General Mobile Radio Service
Encyclopedia
The General Mobile Radio Service (GMRS) is a licensed land-mobile FM
UHF
radio
service in the United States
available for short-distance two-way communication. It is intended for use by an adult individual who possesses a valid GMRS license, as well as his or her immediate family members. Immediate relatives of the GMRS system licensee are entitled to communicate among themselves for personal or business purposes, but employees of the licensee, who are not family members, are not covered by the same license.
GMRS radios are typically handheld portable devices much like Family Radio Service
(FRS) radios, and share some frequencies with FRS. Mobile and base station-style radios are available as well, but these are normally commercial UHF radios as often used in the public service and commercial land mobile bands. These are legal for use in this service as long as they are GMRS type-approved. They are more expensive than the walkie talkies typically found in discount electronics stores, and are generally considered higher quality.
and may renew their existing licenses. No new GMRS licenses are being issued to non-individuals, nor may existing non-individual licensees make major modifications to their licenses.
The license extends privileges of the primary licensee to include communications with the licensee's immediate family members, and authorizes immediate family members to use the licensee's station(s) to conduct the activities of the licensee. Additionally, the FCC rules allow GMRS licensees to communicate with other GMRS licensees. GMRS licensees are allowed to communicate with FRS users on those frequencies that are shared between the two services. The rules require each GMRS user family to have a license, rather than (as in the case of commercial and public safety land mobile license) authorizing a licensee's employees to use the same license.
and the distance to the radio horizon can be estimated based on antenna height. Theoretical range between two hand-held units would be about one or two miles (about one and a half to three km), mobile units have higher antennas and range of around 5 miles (8 km). A GMRS repeater
with an antenna that is high above the surrounding terrain can extend the usable range over a wide area, for example up to 20 miles radius around the repeater station. Obstructions such as hills and buildings can reduce range. Higher power does not necessarily give a proportional increase in range, although it may improve the reliability of communication at the limits of line-of-sight distance.
and repeater
outputs, and another frequency 5 MHz higher for repeater inputs. There are eight channels exclusively for GMRS and seven "interstitial" channels shared with Family Radio Service. GMRS use requires an FCC
license, and licensees are permitted to transmit at up to 50 watt
s on GMRS frequencies (although 1 to 5 watts is more common), as well as have detachable or external antennas.
GMRS licensees are also able to use the first 7 FRS frequencies (the "interstitial" GMRS frequencies) with a few limitations. Specifically, they may be used as long as one-way pages are not transmitted, communications are limited to voice, and transmission power (ERP) does not exceed 5 watts (FCC Code §95.29, section f). This allows GMRS users to transmit on a total of 15 channels. FRS channels 8 through 14 are not available for GMRS use; use of these frequencies requires an FRS transceiver, or a hybrid transceiver operating under FRS rules.
Recently, hybrid FRS/GMRS consumer radios have been introduced with 22 channels, instead of the 14 channels associated with FRS. On this type of radio, channels 8-14 are strictly license-free FRS channels. Transmitting on all channels above channel 14 requires a license. Transmitting on the shared FRS/GMRS channels 1-7 requires a license, if using more than one half watt. It is the responsibility of the radio user to read and understand all applicable rules and regulations regarding GMRS. These hybrid radios are often referred to as "bubble pack" radios, since they are often packed in a plastic shell, for hanging on a display shelf. The massive sales of these radios have led to a term known as "bubble-pack pirates
", persons who use GMRS without a license.
The FCC rules for use of hybrid radios on channels 1-7 require licensing only when operating under the rules that apply to the GMRS. Many hybrid radios have an ERP that is lower than one half watt on channels 1-7, or can be set by the user to operate at low power on these channels. This allows hybrid radios to be used under the license free FRS rules if the ERP is less than one half watt and the unit is certified for FRS operation. Only two makers of hybrid FRS/GMRS radios (Garmin and Motorola) presently sell radios that will operate on the GMRS repeater channels; the common "22 channel" radios cannot be used with GMRS repeaters. The Icom IC-F21GM is a solely-GMRS radio which will also work repeaters.
Hybrid packaging still contains the notice of the FCC licensing requirement. Estimates of the number of hybrid FRS/GMRS radios sold to date range from 20 to 50 million units or more. This is compared with approximately 80,000 active GMRS licensees (per the FCC database). Enforcement against individuals is rarely, if ever, attempted.
