[RFI] Modem PS noise

[Jim Brown]

On Wed, 5 Mar 2008 11:29:58 -0600, dgsvetan at rockwellcollins.com wrote:

>took it apart to see how Astron did the job.  Answer:  lots of ferrites 
>and bypassing (in the correct places), as well as good board layout 
>techniques.  

And I'll emphasize two VERY important phrases in Dale's preceding 
sentence, that he clearly understands but didn't articulate in detail -- 
"in the correct places" and "good board layout techniques." The 
fundamental principles buried within these phrases are 1) current flows 
in a loop and returns to its source; 2) the capacitor provides a path to 
that source; and 3) the importance of keeping that current loop small, 
thus minimizing the magnetic fields that are produced, as well as the 
extent to which the wiring carrying that current acts as an antenna to 
radiate the noise. 

73,

Jim Brown K9YC