[time-nuts] GPS discipline oscillator vs phase lock

[Hal Murray]

jimlux at earthlink.net said:
> sequential tone ranging: by putting a "ranging tone" at, say, 1 MHz,  on the
> carrier

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 
filter out.


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 
constant.

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.  
1953

Small world.  There is a more direct time-nuts connection.
  https://en.wikipedia.org/wiki/Philip_Woodward#W5_clock
  https://en.wikipedia.org/wiki/Philip_Woodward#Achievements_in_horology





-- 
These are my opinions.  I hate spam.