Making of Swr Power Meter Part 2

A Monimatch coupler implemented on a PCB is a compact and practical form of directional coupler used in SWR and RF power meters, particularly for HF and low-VHF applications. In this method, the transmission line itself is formed by wide PCB copper tracks, usually as a 50-ohm microstrip, eliminating the need for bulky coaxial wiring.

The Monimatch PCB coupler works by sampling both line current and line voltage. A ferrite toroidal transformer is mounted on the PCB, with the main RF track passing through the core as a single-turn primary, and a few turns of fine wire as the secondary to sense RF current. Voltage sampling is obtained from the RF track through a high-value resistor network printed or mounted on the PCB. These two samples are combined in proper phase to distinguish forward and reflected power.

The detected RF samples are rectified using low-capacitance Schottky or germanium diodes, then filtered and fed to analog meters or ADC inputs in digital SWR meters. Proper PCB layout—short tracks, wide ground planes, and symmetric routing—is essential to maintain accuracy and frequency response.

Advantages of PCB Monimatch Coupler:

Compact and rugged construction

Good repeatability and stability

Wide bandwidth for HF use

Suitable for high power with thick copper tracks


Due to its simplicity and effectiveness, the PCB Monimatch coupler is commonly found in home-brew and commercial SWR/power meters.

Music:
YouTube music
Heart and soul