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permanent echo[′pər·mə·nənt ′ek·ō]
A signal reflected from an object that is fixed with respect to a radar site.
Radar signals reflected from fixed objects on the earth's surface (e.g., buildings, towers, railway lines, or terrain). Permanent echoes are different from transient echoes, such as those produced by convective weather. Permanent echoes can be deleted from the radarscope by use of an MTI (moving target indicator). See echo and moving target indicator.