Editing Very low frequency (section)

===Amateur equipment===
Radiated power from amateur stations is very small, ranging from 1&nbsp;μW to 100&nbsp;μW for fixed base station antennas, and up to 10&nbsp;mW from kite or balloon antennas. Despite the low power, stable propagation with low attenuation in the [[Earth-ionosphere waveguide|earth-ionosphere cavity]] enable very narrow bandwidths to be used to reach distances up to several thousand kilometers. The modes used are [[QRP operation#QRSS|QRSS]], [[Multiple frequency-shift keying|MFSK]], and coherent [[Phase-shift keying|BPSK]].

The transmitter generally consists of an audio amplifier of a few hundred watts, an impedance matching transformer, a [[loading coil]] and a large wire antenna. Receivers employ an electric field probe or magnetic loop antenna, a sensitive audio preamplifier, isolating transformers, and a PC [[sound card]] to digitise the signal. Extensive [[digital signal processing]] is required to retrieve the weak signals from beneath [[Electromagnetic interference|interference]] from [[Harmonics (electrical power)|power line harmonics]] and [[Radio atmospheric|VLF radio atmospherics]]. Useful received signal strengths are as low as {{val|3|e=-8}}&nbsp;volts/meter (electric field) and {{val|1|e=-16}}&nbsp;tesla (magnetic field), with [[signaling rate]]s typically between 1 and 100&nbsp;bits per hour.