America’s National Maritime Museum
MarinersMuseum.org • (757) 596-2222
Exit 258A from I- 64 • Newport News , VA
;e Mariners’ Museum and Park connects people to the
world’s waters. ;e peoples’ stories that are told through
our world class collection are your stories, your history.
come to life! while long-range performance is excellent, very short ranges
Instead of using strong bursts of power, some newer solid-state radar units instead calculate the difference between
transmitted and received frequencies. The advantage is better
target discrimination at short range; there’s no big burst, so
there’s no main bang. Their range, however, is often more
limited than that of traditional radar.
The latest and greatest units may combine these two
technologies, and some also apply Doppler enhancements.
Remember learning about the Doppler effect in high school?
As an ambulance gets closer and closer, the frequency of its
siren sounds higher and higher, and as it gets farther away, the
frequency sounds lower and lower. Many of the latest marine
radar use this same principle to help determine the speed and
hazard-level of moving targets.
The strength of a radar’s return depends on a number of variables, including the target’s material, shape, and size. That’s
why some items (such as channel markers, which are designed
to maximize radar returns) may appear to be
bigger on radar than a boat 10 times their
size. This is also why small fiberglass boats
may not show up on some radar at all, or
may show up only at very close range. Your
radar’s beam width also has a big impact
on how it sees things. The narrower the
beam, the more gain (intensity) it has, and
the more range it will have at a given power
level. Beam width is determined by antenna
size, which is why larger, open-array units
generally have much narrower beam widths, and hence more
maximum range, than small, enclosed-dome antennas.
What’s most important to recognize about radar range,
however, is that beam width, power, and every other factor
gets trumped by the curvature of the Earth. Radar is “line-of-
It’s much easier to tell what you’re seeing on screen when your
radar is overlaid on your chartplotter. The red areas show the
radar “echo” and clearly delineate the coastal outline.
about Broadband Radar.