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WSHU Chief Engineer Paul Litwinovich explores aspects of vintage radio, from the radio sets themselves to the people and technology that made it all possible.

The Farm Radio

In this day and age, we often hear of various programs, either sponsored or encouraged by the U.S. Government, or initiatives taken by private industry to bring internet service to rural and remote parts of the country. The emphasis is on the importance of making internet access available to all Americans.

From the beginning of broadcast radio, the sheer novelty of the new technology, as well as the soon to be found value in news and entertainment programs, made radio attractive and desirable to the masses. Getting radio signals to rural and remote parts of the country would not be a problem. Radio waves don't limit themselves to urban centers, and they don't stop at the town, county, or state line. Receiving those signals, however, would prove to be a challenge for rural and isolated populations. Radios require electricity, and that is where the problem occurred.

Prior to the Rural Electrification Act of 1936, part of Roosevelt's New Deal programs to spur recovery from the Great Depression, only ten percent of rural America had electricity, compared with 90 percent of urban populations at the time.

If you've been following my series of articles, you already know that the earliest of radios were powered by batteries. In the mid 1930s, newer tube technology and more efficient batteries allowed for portable, relatively light weight battery radios. So why didn't rural Americans simply buy and operate battery powered radios? The truth is that some did. For most though, the budget of the rural American, mostly farmers or agricultural workers, could not afford the relatively expensive and short-lived batteries. Those batteries might be available only by mail order or from a dealer miles or even days away.

Beginning with the market crash of 1929, and the depression that followed, the price of radios declined. Edwin Armstrong's heterodyne circuit and advances in tube technology helped drive prices down even further. By the mid 1930s, radio prices were within range of many rural residents, but without utility electricity, powering them economically was still a problem, and the P.R. Mallory Company solved it. At the time, P.R. Mallory was a manufacturer of capacitors, batteries, and other radio components, and yes, the same company that we recognize today from their Duracell line of alkaline batteries. In 1933 the Mallory Company introduced the electromechanical vibrator, a device which uses a contact driven electromagnet to excite a fast moving pendulum that oscillates at the familiar 60 Hz (cycles per second) that you probably recognize as our AC line voltage frequency. Attached to the pendulum are two more contactsused to create an alternating square wave of AC power that can be stepped up by a device known as a transformer, from 6 or 12 volts to any desired voltage needed by a radio receiver. The oscillating pendulum would give the device a soft, steady vibration that could be felt when touched, hence the name.

Credit P. Litwinovich collection
A Mallory vibrator as used in a farm or car radio.

Radios of the day were already equipped with transformers used to step up 120 volts to the typical 250 volts needed by tube radio circuits, and at the same time step 120 volts down to the 6 volts typically used by the tube filaments. All that manufacturers had to do was outfit an existing model radio with a vibrator and replace the transformer with one that would step up 6 or 12 volts to 250 volts. The tube filaments could be powered directly from the 6 or 12 volt battery source. The line cord was replaced with a cable that looked like one end of a set of car jumper cables, and now you had a radio that could be powered when clipped to a single 6 or 12 volt battery. As such, collectors refer to this type of radio as a "single battery" farm radio.  So how did this solve the economics problem of operating a radio from batteries? I did after all mention that radio batteries were expensive. The high voltage batteries previously used were expensive and short lived, but now these were eliminated by the vibrator power supply.  Almost every farm had a tractor, a truck, or both. These vehicles used a 6 or 12 volt battery to start the vehicle. It was then charged by the vehicle's generator, just as in a modern car.

The farmer could now take his tractor battery in at night, and clip the radio to it. His family could enjoy several hours of reception, leaving enough power to start the tractor or truck in the morning. The battery would then be recharged while the vehicle was used for the daily farming operations, and be ready to go again the next night. The really neat thing about farm radios was the fact that most major manufacturers offered several of their models as farm sets. This meant that the consumer could purchase a small table radio, a medium mantle radio in a cathedral or tombstone style cabinet, or a full size floor console, without sacrificing the features that each style of radio offered. Pictured above is a magazine advertisement for a Zenith farm radio, offered both as a floor console or a table top version. Both radios are identical to their AC powered cousins, except for their power supplies.

The Zenith Radio Corporation, in an idea way ahead of its time, actually offered a mini wind charger to help keep the 6 volt battery charged and ready for use. No need to borrow the battery from the tractor.

Credit P. Litwinovich collection
Advertisement for the Zenith wind charger, as it appeared in a variety of 1930s magazines.

Zenith, as the advertisement claims, is generally attributed to introducing the single battery farm radio. Following the closing of the Atwater Kent factory in 1936, they became the largest manufacturer of mid- to high-end radios in the U.S., leaving them in a good position to develop and market new products. Other major manufacturers, such as RCA and Philco, would quickly follow.

The single battery farm radio was not a system without some hardship. The batteries were somewhat heavy, and they could emit a sulfurous smell when in use. I'm sure occasionally a radio was left on overnight resulting in a dead battery in the morning, but back then most tractors and farm trucks had some means of manual starting which would get things going again. The farm radio did bring rural America into the radio age, bringing all of its advantages to rural life. The farm radio would, however, be a relatively short lived phenomenon. As the rural electrification project took hold, teams of linemen and electricians swept the country, installing power poles and wiring farms and houses. By the end of WWII, there was little need for the battery powered farm radio. Its technology, though, radios that could operate from a single 6 or 12 volt power source, would live on in the form of the car radio until the early 1960s, when tubes were replaced by transistors in car radios.

Farm radios were often ignored by collectors over the years. After all, they were just modified versions of standard AC powered radios. This occasionally presents opportunities to acquire the farm version for substantially less than the AC powered equivalent, especially if you just want the radio for display. There is nothing that makes restoring a farm radio to operation any more difficult than the AC powered version, and you could always power it from a power supply or car battery for demonstration purposes. These radios were an important part of the history of both radio itself, and that of our nation, and they should not be forgotten. Original Zenith wind chargers are rare and highly valued, not only by radio collectors, but by those interested in the history of renewable energy.

Paul was a design engineer and engineering manager in the broadcast industry for14 years before coming to WSHU in 1990. He holds an FCC commercial radio license, and an extra class Amateur radio license.