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.
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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