Channel 70 lots of interference complaint

[paulears]

I discovered a potential snag for ch 70 users I hadn't really thought about. I loaned some of my IEM kit to a friend for a 3 week residency - he wanted try out IEMS rather than wedges. I didn't get rid of all my ch69 stuff, so I have a rack of 6, and put 4 onto Bank 8 which is ch70, on the first four channels, tuned in the receivers and let him source his own in-ears. It never occurred to me that what would happen is that he'd plug the rack in and just leave it on. So 24/7 all the ch 70 free channels had carriers up and running, and other users nearby had the normal swirly interference from the rack. It was only when he mentioned the funny noises the DJ and aerobics lady had had for the last couple of weeks it twigged. I wonder how common this kind of thing is going to be?

[jonathanhill]

Oops.

 

What is Ofcom/JFMG's view on this, I wonder? I would imagine that there are some sanctions that they could impose.

[GR1]

Channel 70 is open on a first come first served basis so JFMG would have nothing to say. If I were on the receiving end of the interference I might be less polite when I found the source.

 

Kit suppliers need to make sure that the people they supply kit to know how it works. Several times I have asked so called 'AV technicians' from supposedly reputable companies what frequencies their radio mics are on and got the answer ' One and Two'. Theres no excuse for sending incompetant crew out on jobs.

[paulears]

Channel 70 has always been a gamble - it's unregulated, so as nobody pays to use it there is zero protection - but in the past it's been reasonably ok, because many people didn't even know where their system, bought from the local music shop transmitted. Sennheiser probably the worst because the free to use bank is the last one, not the first - so unless you knew to change it?................ Sennheiser also made much of the 'tune' feature where the thing would look for empty channels - and as most were empty, you could find you were using very odd ones - but if and when 4G starts to take off, then there will be nasty digital noise on many people's set and forget frequency - so they will scan for quiet ones, or Google, and find out perhaps for the first time that only the channel 70 ones can be used - and that's when mistakes like mine will be annoying. In the countryside, where it's unlikely two venues will be close together 4 or 5 channels(depending on your kit) may give you enough - but plenty of busier areas have rows of bars and clubs. So the fun is waiting to start. Sensible people will buy a license and different kit and go to channel 38, but lots won't have a clue!

[cedd]

Carrier wave only is a really nasty form of interference to deal with. Most Ofcom technical investigation officers will tell you their first port of call when tracing interference is to listen to it. Even if there's no speech there you can tell a fair bit by the background noise. Plain old carrier, motorboating, white noise, audible data transmission (not that common these days with the advent of phase quadrature modulation). They all serve as clues to the source.

When I first started out (about 10 years ago now) my best pair of headphones were wireless over-the-ear ones. I loved them, they freed me of wires and I felt quite posy in my wireless cans. It was only when I started mixing radio mics that I realised these wireless headphones were using channel 70. Sadly I had to return to the world of wires after that!

 

I've also known receiving houses using a channel 70 frequency to get their show feed between the house and backstage. Strictly speaking it's not allowed as it's a fixed link, but I'm not about to go causing trouble at a receiving house when I need their help!

 

Sadly I'm slowly starting to realise that channel 38 isn't as safe as I first thought it was. A show I helped on in a local city centre venue had no end of problems. One night we could hear a motown singer giving it all she had on a principal character's channel, then there was other stuff that we suspect was a bingo hall.

Anything this side of the hill over Bradford is trouble too as there's a tv repeater mast broadcasting in channel 39, which doesn't half cause us trouble. I bought 6 channels of 2.4GHz recently as "extra" channels for supporting cast. I'm now starting to look at them far more as an option for principal characters in these difficult circumstances.

[GR1]

One of the advantages of Channel 38 is also one of it's problems. Channel 69 had defined frequencies and as long as you stuck to them 2 or 3 shows could happen close together without intermod. Channel 38 is a blank frequency band to use as you like and whilst that means top range kit will get a lot of frequencies into it , it also means that a lack of defined frequencies is likely to scupper shows next to each other as different manufacturers kit interacts. It's going to be an adventure.