Features: Connect the radio----ATU antenna tuner----antenna. For the first use, please set the output power of the radio or power amplifier between 20-30W, warning that high-power tuning can easily damage the antenna tuner. Set the radio mode, use FM mode. Choose the antenna band to use, use 20-30W power in FM mode, press the radio PTT, watch the ATU antenna tuner PWR and SWRATU button TUNE use: short press (less than 1 second) ATU button, it is in reset state, long press (more than 1 second) ATU button is in tuning state. If the SWR display of the ATU antenna tuner in the transmitting state is greater than 2.0, it means that the antenna is detuned. Specifications: Material:PCB Color: Black Power Supply Voltage: USB charge,1A Battery: 1350mAh (included) Maximum working power: 100W Maximum possible measurement power: 150W Minimum power required to start tuning: 1W Minimum possible measurement power: 0.1W Measurement steps for power up to 10W: 0.1W Measurement steps with power higher than 10W: 1W Power measurement accuracy: 10% Maximum installation inductance: 8.4uH Minimum installation inductance step length: 0.05uH Maximum installation capacitance: 1870pF Minimum installation capacitance step length: 10pF Display: OLED Note: Please allow 1-2cm errors due to manual measurement,pls make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1x Automatic Antenna Tuner