Wireless Wireless RF Dropout

[BenB]

Hi,
I manage the sound for a church that meets in central London. We've been having some problems with RF dropout on our mics. It seems to affect all 7 of our Shure SLX systems a little, but the Shure SLX bodypack in particular.

So this is our setup:
- 2 Shure UA874 active aerials placed at the back of the auditorium (about 12m from the stage) with an uninterrupted line of sight to the mics.
- The aerials are set to -6dB because this appeared to produce less drop-out on the hand-helds than when they were set to 0dB.
- We have 6 wireless SM58s and 1 wireless body pack with, obviously 7 receivers next to the aerials.
- There is a coaxial cable run of about 2m from the aerials to a Shure antennae distribution unit. That sends the signal out into 3 units and then the forth output goes to another distro unit which does the same thing to another 4 receivers, so 7 in total.
- The frequencies were coordinated using Wireless Workbench 6 beta and have been changed several times.
- We have 7 Sennheiser IEM units which are usually turned off when the body pack is in use. There is no other known source of RF nearby. (But it's central London so there could be loads of RF around.)

I've tried moving the receivers closer to the stage, changing the frequencies, changing the gain settings on the aerials, but nothing seems to get rid of the problem. We used to have passive aerials and adding the actives and dropping the gain by 6dB has helped improve reception, but has not elliminiated the problem. In particular this seems to affect the body pack a lot more than the other receivers, although I'm not sure why. The body pack is used with a Countryman E6 headset mic. Apparently Countryman are optimised to work with Shure gear, so there shouldn't be any problems with that.

Any ideas as to what I should try to resolve this? Help is greatly appreciated!

Thanks,
Ben

 

[Stookeybrd]

What frequencies does your OFCOM license say are to be used?

And what ranges are your SLX in? Different ranges have different output powers. H5, J3, L4 and P4 are all 30mW but the others are 10mW.

 

[Chris15]

But it's central London so there could be loads of RF around.

I'm not sure there's any "could" about it. There will be errant RF garbage floating around.

I do have to wonder if maybe there might also be some chance that these are systems that are affected by the digital transition?

Have you tried moving the antennas around the stage, try from SL and SR, it may be that you have your nicely directional paddle inadvertantly pointed right at an inteference source and if you can get that into a null in the pickup pattern things may improve...

 

[BenB]

What frequencies does your OFCOM license say are to be used?

And what ranges are your SLX in? Different ranges have different output powers. H5, J3, L4 and P4 are all 30mW but the others are 10mW.

Thanks for your resonpses guys. I haven't forgotten about it - I was in the venue yesterday testing the system under different circumstances (i.e. minimizing other RF, trying adding gain on the aerials and pack, and cutting down the complexity of the system so it's just one mic and receiver. I haven't had a chance to look at the recordings yet, but will do so tomorrow and post and update with the results.

Our units are K3E (606 - 630 MHz) and we're operating on the frequencies that our licence covers. I've tried changing the mic's frequency to use one assigned to one of our other mics (with that mic turned off obviously) but it doesn't seem to solve the problem.

I do have to wonder if maybe there might also be some chance that these are systems that are affected by the digital transition?

Have you tried moving the antennas around the stage, try from SL and SR, it may be that you have your nicely directional paddle inadvertantly pointed right at an inteference source and if you can get that into a null in the pickup pattern things may improve...

Yeah I've tried four different positions, the first three on stage - the best results have come from placing them towards the back of the auditorium, but these are by no means perfect. The equipment is all pretty new and was purchased after because of the digital transition when we had to ditch our old gear.

This is weird, thanks for your help though...