Re: [TenTec] Cheap Ferrites (was Orion reset)

[Joe Giacobello <k2xx@swva.net>]

I also bought these split beads from the eBay vendor.  Thanks to Alan, I 
read the  useful and informative tutorial provided by K0BG and decided 
to compare the Ebay ferrites with some others that I had in the shack 
using the technique described by him.  However, I used an MFJ-269 and a 
clip lead for my wire.  The wire was probably about #20 and the 269 
allowed me to go higher in frequency before I exceeded the maximum 
impedance.  The data are shown below:

Ferrite ID               Freq.(MHz)      Resistance      Reactance

Ebay                       2.0                  0                   40
EbayX2                    "                    0                   96   
    
EbayX3                    "                    0                   131
Fair-Rite (1/2")          "                    47                 221
Fair-Rite (1/4")          "                    16                 146
Gray (R/S?)(1/2")      "                    32                 232
Clip lead w/no ferrite  "                      0                  4

I then measured the EbayX3 and the Fair-Rite (1/2") vs frequency up to 
about 11.5 Mhz.  These are the data:

Freq. (MHz)         EbayX3                        Fair-Rite

                        R               X                   R         
     X
2.0                     0               131               53            
  238
3.0                     0               205               96           
   339 
4.0                     0               287              149            
 436
6.0                     16             477*            267              
627   
8.0                     58             712 *           438              833
10.0                  124,141*    978,1032*    680              1060   
11.46                267*          1356*           923              1178

In terms of reactance, it looks like the Ebay ferrites become roughly 
comparable to the Fair-Rites at about 8 MHz.  However, the resistance is 
much lower.  The Ebay units seem to be  increasing in reactance faster 
as the frequency exceeds 10 MHz.  Since the Fair-Rite units are about 
twice the length and five times the mass of the Ebays, it makes sense 
that you would need more of them to get an equivalent effect.  The 
bottom line seems to be that the Ebay ferrites should be useful above 7 
or 8 MHz.  (BTW, the asterisked data were obtained after disassembly and 
reassembly of the three Ebay pieces after making an initial set of 
measurements.  The reproducibility looks to be about plus/minus 10%.)

I was particularly interested in how they worked because I generally use 
an end fed random wire when I operate portable.  RF into the laptop can 
be troublesome to say the least.  I was hoping these might be an easy, 
cheap answer.  They still might be useful at the higher frequencies.

73, Joe
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