On Mon, 19 Feb 2007 15:08:33 -0500, Morse, Earl (E.A.) wrote:
>Since these beads are common they are also very cheap. Especially when
>you get them off of junk box computer cables. At 50 MHz you won't
>notice a whole lot of difference in impedance between the #31 and #43
>for the same size bead.
Yes.
>In selecting sizes of bead you may want to use a larger bead and use
>multiple turns or fit the bead to the size of the cable. I prefer the
>solid beads but realize the issues of getting them on cables that can't
>be disconnected. There is some loss of impedance due to using a split
>material vs a solid material but I can't remember how large it is.
If you study the data, the small air gap of the clamp-ons is mostly a
factor at lower frequencies, but no big deal at higher frequencies. But
the clamp-ons are about twice the cost for equivalent suppression, so
you'll get more bang for your buck with solids (assuming you're buying
new).
Higher Z = more suppression, and at 50 MHz, Z is proportional to length,
so go for a longer bead (and the Z of beads in series adds).
>Try what beads you have around the junk box as they are probably #43 mix
>and see how they work. Then see if you can improve by ordering other
>beads.
Yes. This is one of those relatively few applications where almost any
hamfest clamp-on or cylinder will work fine, because as Earl notes, most
of them are #43. I'm a huge fan of Fair-Rite's #31 mix for HF, but above
10 MHz, #43 is just as good, much cheaper, and much easier to find.
73,
Jim Brown K9YC
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