[RFI] Monitor RFI

EDWARDS, EDDIE J eedwards@oppd.com
Wed, 5 Sep 2001 13:11:48 -0500


Try Surplus Sales of Nebraska (800-244-4567) for split bead ferrites for
1/4", 3/8", & 1/2" I.D. in 43 mix.  I think Radio shack ferrites are also
43-mix and are best for freq attenuation from 14 thru 450Mhz. The peak for
43-mix is around 200Mhz at 33ohms impedance for 101 size bead compared to
around 18ohms impedance at 14Mhz for same bead (per fig 2.23 from ARRL RFI
Book).  A better material for you might be 73 mix, and Surplus Sales may
have some toroids with 73--but can't tell from the catalog.  If not, just
use more 43-mix beads until the noise is gone.

Of course it might be coming from your keyboard or mouse cabling too.  Mine
was!  Discovered this  while leaning over the keyboard to get to back of rig
and the noise changed in level and frequency.  Kinda weird, but the
capacitance must've changed with me leaning on it.  

de ed -K0iL

> -----Original Message-----
> From:	Pete Smith [SMTP:n4zr@contesting.com]
> I am hearing my Sony Multiscan E-100 monitor quite loudly at discrete
> points in the HF spectrum, particularly above 14 MHz.  I want to try
> winding a few turns of the video cable through a ferrite core, but the
> only
> cores I have found so far aren't big enough (ID) for the video cable's
> plug
> to pass through.
> I also have a few of the Radio Shack snap-on cores, and thought about
> trying them, but I have no info about their frequency characteristics.  I
> thought I read somewhere that their mix is best at VHF, but have not been
> able to retrieve that or any other relevant messages from the archive. 
> Advice much appreciated.
> 73, Pete N4ZR
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