[Antennas] ferrite bead source
Patrick A. Thompson Sr.
[email protected]
2002年9月07日 12:33:04 -0400
I've got an Athlon running at 1300MHz that puts a lot of RF trash out on 20
through 6 meters and some still audible on 2 meters. Even the small standby
(wake on LAN) power supply radiates some trash.
Snap-on square ferrites from MFJ didn't help. I suspect they are similar to
the RS ferrites.
I found the Fair-Rite web page. http://www.fair-rite.com/
Which devices seem to help best?
Patrick Thompson
wa4tuk
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Eric Lemmon
> Sent: Saturday, September 07, 2002 11:37 AM
> To: Ed
> Cc: [email protected]
> Subject: Re: [Antennas] ferrite bead source
>>> Ed,
>> I started looking for clamp-on ferrite filters after I discovered
> that my then-new 950 MHz Athlon computer was radiating a pure
> carrier in the 152 MHz business band, locking open a repeater I
> was trying to tune. All of the covers were tightly screwed in
> place, so I believed that the RF was being conducted out of the
> computer case on one or more connecting cables.
>> My first fix, using snap-on ferrite filters from Radio Shack,
> failed miserably. The filters had almost no effect at all. Even
> looping the wires through several times had no effect.
>> I then rang up Fair-Rite, a leading manufacturer of ferrite
> filters. I learned that "all ferrites are Not the same." Indeed,
> the cheaper ferrites often don't begin to filter until very high
> frequencies. Based upon my description of the problem, the
> applications engineer suggested using a ferrite compound that was
> formulated especially for the frequency range that was giving
> me a problem. He even sent me some free samples to test.
>> When the samples arrived, I quickly snapped them onto the cables
> right at the connector plate on the back of the computer. They
> worked perfectly. As a result of this experience, I convinced my
> employer to purchase a large quantity of the same filters to
> solve some similar EMI problems at work. Needless to say, the
> problems were solved.
>> I should make it clear that I have no financial interest in
> Fair-Rite. I believe that other manufacturers of ferrite filters can
> provide similar products and technical support. Since there are
> dozens of different ferrite compositions, each with well-defined
> frequency cutoff and attenuation characteristics, a ferrite
> filter should be carefully selected to optimize its effect on the
> unwanted signals and minimize its effect on the desired signals.
> Choose wisely!
>> 73, Eric Lemmon WB6FLY
>> Ed wrote:
>> > Speaking of ferrite beads what is the best source for the snap
> on variety? I have a difficult time finding them at ham fests.
> > ED YEARY W4TEY
> > 325 CUMBERLAND DRIVE
> > HARROGATE, TN. 37752-6942
> >