I’m using my Hologram Nova in an application where a microphone is built into the same box; the Hologram is streaming the audio from the microphone to a server. My problem is that the Hologram Nova board itself is emitting a squeal centred at around 5 kHz while the 3G connection is up, which rather spoils the party. See below for a spectrum analysis and also attached is a zip file of a brief recording of the noise.
The USB 5V is coming from a battery, so it couldn’t be smoother. I guess the issue is likely caused by the DC to DC converters and/or large inductors on the board. Can anyone suggest a way I might get rid of it, as it’s currently not very usable.
squeal.zip (42.0 KB)