By George Misic View In Digital Edition
Radio technology was developed by Italian inventor Guglielmo Marconi in 1895. However, this technology was not officially implemented in vehicles until the 1930s with the Motorola: the first-ever car radio.
The AM radio was first seen in American cars in the 1920s. Early car radios used the AM frequency, allowing drivers to listen to classics like Louis Armstrong’s jazz or popular “Crooners” everywhere they went.
Vacuum tube radio from a 1950 Ford.
It started to become popular in the 1930s when most of the manufacturers of automobiles began to offer a built-in auto radio that was nicely integrated into the dashboard of the vehicle.
A circa-1930 brochure advertises a Motorola car radio. Courtesy of https://www.theglobeandmail.com.
Other suppliers offered less expensive ways to obtain an auto radio with alternatives to those sold by the car manufacturers. They offered both custom radios that fit into the dashboard like a factory radio and ones to mount under the dash that were more universal, less specialized, and frequently less expensive. Motorola became a big company by making excellent aftermarket automobile radios starting in the 1930s.
The first factory-supplied FM radio by a US automobile manufacturer was offered by the Lincoln Division of Ford Motor Company in 1957 for their 1958 Lincolns. Ford sold the FM tuner for other Ford products except for the Thunderbird because the dash extended to a center console that covered the transmission hump.
FM radios first appeared in the 1950s. Courtesy of https://www.theglobeandmail.com.
I’ve seen reports that General Motors supplied a fully transistorized AM-FM in-dash radio in the 1957-1958 premium Cadillac Eldorado Brougham, which sold for about $13,000 in 1957 dollars. It came with a stainless-steel roof and was the final step up from the Cadillac Eldorado Biarritz convertible and Eldorado Seville two-door hardtop.
The Eldorado Brougham did have an all-transistor radio mounted in the dash, but it was AM with no FM capability; 1956 (when the design was done) was a bit early for transistorized AM-FM radios due to the need to operate at 108 MHz for good stability and sensitivity.
1950 Ford Radio, original six volt.
The 1958 Lincoln FM radio was configured as a separate vacuum tube FM tuner that played through the in-dash hybrid AM radio that used 12 volt heater and plate tubes in the non-audio, RF and IF circuitry, and solid-state audio portions.
Car radios through the 1920s and 1930s all looked about the same. They had a shielding, which was basically a tin box that contained the receiver, a speaker, a control element, and sometimes also the power supply.
The AM-FM selector was placed on the FM tuner located on the transmission hump below the dashboard. Both the FM tuner and AM radio used the same antenna. The antenna inputs of both items were fed by the antenna cable through a splitting device that contained a small capacitor to feed the FM tuner and an RF choke to feed the AM radio.
Early car radios were basically house radios with the components placed wherever they’d fit (source: www.carhistory4u.com/the-last-100-years/parts-of-the-car/car-radio).
The RF choke provided a significant impedance at the FM broadcast band, so that the AM radio didn’t load the FM signals. A small capacitor prevented the FM tuner from shorting out the AM signals.
A cable went from the FM tuner to the AM radio; it brought the AM radio audio to the mode switch on the FM tuner. A second shielded lead brought the selected audio source to the audio portion of the AM radio for volume, tone selections, and amplification playing via the front and rear speakers.
The FM tuner used a transistor inverter to make a bit over 100 volts to operate the vacuum tube circuitry used in the FM tuner.
The first in-dash AM-FM radios appeared in 1961 on the new 1962 model year cars. They were all transistor radios and made by the auto makers usual supply sources: Delco for General Motors, Bendix for Ford, and Mopar or Delco for Chrysler.
The car radio, an accessory only 40 percent of cars had in 1946, was in 90 percent of cars by the 1970s.
Most were very cleverly designed with many transistors being used on both the AM and FM bands with a separate FM front-end tuner.
After-market auto radio suppliers offered both total FM radio receivers and tuners to insert in a manner that played FM radio through the car’s AM radio. Several vendors made products to provide automobiles with FM reception. Motorola, who was very active in starting the car radio business about 35 years earlier, made both complete radios and tuners.
A 1958 Lincoln radio. Courtesy of https://www.pgbildelar.se.
The popular amateur radio manufacturer, Gonset made tuners that went in the antenna line of the car before the AM radio; it provided an output in the AM band for the station dialed in by the tuner, thus providing FM reception.
In the 1950s, drivers still had nearly a decade to go before Super 8 (eight-track) tape players would make their way into vehicles.
The Gonset device employed special 12 VDC heater and plate tubes made for FM reception about 1960; very unusual technology from an era when transistors were not readily available to operate at 108 MHz for FM reception.
About 1965, FM stereo radios began to appear for automobiles from auto manufacturers. Most AM-FM radios with FM stereo reception consisted of two pieces: the basic AM-FM mono receiver and a second piece consisting of the FM stereo multiplex circuitry and a second audio channel.
I have a 1968 Cadillac radio I plan to use in my 1965 Cadillac convertible (it fits perfectly in the dash) that has the FM multiplex unit in the radio and both audio power amplifiers in a separate unit.
Motorola Model 010 car radio. Courtesy of https://www.oldautoradio.com.
Later auto radios with FM stereo were one piece in-dash units with the FM multiplex circuitry and the second audio channel built into a one-piece unit. Later GM auto radios used integrated circuits (ICs) for the audio power output stages.
The FM tuner was available in the 1958 to 1960 Lincolns. I believe it was poorly promoted since it didn’t appear in any of the sales literature I acquired for my 1960 Lincoln Continental Mark V convertible. It’s mentioned, but no repair data or schematic is given for it in the shop manuals I have for the car.
A flyer for a pushbutton Motorola car radio, a common option on cars starting in the late 1930s. Courtesy of https://www.theglobeandmail.com.
A cruise control unit was also available in 1960, but also is not shown in any of the sales literature.
One thing I know for sure is that driving would be far less fun if we didn’t have our radios to listen to — especially when we’re stuck in today’s traffic. NV
