Review: Common-mode current chokes CMCC (Kit) by OK2ZAW (remoteqth.com)

Common mode choke coils act as a simple wire against push-pull current (signal), while acting as an inductor against common mode current (noise).

The kit, concerned on the HAM radio, contains all the necessary materials to quickly assemble a CMCC box. Only a 16mm drill for the PL jacks and another narrow drill bit for the screw feedthroughs are required, apart from the soldering iron. The box is IP55 certified and can be waterproof if you work carefully on the holes. The three central ferrite cores are shrink tubing sheathed, the associated thin coax cable is cut to the correct length sufficient. For a tech-savvy hobbyist, the assembly is easy, even if as in my case the instructions are missing and can not be delivered on request. The substitute transmitted by the manufacturer images of the open finished box could not help. In particular, I could only do the screwing with a number of washers at its own discretion. Since the screw connection also affects the water resistance of the box there are a few points deduction at this point. Also because the screws are not retractable as shown on the website, but come as slotted screws therefore. Another point loses the box due to an oversized wing nut that does not want to fit on any of the screws. Replacement by post was announced after a prolonged contact with the manufacturer.

Two of the boxes are inserted into the coax cable, one 5 m from the antenna's feed point, the other one 5 m from the receiver entrance. From the earth connection of the box a grounding line must be applied to the ground spike. These are not included in the kit. The earth connection is small in size, more than a 1 mm Ø line does not allow the eye with the pin. The wing nut would dress better if one had chosen a larger one. At this point, you can only rework yourself and realize your own ideas of a good ground connection.

The kit cost on the HAM radio 27 €, so 54 bucks for 2 CMCC boxes + a can of cold beer for free, which you can easily drink away while writing the many emails to the manufacturer.

The CMCCs significantly reduce thunderstorm disturbances. The 50-m antenna now has 4 grounding points.