PC-based VLF Reception
VLF signals are often monitored by radio amateurs using simple homemade VLF radio receivers based on personal computers (PCs). An aerial in the form of a coil of insulated wire is connected to the input of the soundcard of the PC (via a jack plug) and placed a few metres away from it. Fast Fourier transform (FFT) software in combination with a sound card allows reception of all frequencies below the Nyquist frequency simultaneously in the form of spectrogrammes. Because CRT monitors are strong sources of noise in the VLF range, it is recommended to record the spectrograms on hard disk with any PC CRT monitors turned off. These spectrograms show many signals, which may include VLF transmitters, the horizontal electron beam deflection of TV sets and sometimes superpulses and twenty second pulses. The strength of the signal received can vary with a Sudden Ionospheric Disturbance. These cause the ionization level to drop in the atmosphere. The result of this is that the VLF signal will reflect down to Earth with greater strength.
Read more about this topic: Very Low Frequency
Famous quotes containing the word reception:
“He’s leaving Germany by special request of the Nazi government. First he sends a dispatch about Danzig and how 10,000 German tourists are pouring into the city every day with butterfly nets in their hands and submachine guns in their knapsacks. They warn him right then. What does he do next? Goes to a reception at von Ribbentropf’s and keeps yelling for gefilte fish!”
—Billy Wilder (b. 1906)