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Could someone tell me how to make a single-wire antenna that can pick
up TV channel 5? I just need to know what length is best and what
material to use.

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Just get a length of any sort of wire and poke one end in the antenna socket
you will find at the rear of the receiver. Get rid of the wire insulation
at the receiver end.

If the signal is weak you will need something a little more elaborate. But
if you are not too far from the transmitter it may work first time.