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General Mobile Radio Service



  The General Mobile Radio Service (GMRS) is a land-mobile UHF radio service in the United States available for short-distance two-way communications to facilitate the activities of an adult individual who possesses a valid GMRS license, as well his or her immediate family members, including a spouse, children, parents, grandparents, aunts, uncles, nephews, nieces, and in-laws (47 CFR 95.179). 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, may not use this service.

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 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, but are higher quality.

Other countries have 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 446MHz known as PMR446

Additional recommended knowledge

Contents

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. No exam is required. Prior to July 31, 1987, the FCC issued GMRS licenses to non-individuals (corporations, partnerships, government entities, etc). These licensees are grandfathered in and may renew their existing licenses, but no new GMRS licenses are being issued to non-individuals, nor may existing non-individual licensees make major modifications to their licenses.[1]

Although the introductory paragraph (as taken from the FCC website) would seem to exclude communications with others that are not part of one's immediate family, the license actually 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 for GMRS state: "A GMRS license authorizes a GMRS station to transmit messages to other GMRS stations at any geographical location within or over the territorial limits of any area where radio services are regulated by the FCC". This means that GMRS licensees are also allowed to communicate with other licensees in the wider GMRS community. Further, the FCC has clarified that GMRS licensees are allowed to communicate with FRS users on those frequencies that are shared between the two services. The issue here is that 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.

Interstitial Frequencies

There are 7 "interstitial" channels shared with Family Radio Service, and 8 channels exclusively for GMRS. The GMRS-only channels are defined in pairs, with one frequency in the 462 MHz range for simplex and repeater outputs, and another frequency 5 MHz higher for repeater inputs. GMRS use requires an FCC license in the US, and licensees are permitted to transmit at up to 50 watts on GMRS frequencies (although 1 to 4 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), but at the lower 5 watt maximum power output, for a total of 15 channels. FRS channels 8 through 14 are not available for GMRS use; use of these frequencies requires an FRS transceiver.[2]

Recently, hybrid FRS/GMRS consumer radios have been introduced that have 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, and transmitting on the shared FRS/GMRS channels 1-7 also requires a license, IF the effective radiated power is greater than 500 milliwatts (1/2 watt). It is the responsibility of the radio user to read and understand all applicable rules and regulations regarding GMRS. The FCC rules and statements regarding the use of hybrid radios on channels 1-7 addresses the need for GMRS licensing only when operating under the rules that apply to the GMRS. Many hybrid radios have an ERP that is lower than 1/2 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 1/2 watt AND the unit is certified for FRS operation on those frequencies. Only one maker of hybrid FRS/GMRS radios (Garmin) presently sells radios that will operate on the GMRS repeater channels; the common "22 channel" radios cannot be used with GMRS repeaters.

The requirement for GMRS licensing in the USA is ignored by the vast majority of users of these frequencies. 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 has led to a lot of consternation among the "non-blister-pack" segment of the GMRS user population, who have significantly more expensive equipment, and have paid $85 for a license. (GMRS and FRS/GMRS radios are often sold in "blister packs" at electronic stores with the required application form for a license included among the warranty cards and safety notices.) Online communities such as GMRS Radio Information and Forums and Popular Wireless Magazines are encouraging GMRS enforcement.

Frequency Chart

The "Friendly Name" of a frequency is the portion of the frequency to the right of the decimal.

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 Freq' values.

Name Lower Frequency (MHz) Upper Frequency Motorola convention Icom F21-GM convention Notes
"550" 462.550467.550 Ch. 15 Ch. 1
"575" 462.575467.575 Ch. 16 Ch. 2
"600" 462.600467.600 Ch. 17 Ch. 3
"625" 462.625467.625 Ch. 18 Ch. 4
"650" 462.650467.650 Ch. 19 Ch. 5 Use not permitted near the Canadian border.
"675" 462.675467.675 Ch. 20 Ch. 6 Nationwide emergency and road information calling. Nationally recognized coded squelch for 675 emergency repeater operation is 141.3 Hz.
"700" 462.700467.700 Ch. 21 Ch. 7 Use not permitted near the Canadian border.
"725" 462.725467.725 Ch. 22 Ch. 8

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.

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

Note: The Personal Radio Steering Group (PRSG) and Popular Wireless Magazines adopted CTCSS 141.3 Hz as the national travel tone for use on all GMRS channels. It is not known how many GMRS licensees have adopted the standard. You can make the travel tone system work by setting one or more of your base-station frequencies to the 141.3 Hz tone.

Some groups have been pushing FRS channel 1 as an emergency/calling channel. FRS radios operate with very little power.

History

GMRS, General Mobile Radio Service, was originally named Class A Citizens Radio Service when it was rolled out in the 1960s. Tube type transceivers were used and output 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 ordered reallocated 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 the 1980s, 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. Repeaters began to proliferate in the 1980s after the prevalence of unlicensed operations in the Class D Citizens Band made HF CB radios unusable in many applications.

GMRS in Canada

In Canada, hand-held GMRS radios up to 2 watts have been approved for use since September 2004. Typically these are dual FRS and GMRS units, with fixed antennas, and operating at 2 watts on GMRS and 0.5 watts on the FRS-only channels. A license is not required in Canada for operation at 2 watts on the GMRS channels. Mobile units (permanently mounted in vehicles), base stations and repeaters are not currently permitted on the GMRS channels in Canada.


See also

Notes

  1. ^ http://wireless.fcc.gov/services/index.htm?job=licensing_1&id=general_mobile
  2. ^ GMRS Rules
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "General_Mobile_Radio_Service". A list of authors is available in Wikipedia.
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