Two-Way Radio Frequencies
- Operate on many different frequencies, which often differ in different countries.
- Usually radio frequencies are preselected so that the user does not have to tune into a certain frequency, but can easily choose a frequency by pushbutton.
- In the US there is a block of 22 channels assigned to the General Mobile Radio Service and Family Radio Service.
- The selection of a frequency for a two-way radio system is affected by:
- Government licensing and regulations
- Local congestion or availability of frequencies
- Terrain, since radio signals travel differently in forests and urban areas
- The presence of noise, interference, or intermodulation
- Sky wave interference below 50-60 MHz and troposphere bending at VHF
- In the US, some frequencies require approval of a frequency coordination committee.
- Each country allocates radio frequencies to different two way services. In the US some examples are: Citizens Band, FRS, GMRS, MURS
- Channel numbers are used as shorthand notation for a frequency in two way radios.
- Amateur radio operators nearly always use frequencies rather than channel numbers since there is no regulatory or operating requirement for fixed channels.