User:Houshfan84

The Walkie Talkie'

A walkie talkie, also known as a handie-talkie or a two-way is a device that passes short bursts of radio waves over a given channel from one location to the next. Unlike dispatch radio which only allows someone to speak with a central operator, a two way radio allows two parties over some distance to converse directly with one another. Even things like cellular phones or mobile phones may be considered two way radios; however they operate on multiple radio channels, while two-ways only operate on one.

History

Wireless Communication

Prior Inventions

The invention of the walkie-talkie is preceded by the discovery of radio and the invention of wireless communication. The invention of wireless communication was made by Guglielmo Marconi. Born in Italy in 1874 to a Catholic father and a Protestant mother, he had an interest in science from an early age. He attended the University of Bologna and studied electro-magnetics before becoming interested in radio. He wanted to create a device which would allow ships to communicate with shores without wires. He built a team of accredited scientists and electricians to help him with the project. Beginning in the 1890’s he was able to send bursts of radio 100 yards and was gradually increasing the distance. By 1897 he was sending signals across the English Channel; in December of 1901 he and his team sent the first transatlantic signal from Canada to Britain. Although he could only send Morse code, his system was then used for ships crossing the Atlantic, including the H.M.S. Titanic. However credit for the device is often also given to his coworker Nikola Tesla, because he and Marconi battled for the patent. In the end the United States Supreme Court granted Tesla the patent over Marconi in 1943, but not before Marconi had made his own company and a rather large profit. [[1]]

Reginald Fessenden

One of the biggest steps in this journey was made by Reginald Fessenden who worked began working with radio in 1897, and also taught Marconi. He invented the receiver in 1900, which allowed machines to better receive incoming radio waves and also expanded the distance within which these machines could communicate. He also designed the first wireless telephone but at first could only send Morse code. Later he improved his designs which soon allowed voices to be transmitted. He sent the first voice transmission on December 24, 1906 on a device known as a “radio telephone.” He also sent the first two way telegraph across the Atlantic from Scotland.

Two Way Radio

In 1933 an American inventor named Frank Gunther invented a two way dispatch radio for use in police cars in Bayonne, New Jersey. Unlike what would soon become the walkie-talkie these devices required an operator to send messages out to other receivers. While these receivers could talk to the operator they could not talk to each other. Also these devices were mounted in cars, and could not yet be carried around easily.

The Walkie-Talkie

Al Gross

Therefore the next step was to make wireless communication like this portable and usable without an operator. However the invention of the portable two-way is generally credited with the American inventor Al Gross. (There are some claims that a Canadian named Donald Hings may have also invented it, but it is more probable that he just developed a different kind a few years later. There is little conclusive evidence showing him as the inventor of the walkie-talkie. Alfred Gross was born on February 22, 1918 in Toronto, Canada. He and his family moved to Cleveland, Ohio not long after his birth. When he was nine, he and his family took a trip on Lake Erie. He was amazed by the ship’s radios and asked the captain to explain how they worked. What started as curiosity seemed to develop into a lifelong pursuit. By the time he was 16, he had reportedly built a radio station, called W8PAL, in his basement using materials from the local junkyard.

During the War

By 1936 Gross had a strong interest in radio, especially operating it above 100 megahertz. He attended what is now Case Western Reserve University in 1938, and created his first portable two way device. He attracted the attention of the Office of Strategic Services, the forerunner of the CIA. They recruited him to help build new technologies for the troops in World War II. In 1941 he had created air to ground two way radios, named Joan and Eleanor, although he had already made ground to ground radios by 1938. He received the patent for the design in 1939. (Daniel Hings received one in 1942.) The elements of Gross’ design were considered classified by the U.S. government until 1975-76. Despite the long time kept under wraps, Gross was unable to make any real money from his designs because he failed to see the usefulness of his inventions. Therefore he did not renew his patents before the U. S. released his work. He is also credited with creating the first cellular phone and the first pager, but did not renew the patents on these inventions either.

The Industry

The First Companies

Gross created his own company Gross Electric Inc. to make two ways for private use. It was during this time that he invented things like pagers, and laid out plans for cellular and cordless phones. Afterwards, Motorola, first owned by the Galvin Manufacturing Company, became one of the first companies to begin mass producing two way radios. They manufactured their first two-way, known as the Motorola SCR-536. Like most early radios, it ran on AM frequency before being officially switched over to FM. The FM frequency allowed for quieter transmissions. Motorola then produced the SCR-300 which was the first portable two-way that operated exclusively on FM. The radios were strapped to the backs of soldiers during World War II and supposedly weighed around 35 pounds. 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.

