If the wireless setup is more complex, for example using wireless microphones and wireless in-ear monitors together, it may be necessary to use a frequency coordination computer program to insure compatibility. The appropriate Group and Channels can be determined from a link to the manufacturer's website or often by using the built-in "Scan" function on the receiver itself. By using Channels that are all in the same Group, compatibility is guaranteed for small setups of like equipment. The simpler method is to use the "Group" and "Channel" frequencies that are already programmed into the wireless systems.
Wireless microphone signal path tv#
To insure a mutually compatible set of frequencies once the local TV channels have been taken into account, it is necessary to use one of two methods. Still, since the locations and assignments of television stations are well known, it's pretty easy to choose relatively safe wireless microphone system frequencies in a particular area. Inside buildings of substantial construction, it may be possible to ignore TV stations as close as 30-40 miles. The good news is that indoor setups are at less risk than outdoor setups because building structures will usually strongly attenuate TV signals. How local is local? "Local" is generally considered to be up to 50 or 60 miles, depending on the coverage area of the particular TV transmitter and on the location of the wireless microphone system. To combat broadcast television interference, avoid using frequencies of local active TV channels. Television transmitters may operate at power levels up to one million watts while wireless microphone systems typically have only 50 mW (fifty one thousandths of one watt!) or less output power. Total net loss should not exceed five dB.Ī properly coordinated set of wireless frequencies must satisfy two criteria: the frequencies must avoid local active TV channels and they must be mutually compatible. The amount of loss depends on the exact length and type of cable used, so follow the manufacturer's recommendations. If the antennas will be connected to the receiver with a length of coaxial cable, in-line antenna amplifiers may be required to overcome the inherent signal loss in the cable.
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If the antennas are far from the stage,use directional antennas to improve reception by picking up more signal from that direction and less from other angles. Beyond one wavelength, extra distance between the antennas will not significantly improve diversity performance, but may allow better coverage of a large stage, church or meeting room. Increasing the separation between diversity antennas up to one wavelength (about 20 inches at 600 MHz) will improve diversity performance. (Short ¼-wave antennas should never be remotely mounted, however, because they need the receiver chassis as a ground plane.) If the receiver will be located away from the performance area (in an equipment closet or a closed rack, for example), ½-wave antennas or directional antennas should be remotely mounted (ideally above the audience) in order to have a clear line of sight to the transmitters. Don't try to use an antenna from another system without double-checking the frequencies first. Antennas can also be frequency band-specific. Try to keep antennas as close to transmitters with line of sight as possible. The receiver antennas should be angled apart in a wide "V" configuration, which provides better pickup when the transmitter is moving around and being held at different angles. One wave length (about 20 inches at 600 MHz) is even better. To ensure good diversity performance, space antennas apart by at least one-quarter of a wavelength (about five inches at 600 MHz). Mistakes in antenna selection, placement or cabling can cause short range, dead spots in the performance area or low signal strength at the receiver that leads to frequent dropouts.ĭiversity receivers offer much better performance than single-antenna types, but the antennas must still be put in the proper locations to maximize the performance and reliability of the system. Receiver antennas are one of the most misunderstood areas of wireless microphone operation, said Shure. Similarly, if the flexible antenna on a body-pack transmitter is coiled or folded, the transmitted signal is severely reduced in strength.
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In addition, if a user cups his or her hands around the external antenna on a handheld transmitter, its effective output can be reduced by 50 percent or more. Largely composed of salty water, human bodies soak up RF energy. The human body will absorb, block, interfere and reflect the RF signal emitted by a wireless mic transmitter.