[time-nuts] Digital Mixing with a BeagleBone Black and D Flip Flop

Robert LaJeunesse lajeunesse at mail.com
Tue Oct 14 12:22:46 EDT 2014

Using 74AC parts on what I think of as a pluggable breadboard (e.g. http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=2295705&MER=bn-me-ca-r1-best-sto-5) is asking for trouble. The parts are RF fast and the pluggable board has not very good contact resistance and certainly more inductance and shunt capacitance than is good for RF. I would highly recommend using dead-bug style on a solid copper plane, as provided by a chunk of unetched PCB material. (Jim Williams did a few like that, see http://1.bp.blogspot.com/-y3xQiBHHzaQ/UP3mLk96qWI/AAAAAAAAAss/ZvPbfN8lmTQ/s1600/eep114.jpg.) This approach allows for extremely short lead lengths and power supply bypassing (to the plane) with a near zero lead length capacitor. 

Bob L.

> Sent: Tuesday, October 14, 2014 at 11:32 AM
> From: "Simon Marsh" <subscriptions at burble.com>
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Subject: Re: [time-nuts] Digital Mixing with a BeagleBone Black and D Flip Flop
> ... 74AC74 ... knocked up on some pluggable breadboard

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