[time-nuts] Phase microsteppers
brooke at pacific.net
Thu Mar 10 16:57:23 EST 2005
In an old Austron brochure is says their model 2055A Phase Microstepper
works with either 1 or 5 MHz signals (no mention of 10 MHz).
The adjustment range is from 0.00000 ns/second to +/- 9.99999 ns/sec.
(i.e. 6 decades). "Exact time base frequency adjustments having a
resolution of 1E-14 may be made." Note that 0.00001 ns/sec is 1E-14.
It also has provision for changing the phase at a constant rate
determined by the thumb wheels on the front panel.
When I was trying to make a 1 PPS saw tooth corrector for the Motorola
GPS receivers I found an IC that was a 1 ns phase shifter and had just
enough range to correct the GPS receiver. I did get it to work but
never could figure out how to get around the bug in the saw tooth data.
This type of chip would be one way to get down to 1 or using another
part number a fraction of a ns time step. But some other method must be
used for finer steps.
Brooke Clarke, N6GCE
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
Carl Walker wrote:
> It's been quite some time since I've seen one of these units. Back a
> decade ago I worked for the
> company that makes LORAN-C solid state transmitters, and the Austron
> Phase Micro-steppers
> were used in the timing racks (one for each redundant Cs standard). I
> don't believe I've ever seen
> one of these units "in the wild" at any place other than a LORAN
> I'd been considering building my own micro-stepper, but as a newcomer
> to the T&F world I didn't
> know if such a venture would be considered crude by today's standards.
> Since I've not been able
> to locate a commercial unit via any of the normal used and surplus
> equipment channels, I'm entertaining
> that design project once again. If some reasonable minimum step time
> was all the resolution required
> (10 nS, for instance) there's really not all that much to it -
> especially with the silicon timed circuits that
> are available for a dollar nowadays. The LORAN timers used lumped
> constant delay lines and muxes
> with counters to drive the tap selection for inserting LPAs (Local
> Phase Adjustments), and a micro-
> stepper could be built the same way.
> I'd be really interested to hear what Tom has to say on the subject of
>> Tom Van Baak wrote:
>>> 3) There's a lesson from the timing labs - they do
>>> not typically adjust their C-fields at all. Instead they
>>> adjust phase or frequency using *external* phase
>>> micro-steppers or simply by *post-processing* the
>>> raw phase data from their counters.
>> Tom, thanks for the always helpful information. I may come back on
>> to ask some further questions about your other points (although they
>> are pretty self-explanatory) but wanted to follow up on this point.
>> I've known about microsteppers for a while, but I've never seen one
>> on eBay or anywhere else that I hang out. Are they possible to find
>> without special connections in the T&F field? What brands/models are
>> good to look for? Sounds like a very interesting gadget to play
>> with, if I could find one.
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