Standing wave ratio(SWR) is a ratio of amplitude of partial standing wave at maximum to amplitude at minimum. Using a Simple Swr Bridge circuit, a SWR can be measured. This circuit give a balanced VSWR meter perfectly, so adjustment is not required. This circuit can be made from a coupler which  formed by a 6.5-inch piece of RG-58A/U coax. Here is the schematic diagram of the circuit:

Simple Swr Bridge circuit schematic

It is easy to build this circuit, the outer plastic jacket must be removed first. then open up the braid a little bid. Then uses a two lengths of #22 tinned bus wire to be thread into Teflon spaghetti. Next, string the insulated wires inside the braid. It must on opposite sides of the center conductor. Since the 50-Ω resistors and 1N67A diodes is very short, it must be taken care. The 1N67A can be replaced by 1N34. The RG-58A/U braid must be grounded at both ends. [Circuit's schematic diagram source: seekic.com]