The Channel Master JoinTenna combiners are designed to combine two separate antennas onto one coaxial cable. These are used when one or more channels are in a totally different direction than the rest of the TV stations you are trying watch, but you prefer to not use a rotator to rotate the antenna to point at those TV stations. The coupler is designed to allow all channels except channel 3 to pass through one port, and to allow only channel 3 to pass through the second port. Two 300 Ohm inputs and one 75 Ohm out.