The Reduction of Static

Author: J.B. Hoag

The static electricity in the air, which in concentrated amounts causes lightning strokes, has been a source of noise in receivers, masking the desired signals, especially while a plane is flying near or through certain types of clouds. This has been greatly reduced by enclosing the receiving loop in a metal shield. The hollow, metal, doughnut-shaped shield completely surrounds the loop, except for a narrow transverse gap, and cuts off practically all electrostatic (but not magnetic) fields.

With high-speed airliners passing through regions in which rain or snow is falling, the shielding of the loop has been found to be insufficient. The removal of some of the " precipitation " static has been accomplished by trailing behind the plane a very fine wire in series with a high-value resistor. The theory behind this device is that the wire acts as a lightning rod to prevent the accumulation of high voltages on the plane. The resistor prevents the electrical discharges from the fine wire from becoming oscillatory in such a way as to produce radio waves of static.