Can't you change channels on these things?

Sorry only use Senny G2 500 series and at AUD2K with a broadcast quality mic they sure ain't cheap but with a range of around 1,000M I've never had a problem and nor have any of our clients.

Realistically if you cannot afford this kind of kit invest a wired lav, Senny make some good quality ones at a reasonable price. Even if you have a good wireless setup a wired lav seems a sensible addition to the kit, just in case things go south. They're so small I'd just keep one with the camera kit.

Bob.

Does anyone know what the causes are,...

Odds are it was a cell phone and/or a blackberry. Check out the electronic zzzzzzzzzzztt type interference thread from the rec.arts.movies.production.sound newsgroup. It's not uncommon and the only real cure is to have everyone (no matter how important they think they are!!) turn them off.

Mike

edit: fixed link

Cordless phones, Nokia "radio" phones, a bad capacitor in a TV/Stereo, the next office's render farm. Yes, the previous advice of on-site testing is a must. I don't think it was your mic, although I'm sure you could probably pay $ thousands for units with all kinds of filters.

The description fits cell phone interference, which can even affect certain (expensive) wired mikes too, but in this case I quite suspect it is radio interference.

Happens to everybody at times.

The only really foolproof solution is Zaxcom's new all digital wireless mic transmitters.

These are far less sensitive to interference, and if the signal should somehow be totally stepped on anyway, the (tiny!) transmitter records everything, with time code even. This can easily be retransmitted on demand after a good take that otherwise would have had to be reshot. Saw it at NAB, so coool.

I just love the audacity of it!

Thanks all. We were thinking cell phone, should have had everyone in the house turn theirs off. Next time.

Also, thanks, Bob. Seems so simple, but you are correct, a wired Lav mic should be in my bag at all times. Would have saved me many hours with a waveform editor last night, trying to remove the interference.

Again, thanks. This forum is a great resource.

Keith

It's a description of interference from an analog cell phone. The digital phones are in a different frequency band but the older analog phones are in the same 900 MHz band. So are microwave ovens and wireless security cameras.

Having done field audio for over twenty years, I can tell you that, unless there's a compelling reason for avoiding the umbilical - such as a moving subject, or a stage situation where the talent can't be miked after his entrance - you're much better off with a wired mic. Invest your money where it will do the most good and cut down on the possible problems at the getgo. A static interview at a few feet's distance certainly calls for a wired microphone.

Microwave ovens operate at 2450 MHz worldwide (good compromise frequency wise for device cost&size, and RF interference).

Most people, myself included (blushing now!), were taught that this frequency was chosen because the resonant frequency of the H20 water molecule in the liquid state is there.

That's not it, although what is true is that "The electromagnetic penetration is infinite in a perfectly transparent substance and zero in reflective material (e.g. metals). At the microwave oven frequency (2.45 GHz), most energy is absorbed by water."

For a more detailed explanation, see this clear treatise from London South Bank University.

I'll leave the proof to you as an exercise. :O)

Now off to get some coffee, I'm still blushing at the thought of my original misinformation. Trust but verify...

"They function by vibrating the water molecules,"

Isn't Ice water too? Isn't it the solid state version of water?

OK, I now kinda unpicked it from your first sentence.

However, molecules of H20 as ice or liquid are the same. It is how they are arranged to allow for this vibration to produce heat via kinetic (vibration) energy.

See edits to my previous post.

I learned something new today!

Now I'm also beginning to wonder about other things I learned as a child.

Is it really true about the tooth fairy? :O)

However, molecules of H20 as ice or liquid are the same. It is how they are arranged to allow for this vibration to produce heat via kinetic (vibration) energy.

Right, ice is crystallized water where the molecules are held in place by strong crystal bindings, making it more difficult for them to boogie to generate heat.