 2016 12:52:21 +0000
From: Lars Walenius <[email protected]>
To: 'Discussion of precise time and frequency measurement'
        <[email protected]>
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz
        and     200Hz from signal.
Message-ID:
        
<vi1pr0701mb19182cc04af1a9ab2a74b8fbf3...@vi1pr0701mb1918.eurprd07.prod.outlook.com>
        
Content-Type: text/plain; charset="iso-8859-1"

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<mailto:[email protected]>
Skickat: den 18 september 2016 14:43
Till: 'Bruce Griffiths'<mailto:[email protected]>; 'Discussion of precise 
time and frequency measurement'<mailto:[email protected]>
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:[email protected]] 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 
<[email protected]> 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:[email protected]] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: [email protected]
Cc: [email protected]
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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------------------------------

Message: 2
Date: Sun, 18 Sep 2016 12:55:49 +0000 (UTC)
From: Bruce Griffiths <[email protected]>
To: "David C. Partridge" <[email protected]>, 'Discussion
        of precise time and frequency measurement' <[email protected]>
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz
        and 200Hz from signal.
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8

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 
<[email protected]> 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:[email protected]] 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 
<[email protected]> 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:[email protected]] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: [email protected]
Cc: [email protected]
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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------------------------------

Message: 3
Date: Sun, 18 Sep 2016 13:11:55 +0200
From: Peter Marczinowski <[email protected]>
To: Discussion of precise time and frequency measurement
        <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz
        and 200Hz from signal.
Message-ID:
        <CAFLUov06di5Pb_J7-BWcYj=hml-bwlefnwy2g1h+x0ynsrn...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

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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------------------------------

Message: 4
Date: Sun, 18 Sep 2016 13:24:42 +0200
From: Peter Marczinowski <[email protected]>
To: Discussion of precise time and frequency measurement
        <[email protected]>
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz
        and 200Hz from signal.
Message-ID:
        <CAFLUov2UvDK2AbnyJ4+9c6vGaN3nDRzeLp6-Ray=458xko_...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

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:[email protected] <javascript:;>] On
Behalf Of Magnus Danielson
Sent: 18 September 2016 11:56
To: [email protected] <javascript:;>
Cc: [email protected] <javascript:;>
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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------------------------------

Message: 5
Date: Sun, 18 Sep 2016 06:23:32 -0700
From: Dan Rae <[email protected]>
To: Discussion of precise time and frequency measurement
        <[email protected]>
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz
        and 200Hz from signal.
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

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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