Out of the box, I have not seen a very clean signal in cabled loopback operation. Is there a way to reset things back to default to see if that makes a difference to the spectrum?
The device is pretty immutable and changes do not persist across reboots. Unless updating the firmware of course.
What you are observing is quite normal, especially if no FIR is enabled.
This is what my spectrum looks like
Can you enlighten me on the steps to clean up the spectrum? I just received my hardware today, so I'm looking for good references or examples of basic uses. What I would like is a clean tone from Tx, feeding the Rx.
If this is typical, what is causing it? Something on the Tx or Rx?
There is no magic bullet for reducing spurs, and harmonics are natural results of imperfections in hardware. Their height will be a function of a few pieces including relative gain, frequency, and signal structure.
A good place to start would be the use of an internal FIR. There are a number of filters provided within IIO-Scope (Doc IIO Oscilloscope [Analog Devices Wiki] ) for different waveforms. If you want to create your own, they can be done with this tool: MATLAB Filter Design Wizard for AD9361 [Analog Devices Wiki]
Useful links for Pluto: ADALM-PLUTO for End Users [Analog Devices Wiki]
Pluto is just a showcase of the AD936X family of chips, so looking at their specs should set your expection: http://www.analog.com/media/en/technical-documentation/data-sheets/AD9363.pdf
What are the setting son the main control plugin?
Try to generate a tone away from DC. Increase TX attenuation when using CW. And enable all QEC, and DC tracking options.
Here are my settings, and the corresponding output for a 2 MHz tone.
I'm mainly really surprised that the spurs are 40dB above noise floor, and 50dB below the tone. If these are expected, then what are they coming from?
Also, the IIO Oscilloscope application preserves some settings from run to run. How can I reset the application.
Please see similar discussion here: https://ez.analog.com/message/338057-re-a-tx-harmonic-tone-question
If you want to clear the preserved settings -
on Windows delete following file: C:\Users\user_name\AppData\Local\.osc_profile.ini
on Linux delete: /home/user_anme/.osc_profile.ini
Thanks. That seems to have helped a bit, though I have no idea what happened as settings don't really look any different.
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