This first set of frequencies shows the split frequency pairs used in duplex operational mode, often used with repeaters. Simplex
(same frequency for receiving and transmitting) mode only utilizes the lower set of frequencies.
All channels are used with narrow-band frequency modulation
.
This second set of frequencies shows the interstitial ranges shared with the Family Radio Service
services. These frequencies can only be used for simplex operations.
In the 1960s, the UHF 450-470 MHz band was re-allocated to 25 kHz channels. This meant transmitter deviation was reduced to ±5 kHz. This doubled the number of channels available across the entire 450-470 MHz band. Class B Citizens Radio Service channels were re-allocated to other radio services.
In the 1970s, allowed power was again changed to 50 watts across the output terminals of the transmitter. In 1987, licensing of business users was discontinued and businesses were allowed to continue operating until their licenses expired. There was congestion on all channels in larger metropolitan statistical areas and moving businesses to Business Radio Service
channels would provide some relief. The radio service was changed to its present name.
In Canada
, hand-held GMRS radios up to 2 watts have been approved for use without a license since September 2004. Typically these are dual FRS and GMRS units, with fixed antennas, and operating at 2 watts on some GMRS channels and 0.5 watts on the FRS-only channels. Mobile units (permanently mounted in vehicles), base station
s and repeater
s are not currently permitted on the GMRS channels in Canada.
Other countries have licensed and unlicensed personal radio services with somewhat similar characteristics, but technical details and operating conditions vary according to national rules. Many European countries use a similar 8 channel system near 446 MHz known as PMR446
. GMRS equipment that is approved for use in the United States will not communicate with PMR446 radios, and generally will not be approved for operation in other countries.
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
UHF
Ultra high frequency
Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...
radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
service in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
available for short-distance two-way communication. It is intended for use by an adult individual who possesses a valid GMRS license, as well as his or her immediate family members. Immediate relatives of the GMRS system licensee are entitled to communicate among themselves for personal or business purposes, but employees of the licensee, who are not family members, are not covered by the same license.
GMRS radios are typically handheld portable devices much like Family Radio Service
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
(FRS) radios, and share some frequencies with FRS. Mobile and base station-style radios are available as well, but these are normally commercial UHF radios as often used in the public service and commercial land mobile bands. These are legal for use in this service as long as they are GMRS type-approved. They are more expensive than the walkie talkies typically found in discount electronics stores, and are generally considered higher quality.
Licensing
Any individual in the United States who is at least 18 years of age and not a representative of a foreign government may apply for a GMRS license by completing the application form (either on paper or through the FCC's Universal Licensing System) and paying the license fee (currently $85.00). No exam is required. A license for a GMRS system is usually issued for a 5-year term. Prior to July 31, 1987, the FCC issued GMRS licenses to non-individuals (corporations, partnerships, government entities, etc). These licensees are grandfatheredGrandfather clause
Grandfather clause is a legal term used to describe a situation in which an old rule continues to apply to some existing situations, while a new rule will apply to all future situations. It is often used as a verb: to grandfather means to grant such an exemption...
and may renew their existing licenses. No new GMRS licenses are being issued to non-individuals, nor may existing non-individual licensees make major modifications to their licenses.
The license extends privileges of the primary licensee to include communications with the licensee's immediate family members, and authorizes immediate family members to use the licensee's station(s) to conduct the activities of the licensee. Additionally, the FCC rules allow GMRS licensees to communicate with other GMRS licensees. GMRS licensees are allowed to communicate with FRS users on those frequencies that are shared between the two services. The rules require each GMRS user family to have a license, rather than (as in the case of commercial and public safety land mobile license) authorizing a licensee's employees to use the same license.
Range
As for other UHF radio services, reliable range is considered to be line-of-sightLine-of-sight propagation
Line-of-sight propagation refers to electro-magnetic radiation or acoustic wave propagation. Electromagnetic transmission includes light emissions traveling in a straight line...
and the distance to the radio horizon can be estimated based on antenna height. Theoretical range between two hand-held units would be about one or two miles (about one and a half to three km), mobile units have higher antennas and range of around 5 miles (8 km). A GMRS repeater
Repeater
A repeater is an electronic device that receives asignal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.-Description:...
with an antenna that is high above the surrounding terrain can extend the usable range over a wide area, for example up to 20 miles radius around the repeater station. Obstructions such as hills and buildings can reduce range. Higher power does not necessarily give a proportional increase in range, although it may improve the reliability of communication at the limits of line-of-sight distance.
