Tek uses ferrite beads in some of the transistor adapters they make for
their curve tracers. These beads are inserted in each (E, B, and C) lead of
the adapter. I always assumed the purpose of the beads is to prevent the
transistor from oscillating but I don't really know this for sure.
Does anyone know what frequency band Tek was concerned about or what ferrite
Tek used? There are many ferrite materials to choose from. The few I am
familiar with are FB-43, FB-61, FB-73, and FB-75B.
The 013-0128-00 adapter specifically for the 7CT1N and 5CT1N uses three
276-0507-00 "SHLD BEAD,ELEK:FERRITE" for example. But there is no more
information than this on the one or two page data sheet that comes with a
I would guess Tek would chose ferrite material that is intended for
relatively low frequencies (maximum resistive loss at 10MHz or less) but
that is only a guess.
Dennis Tillman W7pF