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What is CHIRP Sonar?

What is CHIRP Sonar?

CHIRP (Compressed High-Intensity Radiated Pulse) sonar is a powerful bottom-tracking and fish-finding tool. By continuously sweeping through a range of frequencies, CHIRP fishfinders transmit a longer pulse than traditional sonar, putting more energy into the water column, with a true broadband frequency range of up to 117kHz.

Traditional VS CHIRP

Instead of pinging a single frequency like traditional 2D sonar, CHIRPing devices transmit a sweeping range of frequencies. With each pulse, the transducer starts vibrating at a low frequency, which is then modulated upward to a high frequency over the duration of the pulse (130 to 210kHz, for example).

A traditional sonar transmits about one percent of the time, but CHIRP sonars transmit ascending pulses that are ten times as long in duration. They put dramatically more energy into the water column, 10 to 50 times more, even though CHIRP devices often transmit at lower peak power than traditional fishfinders.

What most of use have always used is called tone burst.....or simply ..single pulse sonar. During 1 duty cycle a tone burst fires a single pulse which travels as a sound wave thru the water and will react to the different targets it meets depending on the density of each target.

We look mainly for fish....and a fish is almost 70% water..so this sound wave sees little change in the density of the fishes body as compared to water..and most passes right thru....except for the higher density of the swim bladder.
It is the higher density gas filled swim bladder that gives the greatest reflection back up to the surface of the sound wave.

So for the older tone burst..one "Ping" down..rates one "Ping" back...and at only one frequency and one cone angle.

To increase the energy onto the bladder a tone burst must increase the wattage.


Look at it this way.

Fire one single .22 short at a concrete block....very little energy onto the target....that is like a single pulse tone burst.
To increase the energy onto the target one must step up in caliber...(or increase the wattage in the sonar)
Now...
At that same block fire 50 .22 shorts with a spacing of a fraction of a second total between them at the same block...far more energy onto the target.

That is the key to CHIRP

Greater energy onto the target with far less actual wattage used..and advanced return signal processing for finer detail and target separation.

CHIRP Frequencies

Which CHIRP frequencies should you choose? The basics are similar to the traditional 2D sonar:

  • High CHIRP (150–240 kHz) is for inland and freshwater; best choice for lure tracking, identifying game fish and baitfish targets, or for targeting game fish near bottom structure. Best for depths less than 600 feet
  • Medium CHIRP (80–160kHz) displays a wider coverage area, scanning large areas more quickly, showing larger fish arches but providing less detail than high CHIRP for seeing smaller objects. Like high CHIRP, it’s best for depths less than 600 feet
  • Low CHIRP (below 80 kHz) is used in deep water over 600 feet, offers amazing depth performance (up to 10,000 feet) and marks targets at all depths in the water column

Is CHIRP Sonar Worth It?

If you're looking for a game changer in sonar technologies that will swiftly receive and process vast information in clear detail to gain unprecedented resolution and vivid definition of targets, the CHIRP on a fish finder is the way to go.

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