Ouch, we have made some mistakes with wireless broadcast rigs in the past to the point where our audio engineers refuse to use gear that was bought to meet a wireless microphone requirement and save money. But you don’t learn anything if you don’t make a few mistakes along the way. Here are a few tips on what to look for in wireless audio rigs. First, a little background. Today there are three kinds of wireless systems used in live sound; Very High Frequency (VHF), Ultra High Frequency (UHF), and Digital wireless. Below that level there are features such as “diversity”, channel selection and noise rejection.
Noise rejection or Radio Frequency Interference (RFI) is the single biggest issue that audio engineers contend with when working with live sound. You should not have any noise on the channel other than the live sound you are there to capture and broadcast. A good wireless system will reject noise for you, a bad wireless system can inject noise into the audio you are capturing. This is one of the great attractions of digital wireless. Digital wireless converts the analog signal entering the microphone into 1’s and zeros and then sends them to the wireless receiver where they are converted back into analog audio at the receiver. Noise cannot get into the transmitted sound since the signal going out to the receiver is not subject to RFI. A seemingly perfect solution, with one large caveat.
The digital wireless systems may have some significant distance limitations, some as low as 50’. If your talent is more than 50’ from the receiver digital wireless may not be a good solution. VHF wireless systems are generally inexpensive. They operate in the same radio frequency bands as house appliances, TVs and air conditioning. Anything with an electric motor (like A/C) in it will generate RFI that a VHF wireless system may not be able to reject.
Distances are good for VHF, but the further away from the receiver you get, the more likely you are to pick up unwanted RFI. UHF systems seem to hold the greatest potential for delivering high quality sound reliably and without interference in most cases. This is where diversity comes in to play. Good UHF wireless rigs will support multiple channels across multiple frequencies. In most cases they are plug and play, the wireless microphone will automatically sync with the receiver on a specific band and you are good to go. There will be occasions when, despite best practices, we will pick up some RFI in a particular band. A good UHF system will allow you to override the automatic band selection and try other bands within each channel until you find one that does not pick up RFI. Distances are good for UHF. You can find popular systems that include a wireless microphone or lavaliere microphone, a receiver, and other accessories for $350 and up.
Paying more for a system does not mean that it will reject all noise, but hopefully this short primer will allow you to ask the right questions when considering a wireless microphone system for your next video broadcast.