Combined standing wave ratio meter and wattmeter for transmitters - has adder and subtraction stage with divider connected to directional coupler

摘要

The direct-reading standing wave ratio meter, esp. for radio transmitters consists of a directional coupler(1) which is connected between a transmitter and an antenna. The coupler has two terminals, at which appear forward and reflected voltage components(1a, 1b). These outputs are buffered (A, A') and connected to the inputs of adders and subtraction circuits(2, 3). The outputs of the addition and subtraction circuits are taken to the respective inputs of a divider circuit(4). The output of the divider(4c) is available to drive an indicating instrument - analogue or digital - direct to display the SWR at the coupler. By throwing a switch(S1-4) to a second position(b) and introducing a 1 Volt source at the divider stage, the circuit can also provide a direct reading of the power of the forward wave.