4. Lack Of Frequency Coordination. Most manufacturers offer software packages, usually free of charge, for the purpose of selecting frequencies for their wireless systems. There’s also third-party software for this purpose, although the best ones are expensive. The offline software I use for frequency coordination is IAS (Intermodulation Analysis Software) from Professional Wireless Systems, by the way.
The goal of any such software is to calculate the frequencies in a manner that eliminates potential intermodulation (intermod or IM) interference. What’s that? Intermods are “phantom” frequencies generated inside the equipment (transmitters, RF amplifiers, receivers) where more than one signal mixes together with another and is re-transmitted or gets added to the overall RF noise floor. These phantom signals can reduce range, cause dropouts, or in lesser quality systems, bring about massive “hits” causing loud signals in system output.
The potential for creation of these IM frequencies is easily calculated with the software but can be arduous to do by hand for any more than a couple of wireless systems. Just keep in mind that, like any software, it’s not a magic solution and experience counts. Note that there’s a free demo version of IAS available for download (at professionalwireless.com) to try out before committing to a purchase.
5. Bad Audio Gain Structure. With any analog wireless system based on FM (frequency modulation) transmission, bad audio gain structure can cause a reduction in range. Normally, the transmitter input gain must be set way too low before this happens, but I’ve seen it several times.
Generally, the goal is to have a “fat” signal going to the transmitter so that there’s a decent signal-to-noise ratio between the audio and the RF channel noise. The receiver is happy and feeds a nice, clean signal to the console, so you don’t have to crank the gain and thus raise the noise floor to audible levels. I recommend running receiver outputs at line level and then feeding signal to the console via its line inputs. The mic preamp is in the transmitter, so why add another one in the chain?
6. Lack Of Proper Maintenance. The most common problems I see: worn-/sweated-out lavalier and headset microphones, corroded battery contacts (from leaving batteries in units too long), moisture damage (mostly from sweat), loose antenna connectors, broken/worn transmitter antennas, and damaged or loose BNC coax cables on receiver antenna systems. These are all things we have control over and should be included in the maintenance budget.
Another common problem is that some folks are still using wireless systems operating in frequency bands that have long been illegal. Here in the U.S., the band between 698 to 806 MHz became unavailable (and illegal for us to use) in 2010. Now we’re also losing the 614 to 698 MHz band, officially effective next month (July 2020). There have been dozens of articles written on this subject, available at ProSoundWeb, and most manufacturers have information pages on the topic as well. (My company’s is at lectrosonics.com/fcc-spectrum-updates.) It’s vital to be educated now and for the future.
As we all move more in the direction of rechargeable batteries for our wireless systems, it’s critical to have a battery maintenance process in place. Modern rechargeables typically perform better than alkaline batteries and are far more cost-effective in the long term. However, if we don’t keep track of when they were first used and how many times they’ve been charged, they may let us down. Finally, use good quality (read more expensive) battery charges so that the batteries are not ruined early.
And that’s it! I imagine that many of you have other items on your own lists but I hope that the one presented here is helpful toward achieving better results with wireless systems at your church.