Wireless Systems

Wireless systems are better in terms of convenience and mobility. But they also come with their trade offs. They have the following parts ...

Receiver --- This is the device that is mounted in the rack and output from it goes into the mixer. It usually has two antennas in the back.

Transmitter --- This device is carried by the person doing the talking. It transmits the radio signals which are picked up by the receiver. It can be in the form of bodypack or built into the handheld microphone. Bodypack transmitter is the one that goes into the pocket from which a cable comes out. This cable terminates into a small condenser microphone.

Microphone --- It is usually a lavalier or a headset small condenser microphone. In case of handheld microphone, the microphone and transmitter are built into a single device.

Antenna Boosters (optional or used only if needed) --- These are used if the transmitter and receiver are not in line of sight or too far apart. As the name suggest they boost the wireless signal of the transmitter which is picked up by the receiver. Signal to noise ratio gets weaker as transmitter and receiver start getting too far apart. It eventually ends up in a buildup of background hissing noise.

When setting up or connecting a wireless system please follow the instructions that come with it. It is important to set the gain staging correctly to get the optimal signal to noise ratio. When doing this check the RF signal on the receiver. It should be around 80 % when the person using the wireless microphone is as loud as one gets in a Masjid. It is OK if the peak red light flashes occasionally during this test. Position the antennas in a way such that dropouts do not occur. This is checked using the power LED or the RF meter.

In layman terms True Diversity means using two antennas to eliminate dropouts. The wavelengths of VHF frequencies are much longer (5-6 feet long) than UHF (12-20 inches) so the transmitter and receiver have to be further apart for a VHF system to operate without dropouts. Location and what is in the room also effects dropouts. There are many types of true diversity systems but we will not discuss them here to keep things simple. A good system has auto switching diversity built into it. It is required to sync the transmitter and the receiver at a frequency for the wireless system to operate.

Another important setting is called Squelch setting. Usually higher the setting the longer the operating range but more prone to RF interference from other electronic devices. Lower the squelch setting the better the protection from RF Interference but shorter the range. Some manufacturers do it the opposite way. So choose one that is right for your equipment. This setting will need some experimentation in the area where you have the wireless system.

By government policy, all frequencies are shared by a large number of users across the country including TV stations, communications equipment and a large number of wireless microphone systems. Hence there is always at least a small chance that someone else in the area might be using the same frequency as your wireless system. So be aware of this and select the frequency which is least used or unused in the area of your masjid. The way to do it is to just leave the receiver on with the transmitter and mixer off and see if the receiver RF meter shows any sign of RF signal. If it does not then you have a good frequency to use. Otherwise play with the various frequencies. Please note frequencies between 698 Hz and 803 Hz are reserved for emergency services and are illegal to use in US. This is generally referred to as the 700 Hz band.

Transmitters output power is measures in milli watts (mW). Most transmitters output power is around 15 mW. The higher the output power, longer the operating range between transmitter and receiver, better signal quality but lower will be the battery life of transmitter. In a typical masjid setup we usually go for a 50 mW transmitter.

VHF or UHF system

VHF frequency spectrum (high band) is from 174 to 216 MHz and the maximum allowable transmitter output power is 50mW. This frequency range includes TV channels 7 to 13.

UHF frequency spectrum is from 470MHz to 698MHz and maximum allowable transmitter power is 250mW. Frequency range between 902 to 928MHz, is currently being used by garage door openers, amateur radio, cordless telephones etc hence it is not a good frequency choice for UHF system. However digital wireless systems like line6 can operate in this range with out any issues. Some of them actually work in the 2.4 GHz to 5 GHz range too.

Both VHF and UHF are good. They just operate in different frequency ranges. The situation you are in demands which one will be better FOR YOU. There are some advantages with UHF systems like less or lower intensity interference because of higher frequency, bigger range of frequencies to choose from etc but they do come with the extra cost associated with these systems. VHF systems might work better when the transmitter and receiver are not in line of sight whereas all UHF systems are line of sight systems. VHF systems also are much cheaper than UHF systems.

Wireless Transmitters and Receivers to listen to different Mosque azaan and lectures.

If you wish to tune into your local masjid or want to listen to lectures from other masajid in your city, you need to dial your receiver into the frequency at which that masjid transmitts. Some products to look into if you are interested into this functionality are listed below.