CHAPTER 16
A DDS VFO
There was a time when a transmitter consisted of a single vacuum tube operating as a keyed oscillator. Well, you can imagine what that sounds like on the air! “CW” was not called “chirpy warble” for nothing. Crystal oscillators improved on the stability of the early transmitters a great deal, but with a crystal, you are, for the most part, stuck on one frequency, which meant you needed a lot of crystals if you wanted to move around the bands. Along comes the Variable Frequency Oscillator or “VFO” and suddenly we were free to move about the bands. But, VFOs still tended to drift a lot during warm-up and were sensitive to many variables, not the least of which might be the operator’s body capacitance.
Today, it seems, we can’t ...
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