And this was at less than 18 heel, over which its performance fell off dramatically. At 2.5 m2, however, just 30% of the returns exceeded the threshold. Had the minimum average RCS been just 2.0 m2, the Lensref would have easily won with 100% of returns greater than the threshold. The Lensref has virtually no nulls its polar plot is a virtual circle. In the double-catch rain position and 20 heel, just 43% of returns were above 2.5 m2. The top-performing reflector six years ago was the Davis Echomaster in the vertex up position with 0 heel, which registered 63% of returns above 2.5 m2. We also tested the Radar Flag, which was practically invisible. Reflectors tested in the 1995 report included the octahedral Davis Echomaster and Emergency the trihedral and dihedral-based Holland Yacht Equipment, Firdell Blipper, Mobri, High Gain Rotation and Cyclops and the Luneburg lens-type Lensref. Many radar units are not continually monitored but set to automatically sound an alarm if a target registers three consecutive “hits.” One big hit wont alert the ship’s crew that a smaller vessel is in the vicinity. So, small reflectors must be looked at with a great deal of suspicion, as there really is no substitute for size.”īesides strength of return, consistency also is critical. Remember that a wavelength is 3.2 cm (1-1/4″) for X-band, and 10 cm (4″) for S-band. 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. Doubling a reflector’s size increases its effective area 16 times. Radar reflector performance is a direct function of size, proportional to the fourth power of its linear size. In our 1995 test, a recommended minimum average RCS of 2.5 m2 was adopted at the suggestion of GEC Marconi, maker of the Firdell Blipper reflector. Radar reflectors are described in terms of their Radar Cross Selection (RCS) and their performance is measured in decibels (dB) relative to some reference, usually a 1m2 sphere (profile). Ship operators generally use their X-band radar near shore because it has better resolution and can pick up smaller targets better than S-band, which is commonly preferred offshore due to its longer range and superior resistance to sea clutter. S-band radar is used aboard large ships and operates at 3 GHz with a wavelength of 10 cm. It operates at a frequency of about 9.4 GHz (9400 MHz) and has a wavelength of 3.2 centimeters (cm). The former is the type commonly carried aboard small boats. Marine radar is of two types: X-band and S-band. Stan also assisted, as did West Marines Chuck Hawley and a third member of this Bay Area brain trust, Jim Corenman. This was made possible thanks to Dick Honey, then a semi-retired senior principal scientist at SRI, uncle to former SRI research engineer, well-known navigator and sailor Stan Honey (also the guy who puts the yellow first-down band across the screen of your TV during pro football games). In the September 1995 issue, we reported results of radar reflector testing done at the Stanford Research Institute in Palo Alto, California.
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