A tri-tet oscillator is a crystal-controlled

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 ...

electronic oscillator An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave or a triangle wave. Oscillators convert direct current (DC) from a power supply to an alternating cur ...

circuit. It is a type of

electron-coupled oscillator In the vacuum-tube radio, an electron-coupled oscillator or ECO oscillator uses a screen-grid tube with the cathode (vacuum tube), cathode, control grid and screen grid forming the elements of the frequency-generating circuit while the plate is ...

(ECO), which uses a

tetrode A tetrode is a vacuum tube (called ''valve'' in British English) having four active electrodes. The four electrodes in order from the centre are: a thermionic cathode, first and second grids and a plate (called ''anode'' in British English). ...

pentode A pentode is an electronic device having five electrodes. The term most commonly applies to a three-grid amplifying vacuum tube or thermionic valve that was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926. The pentode (called a ''tripl ...

tube. The tri-tet was introduced by James J. Lamb in the June 1933 issue of

QST magazine ''QST'' is a magazine for amateur radio enthusiasts, published by the American Radio Relay League (ARRL). It is a membership journal that is included with membership in the ARRL. The publisher claims that circulation of ''QST'' in the United S ...

. In an ECO, the

screen grid A tetrode is a vacuum tube (called ''valve'' in British English) having four active electrodes. The four electrodes in order from the centre are: a thermionic cathode, first and second grids and a plate (called ''anode'' in British English). T ...

acts as a plate for the

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 1 ...

oscillator. Some of the

electrons The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary partic ...

pass through the screen grid to the plate, causing a

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

to flow in the load. This effectively isolates the oscillator portion from the load, so that loading does not affect the operating frequency. In the schematic shown, the C1/L1

tank circuit An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. The circuit can ac ...

control the current through the crystal. It is normally tuned a point between the crystal's fundamental frequency and its first

harmonic A harmonic is a wave with a frequency that is a positive integer multiple of the '' fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', ...

. The C2/L2 tank circuit is tuned to the desired harmonic. D+ acts as the "plate" voltage for the tetrode, and is slightly less than B+.

Tri-Tet in popular culture

Jean Shepherd Jean Parker 'Shep' Shepherd Jr. (~July 21, 1921 – October 16, 1999) was an American storyteller, humorist, radio and TV personality, writer, and actor. With a career that spanned decades, Shepherd is known for the film ''A Christmas Story'' ( ...

occasionally mentioned the tri-tet oscillator in his writing and radio shows. It was used as the oscillator in one of the first

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communi ...

transmitters In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to t ...

he used.

References

{{Reflist Electronic oscillators 1933 introductions