Transmitter power is limited to less than 50 mW, except in the MHz range where up to 1 watt is allowed for assistive listening systems. The high-band VHF range is the most widely used for professional applications, and in which quality wireless microphone systems are available at a variety of prices. In the U. The first band, from - MHz, includes eight specific frequencies designated by the FCC for wireless microphone use by the general public.
These frequencies are often referred to as "traveling frequencies," because they can theoretically be used throughout the U. Legal limits of deviation up to 12 kHz allow high quality audio transmission.
Power is again limited to 50 mW. Unfortunately, the primary users in this "traveling" band include many business band and government operations such as forestry, hydro-electric power stations, and the Coast Guard. Since the secondary user category is not restricted, the potential for interference from both primary and other secondary users is always present.
Also, general RF noise is still fairly strong in this band. Due to the limitation of available frequency bandwidth, and the spacing of the prescribed eight legal frequencies, it is only feasible to operate two or three units simultaneously on traveling frequencies.
These frequencies are not generally legal outside of the U. The primary users of this band are VHF television channels 7 - The possibility of interference from other secondary users and general RF noise exists, but it is much less likely than for low-band VHF frequencies.
In addition, although this range includes the primary users of television channels 7 - 13, there are ample frequencies available, i. The primary physical characteristic of UHF radio waves is their much shorter wavelength of 12 inches to 24 inches. The most apparent consequence of this is the much shorter length of antennas for UHF wireless microphone systems. One less obvious consequence is reduced radio wave propagation both through the air and through other non-metallic materials, such as walls and human bodies.
This results in potentially less transmitting range for comparable radiated power. Another consequence is the increased amount of radio wave reflections by smaller metal objects, resulting in comparatively more frequent and more severe interference due to multi-path dropouts.
However, diversity receivers are very effective in the UHF band and the required antenna spacing is minimal. While the regulations for users and for licensing are essentially the same in the VHF and UHF bands, regulations for the equipment allow two potential differences. This effectively permits greater deviation for potentially wider frequency range and wider dynamic range of the audio signal.
In addition, transmitter power up to mW is allowed. Finally, the available radio spectrum for UHF wireless microphone system use is almost eight times greater than for high-band VHF. Since people need all different types of radio signals a variety of wireless equipment is necessary to satisfy all needs.
The FCC is in control of who operates within each specific band and if anyone has priority over other operators. The primary users are properly licensed radio and television broadcasters as well as commercial communication services such as cell phones and two-way radios.
Very high frequency is commonly used for FM radio broadcast, two-way land mobile radio systems, long-range data communication, and marine communications, just to name a few. VHF waves must not exceed the local radio horizon of miles. VHF frequencies are less likely to be interrupted by atmospheric noise, issues with electrical equipment, and other interferences. There are different bands within VHF frequency, including low-band and high-band.
Low-band VHF range of 49 MHz includes transmission of wireless microphones, cordless phones, radio controlled toys and more. Despite the potential background noise this a popular option because of the low cost equipment. Transmission power is limited to under 50 mW, unless you are operating an assistive listening system in the MHz range. Also, a large antenna booster is necessary, measuring as much as 3 feet in length, thus limiting portability.
High-band VHF range is popular for professional applications. The lowest high-band MHz includes 8 different frequencies designated by the FCC, and is often used by the general public and wireless microphone devices. UHF radios are commonly used for communication in warehouses, schools and retail stores , indoor security environments etc. VHF very high frequency signals occupy the lower end of the radio frequency spectrum.
The longer wavelength of VHF enable it to travel further than UHF, so VHF radios could be right for you if you are primarily looking for two way radios for outdoor use. VHF radios are used exclusively in aviation and marine communication, and are great for grounds maintenance workers, use in open fields, golf courses, and for outdoor security environments.
Unfortunately it's not possible to convert VHF to UHF etc, as each type of radio contains hardware that enable it to operate on a specific frequency range. If you're buying or hiring more radios to work alongside ones you already use, they need to be of the same type.
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