K1TTT Technical Reference

Subject: 
           Re: Ferrite Beads
      Date: 
           Sun, 17 Nov 96 04:25:40 GMT
     From: 
           w2vjn@rosenet.net (George Cutsogeorge)
        To: 
           cq-contest@tgv.com (CQ CONTEST), kwidelitz@delphi.com (K6LA),
           merchant@silcom.com (Stephen Merchant)
References: 
           1


Here is some additional data on ferrite split beads taken on an HP Network 
analyzer.  The type 75 and 43 beads are manufactured split and have lapped 
surfaces.  The 43-S is 0.59 square by 1.125 long with a 0.25 hole.  The 43-L is 
1.02 square by 1.125 long with a 0.500 hole.  

The type 77 beads were cut with a diamond saw after manufacture.  The 77-S is 
about 0.56 OD by 1.1 long with about a 0.21 hole.  The 77-L is about 1.125 OD 
by 0.85 long with about a 0.49 hole.   



       Frequency       Type 75      Type 43-S   43-L    77-S    77-L

        0.15 MHz        -0.3 dB      -0.3       -0.35   -0.1    -0.3
        1.0             -2.4         -2.5       -1.7    -0.8    -2.6        
        3.0             -6.2         -7.1       -5.1    -4.5    -6.0        
        10.0            -11.0        -13.0      -10.7   -11.0   -5.3
        30.0            -16.0        -17.5      -15.4   -9.8    -4.8    
        50.0                         -18.7      -16.4   -8.1    -4.0

The 77 beads were used at K6LA and did a good job keeping RF out of various 
electronic appliances.  The 43 beads are a bit better (and more expensive) 
probably due to the lapped surfaces.  The sawn beads require more pressure on 
the joint to obtain the peak attenuation.  As Ken has stated, two tie wraps, 
pulled tightly, do a good job of clamping the beads together.
----
George Cutsogeorge,  W2VJN                   
Umpqua, OR.
http://www.qth.com/topten