A six-port measuring circuit includes only four hybrids coupling two input orts to four power measuring ports. A first hybrid is connected to one input port and to second and third hybrids; a second input port is connected to the second hybrid; the second and third hybrids are connected to a fourth hybrid; first and second measuring ports are connected respectively to the second and third hybrids; and third and fourth measuring ports are connected to the fourth hybrid. In one embodiment, the first hybrid is a 180.degree. hybrid; and the second, third and fourth hybrids are quadrature hybrids. In a second embodiment, the first three hybrids are 180.degree. hybrids and the fourth a quadrature hybrid. Another embodiment includes three quadrature hybrids as the first three hybrids and a 180.degree. hybrid as the fourth hybrid. A fourth embodiment employs four quadrature hybrids. The basic six-port circuit is useful as a vector voltmeter and may be coupled to a transmission line by means of a directional coupler. Net power and the complex reflection coefficient .GAMMA..sub.l may be computed from the power readings at the measuring ports.