Handie-Talkies

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. 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.

Developments

The first radios did not transmit beyond twenty to twenty five feet. By 1958, Motorola was producing two way radios for cars. Other companies began moving into the field and each strived to make the radios smaller with longer ranges. Now, 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.

How It Works

Basics

The basic explanation of how a Walkie-talkie works begins with one person sending a message encoded in short bursts of radio across radio waves. The receiver receives the message and sends one back over the same channel. This differentiates two-way radio from dispatching. Dispatch radios operate on multiple channels, where as walkie-talkies and other two-ways only operate on one. This is partially because of the lack of available radio frequencies. Two-way radios are similar to some types of radio in the fact that they can use a packet system to transmit and receive information. One person sends out signals from a transmitter; those signals are then relayed from a satellite to a radio control which is often controlled by a central computer system. The radio control then sends out tiny packets of radio to different terminals (receivers.) This is how dispatch radio works. In dispatch however, individuals can only communicate with a central operator sitting at the main radio control who then sends messages back out to the radios. Two-ways cut out the middleman.

The Components

Most Walkie Talkies are made up of six components. They have a transmitter which sends out the message, and a receiver which picks up the message from another radio. The next part is a speaker which relays the message received so that it can be heard. Next, there is a microphone which converts the voice of a person into radio waves which can be sent by the transmitter. The radios also contain a crystal, which helps to set up the channel that the radio operates on. Lastly, like most other radio sources, the walkie talkie must have a power source. Today, that is usually a battery. In modern walkie-talkies, 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.

Its Uses

Radio was originally used between ships and command centers on land to discuss docking times, location or distress signals. Radio signals were also used by the United States Armed Forces as a way to signal disasters out at sea. The Army was first, installing signals in New York by 1899, and was followed by the Navy which began using wireless telegraph transmitters in 1901. Early telegraph transmitters encountered a lot of interference, leading to the inventions of alternators and special vacuum tubes (made by the American inventor Lee Deforest around 1902, who was also incidentally, coined as the first person to use the word radio) which counteracted these problems. Wireless telegraphy then expanded rapidly, leading to telegraphic messages from places as remote as the South Pole. The first transpacific message was sent in 1910. After Marconi, the development of dispatch radio allowed that type of radio to be used in taxicabs, trucks and police cars. The original two way radios, however, were used to coordinate attacks and pass information about surveillance and positions quickly between command centers and troops.

Walkie Talkies Today

Today the two way radio is still widely used in the armed forces, and has even brought about its own lingo, including phrases like: “out,” “roger that,” and “over.” (These mean, “I am done with the communication,” “I understand,” and “I am done talking and awaiting a reply,” respectively. Incidentally it is a common mistake for individuals to use the phrase “over and out,” which really means I am waiting for a reply even though I am done with this communication.) Also thanks to companies like Motorola and Nextel the walkie talkie has been used commercially by civilians, often as a feature of their cellular phones. The personal walkie-talkie has become popular also because of 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. These types of radios are often used between families and friends when going on outings, and also by police officers, doctors, security guards, and other professionals. Today the walkie-talkie allows for short and cheap communication that is considered easy to handle and easy to use.

Text Sources

Dunlap, Orrin E., Jr. Marconi: The man and his wireless. Arno Press., New York: 1971

Harlow, Alvin F. Old Waves and New Wires: The History of the Telegraph, Telephone, and Wireless. Appleton-Century Co., New York: 1936

Herrick, Clyde N. Radio: Theory and Servicing. Reston Publishing Company, Inc., Viriginia 1975

Martin, James. Future Developments in Telecommunications 2nd Ed., Prentice Hall Inc., New Jersey: 1977

Martin, James. The Wired Society. Prentice Hall Inc., New Jersey: 1978

Websites

http://inventors.about.com/od/rstartinventions/a/radio.htm

http://www.motorola.com/content.jsp

http://nobelprize.org/nobel_prizes/physics

http://web.mit.edu/invent/a-winners/a-gross.html

http://www.pbs.org/wgbh/aso/databank/entries/btfore.html

http://www.retrocom.com