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![]() Creative PLL and DDS subsystems of today, designed by others, make it possible for anyone to select 10 Hz increments on any HF band (30,000 frequencies within 300 KHz) with crystal- controlled accuracy. Analog VFOs are continuously variable. Making it possible for anyone to select an *infinite* number of "increments" within a 300Hz bandwidth much less your coarse 300 Khz wide example. Sure, but those old VFOs tended to change the frequency a little over time. AKA "drift". Me thinks one desires to select a frequency and then have the rig stay put on it. Modern rigs can do that to the accuracy and drift of a good crystal oscillator to some set resolution. But for our uses, 10Hz resolution is more than sufficient. And they do it without generating any phase noise or other forms of crud synthesizers toss out. Kellie, define "phase noise" insofar as amateur radio operation is concerned. You, for the limits of your technical knowledge, should call that "incidental FM" which is what the industry term "phase noise" refers. :-) Then you should examine exactly how low that terrible phase noise is. You can use the term "dbc" referring to the number of decibels below the "carrier" (center frequency reference, not a modulated carrier per se). The "crud" (as you term it) is quite far down in relative power and certainly won't affect morse code reception of an on-off keyed station's carrier. Early 2 meter synthesized rigs had some trouble with this (the phase noise would "add" to the FM modulation and produce extra noise. Phase modulation and frequency modulation are closely related, one is the integral (as in calculus) of the other. As for HF CW, some poorly designed novice xtal oscillator circuits probably had it worse than a modern synthesized rig. And then there's chirp... |
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