[TowerTalk] 3M™ External PIM Absorber 1000 | 3M United States

[Jim Brown]

On 11/18/2023 1:40 PM, Jim Lux wrote:
> I’ve used similar products at lower frequencies (<30 MHz) to good
> avail for knocking down RFI carried on power and data cables. It’s
> basically a ferrite/powdered metal in a elastomeric binder, or you can
> get it as an adhesive tape. So the mix of the ferrite is important -
> something like a 31 mix would be better than a mix tailored for higher
> frequencies.
> I think the stuff I’ve used most recently came from Laird.

Thanks for the info, Jim. FWIW, Fair-Rite #31 doesn't do its good stuff 
without winding turns, but there certainly are other mixes that are 
useful at HF, like the #73 mix that W2DU found for his "string of beads" 
chokes. His initial work was with 50, 100, and 200 of them. I don't know 
if he was always working with that small size, but the only bead that 
survives in the Fair-Rite catalog just fits on RG142 coax.

Unfortunately, the only commercial products using that design use the 
smallest number of beads, which limits their effectiveness and leads to 
destructive failures with badly unbalanced antennas.

73, Jim K9YC