[time-nuts] fast switching quiet synthesizer

Al Wolfe alw.k9si at gmail.com
Tue Oct 7 18:44:40 EDT 2014

    This reminds me of a project I did back in the early1990's. (Hopefully 
we have advanced a bit since then.) It used a bunch of quad latches, some 
74138's, a UART, and an RS232 converter. It drove a PTS 40. The UART used 
the first 4 bits for BCD frequency and the last four bits to address which 
decade on the PTS. It was for a frequency hopping amateur radio project that 
I never finished but that part worked as hoped.

    As far as radar frequecy hopping, I spent several years in the US Air 
Force where our X band radar magnatrons were tuned hydraulically. 3000 PSI 
on a slug in the maggie tuned it very fast!

Al, retired, mostly

> At work, I'm putting together a multichannel stepped frequency CW radar
> breadboard, and I'm looking for something to serve as a source that I
> can step quickly.
> I'm looking at stepping every millisecond or so.  Right now, I use a
> Ardunino type microcontroller driving a serial DAC driving a VCO, but
> that's a bit wonky and noisy, although it's easy to get the step timing
> right on.  The spectral purity is, shall we say, downright ugly.
> Since I'm going to be doing precision ranging with this, the spectral
> purity has to be reasonably good (not 1E-15 at 1000 seconds good,
> fortunately)..
> I was thinking about a PTS synthesizers  (beloved of time-nuts for all
> kinds of reason), and they're nice because they are quiet, and switch
> really fast (microseconds).  However, they all seem to have BCD or GPIB
> interfaces (only).  Sure, I can code up something on an Arduino or other
> microcontroller to drive the BCD on the PTS, but maybe there's something
> else out there that might work as well?  And is already off the shelf.

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