This device is designed to offer a high impedance path to remove any unwanted signals from entering your radio from the shield of the coax cable coming from your receive antenna.  This design offers a minimum of 3000 ohms resistance between the input and output shield terminals.  That is enough resistance to prevent the common mode signals being picked up by your antenna coax from adding to the noise floor of your receive system.

To use simply connect this device to the RX input of your radio with a short coax cable and the antenna will connect to the Input of the Common Mode Choke.