calculate swr from impedance
A resistive bridge type SWR meter doesnât actually measure SWR â it measures impedance mismatch or impedance(however you want to look at it). SWR is calculated by the ratio of two volatges on the bridge. The SWR and impedance only relate correctly if the bridge impedance and feedline impedance are the same(50 ohms typically). A resistive bridge works fine but you can do the same thing with a simple resistive divider.