wired external video microphone interference

Question

I'm shooting footage on a college campus using a wired external shotgun. In certain places on campus, there's an occasional buzz--like someone using a sped-up morse code--followed by a few seconds of thumping. It doesn't happen all over campus, and it's not constant. Since the environment is a college campus, there's a ton of stuff "in the air": phones, internet, the campus network, security guards on radios... First, could these be the causes of the interference, and if so, is there something to do about it?

Thanks for any advice.

Answer 1

Those sorts of things could definitely be causes - but you probably can't do much about telling them to stop, so you should concentrate on what you can improve:

The wire between the mic and the camera is going to be the biggest problem - it is acting as an antenna, and as microphone signals are very low you need to improve your signal to noise ratio.

Options:

• Use a shielded or balanced cable - probably your easiest option. You can get balanced cables for mics that are very resistant to interference but this will depend on what your camera supports
• Use a pre-amp at the mic to increase the signal - this reduces the effect interference will have
• Record audio at the mic (thus shortening the wire) and add it to the video later - you will need to look at synchronisation, etc