"The common-mode filter or choke may be one of the best-kept secrets" American Radio Relay League Antenna Handbook If you use End Fed antenna aka 9:1 UNUN with a piece of wire, OCF dipole antenna or have any RFI problem, use the best tool to cure it. Great for CB and HF mobile operation. Do not fall for those coiled coax chokes which can make the problem worse in some cases. There is no shortcut when it comes to curing RFI/EMI problems after all Ferrite materials are invented for that purpose. Ferrite turns the RF energy into heat, coiled coax does not! CMC-154-3K Common Mode Choke / Noise Suppressor / Line Isolator / RFI Suppressor Designed by Danny Horvat, E73M -former Cushcraft antenna designer. CMC-154-3K Common Mode Choke / Noise Suppressor / RF IsolatorThe one and only true Common Mode Filter Choke for 1-54 MHz on the market. It is only product with over 7000 Ohms of CMI on 50MHz while maintaining a Resistive part of CMI for more then50MHz of the frequency spectrum, actually, it has same values all the way up to 85MHz.Perfect to cure RFI/EMI problems.Common-mode attenuation is up to 39dB max. (measured in 50 Ohms systems)Great noise suppressor! It is a cure for noisy locations, reduce the noise floor of your receiver by several S-units instantly. If you have unbalanced antenna such as OCF dipole or your antennas close to your home, adding one CMC-154-3K will greatly reduce RF Interference problems on your equipment and 120/220V wiring inside your home. We do not claim "one size fits all" but actually we design, measure and make such products. Our CMC-154-3K has huge Resistive values of Common Mode Choking Impedance from 1-54MHz or almost whole HF spectrum, click the chart in the gallery for actual measurement data. Unlike other companies, we do not claim unrealistic impedance values or frequency coverage. Most importantly, the value of CMC-330-1K Common Mode Choking Impedance and its Resistive (Rs) part is always higher than Reactive part (Xs) over the working bandwidth. This parameter, Rs>Xs ensure that our CMC will NOT increase common mode currents as could with inferior coaxial cable chokes.We do not sell coaxial choke with RG8X cable claiming legal power or even 2000W capability while catalog values for RG8X are only 360W on 28Mhz and only 1kW on 3.5Mhz!!!Only chokes with Resistive (Rs>Xs) CMI- Common Mode Impedance stops and dissipate unwanted RF or noise coming to your equipment for sure. Coaxial chokes are not nearly effective and they are prone to even increase RF on your feeder.CMC-154-3K Features:SO-239 PTFE (Teflon®) Connectors which produce no impedance bump but the continuity of coaxial cable where the choke is inserted, it helps minimize leakage of RF in multi/contest stations setups.PTFE (Teflon®) insulated coaxial cable used can handle a lot more than legal power (1500W) in the USA. It is rated only to 3kW because of cable limit at the 50MHz.The enclosure is UV stable and could be used outside. Frq.(MHz)Zmag(Ohms)Rs(Ohms)Xs(Ohms)1.852500120022003.7370026002500748003800280010.15900525027501465006300170018.165006500700216400640036024.962506250-182861506150-14050.174007300-1100Zmag-Impedance Magnitude Rs-Series Choking Resistance Xs-Series Choking Reaktance *ICAS = Intermittent Commercial and Amateur Service