Training

GMRS Radio 101

GMRS Radio 101
Dave B. (517)

The GMRS service is readily available for members of the public to gain access to; 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:For information on obtaining a license; see “Getting a GMRS License

 

Frequently Used Terms

 

Term Meaning
Channel 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)
CTCSS 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.
DCS 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.
Duplex 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.
FCC Federal Communication Commission; the branch of government that administers and regulates communication services, including wireless radio.
Frequency 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.
GMRS 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!
Repeater 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.
Simplex 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
UHF Ultra High Frequency; the name for the broad band in which the GMRS and many other radio services are located

 

 

Simplex Operation

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.