Ionosonde

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An IRX-58-23 ionosonde system.

An ionosonde (or chirpsounder) is a specialized radar system for the examination of the ionosphere. An ionosonde is used for finding the optimum operation frequencies for broadcasts or two-way communications in the high frequency range.

Contents

Description

The basic ionosonde technology was invented in 1925 by Gregory Breit and Merle A. Tuve (1) and further developed in the late 1920s by a number of prominent physicists, including Edward Victor Appleton. The term ionosphere and, hence, the etymology of its derivatives, was proposed by Robert Watson-Watt.

An ionosonde consists of:

  • A high frequency (HF) transmitter, automatically tunable over a wide range. Typically the frequency coverage is 0.5–23 MHz or 1–40 MHz, though normally sweeps are confined to approximately 1.6–12 MHz.
  • A tracking HF receiver which can automatically track the frequency of the transmitter.
  • An antenna with a suitable radiation pattern, which transmits well vertically upwards and is efficient over the whole frequency range used.
  • Digital control and data analysis circuits.

The transmitter sweeps all or part of the HF frequency range, transmitting short pulses. These pulses are reflected at various layers of the ionosphere, at heights of 100–400 km, and their echos are received by the receiver and analyzed by the control system. The result is displayed in the form of an ionogram.

Modern ionosondes, like the popular Lowell DIGISONDE(TM), use low power transmitters but compensate by using specialized DSP techniques in the receiver. The result is a portable instrument, which can be easily relocated to interesting HF communications sites.

Ionogram

Ionogram.png

An ionogram is a display of the data produced by the ionosonde. It is a graph of the virtual height of the ionosphere plotted against frequency. Ionograms are often converted into electron density profiles. Data from ionograms may be used to measure changes in the Earth's ionosphere due to space weather events.

See also

References

  1. F.C. Judd, "G2BCX Radio Wave Propagation (HF Bands)", Heinemann, London, ISBN 0-434-90926-2, 1987, pages 12–20,27–37

Further reading


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