[time-nuts] GPS discipline oscillator vs phase lock
hmurray at megapathdsl.net
Tue Jun 20 19:22:19 EDT 2017
jimlux at earthlink.net said:
> sequential tone ranging: by putting a "ranging tone" at, say, 1 MHz, on the
Thanks. The part that attracted my attention was your "spectrally pure
signal" for the VCO.
I think the answer I was fishing for is that the modulation has to be easy to
Many years ago, I did some work on radar. The only part I remember was the
range-velocity ambiguity. It's the radar version of Heisenberg for signal
processing. You can't measure both frequency and time of a signal with high
accuracy. Radar uses distance and velocity rather than time and frequency.
The plot I remember was 3D, range and velocity error in X-Y and probability
or signal-power or something like that in Z. For a simple radar pulse of a
given duration, the plot is a bell curve. Make the pulse longer and the
curve gets narrower in velocity but wider in distance. Make the pulse
shorter and you get better distance but poorer velocity. The volume was
In radar, you can do things like chirp and pulse trains, but they just push
the ambiguity over to someplace else.
> Tone ranging also requires that you have a good a-priori estimate to pick a
> suitable set of tones.
That lets you pick a signal that puts some of the ambiguity someplace where
you can ignore it.
I still have the little red book from those days. I wonder how long it would
take me to get back to where I could understand most of it.
P M Woodward: Probability and Information Theory with Applications to Radar.
Small world. There is a more direct time-nuts connection.
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