Source: Mariners Learning System, By Captain Bob Figular & americanboating.org

All radars have seven main operator controls, though these may be combined with each other, automated, or buried in a system of menus or soft keys along with other controls.

The on/standby/transmit control is used to turn the set on. It will have to be left in its standby mode for at least a minute or two while the magnetron (the component that actually generates the microwaves) warms up. On most modern Radar sets this warm-up period is indicated by a count down timer on the screen. Once the warm-up is completed, switching to transmit mode turns the transmitter on.

The brilliance control determines the brightness of the picture exactly the same as you would adjust your television and should be adjusted to give a clear image. On radars with a liquid crystal display, the brilliance control may have to be used in conjunction with the contrast setting; the two are interdependent, and their adjustment depends on the angle from which you are looking at the screen.

Gain refers to the amount of amplification applied to the returning echo. Some new Radar operators confuse the effect of the gain control with that of brilliance because turning it up makes weak contacts look bigger, brighter and more consistent. The two are not interchangeable, however: brilliance is adjusted to make the picture clearer or more comfortable to look at; whereas the setting of the gain control can determine whether some contacts appear at all.

The range control, as its name suggests, is used to adjust the operating range of the set, typically you will find eight separate settings from one eighth or one quarter of a mile, to between 16 and 48 miles. Short ranges (between half a mile and 4 miles) are generally of most use for piloting in ports and harbors; medium ranges (4, 6 or 8 miles) for collision avoidance and long ranges (8 to 24 miles) for coastal and offshore navigation.

The tuning control is used to adjust the receiver so you get best possible reception of incoming signals. The radar’s tuning control offers a very fine adjustment allowing for small variations in the transmitting frequency. These variations are normally caused by changes of temperature.

Sea clutter control is sometimes called STC or swept gain, and is used to remove the clutter caused by echoes from waves, that can otherwise form a bright circle or starburst pattern in the center of the Radars screen.

Rain clutter control is sometimes known as FTC or differentiation and, as its name suggests, is used to remove the clutter caused by meteorological effects such as rain, snow or hail. A heavy rain shower can be quite an effective reflector of radar pulses, but it does not reflect them in the same way as a solid object. Instead of returning an echo which is a crisp copy of the transmitted pulse, rain echoes are weaker but more drawn out. On the screen this produces a large but relatively diffuse contact, often described as looking like a smudge or ‘cotton wool’.