On Tue, 11 Jul 1995, Dana Raymond wrote:

> Yes, I believe so. A PLL CAN track a signal outside its capture range if
> it has been locked onto it in the first place and its loop
> characteristic are such that it resists change that is too fast (a
> change from the fundamental to a harmonic can be considered a fast
> change).

Okay yeah this makes sense.  I just need to make the loop fast enough to
lock onto the fundamental before the harmonic gets too strong (500 ms
response is plenty good enough) but slow enough that the almost-instant
switch to the harmonic doesn't -- scuse the pun -- phase it.

I'd really like to try this approach.  What would be some audio PLLs to
use?  Perhaps a 565?  567?  Or are there more modern, better ones?  I've
worked extensively with RF type PLLs (gotta whole drawer full of motorola
chips) but never worked with audio PLLs.

Incidentally, for anybody wanting to use a PIC to tune an RF circuit, I
highly recommend the MC145170 chip.  It's cheap (about $8), readily
available (Hamilton Hallmark, Newark), and miraculous.  Programmed with 3
wire interface.  Reference modulus can be any number from 4(?) to 32767.
Programmable divider from 40 to 65535.  Can be programmed to be
single-ended or dual-ended.  Ref. output available.  Sign of loop can be
inverted by programming.  Can directly synthesize up to 160 mc.  XTAL ref.
osc. on-board.  16 pin package.  I've used these with PICs and they work
great.

David
--
Their address sums up their attitude: One Microsoft Way
        http://www.rt66.com/dthomas/