Variable Frequency Oscillators (VFOs)

1. Chapter 10, Harris CRYSTAL SETS TO SIDEBAND. Frank W. Harris 2010, REV 12. Chapter 10. Variable Frequency Oscillators ( vfos ). Sooner or later you'll become frustrated with being stuck on a few crystal-controlled frequencies. You would like to have a Frequency -tuning knob that covers the entire band and not just a few kilohertz. This sounds simple, but isn't. It's difficult because, without the stability of a crystal, an ordinary RF oscillator will drift hundreds of hertz while you're sending. The fellow you're talking to probably has a modern transceiver with a narrow, stable passband. From his perspective your signal quickly drifts out of his passband. His digital readout may be calibrated to tenths of a Hertz and he will take great delight in telling you about YOUR PROBLEM. Drift is a big deal today In the old days, like 1950, receiver passbands were usually huge, like 10 or 20 kilohertz. So you could drift quite a distance before your contact even noticed, let alone could no longer hear you.

Variable Frequency Oscillators (VFOs) Sooner or later you'll become frustrated with being stuck on a few crystal-controlled frequencies. ... The circuit above is essentially what you will find in your ARRL handbook. It uses a JFET transistor. The oscillator is a Colpitts …

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  Handbook, Variable frequency oscillators, Variable, Frequency, Oscillators, Vfos, Arrl, Arrl handbook

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