The General Mobile Radio Service (GMRS) is a licensed radio service that uses channels around 462 MHz and 467 MHz. The most common use of GMRS channels is for short-distance, two-way voice communications using hand-held radios, mobile radios and repeater systems. In 2017, the FCC expanded GMRS to also allow short data messaging applications including text messaging and GPS location information.
Services that provide functionality similar to GMRS include the Citizens Band Radio Service (CBRS), the Family Radio Service (FRS) and the Multi-Use Radio Service (MURS).
For new users of GMRS , how to operate and use, I thought it would be useful to put together a brief primer to fill in newcomers interested in using the services with a few of the basics:
1, Frequently Used Terms
2, Simplex Operation
3, Repeater “Duplex” Operation
4, Coded Squelch Systems
5, Common operational practices
Before you are ready to buy GMRS radio, you need to get a GMRS license, You may apply for a GMRS license if you are 18 years or older and not a representative of a foreign government. If you receive a license, any family member, regardless of age, can operate GMRS stations and units within the licensed system. For information on obtaining a license; see “Getting a GMRS License“
A common frequency standardized either within a radio service or within a manufacture of radios. The GMRS has 22 channels defined by the FCC, and an additional 8 channels to be used as repeater input frequency (for a total of 30)
Continuous Tone Coded Squelch System, also marketed as Private Line (PL), Privacy Code or Sub-Channels, this is a constant tone which the radio sends out when transmitting, that is usually outside of the audible portion of a radio’s receiver and thus not apparent to the user. The tone is used to control the squelch on the receiving end, and lets radios and repeaters better handle channel interference, either from other stations on the same frequency, or other sources. Almost all repeaters require the use of a CTCSS tone, although they can use an open squelch for operation.
Digital Coded Squelch; a digital variant of the CTCSS tone. The radio sends out a continuous data pulse that represents a squelch code, again, typically outside of the audible portion of a radio’s receiver. DCS is less common on repeaters, but still commonly used. It is more resilient to interference than CTCSS, but also more sensitive to weak-signal problems.
A method of radio operation where users transmit on one frequency/channel, and receive on another. This method of operation is used for operations with repeater stations.
Federal Communication Commission; the branch of government that administers and regulates communication services, including wireless radio.
The rate at which something oscillates, usually measured in terms of oscillations per second. Megahertz is a unit of measurement for frequency, meaning millions of oscillations, or cycles, per second.
General Mobile Radio Service; the name of the radio service created by the FCC located around 462Mhz and 467Mhz that is available for licensed use, and what we’re all about!
A remote radio station that receives and rebroadcasts signals in real time. They are typically located at advantageous sites in terms of height above average terrain, including mountain and hilltops, on top of tall buildings or radio towers, or both! Repeaters can greatly boost the coverage range for radio communication devices, such as walkie talkies, vehicle mounted (mobile) stations, and fixed (base) stations.
A method of radio operation where users transmit and receive on the same frequency/channel. This is most common for consumer-type handheld and mobile radios, and common in direct radio-to-radio communications
Ultra High Frequency; the name for the broad band in which the GMRS and many other radio services are located.
Simplex operation is a direct radio-to-radio method of using a radio, in which all users receive and transmit on the same channel; it is the most common type of operation that people are familiar with. You turn on the radio, dial in a channel (or frequency), and start talking. So long as everyone is on the same channel with the same squelch settings, and everyone is in range, all parties can hear one another.
Simplex operation generally works well over shorter distances, or when communicating using a base, mobile or handheld station that’s in a high location. Since there is no repeater, coverage is generally limited to a few miles, although depending on topography, much greater ranges may be possible. It is most easily deployed in the field among groups of people.
It’s important not to take certain formalities too seriously; one should focus on using the radio in a matter that works well for them. With that said; there are a few general rules to keep in mind for starters:
GMRS users must identify their transmissions with their FCC issued call-sign every 15 minutes, or at the end of a series of transmissions.
Foul language is not allowed by the FCC
Keep a brief pause between transmissions so other stations can have a chance to break in if they need to.
When using a repeater, wait until after the courtesy tone to transmit – this is a brief beep or tone you may hear shortly after someone keys up the system. The intent is to give a pause for other stations to break in. Some repeaters will time-out after a few minutes if this is not followed and cease to transmit for a brief duration. Not all repeaters will have this.