The rain clutter control will reduce the interference on the screen due to the rain and increase the chance of seeing targets within rain showers. The effect on returning echoes from rain on the screen is usually no more than a transparent smear, looking a little like cotton wool, but it can be dense enough to conceal other echoes within the shower. In a tropical downpour however, the rain can completely block out all echoes, at times requiring the operator to stop the vessel.
The rain clutter control works by making use of the fact that the returning echo from rain is different from the returning echo of a solid object. The returning echo from rain is much longer and very much less dense than the echo from a solid object. The rain clutter circuitry works by passing on to the receiver only the leading edge of a returning echo. This does not affect the returning echo from a solid object like a ship, but drawn out, weak returning echoes from the rain however, will be weakened considerably.
In practice however all returning echoes will be affected, resulting in a reduction in strength from all returning echoes and a reduction in picture quality. Sometimes the sea clutter control may be used to better effect, to see through the rain. However, if you adopt this approach remember that close-in targets will also be lost, which may defeat the purpose.