THE HISTORY OF CAR RADIO
In 1901, the MARCONI COMPANY in England installed A Mobile Wireless Telegraph Station, on one of the first steam engine vehicles. The purpose of this experiment was short range mobile communication for military applications. The wireless telegraph on those days was based on spark-gap transmitters operating on long waves (low frequencies) and it was necessary to use a very long wire antenna. Marconi tried to reduce the dimensions of the antenna and designed an antenna made of a large diameter metal cylinder vertically mounted on the vehicle roof. The results of these experiments enabled transmission of telegraph messages at ranges of up to 30 kilometers.
During world War one, the British Army installed Mobile Wireless Telegraph Apparatus of 1,500 Watts on wagons. The front wagon included a MARCONI spark-gap transmitter-receiver. The rear wagon included the storage batteries and it was possible to move it to the generator wagon for charging the batteries. England supplied these Wireless Telegraph Wagons to the allied countries during world war one.
One of the pioneers that operated a radio-telephone on car was Alfred Grebe from Long Island, N.Y. In 1907, at the age of 12 he constructed and operated crystal and later on vacuum tube receivers. In 1919, he constructed a radio-telephone transmitter-receiver that operated on the 2 MHZ band (150m) that was allocated for Radio Amateurs and experimenters. The receiver was a TRF (Tuned Radio Frequency) type. Alfred Grebe installed the equipment on his car for radio communication experiments. The filament voltage for the tubes was supplied from the battery and the high voltage from a dynamotor. The antenna was made of a frame with six wires.
Alfred Grebe’s article about the process of construction and installation of his mobile radio telephone, was published in the August 1919 issue of “Radio Amateur News” magazine. In this article, he forecasted that radio communication will be used on aircrafts and to very far locations, unreachable by telephone lines. At that time, Alfred owned a company named A.H. Grebe that produced equipment for radio amateurs. In the coming years, A.H. Grebe produced high quality home TRF radios.
In 1920 the British Army equipped three wheels “Douglas” motorcycles with Marconi B1 Mk2 portable wireless telegraph transmitter-receiver sets. The B1 Mk2 sets were originally intended for mounting on Mules and horses.
The first experiments with radio receivers on cars started in 1921 by hobbyists, when the first public broadcast stations started to operate in the USA. In those days, the radio receivers operated by dry batteries. The hobbyists installed the home radio set with the batteries on the car, but there was a problem with the antenna. The home radio operated with a long wire antenna, so the hobbyists used a multi-turn Spiral antenna on the car roof.
1922 – George Frost of the Chicago Radio Club installed a radio receiver on a FORD Model T car. In England a MARCONI 8 receiver was installed on “Daimler Light 30” car with a large frame antenna on the roof. In the USA, it is possible to purchase a “Chevrolet” car with a “Westinghouse” radio with the additional cost of 200 dollars.
1923 – The Daimler Company in England installed Marconi-Phone 8 radios on part of the cars, at a price increase of one third of the car value. This optional radio was cancelled later on due to the very high cost.
1924 – A mobile radio-telephone set of Bell Laboratories was installed on a car with a rotary loop antenna (see the picture).
1926 – A patent was granted to Mr. William Heina for car radios and he established a new company named HEINAPHONE.
1927 – Mr. Russell Feldman in the USA established the Automobile Radio Corporation – ARC and started to produce car radios under the brand name TRANSTONE. ARC acquired the HEINAPHONE Company, which was the car radio patent rights owners.
1930 – ARC was acquired by PHILCO (a leading manufacturer of car batteries) and became the owners of the car radio patent rights. Philco became the first mass-production manufacturer of car radios in the USA, using the TRANSITONE brand during the coming years.
Silver-Marshall Auto 770 (1929) Transitone (1930) Crosley Romaio 91 (1931)
The triode tubes that have been used in the 1920’s operated with a filament voltage of 2.5 and 5.0 volts and high voltage of 45-135 Volts from dry batteries. The audio output of these tubes was quite low. Higher audio power was necessary to overcome the engine and road noises in car radios. New vacuum tubes have been developed for operation on 6.3 Volts from the 6 volts car battery. The high voltage was obtained from a dynamotor or vibrator-transformer circuit that supplied more than 200 volts.
1929 – The manager of WGN radio station in Chicago proposed to the Chicago Police the idea of transmitting announcements by the WGN station to the police patrol and detective cars. The Chicago Police accepted the proposal and it was decided to start with an experimental operation. Eight police cars were equipped by WGN with Sparks-Withington Model AR-50 radio receivers.
The current broadcast of WGN was interrupted when an announcement came from the police and it was transmitted from the WGN studio. The police cars with radio receivers reacted and arrived to the scene immediately. Chicago Police was very satisfied of the results and asked the city council to approve a budget for equipping a large number of police cars with radio receivers. The budget was approved and three police broadcasting stations operated on special police frequencies. Until the end of 1930, 96 police cars have been equipped with radio receivers. This one-way communication system was in use for a long time until 1939, when and the Chicago Police changed it to a two-way radio system.
1930 - Galvin Manufacturing Corp. started to market a car radio Model 5T71 that they developed. Galvin used the brand name MOTOROLA for their car radios, combining the word MOTOR with the very popular ending OLA, that was used with many products at that time. The MOTOROLA brand car radios became very popular in the USA, so Galvin Mfg. Corp. decided to change its name to Motorola. Since then Motorola continued to develop and became one of the world’s leading mobile radio communications companies.
GALVIN 5T71
The car radios in the 1920’s were TRF (Tuned Radio Frequency) types, which required tuning of 1-3 knobs for best reception. In the 1930’s the Super-Heterodyne circuit enabled stations tuning with only one knob. Until the end of the 1930’s, the car radio was made of two parts. The main unit was mounted on the floor beneath the dashboard. A small control unit was mounted on the dashboard. With the development of smaller vacuum tubes, the dimensions of the car radio were reduced enabling to mount it inside the dashboard. Push-Buttons were added to the front panel to select stations easily while driving. The variable tuning condenser was replaced with slug-tuned coils, to improve the frequency stability.
In 1939 the Sylvania Company developed new line of LOCKTAL vacuum tubes with locking socket, for mobile car applications. European manufacturers developed their own versions of the LOCKTAL tubes. When the car battery voltage was changed to 12 Volts, new versions of vacuum tubes have been added with 12.6 Volts filament.
Vacuum tubes have been used in car radios until the mid 1960’s, when the new transistors and specially the Silicon Transistors became the building blocks in all the electronic products. The dimensions of the transistorized car radios became much smaller, enabling to be mounted on any car dashboard. The car radio continued to be developed and the FM band was added to the AM band. 8-Track magnetic tape cassette players have been included in the new models. At the end of the 1960’s the PHILIPS Compact-Cassette replaced the 8-Track Cassette. The magnetic tape cassette era came to its end with the CD – Compact Disc. In the 2010’s, a computerized entertainment system is installed on the car dashboard with wireless connectivity to the Mobile Smart-Phone, with all the various applications.
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