able to see small objects at long distances, especially one that can also detect those objects at shorter distances. With modern electronics it is relatively simple to arrange for a radar to have different PRFs and duty cycles to allow operation over a wide variety of ranges, but with tube-based electronics from the 1950s this was extremely expensive. There is also a mechanical effect that also bears on the returned signal. A radar antenna is normally arranged to produce a very narrow beam, in order to improve angular resolution. Beam widths of 2 to 5 degrees are common for long-range radars. Intertwined with beam width is the speed of the antenna’s rotation, because it also determines the amount of time that a spinning radar will spend painting a given object on every scan. For example, consider a radar with a beam width of one degree and an antenna that rotates once every ten seconds, or 36 degrees per second. An object will be painted by the beam for only 1/36 of a second as the one-degree beam sweeps over it. If the radar has a PRF of 500, the object will be painted with 14 pulses per scan at most. Moreover, Cold-War radar systems were far from perfect. The system created a visible blip on the operator’s display if and only if it received enough returns with enough energy to rise above the background noise of the system. Atmospheric conditions, electronic interference from internal components, and other factors sometimes created false returns known as “clutter”, concealed real returns, or made blips difficult for the operator to interpret correctly. These design characteristics and susceptibility to glitches combine to determine a radar's blip/scan. Avoiding detection To understand how these various effects can be used to avoid detection, it is useful to consider a real-world example. During the time period being discussed, one of the most common radars in the Soviet fleet was the P-20 radar and its various modified versions. This had a PRF of about 375 to 750 PPS depending on the mode, its antenna rotated at about 6 RPM and had an angular beamwidth of 2 degrees. Against a bomber-sized target flying at common altitudes, it would have a detection range on the order of . It had a maximum altitude angle of 28 degrees, which meant a significant area above the station was not scanned. Consider a typical early-era