[time-nuts] Frequency subtraction with D-flip flops

[Bob Stewart]

I haven't followed this discussion, and I probably do not understand it well enough to comment, but here goes, anyway.

Have you considered the situation of using two J/K flip flops and an AND gate to subtract one bit stream from another?  I drew up a circuit back in the 70s and never tried it out.  However, I have a parts layout (no schematic) of a board used to do digital mixing of the 3 signals in an HF rig, and the chips on the board would seem to validate the simple circuit I drew out.  I doubt the output would be "clean", and it's more of a pulse-stream subtracter than an actual mixer.  It would probably only be useful to drive a frequency counter where the precision was just what's necessary for ham radio purposes just due to mixing jitter.  NB: it's also possible I saw the circuit somewhere else and have a false memory that it's mine.  I've had this piece of paper in my notes for LONG time.  =)


Bob - AE6RV



----- Original Message -----
> From: ed breya <eb at telight.com>
> To: time-nuts at febo.com
> Cc: 
> Sent: Monday, June 24, 2013 7:13 PM
> Subject: [time-nuts] Frequency subtraction with D-flip flops
> 
> I am revisiting that tracking generator reference I brought up here a while 
> back, and trying to get my head around how a DFF can take the difference between 
> two frequencies.