Use these high powered radios in places wheremobile phones just don’t cut it.
FRS and GMRS: Super Walkie-Talkies Use these high powered radios in places where mobile phones just don't cut it. In the last couple of years, a number of. Considered the first 'walkie talkie', these devices weighed roughly 25 pounds and had a 5-mile range. They were widely used for infantry battalion and company intercommunication during World War II. Next came the SCR-300 radio transceiver, developed for the U.S. Military by Motorola. This time a portable FM radio, it weighed anywhere from 32 to.
In thelast couple of years, a number of manufacturers have come out with“highpower” radios for general use, marketed as family orrecreational communication devices and sold as impulse buy items atdepartment stores. They claim a couple of milesrange, operate on a chargeablebattery pack or AA batteries, and most are surprisingly rugged andsimple to use.
The two technologies behind these popular radios are
FRS
and GMRS
. While sold insimilar packaging and frequently sitting on shelves right next toeach other, these two types of radios are quite different incapabilities and operating rules.FRS stands for Family RadioService, and was approved by the FCC forunlicensed use in 1996. It operates around 462 and 467 MHz, and issometimes referred to as 'UHF CitizensBand.” It is not a Part 15device like 802.11 radios, but is governed by FCC Part 95,
Personal RadioServices
. FRS radios share some channels withGMRS radios but are restricted to 500mW maximumpower. Manufacturers typically claimtwo miles as the maximumrange of FRS radios. FRS radios comewith fixed antennas, and cannot be legally modified to accommodateantennas or amplifiers.FRS channels 1 through 7 overlap with GMRS and can be used tocommunicate with GMRS radios. If you need to talk only to other FRSradios, use channels 8 through 14 to avoid possible interference withlow band GMRS users. See Table 1-1 for the fulllist of FRS and GMRS frequencies.
GMRSstands for
General Mobile Radio Service
, and isalso known as “Class A Citizens Band.” Itsuse is also covered by FCC Part 95, but requires a license tooperate. As of this writing, a personal license costs $75 and can beobtained online athttp://wireless.fcc.gov/uls/.Handheld GMRS units can put out up to 5 Watts ofpower, although 4-Watthandheldsare more common. While fixed-base stations can use up to 15 Watts onmost frequencies, they are restricted to 5 Watts when communicatingon the FRS channels. Repeater stations are allowed and cantransmit as high as 50 Watts. Both fixed-base stations and repeaters canonly transmit on the lower “462”frequencies, while handhelds can operateon any GMRS frequency. Again, see Table 1-1 forthe full list of FRS and GMRS frequencies. GMRS gear can includeremovable antennas, making it simple to use a handheld with a carmount or stationary antenna. Combined with the ability to userepeaters, GMRS can be used to communicate over considerabledistances.
Table 1-1. FRS and GMRS frequencies
Lower frequency | Upper frequency | Purpose |
---|---|---|
462.550 | 467.550 | GMRS “550” |
462.5625 | -- | FRS channel 1, GMRS “5625” |
462.575 | 467.575 | GMRS “575” |
462.5875 | -- | FRS channel 2, GMRS “5875” |
462.600 | 467.600 | GMRS “600” |
462.6125 | -- | FRS channel 3, GMRS “6125” |
462.625 | 467.625 | GMRS “625” |
462.6375 | -- | FRS channel 4, GMRS “6375” |
462.650 | 467.650 | GMRS “650” |
462.6625 | -- | FRS channel 5, GMRS “6625” |
462.675 | 467.675 | GMRS “675” |
462.6875 | -- | FRS channel 6, GMRS “6875” |
462.700 | 467.700 | GMRS “700” |
462.7125 | -- | FRS channel 7, GMRS “7125” |
462.725 | 467.725 | GMRS “725” |
467.5625 | -- | FRS channel 8 |
467.5875 | -- | FRS channel 9 |
467.6125 | -- | FRS channel 10 |
467.6375 | -- | FRS channel 11 |
467.6625 | -- | FRS channel 12 |
467.6875 | -- | FRS channel 13 |
467.7125 | -- | FRS channel 14 |
Typically, handheld GMRS units use lower frequencies to communicatewith each other when possible, and transmit on the upper frequencies(while listening 5 MHz lower) to talk to a repeater. This allowsanyone listening on the “462” sideto hear traffic both from handhelds as well as from anyone using therepeater. Always use the lower frequencies and the lowest powersettings whenever possible to help avoid unnecessaryinterference with other GMRS users. Userepeaters only when you can’t otherwise establishcommunications.
While higher power radioscan help extend your range a little, the best method for increasingyour range is to increase your altitude. UHF radios can reachsignificantly further when the antenna is high in the air, even withlimited power. This is one reason why the Part 95rules limit “small controlstations” to antennas no more than 20 feet higherthan the structure to which they are mounted. To make the best use ofyour FRS or GMRS radio, find high ground when transmitting. In somecases, this can push your available range out many, many miles. Ifyou are using a GMRS radio, attaching it to a tall antenna cansignificantly improve your effective range.
While these radios are half duplex and allow only limited datatransmissions, they are handy in a number of situations. For example,when fine tuning a long distance point-to-point 802.11 link, you mayfind them far more useful than mobile phones. Any time you areworking far away from a city, particularly on hills and mountains,FRS and GMRS radios can work considerably better than a phone. Butdon’t get any bright ideas about connecting a radioto a telephone patch; this is prohibited on both FRS and GMRS.
This writing is by no means authoritative on the labyrinthine FCCrulebook, but should give you an idea of what each technology is goodfor. If in doubt, see the rules for yourself online at http://www.access.gpo.gov/nara/cfr/waisidx_00/47cfr95_00.html.If you are looking for more information about FRS and GMRS, there isalso a wealth of information available from the Personal RadioSteering Group at http://www.provide.net/~prsg/rules.htm.
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