1-11The number of strikes per antenna revolution is referred to as HITS PER SCAN. During each revolutionenough pulses must be transmitted to return a usable echo.NOTE: The more pulses transmitted to a given area (at slower antenna speeds), the greater thenumber of hits per scan.As an example, if the antenna rotates at 20 rpm, it completes a revolution in 3 seconds. During thistime, a transmitter with a prf of 200 pulses per second (pps) transmits 600 pulses. Since 360 degrees ofazimuth must be covered, the following formula shows the number of pulses for each degree of azimuth:Such a low number of pulses for any given target area greatly increases the likelihood that sometargets will be missed entirely; therefore, prf and antenna speed must be matched for maximumefficiency.Q6.Atmospheric interference with the travel of electromagnetic energy increases with what rf energycharacteristic?Q7.How is prt related to prf?Q8.What type of radar transmitter power is measured over a period of time?Q9.What term is used to describe the product of pulse width and pulse-repetition frequency?BEARINGThe TRUE BEARING (referenced to true north) of a radar target is the angle between true north anda line pointed directly at the target. This angle is measured in the horizontal plane and in a clockwisedirection from true north. The bearing angle to the radar target may also be measured in a clockwisedirection from the centerline of your own ship or aircraft and is referred to as the RELATIVE BEARING.Both true and relative bearing angles are illustrated in figure 1-8.Figure 1-8.—True and relative bearings.
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