[sdiy] Aztec Revisited

[Ian Fritz]

At 10:50 PM 1/11/2008, mike ruberto wrote:

>Also the multiplier pulse output is a bit on the indecisive end.
>Certain conditions lead to some very dramatic toggling. Fun to watch
>on the scope and even more interesting to hear. While I'm sure I could
>stableize this I'm not sure I want to. Compared to the samples of
>Ian's 5Pulser this circuit is much less subtle and clean about
>introducing a new octave. Yes it's something like PWM but with a bad
>attitude.

Hi Mike --

Cool stuff!

I found a lot of the same "indecisive" behavior in working on the 5Pulser. 
I also saw a lot of the same HF oscillations. All this turned out to be 
caused by spurious x-coupling via radiation. These circuits splash RF all 
over the place!  On the whiteboard I had to keep all the traces separated, 
with the inbetween rows grounded.  It was also very important to keep the 
output lines well separated from the inputs.  Twisted pairs for the I/O 
lines helped a lot.

On the PC board I made, I built the digital (pulsed) part of the circuit 
over a ground plane.
http://home.comcast.net/~ijfritz/sy_cir8.htm
You can see the ground plane through the board. This got rid of all the 
litttle nasties.

Of course, I'm not saying you need to do any of this, but at least you 
know.  :-)

Ian