Abstract: A balun is formed by printed tracks (20,22) on a printed circuit board. A first conductor to one side of the board extends between ground (13) and single ended signal port 11. A second conductor to the other side of the board extends between ground 21 and a balanced signal port (12) in electrical symmetry. The arrangement provides a construction wherein the balanced side of the balun is entirely on one side of the board, resulting in symmetrical parasitic effects in the balanced limbs. Also cross board connections are not required. The balun allows a printed circuit form to be used where parasitic effects are likely, such as high frequency power amplifiers with their associated large heat sink, replacing other forms, such as coaxial cable types.