Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.
Using John Miles PN.exe and Agilent E4406A
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Magnus Danielson
Sent: 18 September 2016 12:47
To: time-nuts@febo.com
Cc: magnus@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
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-bounces@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
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-bounces@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 <magnus@rubidium.dyndns.org> 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-bounces@febo.com] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: magnus@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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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. Partridgemailto:david.partridge@perdrix.co.uk
Skickat: den 18 september 2016 14:43
Till: 'Bruce Griffiths'mailto:bruce.griffiths@xtra.co.nz; 'Discussion of precise time and frequency measurement'mailto:time-nuts@febo.com
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-bounces@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 <magnus@rubidium.dyndns.org> 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-bounces@febo.com] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: magnus@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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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 <david.partridge@perdrix.co.uk> 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-bounces@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 magnus@rubidium.dyndns.org 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-bounces@febo.com] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: magnus@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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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
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 david.partridge@perdrix.co.uk 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-bounces@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 <magnus@rubidium.dyndns.org> 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-bounces@febo.com] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: magnus@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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<Thunderbolt pn3.png>_______________________________________________
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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
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-bounces@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-bounces@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 <magnus@rubidium.dyndns.org> 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-bounces@febo.com] On Behalf Of
Magnus Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: magnus@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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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
