Joop66 schreef :
Overigens: uit eigen ervaring, de kleine trilens is echt niet goed genoeg als er ook maar een klein beetje zee staat. Zoek bij "Joop schrijft" naar "Scheveningen 2".
Dat kwam al naar voren uit
een artikel in Practical Sailor in 2001.
Practical Sailor schreef :
Marine radar is of two types: X-band and S-band. The former is the type commonly carried aboard small boats. It operates at a frequency of about 9.4 GHz (9400 MHz) and has a wavelength of 3.2 centimeters (cm). S-band radar is used aboard large ships and operates at 3 GHz with a wavelength of 10 cm.
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Radar reflector performance is a direct function of size, proportional to the fourth power of its linear size. Doubling a reflector’s size increases its effective area 16 times. In the 1995 report, we wrote: “As the smallest dimension of a reflector gets down to a few wavelengths of the radar signal, it quits acting as a reflector and starts to act as a lump of metal. Remember that a wavelength is 3.2 cm (1-1/4″) for X-band, and 10 cm (4″) for S-band. So, small reflectors must be looked at with a great deal of suspicion, as there really is no substitute for size.”
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The Tri-Lens has a novel configuration of three modified Luneburg lens reflectors oriented about a vertical axis. It was measured only at X-band.
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At 0 heel, 90% of returns exceeded the 2.5 m2 threshold; at 20 heel 70% exceeded the threshold and at 25 heel 69%. The Tri-Lens easily outperformed all other reflectors in the 1995 test.
Honey nevertheless had criticism of the Tri-Lens.
“Our reservations,” he wrote, “are not with the angular coverage, but with the magnitude of the reflection. (This same reservation applies to virtually all passive radar reflectors on the market today!) The Rozendal reflectors use 5.25-inch diameter spheres inside a somewhat larger radome, the spheres being approximately 4.2 wavelengths across at X-band, but only 1.4 wavelengths across at S-band. This means that they may not be much better at scattering S-band radar signals back towards the radar than the average winch, and S-band may be the only radar in use on the high seas (if any).
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“Rozendal also offers a Mini-Lens reflector, which as expected given its small size, cannot compete with any reflector on the market except for the Mobri."