International Frequency Coordination

[Nitin Sidhu]

Hello!

I was wondering, there has been gig that I have had the opportunity to engineer a few times, elaborate, and we have used in excess of 50 channels of RF (iem + HH)

Im no wireless expert and dont take the responsibility. But it hasn't really been working.

Everyones been relying on WB6 or WSM to get the needful done. But the IEM's have a constant issue, so much so that the artists now consider it a given with iems. I know that we can face similar issues even if using 2 iem packs instead of 20. I also know that with proper coordination we can get many channels of iems to work.

Antenna placement and the drill aside, 3 questions.

1. Im not too sure if the likes of WB or WSM can actually do frequency 'coordination', when multiple units can come in proximity and cause inter modulation etc ?

2. And then, why is it always the IEM's that give issue ? A higher number of HH's all seem to work clean most of the time ?

3. Thirdly, there seems to be a solid foundation with FCC in the US where TV channel frequencies etc are easily available in the public domain.... but in India, and for example, Malaysia or Singapore, how would one work with something like the Professional Wireless software etc ?

Tx a ton!
Sidhu

 

[TJ Cornish]

Re: International Frequency Coordination

Intermodulation calculation is mathematics, and should work the same internationally, as you are simply finding frequencies for your equipment that are compatible with each other. This does not take into account external interference - that will have to be measured. A device like this should help: http://rfexplorer.com/

IEMs shouldn't be different than mics in general with regard to spectrum use, but the antenna configuration is different. How are you currently set up?

 

[David Sturzenbecher]

Re: International Frequency Coordination

Also, a reliable scan on location holds more value then a list of TV channels to avoid. Can you use some of your wireless mics to scan spectrum with WWB?


Sent from my iPhone

 

[Milt Hathaway]

Re: International Frequency Coordination

Addressing number 2: If you are running stereo IEMs there are factors regarding how the stereo signal is detected and handled that can reduce signal reliability in some situations. It's even possible for the audio signal feeding the transmitters to cause apparent RF issues.

This Shure article describes the phenomenon much better than I do: http://shure.custhelp.com/app/answe...2LzEvdGltZS8xNDAxNDcyMTgwL3NpZC9PajNLNUFWbA==

 

[Chris Johnson]

Re: International Frequency Coordination

Hello!
1. Im not too sure if the likes of WB or WSM can actually do frequency 'coordination', when multiple units can come in proximity and cause inter modulation etc ?

They can indeed. Both WSM and WWB have proper frequency calculation systems that check for intermodulation between transmitters.

2. And then, why is it always the IEM's that give issue ? A higher number of HH's all seem to work clean most of the time ?

Without knowing anything about your system, I'd suggest the antenna setup would have something to do with it. How do you have it configured?

3. Thirdly, there seems to be a solid foundation with FCC in the US where TV channel frequencies etc are easily available in the public domain.... but in India, and for example, Malaysia or Singapore, how would one work with something like the Professional Wireless software etc ?

Well, I can't say with certainty, but there must be some information somewhere about what TV transmitters broadcast what channels in what frequency ranges? Once you have this information, you have a baseline.

That said, nothing is a substitute for an on location scan of the actual airborne RF. Most modern IEM and Mic systems have a scan function built in that can help you determine what areas of spectrum you need to avoid. With this information to hand, you can tell your software of choice (WWB, IAS, WSM, RFGuru) to avoid certain TV channels when coordinating new frequencies.