Re: Choosing a ferrite bead
John Perry wrote:
Hm. I'm not an rf type, but I distinctly remember my lead engineer in
the 70's, who was an rf type, telling me that ferrite beads were
predominantly lossy, so acted more to increase trace resistance than
like chokes. That's why he could get about as much effect from tacking
one on top of the trace as he could cutting the trace and running it (a
connecting wire, actually) through the bead, as I wanted to.
Am I misremembering, or are things different now, or...?
The effect is certainly reduced when the core does not wrap all the way
around a conductor, but there is measurable and, I guess useful effect
in having the material only on one side of flat circuits. Steward
now sells thin, flat squares and disks of ferrite with pressure
sensitive adhesive, to be placed over some flat circuit elements.
http://dkc3.digikey.com/PDF/T061/0999.pdf
I haven't used them for this purpose, but someone must be.
.
