My antenna common mode choke. Our Common Mode Chokes – CMC are carefully designed and measured for maximum resistive choking impedance over the bandwidth desired based on Multi-Zs™ Technology. NEC computes currents vs length for every element of the antenna, and can display them graphically and as table. This article is about the different options for a common mode choke for ham radio bands. A good choke at the feedpoint breaks the connection of the feedline to the antenna in the common mode circuit, so that it’s no longer part of the antenna -- it’s only a feedline Visualize the common mode current's direction of travel: from the antenna to the radio, the coax shield ground comes first, then install the common mode choke between the Grounding Block and the coax entry to your shack. Jul 14, 2020 ยท A common mode choke at the antenna feedpoint will have little to no affect on whether received RF induces signals on the outside shield of a long (relative to the wavelength) coax. It is a reactive choke, as it relies on the inductive reactance of the coil to pres-ent an impedance to the CM current. Typical symptom is signal reports saying you sound like you are talking underwater. I needed to find a common mode choke, also called a 1:1 balun or RF line isolator, that is effective on this 10 MHz bandwith. If you have easy enough access, I would try various locations and look for improvement in the signal. Coax Common Mode Chokes Common Mode Current (CMC) carried on the outside of a coaxial cable braid from your antenna can cause unwanted RF in your radio shack and can radiate this unwanted RF into you and your neighbor’s electronic devices. evz8j bt9f jdwr9 ucpld ge6kno kg8z d0ai vefs n0yp whte