Technical data

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TruEcho CHIRP
TruEcho CHIRP combines the benefits of CHIRP broadband with
Furuno’s legendary Digital Signal Processing, along with unique
Furuno features like Bottom Discrimination and Accu-Fish.
What is CHIRP?
CHIRP, or Compressed High Intensity Radar Pulse, has been used
by the military, geologists and oceanographers since the 1950’s.
It is only recently that this technology has become available for
widespread use on personal vessels, and it’s taken the sport fishing
world by storm.
CHIRP transducers employ sinusoidal waveforms whose instantaneous frequency increases or decreas-
es linearly over time.
Wait, what?
In plain language, this means that the transducer elements vibrate across a range of frequencies. With
each pulse, the transducer will begin vibrating at a low frequency, which will then be modulated upwards
to a higher frequency throughout the duration of that pulse. Sonic information is sent and received at
each individual frequency in the range, which is represented as a single waveform. These waveforms are
commonly referred to as linear chirps or simply chirps. So, a single CHIRP sounder will transmit and
receive information across as many as 90 different frequencies.
So, what is the benefit of a CHIRP sounder over a single- or dual-frequency sounder? Let’s take a look at a
standard, dual-frequency sounder. Most non-CHIRP fishfinders operate at discrete frequencies of 50kHz
and 200kHz. They transmit a pulse only at these discrete frequencies. Typical Non-CHIRP fishfinders
operate with a maximum duty cycle of 1%, meaning they transmit a voltage to the transducer no more
than 1% of the time. The rest of the time, they are listening for return echoes. Consequently the transmit
pulse can be high power but of very short duration, limiting the total energy that is transmitted into the
water column. CHIRP sounders use a precise sweep pattern modulated within a range of frequencies all
within a single long-duration transmit pulse. Because the transmission lasts for a longer amount of time,
more energy is directed into the water column. The equivalent sound energy transmitted into the water
can be up to 1,000 times greater than a conventional fishfinder, resulting in more energy on target. The
results are up to 5x greater resolution and depth capability than standard fishfinders.
"Q" - What is it, and why does it matter?
Q is a measure of a transducer’s quality factor. It is a number between 2 and 35 that describes the amount
of bandwidth, as well as the ringing the ceramic element or elements undergo when voltage is applied to
the transducer. The lower the Q rating, the better the performance. A high Q rating means the transmit-
ted acoustic pulse is extensively elongated, while a low Q means the acoustic pulse has minimal elonga-
tion. What this means is that with a high Q transducer, two close targets will blend together, and will not
be displayed as individual targets. With a low Q transducer, those two close targets can be distinguished
individually (better target discrimination), and each target will be resolved on the display.
Through Hull
Through-hull transducers require that a hole is cut in the hull, so
their installation is more involved than a relatively simple tran-
som mount. They are also more difficult to access for periodic
cleaning, which they may require more often than a typical tran-
som mount transducer. Owners of trailerable boats with through-
hull transducers must be careful not to damage it when launching
or loading the boat.
To keep the transducer facing squarely downward into the water
column, a fairing block must be used. The fairing block is installed
parallel to the flow of water to ensure proper boat handling, and
this will not necessarily be the same from hull to hull.
A fair amount of skill is required to achieve a proper through-hull installation. If in doubt, don’t go
it alone - consult your local Furuno dealer for assistance.
Transom Mount
Transom mounting is the simplest method of transducer installation and is
most common among smaller boats. The transducer is installed on the tran-
som, slightly below the waterline. The transducer face should be at a slight
angle forward so as to reduce the effects of turbulence and aerated water.
In-Hull or Shoot-Through
A third option when mounting your transducer is referred to as
an in- hull, or shoot-through installation. An in-hull transducer is
mounted on the inside of the hull. The transducer signal ‘shoots
through’ the fiberglass and so the hull does not require a hole
cut in it, although certain hull types may need to be bored out
to remove any flotation material. When properly installed the
effects of turbulence and aerated water are minimized. Because
the transducer face does not touch water, there is no real mainte-
nance involved with an in-hull transducer. These are compelling
arguments for shoot-through installations.
These benefits do not come without a price, and that price is performance. The signal will experi-
ence loss when shooting through the hull material. This means that the performance of your fish
finder will suffer. Most modern in-hull transducers are designed to compensate for this loss.
Boats with wood, aluminum or steel hulls will not be able to use in-hull transducers, as these mate-
rials act as a very effective barrier against the acoustic signal. Sound waves simply will not propa-
gate through these materials. Only fiberglass boats, with no flotation core, can utilize an in-hull
transducer. Fiberglass boats with foam or balsa cores or those with air pockets will need to be ‘dug
out’ so that the face of the transducer touches the fiberglass. This can make installing an in-hull
transducer a tricky proposition.