sentences:  Since the wavelength of VLF radio signals is huge (a frequency of 10 kHz corresponds to a wavelength of 30 kilometers, or 18.64 miles), the Siple Station had an antenna that was thirteen miles long.The antenna was used to transmit VLF radio signals into Earth's magnetosphere, to be detected half a world away in Canada.It was possible to inject these signals into the magnetosphere, since the ionosphere is transparent to these low frequencies.