[RFI] Ferrite Beads

[Ford Peterson]

Jim Brown wrote:

...snip...

> Unless 1) our labor is worth only a few pennies per hour or 2) you want to reinvent the 
> wheel, or 3) you want to turn this into a science project, I STRONGLY suggest that you 
> proceed as follows. 1) STUDY the Fair-Rite catalog. 2) Choose the parts that will do you 
> job. 

Ah the rub!  Just exactly what job is it that I need done?  Do I need 30 ohms? 60 ohms? 300 ohms?  3K ohms?  What measurements do I need to make to determine what is needed?  Just exactly what is it that one is supposed to 'study' in the catalog?  Although I have not looked yet, the Fair-Rite catalog, to my knowledge, does not have a chart called "Number of split beads needed to suppress a noisy COP on a Toyota V8."  Sorry to sound sarcastic here, but the notion of what is adequate for suppression is somewhat illusive to me.  Even a hip shot guess from somebody who has done this before would be great. 1 bead or 10 beads per COP?  

New plan...  I split a 1/2" OD toroid, wound 8 turns on each 1/2, and mounted this in a plastic clothes pin (glued in).  I'm going to attempt to look at each of the 4 wires running to the COP with an O'Scope using this nifty little clothes pin RF sniffer gismo I made.  (It might even work for looking at current on my Topband radials too)  Maybe I can isolate which of the 4 lines running to the COP is doing the radiating by looking at them one at a time.  I could also look at this in the frequency domain with my spectrum analyzer.  But I still do not understand how I will equate my measurements to what "parts that will do you the job" (your #2 recommendation above). 

> 3) Do a search for distributors on their website, and ask for a quote on some 
> reasonable quantity (20-50 is a good start). I strongly suspect you will be quite surprised at 
> how cheap they are when you don't try to buy onesey-twosey. And if you have chosen the 
> parts well, you will find lots of other uses for them both in your own home and those of your 
> friends. 
> 
> 
> Jim Brown  K9YC

I can tell you this, if you have a product you want to introduce and start selling, most manufacturers will send you sample lots of double the number you indicated (read FREE).  If you are just a one time buyer, they send you to distributors.  $1.20 to $1.70 each, depending on size and mix.

Thanks for the input.

Ford-N0FP
ford at cmgate.com