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EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
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Old 14th June 2019, 03:06 PM   #131
Frex is offline Frex  France
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Join Date: Nov 2009
Hello,

Please look at the document named "EOSC10KV3_History" at the root of design folder,
and page 2 of schematics.
The oscillator can be supplied using standard low cost regulator (LM317/LM337) OR
with low noise type regulators. Some others parts are different depending on regulators type is choose.
Note that both 1k/10kHz bom files are for low noise regulator version.
Regards.

Frex
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Old 15th June 2019, 11:45 PM   #132
niss_man is offline niss_man  Australia
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Thanks Frex. Parts are now ordered.
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Old 18th July 2019, 03:54 PM   #133
Morde is offline Morde  Finland
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EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Hi Frex.
I sent you PM about buying a 1kHz oscillation board. I hope they are still available?
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Old 26th March 2020, 06:10 PM   #134
Campi is offline Campi
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Some time ago I put my hands on a board like this ... Thanks Frex!

I'm having trouble getting the results that others had better than <-120dBv.

I'm using my oscilloscope (FFT) and the best value I have is -65dBv and on my THD meter (MARCONI) (very old) the value is 0.05% THD.

Could someone help me to try to solve this?
Am I measuring wrong?

IMG_20200326_095910.jpg

IMG_20200326_144232.jpg

Last edited by Campi; 26th March 2020 at 06:15 PM.
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Old 26th March 2020, 06:33 PM   #135
Frex is offline Frex  France
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Hello,

Start to check if nothing is wrong on time domain with the oscilloscope.
You must show a very clean sine-wave without spurious noise.
Check if there is no high frequency oscillation too.
What coaxial cable length do you use on output ? You have tried both outputs ?
What type of power supply is used ?
Do you have cleaned the PCB after soldering to remove all flux trace ?
I hope that help.
Regards.

Frex
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Old 26th March 2020, 07:24 PM   #136
Campi is offline Campi
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Frex, Thanks for the reply.

The wave on the oscilloscope is clean and in high resolution. I did not find high frequencies in the signal.

My coaxial cable is 1m long.
The two exits have exactly the same signal.
I'm using a symmetrical bench source, but I've tested it with LiPo batteries and with the same results.

I have been trying to eliminate these Armonicas for some time and one of the things that is emphasized in the instructions is the cleaning of the PCI. It was very clean after assembly, but I have cleaned it twice more and the result remains the same.
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Old 27th March 2020, 05:34 AM   #137
xx3stksm is offline xx3stksm  Japan
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EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
I would say you can't have more than 80dB THD with a scope because a scope usually employs a wide frequency range amplifier and high sampling rate ADC, where the best SFDR is probably 80dB. The best scenario to measure a low distortion oscillator is DSM ADC, like AD7768.
As long as I have tried, SAR ADC is superior to DSM one in SNR but inferior in THD. The pic is my measurement with AD7768. Mine can have better performance than this because I modified some filter values to stop high-frequency oscillation. I'm sure I still need some hacking.
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File Type: jpg Frex_ad7768.jpg (284.3 KB, 60 views)
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Old 27th March 2020, 12:09 PM   #138
lemon is offline lemon  Greece
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You can't measure the limit of EOSC10Kv3 with that equipment that you have.
The Marconi the best THD is 0.01% with the right calibration, the Spectrum FFT of your oscilloscope probably is 8bit vertical resolution (!).
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Old 27th March 2020, 02:40 PM   #139
Campi is offline Campi
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Thanks for the comments

xx3stksm...
I am clear that I will not get values lower than my noise floor. But the peaks of the harmonics that appear, are right above my noise floor.

Lemon ...
You're really right and i put it wrong ... My THD meter is Radford and its smallest measurement is 0.00001%. Sorry for the wrong information.
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Old 27th March 2020, 02:50 PM   #140
Campi is offline Campi
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As both exits have the same signal, I believe that the problem with the harmonics must be something that is wrong for both exits.
In the image there is a point on the circuit where I found a frequency of approximately 880kHz and I don't know if this is correct.

Would anyone know how to say?
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File Type: png Circuito.png (29.3 KB, 23 views)
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