Antenna tuner
![Automatic ATU for amateur transceiver](/Images/godic/202412/21/Ldg-antenna-tuner-0a3507.jpg")
![](/Images/godic/202412/21/136_to_174_MHz_base_station_antennas3507.jpg")
![1:1, 1:4 and 1:9 autotransformer](/Images/godic/202412/21/Widebandatu.svg3507.png")
![Basic network](/Images/godic/202412/21/Basicnetworkatu.svg3507.png")
An antenna tuner, a matchbox, transmatch, antenna tuning unit (ATU), or antenna coupler is a device connected between a radio transmitter or receiver and its antenna to improve power transfer between them by matching the impedance of the radio to the antenna’s feedline. Similar matching networks are used in other equipment (such as linear amplifiers) to transform impedance.