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Wednesday, 6 April 2016

Mobius HD Actioncam and RFI.

Now, being a gadget lover that I am, I decided to upgrade the rather old dashcam in my car to something a little more "HD". After doing a bit of research, and seeing the footage of a colleagues camera, I decided to get a Mobius 1080P Actioncam, purchased from a reputable source (beware the fakes). Good choice. Small unit, great pictures, sound is OK... except....

... 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.









Brilliant....














... and after some field tests, reception restored!


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