Currently, in many cities the number of TV channels broadcasting in the decimeter range exceeds the number of channels located in the meter wave range. A single TV equipped with an appropriate band selector is not enough to receive these channels. A dedicated antenna is also required.
First, make sure you really need a decimeter antenna. To do this, connect the collective antenna cable to the TV (if there is one in your house) and perform auto-tuning. Make a list of the received channels. Then, instead of the collective antenna, connect a piece of wire and auto-tune again. If, at the same time, any channels were received that are not received by the collective antenna, you need a decimeter antenna. Be sure to unplug the TV before connecting or disconnecting the community antenna cable, as the cable sheath is grounded.
Of all the designs of indoor decimeter antennas, the so-called ring antenna has the best combination of efficiency and ease of manufacture. To make it, take the antenna plug and connect the ring and pin contacts with a ring of wire with a diameter of about 10 centimeters. To do this, you need a piece of wire about 30 centimeters long (high accuracy is not required, so the number "pi" can be taken as exactly 3).
Most modern TVs are equipped with a combined input for connecting an all-wave antenna. To connect two antennas to it at the same time: meter (or collective, if available) and decimeter, use a special adder. It is sold in hardware stores. Disconnect the TV from the mains before making the connection, if you are using a shared or grounded external antenna. Then tune the unit so that each antenna receives the channels that those antennas provide with better reception. Do not neglect the use of a combiner, as simply connecting the plugs to the TV one at a time will quickly deteriorate the input jack. In addition, it is inconvenient, because even if you have a remote control, you need to approach the TV. It is especially dangerous to connect the antennas one by one to the TV hanging on the wall: it may fall.