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About Regenerative Radio Receivers

Despite its great success and inexpensive nature, the crystal radio set was not without limitations. Tuning was not very selective, a problem that radio enthusiasts often solved by using ingenious circuitry such as absorption wave traps to null out unwanted interfering radio signals. A major problem was that the basic crystal set had no circuitry to amplify the desired incoming radio signal. For broadcast radio to achieve the overwhelmingly popularity that it eventually did achieve, a more refined receiving circuit was needed.

The regenerative radio receiver evolved in a line of research that ran parallel to crystal radio research. Thomas Edison’s work with evacuated light bulbs led him to observe that, in an evacuated tube, electrons would flow in one direction from an incandescent filament to a positively charged plate. Soon after, Sir J. A. Fleming of England used the same basic circuit to detect radio signals. This was known as the Fleming valve. The Fleming valve worked at least as well as a crystal radio detector, but it was complex, expensive to build, and required an external source of power to operate. Around 1906, the American, Dr. Lee deForest, successfully introduced a third element—the grid—between the Fleming valve’s cathode and plate, making it possible to amplify the incoming radio signal. DeForest called his new vacuum tube the Audion.

In 1912, the brilliant American inventor, Edwin Howard Armstrong, discovered a method of feeding the signal from the Audion’s plate back through its grid, which increased the amplification capabilities of the circuit many times. He found that increasing this feedback caused the tube to oscillate at radio frequencies. This tube made selective reception and amplification of radio signals not only possible, but easy. Armstrong’s invention was unique in that it performed three functions in one circuit: it was a rectifying detector, a positive feedback amplifier, and a heterodyne oscillator­all in one envelope. This stunning invention, known as the regenerative detector, raised the radio receiver to a level that made broadcast radio reception accessible to the masses of the world.

During World War I, Armstrong developed an even better radio-receiving circuit, the superheterodyne radio receiver, which eventually became the industry standard. Although this and other popular circuits found their way into the homes of radio listeners, many radio enthusiasts regarded the regenerative receiver as the best performer for the cost, based on its simplicity and ease of construction, and it continues to be a very popular receiving circuit to this day.

PV Scientific Instruments is pleased to offer several models of regenerative receivers (two shown in our Online Catalog) that make use of the most ingenious circuits developed since Armstrong's original design. We are proud to use only top-quality antique tubes and parts in the construction of our elegant regenerative receivers.

For more information, please visit our online catalog, drop us a line at pvsci@arcsandsparks.com, or give us a call at 607-387-6752.

Single Triode Regenerative Receiver

Twin Triode Regenerative Receiver