>Just a question. Has there been any research on the use of ferrite
>beads for RF chokes ?. Could they be used along with an existing RF
>choke to improve performance, or, as a replacement. For example; a
>FT43-1020 can give about 320 uh inductance with 10 turns of wire.
> Just curious as to whether any work has been done in this area.
I think the main problem with ferrites is that they tend to saturate at
high power levels. Then they don't do anyone any good and can actually
cause lotsa problems. As the ferrites saturate the get lossy. Lossy
material means heat is generated, etc. The problem is also exacerbated
as you go up in frequency and the ferrites get more and more expensive.
But lots of chokes use ferrites in them:
Most people wind the input matching net coils on ferrites, they wind
filament chokes around ferrite cores in the filament supply, etc. But
all these are at low power. And of course I think all of us realize this.
Now you are asking about beads. So if I get your question, you are
talking about a ferrite bead effectively in series with a choke? I think
you still have the same problem at high power levels and that is
saturation of the ferrite itself. Rich Measures, AG6K, recommends in
some of his supressor circuits to add a small ferrite bead in series with
the plate choke. This is meant though as more of an additional choke to
dampen out VHF resonances and not to increase the inductance of the plate
choke at HF.
I think the saturation is the biggest deal at high power. And at low
power, where you could put a choke in series, why not just wind the choke
on the core itself and get a better inductor with a smaller coil.
Perhaps I don't understand you question completely.
73,
Jon
KE9NA
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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