One way to make a radio antenna is to use a length of copper wire. The wire can be any size, but the larger the diameter, the better the performance. To create an antenna, simply wrap the wire around a support structure, such as a metal rod or pipe. The exact dimensions are not critical, but the overall length should be around one quarter of a wavelength of the desired signal. For example, for AM radio signals (around 1000 kHz), a quarter wavelength antenna would be around 62.5 meters long.