Wireless microphones have moved from a place of luxury to practically a necessity in church settings. There are many advantages to wireless microphones. With the increasing popularity of wireless technology, frequency selection also continues to get more complicated.
In this article, you will learn about the frequency bands, frequency selection and a new wave of wireless technology that eases the frequency-selection process.
Primary Frequency Bands for Wireless Microphones
Wireless microphones operate in three frequency bands. The lowest, VHF, stands for Very High Frequency. It starts at about 25 MHz and extends to 216 MHz. UHF (Ultra High Frequency) ranges from 450 MHz to 955MHz. The most recent band, 2.4 GHz, was recently allocated by the FCC.
The lowest is the Lo band VHF, which is 25-50 MHz and 72-76 MHz. The Lo bands have a definite cost advantage, but are also very susceptible to interference from cordless telephones, toys, and garage door openers. This band is not currently used by major manufacturers for wireless microphones.
Presently, the most used band is the Hi band VHF, which is 169-216 MHz. Systems in this frequency band are affordable and reliable. The better systems can operate many wireless microphone systems at one time without interference (if the frequencies are properly selected). However, this band is becoming congested in many areas. Frequency coordination with other nearby users is important if you want to add an additional wireless microphone and not have interference problems.
Traditionally, the highest frequency band has been the UHF band, which is primarily between 450-955 MHz. The UHF band provided very low interference. The equipment available on these frequencies was of high quality and reliability. Many systems can operate at the same time without interfering with each other. It has also been very expensive in the past, often limiting their use to professional theatre or broadcast. Fortunately, these systems have become much more affordable. There are now UHF systems in almost every price bracket. However, the increased sales also means more congestion and the interference that follows.
The newest band, 2.4 GHz, has recently been allocated by the FCC (Federal Communications Commission). It is available for unlicensed devices such as wireless microphone systems.
Frequency Selection:
It is a fairly easy process to select a frequency for a single wireless system. The major consideration is the other wireless systems within a mile. This becomes a more difficult task as wireless microphones become even more popular. There are few churches that don't have at least one system.
When a second system is added, there must be at least 400 kHz between the two system's frequencies. A complex equation is used to discover which frequencies are compatible.
As more systems are added, the math becomes increasingly complex. With the addition of a third system, another phenomenon called intermodulation (IM) must be considered. Basically, IM occurs when transmitters are in close proximity. The signals combine to form a new, different frequency which can be picked up by a receiver on a corresponding frequency.
Figure 1
The top two units in the wireless rack above have over 1400 selectable frequencies.
As a systems contractor, we would like to help you select a frequency without having to learn the in-depth equations and theories. When you're ready to purchase a new wireless microphone, make a list including: 1. Your church's present models and their frequencies. 2. Nearby frequencies that are being used. 3. A list of local TV stations. Don't forget the new digital TV channels.
With the advent of digital TV, many TV channels have been assigned new digital channels in the UHF band. These could be operating or will be operating at frequencies where some existing UHF wireless microphones are operating.
Wireless microphones are mostly unlicensed, so any TV channels have priority. If you are experiencing interference from a digital station on a fixed frequency wireless microphone system, you are unfortunately out-of-luck. Your only option is to have the frequency changed. Let us know if you need help.
New Technology:
Many new UHF systems are multichannel. If you have interference, it is simple to change the frequency of your system. Figure 1 shows a rack of wireless microphones. The top two units have over 1400 selectable frequencies in their frequency band.
Many systems also have the ability to find the frequencies with the least amount of interference. Just push a button on the receiver and it scans the available frequencies and picks one. Then the transmitter is manually tuned to the same frequency and you're ready to go.
Figure 2
Frequency is automatically selected.
Figure 2 shows a system that can automatically tune each receiver in multiple systems. Just push a button and the first receiver scans the band for least interference. Then the other receivers are set automatically to provide interference-free operation between themselves. All the operator needs to do is adjust the transmitters to the auto-selected frequencies.
Figure 3
2.4 GHz wireless system.
In the past, it has been said that no UHF wireless microphone could operate legally around the world. However, now there is product available that seems to be the solution for traveling ministry groups. The wireless microphone system shown in Figure 3 operates in the 2.4 GHz band. This is even higher than the UHF frequency band. It still remains the users responsibility to know the local frequency operating rules.
We're Here to Help:
There is more to selecting a wireless microphone system than many people realize. When you're ready to upgrade your system, please let us know. We'd be glad to recommend the best one to fit your unique needs.
