Hello,

       I am using the Olimex OLinuxino and I find a constant noise at about 866.725MHz or thereabout in every board. While low, at -100dBm, when using it with IoT radios this is the band in India and it is quite a pain in applications requiring high sensitivity. This particular board had it pretty nasty at -86dB.

 

I have tried with changing the DDR frequency as well as the CPU clock, however this nuisance refuses to go away. 

 

What can be done to get rid of this noise ? I have tried multiple boards -- Olinuxino (multiple), Marsboard, but each has some noise in exactly same band near 866MHz. 

Please advise.

 

I chased down EMI problems with A20-Micro in the past.  We were using inside and enclosure with some sensitive ADCs.

Had no access to a DSA, but main causes in my case were(in order of importance):

 

-Power supply- We had a switching wall-wart type supply @12v. Replaced with battery, then with a better quality power supply. Ferrites on the supply cable helped a lot too.

-Buck converter on board the A20-Micro is noisy- Try powering board by the 5v_Ext pins (obviously don't exceed 5v)

 

If you get an improvement, please share another shot from your DSA.