square feet of reflecting in front of a small hand held antenna. An area survey is required to determine if hand held devices will operate reliably because unobserved roadway traffic and trees behind the operator can interfere with observations made in front of the operator. This is a typical problem with radar speed guns used by law enforcement officers, NASCAR events, and sports, like baseball, golf, and tennis. Interference from a second radar, automobile ignition, other moving objects, moving fan blades on the intended target, and other radio frequency sources will corrupt measurements. These systems are limited by wavelength, which is 0.02 meter at Ku band, so the beam spread exceeds 45 degrees if the antenna is smaller than 12 inches (0.3 meter). Significant antenna side-lobes extend in all directions unless the antenna is larger than the vehicle on which the radar is mounted. Side-lobe suppression and FM range modulation are required for reliable operation. There is no way to know the direction of the arriving signal without side-lobe suppression, which requires two or more antennae, each with its own individual receiver. There is no way to know distance without FM range modulation. Speed, direction, and distance are all required to pick out an individual object. These limitations are due to the well known limitations of basic physics that cannot be overcome by design. See also Doppler radar Pulse-Doppler radar Bibliography Luck, David G. C. Frequency Modulated Radar, published by McGraw-Hill, New York City, 1949, 466 pages. Stimson, George W. Introduction to Airborne Radar, 2nd ed., SciTech Publishing, 584 pages. References External links Fairly modern invention mechanization Radar