Benefits of CHIRP sounders:
Standard, non-CHIRP Fish Finders operate at one or two individual frequencies
and are generally capable of detecting targets and displaying them only within
those narrow frequency bands. CHIRP Fish Finders transmit pulses across a wide
range of frequencies, allowing superior digital signal processing (DSP) to
display fish and structure targets with unparalleled clarity, accuracy and
Typical Non-CHIRP Fish Finders operate with a maximum duty cycle of 1%
- meaning they transmit a voltage to the transducer no more than 1% of the time.
Consequently the transmit pulse can be high power but very short duration,
limiting the total energy that is transmitted into the water column.
The CHIRP Fish Finders uses a precise sweep pattern across frequencies
within a long-duration transmission. The equivalent sound energy transmitted
into the water is 10 to 1,000 times greater than a conventional Fish Finder,
resulting in more energy on target. The results are up to 5x greater resolution
and depth capability than comparably powered, standard Fish Finders due to the
advanced signal processing of the return echo.
Airmar offers "True Broadband" Transducers that can operate at a "broad
band" of frequencies, not just the traditional 50kHz and 200kHz frequency
selections of traditional fishfinders. See the image below that explains this.
Airmar achieves superior results by using a unique ceramic
material. It lets transducers operate over a broad range of
frequencies while maintaining sensitivity. These Broadband
Transducers are, by definition, low-Q devices (refer to “Q”
paragraph). In other words, they exhibit very low ringing.
There is little variation from transducer to transducer.
Additionally, Broadband Transducers are relatively immune
to the effects of aging, so their frequency range remains
stable over time.
Airmar is the first to introduce affordable Broadband
Transducers. This is an enabling technology that provides
better fish detection today and will lead to dramatic
advances in echosounder performance in the future. While
these transducers are more costly to manufacture, the
present and future benefits are huge.
Broadband Transducers enhance fish detection on virtually
all of today’s fishfinders. They give better definition; it is far
easier to distinguish among individual fish and between fish
and the bottom.
Broadband Benefits Today
Manufacturers now market echosounders that can adjust
operating frequency and power output. While these are
premium products, the designs are a precursor of things to
come. With the ability to adjust frequency, an echosounder
can operate Airmar’s broadband ceramics anywhere in
the frequency band. By selecting different operating
frequencies, two or more sounders can work simultaneously
without interference. The frequency can also be adjusted to
the mission. Lowering the operations frequency increases
the beamwidth and depth capability; raising the frequency
narrows the beamwidth, increases echo definition, and
improves high-speed performance.
Broadband Future Benefits
Here is where it gets really exciting. In today’s fishfinders,
good fish detection is obtained by transmitting a long
pulse. This puts more energy on the target. With a long
pulse, closely-spaced fish cannot be separated—you get a
big blob. Fish close to the bottom appear attached to the
bottom and are difficult or impossible to detect.
Airmar’s broadband transducers enable frequency
modulated (FM) transmissions; a.k.a. CHIRPor
transmissions. Using FM transmissions, you can achieve both
the benefits of long pulse, more energy on target, and short
pulse, segregation of closely-spaced fish and identification of
fish on or close to the bottom. This is because the coding of
the transmission is known and the return echoes are similarly
coded. The technique is also known as pulse compression.
In summary, fishfinders of the future with FM transmissions
will have dramatically improved target resolution and
signal-to-noise ratio. Airmar’s broadband transducer
technology will enable this to happen.
A Transducer’s quality factor, or “Q” describes the amount
of ringing the ceramic element or elements undergo when
power is applied to the transducer. Think of a church bell
analogy—as the bell is struck it vibrates rapidly and then the
vibration will eventually stop until the bell is struck again.
Most competitor’s recreational transducers have an average
Q between 25 and 35. Airmar Q values range from 1 to 30,
depending on models. The lower the “Q” number the less
ringing in the transducer and the better the performance.
Less ringing greatly improves individual fish separation along
with bottom imaging in rapidly changing water depths such
as ledges and offshore canyons.
Due to the nature of CHIRP
transducers generate more heat than traditional tone burst
transducers operating at distinct frequencies. CHIRP
require heat sinks in their construction to dissipate this heat. Airmar's
transducers have been designed to be installed in specific ways
according to the number and placement of these heat sinks. To install a
transducer in a way other than intended by the manufacturer would
lead to the transducer overheating and could result in transducer failure.
External thru-hull mount transducers must be installed as external
thru-hulls. They can not be flush mounted or keel mounted or pocket mounted or
fiberglassed into the hull in any way. If you wish to mount a transducer this
way, be advised that Airmar makes equivalent transducers with extra heat sinks
that are appropriate to be installed this way. See the Pocket/Keel Mount
CHIRPbrochure available for viewing on Airmar's home page by clicking
the link near the bottom of the page or click the link below.