GMR And FRS from Wikipedia 

The Family Radio Service (FRS) is an improved walkie talkie system authorized in the United States since 1996. This personal radio service uses frequencies in the ultra high frequency (UHF) band, and so does not suffer the interference effects found on citizens' band (CB) at 27 MHz, or the 49 MHz band also used by cordless phones, toys, and baby monitors. FRS uses frequency modulation (FM) instead of amplitude modulation (AM), and has a greater reliable range than license-free radios operating in the CB or 49 MHz bands.

Initially proposed by Radio Shack in 1994 for use by families, FRS has also seen significant adoption by business interests, as an unlicensed, low-cost alternative to the business band.

FRS radios are limited to 500 milliwatts in the U.S., according to FCC regulations. Channels 1 to 7 are shared with GMRS, the General Mobile Radio Service. A license is required for those channels only if the power output is over FRS limits, up to GMRS limits. Unlike Citizens' Band (CB) radios, FRS radios frequently have provisions for using sub-audible tone squelch (CTCSS) codes, filtering out unwanted chatter from other users on the same frequency. Though these codes are sometimes called "privacy codes", they offer no protection from eavesdropping and are only intended to help share busy channels.

The use of repeaters and interconnects to the telephone network are prohibited, unlike in GMRS. FRS radios must use only permanently-attached antennas, which restricts the range of communication but also limits interference to other users.

FRS manufacturers generally claim an effective range of 3 km (2 miles), but actual performance varies widely. The presence of large metal buildings can reduce range, but hobbyists have found that under exceptional conditions, like hill-top to hill-top, communication is possible over 50 km (30 miles) or more. Under normal conditions, FRS generally has an effective range of approximately 1.5 km (1 mile).

Recently, the personal electronics industry has begun producing 22-channel FRS/GMRS hybrid radios. Use of the GMRS channels on such radios requires a license from the FCC.

FRS radios are limited to 500 milliwatts in the U.S., according to FCC regulations. Channels 1 to 7 are shared with GMRS, the General Mobile Radio Service. A license is required for those channels only if the power output is over FRS limits, up to GMRS limits. Unlike Citizens' Band (CB) radios, FRS radios frequently have provisions for using sub-audible tone squelch (CTCSS) codes, filtering out unwanted chatter from other users on the same frequency. Though these codes are sometimes called "privacy codes", they offer no protection from eavesdropping and are only intended to help share busy channels.

The use of repeaters and interconnects to the telephone network are prohibited, unlike in GMRS. FRS radios must use only permanently-attached antennas, which restricts the range of communication but also limits interference to other users.

FRS manufacturers generally claim an effective range of 3 km (2 miles), but actual performance varies widely. The presence of large metal buildings can reduce range, but hobbyists have found that under exceptional conditions, like hill-top to hill-top, communication is possible over 50 km (30 miles) or more. Under normal conditions, FRS generally has an effective range of approximately 1.5 km (1 mile).

Recently, the personal electronics industry has begun producing 22-channel FRS/GMRS hybrid radios. Use of the GMRS channels on such radios requires a license from the FCC.

GMRS

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 over the general area of their residence or during recreational group outings, such as camping or hiking.

GMRS radios are typically handheld portable devices much like Family Radio Servicewalkie talkies typically found in discount electronics stores, but are higher quality. (FRS) radios, and share some frequencies. 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

Other countries have personal radio services with somewhat similar characteristics, but technical details and operating conditions vary according to national rules.

There are 7 "interstitial" channels shared with Family Radio Service, and 8 channels exclusively for GMRS. GMRS use requires an FCC license in the US, and licensees are permitted to transmit at up to 50 watts on GMRS frequencies (1 to 4 is more common), as well as have detachable antennas. GMRS licensees are also able to use the first 7 FRS frequencies (the "interstitial" frequencies), but at the lower 5 watt maximum power output, for a total of 15 channels. Radios programmed for GMRS may also use repeater systems. FRS channels 8 through 14 are not available for GMRS use; use of these frequencies requires an FRS transceiver. http://www.provide.net/~prsg/part95ae.htm

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, only 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, as is the usual case, the effective radiated power of the radio 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 requirement for GMRS licensing in the USA is not followed by many users of these frequencies. Nonetheless, there are over 80,000 GMRS licensees. Reports of GMRS enforcement are encouraging. However, enforcement against individuals is rare, if ever attempted. This has led to a lot of consternation among the "non-bubble-pack" segment of the GMRS user population, who have significantly more expensive equipment, and have paid approximately $80 for a license. Online communities such as www.gmrs.net.tc and http://www.popularwireless.com are working to solve this problem by encouraging GMRS enforcement.

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 unlicenced operations in the Class D Citizens Band made HF CB radios unusable in many applications.

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 licence 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.

The Multi-Use Radio Service (MURS) is a small two-way radio service consisting of five frequencies in the VHF spectrum. Established by the U.S. Federal Communications Commission in the fall of 2000, MURS created a radio service allowing for unlicensed operation, with a power limit of 2 watts, four times that of FRS radio. In the fall of 2002, the FCC further amended the MURS rules; these rule modifications included changing the 2 watt transmitter power limitation to be based on Transmitter Power Output (TPO), rather than Effective Radiated Power (ERP), so there is no longer an ERP limit with MURS, and external gain antennas may be utilized. The FCC formally defines MURS as "a private, two-way, short-distance voice or data communications service for personal or business activities of the general public."

MURS comprises the following five frequencies

• 151.820 MHz
• 151.880 MHz
• 151.940 MHz
• 154.570 MHz (also part of the business band)
• 154.600 MHz (also part of the business band)