Broadband choke, siple, clamp on (2026_clamp_choke_pe)

Finished common-mode choke.

Clamp-on ferrite and 3D printed part made of PETG.

Large clamp-on ferrite, material 31.

The cable is inserted, loops not yet pulled tight. The ferrite is clamped and the cables are pulled out so that the windings sit snugly.

Secured with cable ties

Measurement with NanoVNA V2 plus 4. Measurement without choke: "leads"

Only large ferrite with 3 turns: "0431176451_n3"

Complete filter: "0431176451_n3_and_6_zcat1730"

Measurement of S21. A common method to measure chokes. The shield of the cable is connected.
At 160m band at -20 dB and even lower at higher frequencies. The artifacts (dips) at higher frequencies are already visible in the measurement with only the lead cables. In the final application, when the common-mode choke is between the measuring instrument and the antenna, the leads are further apart and the isolation should be better than -30 dB.