Abstract: An antenna has two output terminals and is operative for receiving electromagnetic radiation and converting the same into electrical signals appearing across the two antenna output terminals. There are provided a first and a second transmission channel, each having a respective input comprised of a pair of input terminals, and respectively operative for transmitting electrical signals having frequencies lying in a predetermined first frequency range and in a predetermined higher second frequency range, one of the input terminals of the first channel being connected to one of the two antenna output terminals. A transformer includes a primary winding connecting the other of the input terminals of the first channel to the other of the two antenna output terminals. The transformer further includes a secondary winding connected across the two input terminals of the second transmission channel.