Wednesday, 6 April 2016
Mobius HD Actioncam and RFI.
... it ruined my radio reception.
Now I have a newish car, and it's fitted with a DAB radio. After fitting the camera to my windscreen, I noticed DAB reception of my favourite station, Planet Rock, became patchy. Disconnecting the camera solved the issue.... hmmmm ... RFI ... Radio Frequency Interference.
So what was going on? I broke out my ancient spectrum analyser, and, equipped with a simple whip antenna, took some measurements....
Here's the DAB reception, centred on 220MHz, with the Mobius disconnected. The two humps are the two DAB Mux's (multiplexes) I can receive at home...
... and here's the same shot with the camera connected... yuck. I suspect the big peak to the right of the mux is effecting the AGC of the radio, and there's a lot of hash underneath it too, upsetting the signal to noise ratio... boo!
I tried a simple method of preventing RFI radiating from the cable of the device. I wrapped as many turns of the USB power lead round a random (ex-computer power supply) ferrite ring.
... and after some field tests, reception restored!