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In article lXI_b.395225$na.763604@attbi_s04, Harold E. Johnson
writes "Paul Burridge" wrote in message news ![]() Hi, I'm trying to track down the name for a certain type of oscillator which I dimly recall seeing in an old book called Radio & Line Transmission that I bought and lost over 3 decades ago. In simple terms, it has a crystal in the base/emitter circuit and a C/L tank for the resonant frequency of the crystal in the collector circuit. In this way it can't flip into an overtone since it only has gain at the crystal's fundamental. Anyone know the name for it? Why don't you think the crystal goes low impedance at it's odd harmonics? If you'll design the circuit properly, it will give no trouble with overtone operation. Don't remember ever having any problems selecting one to operate on the fundamental, usually, it's selecting between 5th and 7th overtone or 7th and 9th that gets a little sticky. W4ZCB A universal series resonant circuit "Butler?" meets most of your criteria. I dont like these names myself. Collector to +ve supply via tank LC with the C = 2 C in series the base decoupled to ground with a potential divider to set base bias and a low value (220R?) in the emitter to ground. The crystal goes from the junction of the 2 tapped capacitors and the emitter. The 2 Cs are arranged to lower the o/p impedance from the collector tank i.e. the C nearest the collector would be 100pF and the C to the +ve supply 330pF. With the LC arranged to resonate at the crystal frequency. The beauty of the circuit is that the crystal can be replaced by a 50R resistor and the circuit L and C tweaked to oscillate at the crystal freq. Can be used to select overtone or fundamental. -- ddwyer |
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