Principle: The QRM canceller is inserted into the feeder of the antenna without any other modifications to the radio. The box has a built-in PTT control to keep the canceller connected during transmission. However, an additional auxiliary receiving antenna is required, such as a 2m antenna or only a few meters of wires in a shed. The two antennas receive unwanted signals, resulting in different phases. The QRM canceller now allows adjustment of the phase angle and amplification to cancel unwanted signals before they reach the receiver front end It is based on a completely innovative concept and cannot be compared with the normal "silencer" performance. Features: The QRM canceller is inserted into the feeder of the antenna without any other modifications to the radio. Aluminum alloy outshell design, solid and firm, wear resistance and can provides long service time. Built-in PTT control to keep the canceller connected during transmission. Phase adjustable, two gains adjustable, easy to adjust by the rotation knob. The QRM canceller allows adjustment of the phase angle and amplification to cancel unwanted signals before they reach the receiver front end. Specifications: Material: aluminum alloy Color: black Item size: 115 * 133 * 49mm / 4.53 * 5.24 * 1.93in Item weight: 355g / 12.52ounce Packing List: 1 * QRM Eliminator 1 * Cable