16 September 2011

Hunting Schumann Resonances

Quote Wikipedia: The Schumann resonances are a set of spectrum peaks in the extremely low frequency portion of the Earth's electromagnetic field spectrum. Schumann resonances are global electromagnetic resonances, excited by lightning discharges in the cavity formed by the Earth's surface and the ionosphere.This global electromagnetic resonance phenomenon is named after physicist Winfried Otto Schumann who predicted it mathematically in 1952. Schumann resonances occur because the space between the surface of the Earth and the conductive ionosphere acts as a closed waveguide. The limited dimensions of the Earth cause this waveguide to act as a resonant cavity for electromagnetic waves. The cavity is naturally excited by electric currents in lightning. Schumann resonances appear as distinct peaks at extremely low frequencies around 7.83 (fundamental), 14.3, 20.8, 27.3 and 33.8 Hz.
Observations of Schumann resonances have been used to track global lightning activity. Owing to the connection between lightning activity and the Earth's climate it has been suggested that they may also be used to monitor global temperature variations. It has been speculated that extraterrestrial lightning (on other planets) may also be detected. A new field of interest using Schumann resonances is related to short-term earthquake prediction.
Today Schumann resonances are recorded at many separate research stations around the world. The sensors used to measure Schumann resonances typically consist of two horizontal magnetic induction coils for measuring the north-south and east-west components of the magnetic field, and a vertical electric dipole antenna for measuring the vertical component of the electric field. The Schumann resonance electric field amplitude (~300 microvolts per meter) is much smaller than the static fair-weather electric field (~150 V/m) in the atmosphere. Similarly, the amplitude of the Schumann resonance magnetic field (~1 picotesla) is many orders of magnitude smaller than the Earth magnetic field (~30–50 microteslas).

It is not an easy task to receive Schumann resonances, especially if you live in a radio polluted area, disturbancies from grid power, community trains exciting strong magnetic field, sound waves from nearby power heating stations and even electrostatic popping noise from flowers and trees in the garden! This has not scared Sven, SM5LE in building a station for reception of Schumann resonances. He is very fond of difficult technical challenges. In front of Sven is his vertical antenna for receiving the Schumann resonances´ electric field part. The big box contains an amplifier, built with a single transistor. The amplifier feeds his indoor PC sound card. The amplifier is battery operated and the battery is charged by solar power.

Sven points the trace of a Schumann resonance at 7.83 Hz. His attic is almost occupied by a loop antenna, which is near completion for receiving the magnetic field part of Schumann resonances.

A lot of information about receiving Schumann resonances and other very low frequency signals can be found in Renato Romero´s, IK1QFK, home page Radio waves below 22 kHz.

Live data can be seen from IK1QFK station.

Sven is the right guy for this type of complex technical design. In the 80´s he was a world first to receive the WAC diploma, Worked All Continents by moonbounce on 432MHz. In the 90´s he repeated this by building a moonbounce station at the then nearby club station SK0CC. My QTH is very bad for DXing on VHF and higher frequency bands. The only way is to point an antenna straight up in the sky. So, five years ago I built, with great assistance from Sven, a 1.8 m dish for receiving moonbounce signals on the 23 cm band. As receiving was successful with this small antenna Sven built a 2.2 m dish at his home. In two years time he received the WAC diploma for the 23 cm band. I think that he is the only one to have accomplished this with such a small moonbounce station. Three years ago I had my first 23 cm moonbounce QSO´s with my 1.8 m dish and only 70 W at the antenna feed. Also this with great assistance from Sven.