Wunderlich refers to a series of
vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied.
The type kn ...
s introduced in the early 1930s. Wunderlichs were designed to be used as full-wave
detectors
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
in
AM radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
receivers. However, because of their unusual design, they were rarely used in commercially manufactured receivers. The tube is named for its inventor, Norman Wunderlich.
Structure
The Wunderlich tube is a twin medium-mu
triode
A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 19 ...
. The tube has two identical control grids that operate in tandem with a common heater, indirectly heated
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
and plate.
Function
Typically, the two grids are connected to opposite ends of the center-tapped secondary of the final
IF transformer. The center tap of the secondary is then connected to ground through a parallel-connected resistor and capacitor circuit. This causes the tube to act as a full-wave
grid leak
A grid leak detector is an electronic circuit that demodulates an amplitude modulated alternating current and amplifies the recovered modulating voltage. The circuit utilizes the non-linear cathode to control grid conduction characteristic and ...
detector. In some circuits, the center tap also provides
AVC
AVC may refer to:
Organizations
* Asian Volleyball Confederation, the continental governing body for the sport of volleyball in Asia
* Advanced Video Communications, owner of Stickam
* ¡Alfaro Vive, Carajo!, a defunct left-wing group in Ecuador
...
bias voltage to the converter and/or IF amplifier. Some Wunderlichs, like the Wunderlich B, have a diode plate or a second grid that provide AVC bias voltage.
External links
Schematic of the Mission Bell model 19 car radio. One of the few radios produced in the United States to use a Wunderlich detector (type 70).
* Radiomuseum.org discussion page about Wunderlich tubes.
*{{Cite web , url=http://www.vacuumtubesinc.com/TubeTidbits/WunderlichTubes.aspx , title=Vacuum Tubes, Inc Vacuum Tubes Inc. article about Wunderlich tubes.
Analog circuits
Radio technology
Vacuum tubes