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Airplanes and Rockets:
RADAR HORIZON /
LINE OF SIGHT
Range (to horizon):
In obtaining the radar horizon equations, it is common practice to assume a value for the Earth's radius that is 4/3 times the actual radius. This is done to account for the effect of the atmosphere on radar propagation.
For a true line of sight, such as used for optical search and rescue, the constant in the equations changes from 1.23 to 1.06.
A nomograph for determining maximum target range is depicted in Figure 2. Although an aircraft is shown to
the left, it could just as well be a ship, with radars on a mast of height "h". Any target of height (or altitude)
"H" is depicted on the right side.
See also Section 5-1 on ducting and refraction, which may increase range beyond these distances.
This data was expanded in Figure 3 to consider the maximum range one aircraft can detect another aircraft using:
It can be used for surface targets if target = 0. It should be noted that most aircraft radars are limited in power output, and would not detect small or surface objects at the listed ranges.
Figure 4 depicts the maximum range that a ship height antenna can detect a zero height object (i.e. rowboat etc).
In this case "H" = 0, and the general equation becomes:
Where hr is the height of the radar in feet.
Table of Contents
for Electronics Warfare and Radar Engineering Handbook
Introduction | Abbreviations | Decibel | Duty Cycle | Doppler Shift | Radar Horizon / Line of Sight | Propagation Time / Resolution | Modulation | Transforms / Wavelets | Antenna Introduction / Basics | Polarization | Radiation Patterns | Frequency / Phase Effects of Antennas | Antenna Near Field | Radiation Hazards | Power Density | One-Way Radar Equation / RF Propagation | Two-Way Radar Equation (Monostatic) | Alternate Two-Way Radar Equation | Two-Way Radar Equation (Bistatic) | Jamming to Signal (J/S) Ratio - Constant Power [Saturated] Jamming | Support Jamming | Radar Cross Section (RCS) | Emission Control (EMCON) | RF Atmospheric Absorption / Ducting | Receiver Sensitivity / Noise | Receiver Types and Characteristics | General Radar Display Types | IFF - Identification - Friend or Foe | Receiver Tests | Signal Sorting Methods and Direction Finding | Voltage Standing Wave Ratio (VSWR) / Reflection Coefficient / Return Loss / Mismatch Loss | Microwave Coaxial Connectors | Power Dividers/Combiner and Directional Couplers | Attenuators / Filters / DC Blocks | Terminations / Dummy Loads | Circulators and Diplexers | Mixers and Frequency Discriminators | Detectors | Microwave Measurements | Microwave Waveguides and Coaxial Cable | Electro-Optics | Laser Safety | Mach Number and Airspeed vs. Altitude Mach Number | EMP/ Aircraft Dimensions | Data Busses | RS-232 Interface | RS-422 Balanced Voltage Interface | RS-485 Interface | IEEE-488 Interface Bus (HP-IB/GP-IB) | MIL-STD-1553 & 1773 Data Bus |
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