Frequency assignments and FRS
The GMRS-only channels are defined in pairs, with one frequency in the 462 MHz range for simplexSimplex
In geometry, a simplex is a generalization of the notion of a triangle or tetrahedron to arbitrary dimension. Specifically, an n-simplex is an n-dimensional polytope which is the convex hull of its n + 1 vertices. For example, a 2-simplex is a triangle, a 3-simplex is a tetrahedron,...
and repeater
Repeater
A repeater is an electronic device that receives asignal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.-Description:...
outputs, and another frequency 5 MHz higher for repeater inputs. There are eight channels exclusively for GMRS and seven "interstitial" channels shared with Family Radio Service. GMRS use requires an FCC
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
license, and licensees are permitted to transmit at up to 50 watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
s on GMRS frequencies (although 1 to 5 watts is more common), as well as have detachable or external antennas.
GMRS licensees are also able to use the first 7 FRS frequencies (the "interstitial" GMRS frequencies) with a few limitations. Specifically, they may be used as long as one-way pages are not transmitted, communications are limited to voice, and transmission power (ERP) does not exceed 5 watts (FCC Code §95.29, section f). This allows GMRS users to transmit on a total of 15 channels. FRS channels 8 through 14 are not available for GMRS use; use of these frequencies requires an FRS transceiver, or a hybrid transceiver operating under FRS rules.
Recently, hybrid FRS/GMRS consumer radios have been introduced with 22 channels, instead of the 14 channels associated with FRS. On this type of radio, channels 8-14 are strictly license-free FRS channels. Transmitting on all channels above channel 14 requires a license. Transmitting on the shared FRS/GMRS channels 1-7 requires a license, if using more than one half watt. It is the responsibility of the radio user to read and understand all applicable rules and regulations regarding GMRS. These hybrid radios are often referred to as "bubble pack" radios, since they are often packed in a plastic shell, for hanging on a display shelf. The massive sales of these radios have led to a term known as "bubble-pack pirates
Pirate radio
Pirate radio is illegal or unregulated radio transmission. The term is most commonly used to describe illegal broadcasting for entertainment or political purposes, but is also sometimes used for illegal two-way radio operation...
", persons who use GMRS without a license.
The FCC rules for use of hybrid radios on channels 1-7 require licensing only when operating under the rules that apply to the GMRS. Many hybrid radios have an ERP that is lower than one half watt on channels 1-7, or can be set by the user to operate at low power on these channels. This allows hybrid radios to be used under the license free FRS rules if the ERP is less than one half watt and the unit is certified for FRS operation. Only two makers of hybrid FRS/GMRS radios (Garmin and Motorola) presently sell radios that will operate on the GMRS repeater channels; the common "22 channel" radios cannot be used with GMRS repeaters. The Icom IC-F21GM is a solely-GMRS radio which will also work repeaters.
Hybrid packaging still contains the notice of the FCC licensing requirement. Estimates of the number of hybrid FRS/GMRS radios sold to date range from 20 to 50 million units or more. This is compared with approximately 80,000 active GMRS licensees (per the FCC database). Enforcement against individuals is rarely, if ever, attempted.
Frequency chart
The "Friendly Name" of a frequency is the portion of the frequency to the right of the decimal (the kHz portion).This first set of frequencies shows the split frequency pairs used in duplex operational mode, often used with repeaters. Simplex
Simplex communication
Simplex communication refers to communication that occurs in one direction only. Two definitions have arisen over time: a common definition, which is used in ANSI standard and elsewhere, and an ITU-T definition...
(same frequency for receiving and transmitting) mode only utilizes the lower set of frequencies.
