Typically, amateur designs use an SWR meter based on a directional coupler, which has an incident and reflected wave switch and a sensitivity control. When setting up the transmitter, you have to perform a large number of manipulations not only with the P-circuit adjustment controls, but also with the SWR meter.

The device described below simplifies the procedure for matching the transmitter and load. The LED panel directly displays the SWR measurement result. In addition, the device has automatic sensitivity adjustment.

The SWR meter is based on a single-chip ATTINY13 microcontroller. The program recorded in the microcontroller continuously measures the level of the incident and reflected waves, calculates the SWR and displays it on the LED display in the following form. If the SWR level is less than 1.1, all LEDs are off. If the SWR level exceeds 1.1, 1.5, 2, 3, the corresponding LEDs light up sequentially. Thus, it is enough to adjust the P-circuit to extinguish all the LEDs.

The voltage level supplied to the input of the circuit should not exceed 5V. Exceeding the signal level is safe for the circuit, but will lead to an error in the SWR measurement.

The printed circuit board measuring 50x30mm is made of single-sided foil PCB.