ferrite beads

Kill GSM radio buzz with $1 ferrite beads
http://gadgets.boingboing.net/2008/08/02/kill-gsm-radio-buzz.html

http://en.wikipedia.org/wiki/Ferrite_bead
Ferrite bead

http://lists.openmoko.org/pipermail/community/2008-August/025173.html

The ferrite is increasing the common mode inductance of the cable because the
ferrite has a better magnetic permeability than air. Taping the ferrite to
the cable is a bit like a half turn on a ferrite rod. It will still affect
the inductance, but not as much as if it went through a ferrite ring.