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How each method works?

Frequencies for two way communications

There are many types of frequencies for radio communications but there are only two frequency types for two way communicating system. They are

Very High Frequency (VHF)

Ultra High Frequency (UHF)

Very High Frequency

Very high frequency (VHF) is the radio frequency between 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). VHF frequencies' broadcast characteristics are perfect for short-distance terrestrial communication. Very high frequency (VHF) is also less involved by atmospheric noise and interference from electrical equipment than low frequencies. It was also easier to construct efficient transmitters, receivers, and antennas for it in the earlier days of radio. In most countries, the VHF spectrum is used for broadcast audio and television, as well as commercial two-way radios (such as that operated by police), marine two-way audio communications, and aircraft radios. Common uses for VHF are FM radio broadcast at 88-108 MHz and television broadcast (together with UHF).

Ultra High Frequency (UHF)

Ultra high frequency (UHF) radio frequencies are in the range between 300 MHz and 3.0 GHz, which is higher than those of very high frequency (VHF). UHF and VHF are the most common frequency bands for television. The frequencies of 300-3000 MHz are always at least an order of magnitude above the MUF (Maximum Usable Frequency). The MUF for most of the earth is generally between 25-35 MHz. Higher frequencies also benefit less from ground mode transmission.

Full and Half Duplex

Duplex is a method which transmit radio frequency on various channels. There are two types of duplex - Half duplex and full duplex.

Half Duplex to communicate with half duplex, push to talk switch is necessitate.

Full Duplex transmit and receive conversation like mobile phones capability. This can transmit signals by two-way simultaneously at the same time.

Legal requirements

If a radio broadcasting system, it will need licensing for those transmissions. Other private business radios operate on either VHF or, UHF radio frequencies are identical for some time. For a police department it is necessary to license the frequency for the secure radio conversation and some legal issues. There are benefits of a licensed frequency such as: larger range, less interference from other users.

Licensing requirement

If the range of the two-way radio frequency is more than two miles, there would be registration with FCC-Federal Communication Commission. Following are the minimum requirement for the registration.

Type of frequency to use

Type of equipment to use

Model No. of the equipment

Supplying company

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