RF noise from arduino

[Mek7]

Hi, this "issue" is not an issue with your sketch... just a place to discuss. I built the following circuit on a 2-sided board where the top side is GND. Now the problem is that, without antenna connected, a strong local station sounds distorted and with noise (like when it has a weak signal), but when I push the Reset button on the arduino, noise disappears and audio is very crisp. It also happens when the arduino is being programmed from arduino IDE - which holds the atmega in reset as well. I would very much like to have this reception quality always, not only when pressing the reset button. But everything I tried, failed:

• ferrite bead or 220uH choke on Arduino +5V with 220uF and 100n capacitors on both sides of the choke
• various sleep modes in arduino code
• disabling any I2C/serial communication after tuning to a station (I am trying to make this a standalone tuner, not requiring a PC for basic tuning) I don't know what to do next. Maybe shielding the arduino module with sheets of metal? I didn't connect the antenna on purpose, to test this. You can try it as well if you wish. I'm not able to find anything on arduino making RF noise (I encountered this problem also in my other circuits with bare atmega, where I wasn't able to solve it either). Any suggestions, please?

[biglee991228]

please try to use an IIC isolator such as iso1540 or si4703 or adum1250

[Mek7]

Hello, the problem is not due to I2C communication (as I wrote, I tried stalling it), but merely due to the fact that the atmega is running and processing instructions. So an I2C isolator would not help in this situation IMHO. Since then, I also tried shielding the arduino module with metal casing - with no improvement at all.