FREQUENCY
The higher the frequency of a radar (radio) wave, the greater is the attenuation (loss in power), regardless of weather. Lower radar frequencies (longer wavelengths) have, therefore, been generally superior for longer detection ranges.
PEAK POWER
The peak power of a radar is its useful power. Range capabilities of the radar increase with peak power. Doubling the peak power increases the range capabilities by about 25 percent.
PULSE LENGTH
The longer the pulse length, the greater is the range capability of the radar because of the greater amount of energy transmitted.
PULSE REPETITION RATE
The pulse repetition rate (PRR) determines the maximum measurable range of the radar. Ample time must be allowed between pulses for an echo to return from any target located within the maximum workable range of the system. Otherwise, echoes returning from the more distant targets are blocked by succeeding transmitted pulses. This necessary time interval determines the highest PRR that can be used. The PRR must be high enough, however, that sufficient pulses hit the target and enough echoes are returned to the radar. The maximum measurable range can be determined approximately by dividing 81,000 by the PRR.
BEAM WIDTH
The more concentrated the beam, the greater is the detection range of the radar.
TARGET CHARACTERISTICS
Targets that are large can be seen on the scope at greater ranges, provided line-of-sight exists between the radar antenna and the target. Conducting materials (a ship’s steel hull, for example) return relatively strong echoes while non conducting materials (a wood hull of a fishing boat, for example) return much weaker echoes.
RECEIVER SENSITIVITY
The more sensitive receivers provide greater detection ranges but are more subject to jamming.
ANTENNA ROTATION RATE
The more slowly the antenna rotates, the greater is the detection range of the radar. For a radar set having a PRR of 1,000 pulses per second, a horizontal beam width of 2.0°, and an antenna rotation rate of 6 RPM (1 revolution in10 seconds or 36 scanning degrees per second), there is 1 pulse transmitted each 0.036° of rotation. There are 56 pulses transmitted during the time required for the antenna to rotate through its beam width. With an antenna rotation rate of 15 RPM (1 revolution in 4 seconds or 90 scanning degrees per second), there is only 1 pulse transmitted each 0.090° of rotation. There are only 22 pulses transmitted during the time required for the antenna to rotate through its beam width.
From the foregoing it is apparent that at the higher antenna rotation rates, the maximum ranges at which targets, particularly small targets, may be detected are reduced.
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