3-23
The range of a radar contact is determined by special RANGING CIRCUITS. The following three
basic types of ranging circuits are used.
RANGE-GATE GENERATORS produce a movable gate that measures range based on elapsed
time and can be used on A-scope and ppi displays.
RANGE-MARKER GENERATORS produce fixed interval range marks that can be used to
estimate the range to a detected target. Range marks appear as an intensified series of vertical dots on an
rhi and as concentric circles on a ppi.
The RANGE-STEP GENERATOR produces a movable step that is displayed on an A-scope
presentation.
RADAR ANTENNAS are usually directional antennas that radiate energy in a one directional lobe
or beam. The two most important characteristics of directional antennas are directivity and power gain.
Radar antennas often use parabolic reflectors in several different variations to focus the radiated energy
into a desired beam pattern. Other types of antennas used with radar systems are the corner reflector, the
broadside array, and horn radiators.
ANSWERS TO QUESTIONS Q1. THROUGH Q17.
A1. Range, bearing, and elevation.
A2. Triggers, video, and antenna information.
A3. Range and elevation.
A4. Range and bearing.
A5. Electromagnetic.
A6. Fixed.
A7. Range gate or range step.
A8. Transmitter.
A9. The radar mile (12.36 microseconds).
A10. The A scope.
A11. Directional.
A12. Directivity.
A13. Plane.
A14. One.
A15. Half-wave.
A16. Two or more half-wave dipoles.
A17. Waveguide impedance matching devices.
