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Tom, wb6b Using H&P to "stabilize"? a 10 MHz VFO or crystal oscillator with a low? frequency clock derived for GPS or WWV sounds interesting.? Way back? when we were playing with H&P, I did something similar but used the 60 Hz? mains as a reference clock.? That proved that using the mains as a? reference is not really a good idea.? Large current loads going?on and off? cause significant frequency shifts in mains.? I even visited a local mains power? hydro-electric generating station to see how mains frequency is controlled. They have a flow control system that uses a GPS clock for a frequency? reference.? This allows the mains frequency to move up or down by several? Hz but still maintains an average 60 Hz so our clocks are usually accurate. Since H&P only corrects HF frequency during each cycle of the LF clock there is a possibility of overshoot if the delta-C is too large.? This stabilizes? for average frequency but at the same time it can introduce phase and? frequency jitter at the LF rate. Very?low LF clock frequencies are interesting because the sampling rate can? become so slow that it actually allows frequency drift to occur, between? phase comparison samples. It is possible to run the LF clock much faster. There are some examples of? this FAST H&P on Hans web site. Your idea of H&P stabilization with an LF clock derived from GPS or WWV? is intriguing, but remember that H&P is never really stable.? It just holds? the HF part very close to some multiple of the LF clock.? Think of H&P as a? frequency multiplier that holds an HF signal close to some multiple of the LF? reference frequency.? It has jitter (frequency shift) but that is very slow and? is based on the LF reference frequency. Arv _._ On Sat, Nov 14, 2020 at 8:27 PM Tom, wb6b <wb6b@...> wrote: On Sat, Nov 14, 2020 at 06:08 PM, Jerry Gaffke wrote: |
