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The Basics
FCC definition: "General Mobile Radio Service . A mobile two-way voice communication service, with limited data applications, for facilitating activities of individual licensees and their family members, including, but not limited to, voluntary provision of assistance to the public during emergencies and natural disasters."
The General Mobile Radio Service channelizes frequencies in portions of the 462 MHz and 467 MHz UHF band. GMRS users can access 30 channels; 22 of these channels are shared with the Family Radio Service (FRS). GMRS users have access to additional frequencies which are exclusive to repeater input operation only. FRS radios are not authorized to use repeaters.
The key differences between GMRS and FRS relate to bandwidth and power output. FRS operates on a bandwidth of 12.5khz on all channels with a maximum power output of 2 watts. GMRS is authorized with the following bandwidths and power outputs.
GMRS bandwidth varies based on channel
Channels 1-7 = 25khz
Channels 8-14 = 12.5khz
Channels 15-22 = 25khz
GMRS power output varies based on channel
Channels 1-7 = 5 watts
Channels 8-14 = 0.5 watts
Channels 15-22 = 50 watts
Repeater inputs
15R - 22R (467mhz)
When using a FCC type accepted GMRS radio, a user does not need to be concerned about bandwidth or power output settings, as they are programmed by the manufacture to be in compliance. Radio manufactures may give the user the option to adjust transmitter power as long as it does not exceed the maximum authorized power. The above explanation of FRS and GMRS differences is for information purposes.
GMRS Qualities
Three of the most appealing qualities of the General Mobile Radio Service are the range, power output, and use of repeaters.
Range: The UHF frequency band works on the line-of-site principle. Any obstructions between two radio transmitters such as hills, valleys, and buildings will block or deflect the radio signal and reduce range.
Handheld - generally 1-2 miles with limited obstructions
Mobile/Base - 5-25 miles is reasonable. Greater distance is possible.
Repeater - up to 50+ miles
The most important factor in determining range is antenna height.
Power output: The maximum power output authorized by the FCC for the General Mobile Radio Service is 50 watts, which can enable great range with the right antenna system and terrain.
Repeaters: A repeater can be thought of as a relay. It is a special radio that receives a radio signal on one frequency, and re-transmits it on another. GMRS repeaters provide greater range due to their antennas being high above obstructions, high-gain antennas, and higher power output.
Repeater benefits
Extended coverage
Improved signal quality
Enhanced reliability
How Can GMRS Benefit You?
Support for routine and emergency communications: A backup communication system is crucial. There is no guarantee that cellular service, the internet, and the power grid will remain operational during times of crisis - disruption of these vital communication services places lives at risk.
GMRS allows a robust way to maintain contact with friends, family, and other licensed users in the community. GMRS can also be used for daily, routine communication.
Family licensing for a single fee: A licensing fee of $35 covers all immediate family members for a period of 10 years, regardless of age.
Extended range with repeaters: GMRS allows integration with repeaters that greatly extend the talk range and reliability of communications. Depending on a repeater’s location, antenna system, terrain, and power output, a repeater can allow communication for 50+ miles.
A gateway to other areas of radio communication: GMRS offers a way to network with people who are licensed in other areas of radio communication, such as Amateur Radio.
An investment for safety: Being able to communicate in real-time is crucial for organizing, responding, and mitigating hazardous and emergency situations.
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