Text: The general term used to imply any undesired sounds produced in or by a radio receiver. Howling is usually caused by feed-back effects. The most common example of howling is in the case of a regenerative receiver. Here the detector tube may have a tendency to generate its own oscillations. As long as these oscillations are equal in frequency to any incoming signals there will be no howling, but should these local oscillations differ in frequency from the incoming series of signals, the result will be a howl resulting from the beats (q.v.) established owing to the difference between the two sets of oscillations. This is essentially the principle of heterodyne or "beat" reception, but in the case of a heterodyne, the effect is desirable and utilized, whereas in the case of a regenerative receiver it is undesirable. Interaction between various parts or different parts of a circuit may often lead to howling. (See Feed-Back, also Regeneration, Refless, Beats and ReRadiation.)

See Also:

Source: 190