When tested on a Rhode & Swartz Network Analyzer, this Parallel Line Return Loss Bridge covered 1 - 500 MHz and measured a 56 dB return loss when configured as described below.

A quality 50 Ohm reference termination was on the "REF" port, a 50 ohm generator signal sweeping between 1 - 500 MHz was connected to the 50 Ohm Gen IN port, a spectrum analyzer was connected to the port marked as "Diode Detector", and a quality 50 ohm term was used on the "DUT" port (Device Under Test" port). An open or short on the DUT port generated a reference level where all the generator signal was reflected. Placing the 50 ohm termination on the DUT port resulted in a 56 dB drop in the reflected signal.

This device can be used with a fixed generator frequency input and a diode detector attached to the Diode Detector port. A larger DC voltage will be measured at the Diode port if the DUT port is shorted or open. Place a quality 50 Ohm termination on the DUT port and record the DC voltage. Then connect the supposed 50 Ohm antenna on the DUT port and measure that detected voltage. Using SWR formulas it is possible to calculate the return loss and the SWR of the antenna under test.