Mobile Phone creating interference on picture: anyone ever seen this?

I'd guess pickup on the boundary mic - as I understand it when somebody rings a mobile it gets 'rung' in a group of cells centred on the last response from the mobile, then the phone transmits with a high power "I'm here" burst, that the system then hones in on to direct te system to the correct individual cell. Once the link is established, power drops down to a lower level.  RF gets picked up on the cable, and it gets into the camera that way. Very often wrapping a few turns arround a ferite ring will do the trick. If it's thin cable, then the ones you can buy that come in two pieces work pretty well. A less pretty but often better solution is to find an old loudspeaker magnet, whicg are circular - wrap half a dozen turns through it, cover with tape and away you go. However - keeping the magnet away from tapes and any other item likely to be magnetised is important. Sticking it in the camera bag is a BAD move. Long mic cables make really good aerials passing through the area where people have phones in their pockets and handbags.

 

The theatre world have been trying to deal with this for years now - with only moderate success. A few have even tried importing foreign phone jammers - but the fines are pretty steep. Stopping people with phones just doesn't seem to work.

In todays "Mail" there was an article saying tha the new 4G phones may interefere with some Freeview transmissions!

The snag seems to be that the new 4G mobile transmit frequencies are in the old channel 69, and the info so far is that they will spill into ch 70 (bad news for radio mic users) and ch68 - (bad news for some freeview channels, if they're in use in your area. The doom and gloom merchants have been predicting severe interference from these services - but because the danger frequencies are for the mobiles, nobody is quite sure what will happen because it will depend on how many people have the phones close to TVs and radio moc recievers.

Thanks Paul, that makes a lot of sense: particularly as that theatre (Jacksons Lane in Highgate, north London) has a notoriously poor mobile signal. Great for a quiet night at the theatre, not so great if you're trying to work there! The high power burst must have been very high indeed to make the phone ring, and perhaps it was that exceptional strength that caused picture interferene.

Have just ordered some of those Ferrite things from CPC. Thanks for the top tip.

 

The 4G signal that is next to the free-to-use radio mic spectrum hasn't come into operation yet.... next year we'll see what delights that brings!