vackar vfo oscillator


Posted on Feb 5, 2014

It is probably the most stable VFO oscillator known. Vackar configuration is rarely used because of known reason. (The NIH, not-invented-here syndrome). The frequency tuning range is above 2. 5, not observable in any other type of oscillator. The Coupling ratio is fixed; typical range is 1:4 up to 1:9. The tuning is provided independently of coupling. Transistor`s parametric variables are isolated from the resonator.


vackar vfo oscillator
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The transistor input is not overloaded as Clapp or other circuits. The collector output is at low impedance providing low gain just to maintain the oscillation. The feedback division ratio is fixed. Even if the VFO is tuned, the impedance divider is fixed. The stability is close to XO. Jiri Vackar published his work in a book, providing theory and analysis of each type of his oscillator. What was the last model, V66 Who knows A while ago, I thought about subtracting oscillator for PLL VHF synthesizer. Few designs failed high expectations. I used Colpitts, Clapp, Hartley, Pierce, and Seiler. Junk. The Butler is better than single active component oscillator, but it is not good enough. Commonly used oscillator configuration does not guarantee good performance. The signal clipping by diodes guarantees additional phase noise and thermal frequency drift. The best oscillators very commonly use two or three active devices. This is valid for VCOs, TCXOs and OCXOs. The second device acts as an impedance converter, isolation amplifier, AGC circuit, and a phase shifter. The articles in QST very often copy old mistakes, and limiter diodes. U. L. Rohde from Univ. of Washington wrote few articles about the poison of limiter diodes in oscillators. TS-950 use diodes in oscillators. Ordinary oscillator has poor tuning range, the output voltage swing is unstable, and the frequency stability is poor as well. The industry tries hard to make...




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