Tri-Tet Oscillator


Posted on Feb 5, 2014

QST`s most recent development ”the Tri-tet oscillator ”has made the single-tube crystal transmitter a really practical affair at last. Practical because it is now possible to work equally well in two ”and, in a pinch, in three ”amateur bands with a single crystal. Unless we miss our bet, this particular set marks the beginning of the era in wh


Tri-Tet Oscillator
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ich the new amateur`s first transmitter will be crystal controlled. ”from the deck of George Grammer, "A One-Tube Crystal-Controlled Transmitter, QST, March 1934, pages 8 12, 88 The tri-tet (triode-tetrode, also commonly spelled tritet) oscillator circuit (Figure 1) was announced in James Lamb, W1CEI, "A More Stable Crystal Oscillator of High Harmonic Output, " QST, June 1933, pages 30 32, as an improved means of generating radiofrequency (RF) power at harmonics (multiples) of the frequency of an oscillating piezoelectric frequency-control crystal. Misunderstood and misused, it went on to be reviled as a temperamental crystal destroyer. This page discusses the tri-tet`s genesis, characteristics, and adjustment, and shows how the tri-tet, properly used, is nonetheless an excellent means of achieving good keying and high power output in a one-stage radio transmitter. Figure 1 ”(A) The Lamb tri-tet oscillator as diagrammed for transmitting use in the June 1933 QST magazine article that introduced it. (B) The Lamb tri-tet redrawn with its screen-grid tube portrayed a bit more modernly, and ”to resistively load the crystal less, and to allow cathode-only keying (as opposed to B keying) by breaking the dc connection between the cathode tuned circuit and common ”with its grid-leak resistor decoupled by an RF choke and returned to common rather than to the tube cathode. The cathode tuned circuit, L1C1, is relatively high-C and is...




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