The General Mobile Radio Service (GMRS) is a service designed to cater to families who have need for two-way radio communication in the United States. It is an FM band and is designed for short-range communication, especially during recreational outings. It is very similar to the Family Radio Service (FRS), but its radios are allowed transmission over greater distances.
The main difference between the FRS and GMRS, in addition to the transmission range, is that the latter's radio usage must be licensed with the Federal Communications Commission (FCC). While the licenses are for five years and currently run less than $100 US Dollars (USD), it is a requirement. Those who purchase radios capable of being used on GMRS frequencies should be aware of those requirements before purchasing.
The transmission range for a GMRS radio is supposed to be somewhat enhanced over an FRS radio. This is due to a number of different reasons. These radios have increased wattages over FRS radios. FRS radios have a maximum wattage of less than one. GMRS radios can have a wattage of one to five. Often, though not always, that translates to an increased range. Further, FRS radios can only have internal antennas. GMRS radios are not limited to internal antennas and that also helps increase their effective ranges.
While there are some frequencies shared between the two services, the GMRS also has some exclusivity on some frequencies. The frequencies available for use are available to all with a GMRS. However, with the licensing requirements, there should be enough open channels that nearly exclusive two-way communication is possible. However, as with any public radio service, it is not advisable to broadcast personal information over the air.
Licensure of GMRS radio is done for a number of different reasons. First, the FCC wishes to restrict the channels to those family members needing to communicate. Second, the FCC wants to restrict access to the number of authorized individuals on certain frequencies, to make sure practical communication remains viable. Violating the law by operating one of these radios without a license subjects the user to fines and possible criminal prosecution, though the FCC does not monitor the channels very often.
Though some GMRS radios may advertise many different channels, or channel configurations, in reality there are only 15 channels. Therefore, these radios are only be able to utilize one of these channels, which are located in a range of 462 MHz.