DAVIS EchoMaster Radar Reflector - Manual (Page 10)

10
To better illustrate the advantage that can be gained by placing the radar reflector
higher above the water, study the table below.
REFLECTOR HEIGHT DISTANCE TO RADAR HORIZON
5 ft. (1.5 m) 2.5 nautical miles (4.6 km)
10 ft. (3.1 m) 4.0 nautical miles (7.4 km)
15 ft. (4.6 m) 4.5 nautical miles (8.3 km)
20 ft. (6.1 m) 5.5 nautical miles (10.2 km)
25 ft. (7.6 m) 6.0 nautical miles (11.1 km)
30 ft. (9.1 m) 6.5 nautical miles (12.0 km)
35 ft. (10.7 m) 7.0 nautical miles (13.0 km)
The values in the table are not directly proportional, since radar waves are bent from a straight
line path toward the earth as they travel outward from a ship’s antenna. Refraction, or bending, is
due to the density and water vapor content of the atmosphere, allowing X band waves to travel
about 6% beyond the optical or line-of-sight horizon. Values in the table are approximate; reliable
detection ranges for common radar reflectors seldom equal the radar horizon distances indicated
above.
If you have a radar installation on your boat, it may be necessary to keep
the Echomaster reflector a minimum distance away from the radar antenna. You
should consult with your radar dealer or manufacturer to avoid possible damage to
equipment or adverse performance.
Avoiding shadowing by the sails is important. In
the diagram at right, radar beams in the shaded
sector are not reflected well because the sails, if
wet, shadow the radar reflector. Higher mounting
minimizes this.
Positioning the Reflector
Cabins, deckhouses, sails, stacks, etc. have a “shadow effect,” blocking a radar sig-
nal. To minimize this, the reflector should be fitted as high as possible. Height also
helps eliminate the effect of heavy sea and swell
conditions which might otherwise blend the
observed signal into sea clutter on the radar dis-
play.
ECHOMASTER INSTALLATION