Walkie-talkie

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Recreational, toy and amateur radio walkie talkies

A Picture of two Walkie Talkies.

A walkie-talkie is a hand-held portable, two-way radio transceiver. The first walkie-talkies were developed for military use. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen) and a push-to-talk switch that starts transmission. Typical walkie-talkies resemble a telephone handset, possibly slightly larger but still a single unit, with an antenna sticking out of the top. Where a phone's earpiece is only loud enough to be heard by the user, a walkie-talkie's built-in speaker can be heard by the user and those in his immediate vicinity. Hand-held transceivers may be used to communicate between each other, or to vehicle-mounted or base stations.

1 History
2 Uses
3 See also
4 External links

[edit] History

The first radio receiver/transmitter to be nick-named "Walkie-Talkie" was the backpacked Motorola SCR-300, created by an engineering team in 1940 at the Galvin Manufacturing Company (fore-runner of Motorola). The team consisted of Dan Noble, who conceived of the design using frequency modulation, Henryk Magnuski who was the principal RF engineer, Marion Bond, Lloyd Morris, and Bill Vogel.

Motorola also produced the hand-held AM SCR-536 radio during World War II, and it was called the "Handie-Talkie" (HT). The terms are often confused today, but the original walkie talkie referred to the back mounted model, while the handie talkie was the device which could be held entirely in the hand (but had vastly reduced performance). Both devices ran on vacuum tubes and used high voltage dry cell batteries. Handie-Talkie became a trademark of Motorola, Inc. on May 22, 1951. The application was filed with the U.S. Patent and Trademark Office,and the trademark registration number is 71560123.

Early Handie-Talkies had tubes and ran on 4, 45-volt dry cells or 12V Nickel-Cadmium batteries.

The abbreviation HT, derived from Motorola's "Handie Talkie" trademark, is commonly used to refer to portable handheld ham radios. Surplus Motorola Handie Talkies found their way into the hands of ham radio operators immediately following World War II. Motorola's public safety radios of the 1950s and 1960s, were loaned or donated to ham groups as part of the Civil Defense program. To avoid trademark infringement, other manufacturers use designations such as "Handie Transceiver" for their products.

Al Gross also worked on the early technology behind the walkie-talkie between 1934 and 1941, and is sometimes said to actually have invented it.

Canadian Donald L. Hings was formally decorated for the invention of the walkie-talkie and its significance to the war effort. Hing's model C-58 "Handy-Talkie" was in military service by 1942, following a secret R&D effort that began in 1940. The C-58 was in turn based on a civilian model originally developed by him in 1937.

[edit] Uses

Motorola HT1000 two-way radio

Hand-held transceivers became valuable communication tools for police, emergency services, and commercial and industrial uses (such as on a construction site), using frequencies assigned for these services. Walkie-talkies are also popular with some amateur radio operators, operating with an amateur radio license in several different frequency bands.

Since even a powerful commercial walkie-talkie is limited to a few watts of power output and a small antenna (the physical size of the package limits both battery capacity and antenna size), hand-held communication range is typically quite short, not exceeding the line-of-sight distance to the horizon in open areas, and very much less in built-up areas, within buildings, or underground. Many radio services permit the use of a repeater which is located at some high point within the desired coverage area. The repeater listens on one frequency and retransmits on another, so that reliable hand-held to hand-held unit range can be extended to a few score miles (kilometers) or further, using repeaters linked together.

Walkie-talkies for public safety, commercial and industrial uses may be part of trunked radio systems, which dynamically allocate radio channels for more efficient use of limited radio spectrum.

Low-power versions, exempt from licence requirements, are also popular children's toys. Prior to the change of CB radio from licensed to un-licensed status, the typical toy walkie-talkie available in retail stores in North America was limited to 100 milliwatts of power on transmit and the 27 MHz citizens' band channels using amplitude modulation (AM) only. Later toy walkie-talkies operated in the 49 MHz band, some with frequency modulation (FM), shared with cordless phones and baby monitors. The lowest cost devices are very crude electronically, may employ superregenerative receivers, and may lack even a volume control, but they may have elaborate packaging. Unlike more costly units, low-cost toy walkie-talkies may not have separate microphones and speakers; the receiver's speaker typically doubles as a microphone while in transmit mode.

The personal walkie-talkie has now become popular again with the new U.S. Family Radio Service (FRS) and similar unlicensed services in other countries. While FRS walkie-talkies are also sometimes used as toys because mass-production makes them low cost, they have proper superheterodyne receivers and are a useful communication tool for both business and personal use. Operation in the Family Radio Service is restricted to walkie talkies limited to 500 milliwatts of effective RF power. Some FRS models also include the surrounding General Mobile Radio Service (GMRS) channels, which require a license.