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Old 30th March 2013, 01:04 AM   #2001
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by 1audio View Post
I not getting the same spectra as you are. You need the monitor output to look at that.
I said i am using the monitor output. Looking at just the residual from the notch.

I have 2 ports.... one labelled Normal (the one I am using) and the other labelled Analyzer (which appears to be an FFT port).

Does your analyzer have 2 ports?

Good question was what are you measuring for a noise floor via your port?

-Richard

Last edited by RNMarsh; 30th March 2013 at 01:07 AM.
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Old 30th March 2013, 01:31 AM   #2002
davada is offline davada  Canada
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Default Lamp Multipler

I have the lamp multiplier in isolation.
This is some noise spectra of the output with no input connected from the SVO and no notch.
The multiplier has a large Vc to multiplier zero offset.
The yellow overlay is the EMU0204 with input shorted.
All measurement is referenced to 0dB FS. 192ksps 131072 points and linear smoothing.


The second image is with no Vc input so the lamps are cold at minimum R. The noise gain of (6.8) of the multiplier is at maximum in the non inverting mode. The signal gain is maximum. This represents the minimum range frequency of the OSC.

The first image is with maximum input Vc. The lamps are brightly lit. The noise gain is at minimum and the multiplier is in inverting mode at maximum signal gain. This represents the maximum range frequency of the OSC.
Attached Images
File Type: gif mul max.GIF (60.3 KB, 169 views)
File Type: gif Mul min.GIF (61.0 KB, 161 views)
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Last edited by davada; 30th March 2013 at 01:41 AM. Reason: oops got the pic s backwards
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Old 30th March 2013, 01:57 AM   #2003
RNMarsh is offline RNMarsh  United States
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with and without the multiplier lamp?
6db to 2-3 db upper freqs. Does not add much to the noise.
We can infer from this that most if not all oscillators do not have a great deal of noise from their multiplier?
[I know thats a stretch if you havent done same with several types of ultra-oscillators/multipliers].

-145dB noise floor?

Thx-RNMarsh

Last edited by RNMarsh; 30th March 2013 at 02:18 AM.
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Old 30th March 2013, 02:02 AM   #2004
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by RNMarsh View Post
I said i am using the monitor output. Looking at just the residual from the notch.

I have 2 ports.... one labelled Normal (the one I am using) and the other labelled Analyzer (which appears to be an FFT port).

Does your analyzer have 2 ports?

Good question was what are you measuring for a noise floor via your port?

-Richard
Also - info> I am using a 30Hz bandwidth resolution at 1KHz per/Div. Smoothing On.
And Log vertical scale (10db/div).
[no FFT averaging to remove noise-- just filtering]

-RNM

Last edited by RNMarsh; 30th March 2013 at 02:28 AM.
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Old 30th March 2013, 02:49 AM   #2005
davada is offline davada  Canada
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Default Lamp Multipler

Every thing here is the same as the above post but with the addition of Victor's 1kHz oscillator.
The osc output is 1Vrms into the multiplier input.

The pics show the natural attenuation of the multiplier at min and max Vc.
Attached Images
File Type: gif vic min.GIF (61.3 KB, 153 views)
File Type: gif vic max.GIF (61.0 KB, 150 views)
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Old 30th March 2013, 02:49 AM   #2006
1audio is offline 1audio  United States
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The last plot was from the monitor port using the fft. The first pair are FFT vs. swept on the distortion analyzer port. That port is just harmonics with the noise removed. The phase relationship of the harmonics is retained as well. you can reconstruct them using the trigger jack to trigger the scope which can help identify sources of distortion by their relationships.

I'll look at the monitor output shortly.
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Old 30th March 2013, 03:03 AM   #2007
davada is offline davada  Canada
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Quote:
Originally Posted by RNMarsh View Post
with and without the multiplier lamp?
6db to 2-3 db upper freqs. Does not add much to the noise.
We can infer from this that most if not all oscillators do not have a great deal of noise from their multiplier?
[I know thats a stretch if you havent done same with several types of ultra-oscillators/multipliers].

-145dB noise floor?

Thx-RNMarsh
It's not bad. I am happy with this but we can do better.

With 20dB of decoupling between multiplier and OSC I think the noise is out of the way.
I'm at the measurement limit for what I have so further improvement will be difficult to confirm without more gear.
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Old 30th March 2013, 03:11 AM   #2008
RNMarsh is offline RNMarsh  United States
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That was my problem too and why I got a couple ADC's to follow along with you. Then this ShibaSoku analyzer dropping into my lap and then I started using it. It has allowed me to see the effects of changes I could make/try to oscillators.
But if the adc system is as good or even almost as good, it is small, more portable and allows for better integration with files/software on a PC. I would use both.
I do need assurance that the drivers will work on old and new PC's (XP and WIN7 and maybe soon Win8) without hitches. The software must have its drivers kept updated to always be compatable with Microsoft upgrades and changes.

Thx-RNMarsh

Last edited by RNMarsh; 30th March 2013 at 03:19 AM.
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Old 30th March 2013, 06:15 AM   #2009
1audio is offline 1audio  United States
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Neither the 7L5 nor the Wavetek have a narrow enough bandwidth to see into the noise. These are first the distortion analysis out showing the relative amplitudes of the harmonics without the noise and second the monitor output with the narrow bandwidth of the QA400 allowing a much deeper view into the noise. The distortion analysis is a reconstructed signal with the fundamental around 500 Hz regardless of the input frequency. The generator is set to 1KHz at 10V. It has a source impedance of 600 Ohms. In the first picture 0dB is -100 dB, the second 0 dB is - 90 dB out (I think, I need to check). With .6 Hz bandwidth the noise floor is about -160 dB. Translating that to meaningful SNR or equivalent nV/RtHz shall we say "is an exercise left to the reader".
Attached Images
File Type: png 725 analyzer out 10V in.png (56.3 KB, 148 views)
File Type: png 725 monitor out 10V in.png (34.3 KB, 49 views)
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Old 30th March 2013, 06:25 AM   #2010
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
Neither the 7L5 nor the Wavetek have a narrow enough bandwidth to see into the noise. These are first the distortion analysis out showing the relative amplitudes of the harmonics without the noise and second the monitor output with the narrow bandwidth of the QA400 allowing a much deeper view into the noise. The distortion analysis is a reconstructed signal with the fundamental around 500 Hz regardless of the input frequency. The generator is set to 1KHz at 10V. It has a source impedance of 600 Ohms. In the first picture 0dB is -100 dB, the second 0 dB is - 90 dB out (I think, I need to check). With .6 Hz bandwidth the noise floor is about -160 dB. Translating that to meaningful SNR or equivalent nV/RtHz shall we say "is an exercise left to the reader".
"Translating that to meaningful SNR or equivalent nV/RtHz shall we say "is an exercise left to the reader". "

Oh thanks a lot make me do all the work.

Kidding of course.
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