Microphone noise with USB WiFi adapter

[pavelso]

Hi

i have couple of A64 boards. I use them with microphones and usb WiFi adapters (Ralink)

i have following problems. If i connect USB WiFi adapter with external antenna (not the small dongle with built in antenna), i get extensive digital noise on microphone input. I don't get this noise when USB WiFi adapters with built ion antennas, i don't get this problem. I even tried to use short USB extension to move the adapter a bit further from the board, but the noise is still present.

For power i tried bot battery and external 5V adapter.

The microphone is standard electret capsule connected via shielded cable and 3.5mm jack.

Anybody ever encountered similar problem?

[LubOlimex]

There is some logic behind this happening, what you can easily try is use extension USB cable so that the USB-WIFI adapter is not plugged next to the board and away from the MIC. Using extension cable will help you determine where the distortion comes from empirically.