[RFI] Info needed

[Wes Stewart]

 Did you actually read what the OP said?  It's a rhetorical question; of course you didn't, otherwise you would not have issued your usual answer to anything ferrite.  He has a specific need, a suppressor bead he can slip onto a wire near the pins of tube sockets.  You want him to wrap ten turns of wire through a big core.  He wants a BEAD.  As far as I can determine, you can't buy a BEAD in mix 31.  (If you can, please pass along the source)  Mix 43 has been used successfully for this purpose for years.  You can actually buy a mix 43 bead.  A wise old engineer once told me, "You should never use parts you ain't got."
Wes  N7WS

    On Wednesday, July 17, 2024 at 12:53:40 PM MST, Jim Brown <jim at audiosystemsgroup.com> wrote:  
 
 On 7/17/2024 12:16 PM, Dave (NK7Z) wrote:
> If you are trying to suppress 14 MHz and lower I would use mix31, if 
> above 14, mix43.

Fair-Rite #43 is NEVER a good choice below 30 MHz. Mix #31 is the only 
good choice for 160M through 10M, and slightly better than #43 for 6M.
> 
> Place about 7 to 10 wraps of cable on a ferrite.  Each pass through 
> center counts as a turn...

Number of turns needed depends strongly on the core. For most #31 
clamp-ons, 2 turns is about right for 6M, 3 for 10M, 5 for 40-10M.

It is CRITICAL that turns are sequential around the center of the core. 
Out of sequence turns cancel. I ran into this with the year-plus of lab 
research that produced the latest (2018) Cookbook. It can be difficult 
to get 5 turns in sequence through a clamp-on and have them stay that 
way, although cable-ties can help. Depending on the o.d. of the cable 
and the i.d. of the core, even 4 turns can be difficult. There are a 
couple of photos showing this on page 22 of my latest update of my 
original RFI tutorial.

http://k9yc.com/RFI-Ham.pdf

73, Jim K9YC






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