CHIRP
Also called compressed high intensity radar pulse
Sonar that sweeps a range of frequencies instead of firing one, producing sharper arches and better separation.
Traditional sonar sends a single frequency pulse. CHIRP sends a sweep across a band, which means each return carries more information and the unit can distinguish objects that a single frequency would blur together.
What you actually see is separation. Two fish sitting a foot apart show as two marks rather than one blob, and a fish holding tight to a brush pile stays distinguishable from the brush. That is exactly the situation where a fish finder earns its money.
CHIRP is now standard on all but the cheapest units, so it is less a feature to hunt for than a reason not to buy the very bottom of the range. Where it still varies is the transducer, since a unit only sweeps the bands its transducer can produce.
The sweep also cuts noise. Because the return carries a known signature, the unit can discard echoes that do not match. A CHIRP screen therefore looks cleaner at speed and in choppy water than a single-frequency one.
On a mixed unit, run high CHIRP frequencies in shallow water for detail and lower ones in deep water for range.
Related terms
Where this comes up
The guides that use chirp and show it on real gear.
CHIRP is one of 206 terms in the glossary.
Browse the full fishing glossary