On Thu, 10 Dec 2009 18:10:37 -0800 (PST), Al
wrote:

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/...ct&R=260682 4

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

http://www.we-online.de/katalog/de/we/katalog/index.php?language=en&key=EMC_Ferrites%2FFerrites_ for_PCB_assembly%2FKatalog%2FWE-UKW

Shove 25Mhz or 100MHz into the existing ferrite bead and measure it's
impedance. Just a signal generator, the bead, and a 1Kohm load.
Measure the voltage out of the generator, and the voltage across the
load, using an RF volts guesser, or an oscilloscope. The rest is
calculating the divider ratio between the bead impedance and the 1Kohm
load.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558