Are these any good for RF use or should they go into the trash?

It depends on what they were doing on that motherboard. If they were
part of an RF interference filter, they may have other RF uses. If
they were the energy storage inductor in a switching regulator, they
may have their best performance under 1 MHz. You might look up some
of the common color codes and standard core sizes, and measure the
inductance and calculate the permeability of your cores to see if they
match any of the code specs. This could help to nail down the useful
frequency range.
================================
A practical way to determine suitability at HF and higher is to fit the
toroid with a bifilar winding ,being the primary and secondary of a
transformer.

Connect a signal generator to one winding and a RF millivolt meter or scope
to the other. By changing the frequency you quickly know in which
frequency range the toroid will be useful.

Usually 'blue' coloured toroids are ferrites for the lower frequencies
serving in SMPSes and AC supply filters.

Frank GM0CSZ / KN6WH

PaoloC wrote:

Motherboards and other circuits have some/many pass-through ferrite
beads which I find very useful to recycle as RF-block inductors in my
circuits.
(snip)
Unfortunately I have never been able to find any datasheet for those beads.
(snip)

Fair-rite makes many of these beads, and their catalog has some
impedance versus frequency data for them:

http://www.fair-rite.com/products.htm

You can also roughly sort ferrite material roughly versus frequency
capability by measuring the resistance with an ohm meter. Low
frequency power types measure in the hundred or thousands of ohms
between contact points, RF suppression types measure in the high kilo
ohms, while high Q RF types measure in the meg ohms. Having a few
known samples for calibration purposes helps.

--
John Popelish

PaoloC wrote:

Motherboards and other circuits have some/many pass-through ferrite
beads which I find very useful to recycle as RF-block inductors in my
circuits.
(snip)
Unfortunately I have never been able to find any datasheet for those beads.
(snip)

Fair-rite makes many of these beads, and their catalog has some
impedance versus frequency data for them:

http://www.fair-rite.com/products.htm

You can also roughly sort ferrite material roughly versus frequency
capability by measuring the resistance with an ohm meter. Low
frequency power types measure in the hundred or thousands of ohms
between contact points, RF suppression types measure in the high kilo
ohms, while high Q RF types measure in the meg ohms. Having a few
known samples for calibration purposes helps.

--
John Popelish

John Popelish wrote:

Unfortunately I have never been able to find any datasheet for those
beads.

(snip)

Fair-rite makes many of these beads, and their catalog has some
impedance versus frequency data for them:

http://www.fair-rite.com/products.htm

OUCH! I never thought ferrite beads could end up in such a complete
catalog! I feel quite stupid :-) I'm reading the PDF as fast as kids do
with Harry Potter's latest adventures :-)

You can also roughly sort ferrite material roughly versus frequency
capability by measuring the resistance with an ohm meter. Low

[snip]

Thanks for the extra-useful tips John. I owe you a drink if you happen
to pass by here :-)

Paolo ik1zyw

John Popelish wrote:

Unfortunately I have never been able to find any datasheet for those
beads.

(snip)

Fair-rite makes many of these beads, and their catalog has some
impedance versus frequency data for them:

http://www.fair-rite.com/products.htm

OUCH! I never thought ferrite beads could end up in such a complete
catalog! I feel quite stupid :-) I'm reading the PDF as fast as kids do
with Harry Potter's latest adventures :-)

You can also roughly sort ferrite material roughly versus frequency
capability by measuring the resistance with an ohm meter. Low

[snip]

Thanks for the extra-useful tips John. I owe you a drink if you happen
to pass by here :-)

Paolo ik1zyw

PaoloC wrote:
(snip)
Thanks for the extra-useful tips John. I owe you a drink if you happen
to pass by here :-)

You are welcome. And it is nice to have a drink waiting.

--
John Popelish

PaoloC wrote:
(snip)
Thanks for the extra-useful tips John. I owe you a drink if you happen
to pass by here :-)

You are welcome. And it is nice to have a drink waiting.

--
John Popelish