All channels are used with narrow-band frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
.
| Name | Lower frequency (repeater output) (MHz) | Upper frequency (repeater input) (MHz) | Motorola convention | Icom F21-GM convention | Notes |
|---|---|---|---|---|---|
| "550" | 462.550 | 467.550 | Ch. 15 | Ch. 1 | |
| "575" | 462.575 | 467.575 | Ch. 16 | Ch. 2 | |
| "600" | 462.600 | 467.600 | Ch. 17 | Ch. 3 | |
| "625" | 462.625 | 467.625 | Ch. 18 | Ch. 4 | |
| "650" | 462.650 | 467.650 | Ch. 19 | Ch. 5 | Use not permitted near the Canadian border. |
| "675" | 462.675 | 467.675 | Ch. 20 | Ch. 6 | Suggested nationwide emergency and road information calling. Nationally recognized coded squelch for 675 emergency repeater operation is 141.3 Hz. |
| "700" | 462.700 | 467.700 | Ch. 21 | Ch. 7 | Use not permitted near the Canadian border. |
| "725" | 462.725 | 467.725 | Ch. 22 | Ch. 8 |
This second set of frequencies shows the interstitial ranges shared with the Family Radio Service
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
services. These frequencies can only be used for simplex operations.
| Name | Frequency (MHz) | Motorola convention | Icom F21-GM convention | Notes |
|---|---|---|---|---|
| "5625" or "FRS 1" | 462.5625 | Ch. 1 | Ch. 9 | |
| "5875" or "FRS 2" | 462.5875 | Ch. 2 | Ch. 10 | |
| "6125" or "FRS 3" | 462.6125 | Ch. 3 | Ch. 11 | |
| "6375" or "FRS 4" | 462.6375 | Ch. 4 | Ch. 12 | |
| "6625" or "FRS 5" | 462.6625 | Ch. 5 | Ch. 13 | |
| "6875" or "FRS 6" | 462.6875 | Ch. 6 | Ch. 14 | |
| "7125" or "FRS 7" | 462.7125 | Ch. 7 | Ch. 15 |
History
The predecessor to GMRS was named Class A Citizens Radio Service when it was rolled out in the 1960s. Tube type transceivers were used, and transmitter power was limited to 60 watts (plate input power to the final amplifier tube). The original service ran wideband FM with ±15 kHz transmitter deviation and 50 kHz channel spacing. At the time, this was the norm for all U.S. land mobile services. There was also a Class B Citizens Radio Service which used a different set of 461 MHz channels and was limited to 5 watts output. Business users were permitted to license in this radio service. Radios were built by consumer electronics firms and commercial two-way radio vendors.In the 1960s, the UHF 450-470 MHz band was re-allocated to 25 kHz channels. This meant transmitter deviation was reduced to ±5 kHz. This doubled the number of channels available across the entire 450-470 MHz band. Class B Citizens Radio Service channels were re-allocated to other radio services.
In the 1970s, allowed power was again changed to 50 watts across the output terminals of the transmitter. In 1987, licensing of business users was discontinued and businesses were allowed to continue operating until their licenses expired. There was congestion on all channels in larger metropolitan statistical areas and moving businesses to Business Radio Service
Business band
The business band is the name used by US radio users and scanner hobbyists who listen to Federal Communications Commission licensees using Industrial/Business pool frequencies...
channels would provide some relief. The radio service was changed to its present name.
Use of GMRS equipment in other countries
The use of radio transmitters is regulated by national laws and international agreements. Often radio equipment accepted for use in one part of the world may not be operated in other parts due to conflicts with frequency assignments and technical standards. Some of the roles that the licensed GMRS service fills in the United States are, in other countries, filled by unlicensed or class-licensed services. Generally these services have strict technical standards for equipment to prevent interference with licensed transmitters and systems.In Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, hand-held GMRS radios up to 2 watts have been approved for use without a license since September 2004. Typically these are dual FRS and GMRS units, with fixed antennas, and operating at 2 watts on some GMRS channels and 0.5 watts on the FRS-only channels. Mobile units (permanently mounted in vehicles), base station
Base station
The term base station can be used in the context of land surveying and wireless communications.- Land surveying :In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS...
s and repeater
Radio repeater
A radio repeater is a combination of a radio receiver and a radio transmitter that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. This article refers to professional, commercial, and...
s are not currently permitted on the GMRS channels in Canada.
Other countries have licensed and unlicensed personal radio services with somewhat similar characteristics, but technical details and operating conditions vary according to national rules. Many European countries use a similar 8 channel system near 446 MHz known as PMR446
PMR446
PMR446 is a part of the UHF radio frequency range that is open without licensing for personal usage in most countries of the European Union. It has roughly the same use as FRS or GMRS in the United States and Canada. Depending on surrounding terrain range can vary from a few hundred metres to a...
. GMRS equipment that is approved for use in the United States will not communicate with PMR446 radios, and generally will not be approved for operation in other countries.