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Understanding chirp..Sort of...

Old 03-01-2015, 08:12 PM
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Thumbs up Understanding chirp..Sort of...



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CHIRP..
How does it work.?
How is it different from what I am used to?
And do I really want it?

I hear these questions many times a day and all are valid questions...here is a very simplified explanation.


Comparing CHIRP and tone burst.

What most of use have always used is called tone burst.....or simply ..single pulse sonar.
During 1 duty cyle 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 blader 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.


......................

Now we look at CHIRP...

For one duty cycle instead of one "Ping" onto the swim bladder the CHIRP system fires multiple pulses.
If using a B175m for example...you will have a total of 50 pulses...sweeping from 85 kHz thru 135 khz and with a cone angle changing from 16 thru 10 degrees.
Each pulse a different frequency..and the cone coverage varying during the sweep.
So now without increase the wattage.. the energy onto the swim bladder is massive as compared to the tone burst system.
Add to that the CHIRP sonar compares the returned band to the one it sent out...more able to differentiate target information.
And CHIRP transducers are far more sensitive to the return signals.


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.
(And far greater returned energy to the surface in a CHIRP sonar system..with not needed increase in wattage.)

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.

Now it is hard to find any system that does employ one level of CHIRP..so it seems it is here to stay.




CHIRP ....I will show them real CHIRPING !

Last edited by semperfifishing; 02-08-2018 at 11:30 AM.
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Old 03-08-2015, 07:17 PM
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WOW Gil. That was one damn impressive answer...I am convinced and I will finish scraping together my pennies
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Old 03-08-2015, 08:13 PM
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Originally Posted by tedfest1 View Post
WOW Gil. That was one damn impressive answer...I am convinced and I will finish scraping together my pennies
Welcome to the forum. ...
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Old 04-02-2015, 01:57 PM
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Question Specific frequencies for targeting specific species

Is it true that specific frequencies are used to target specific fish species? Meaning certain fish will resonate better at various frequencies based upon their swim bladder density? If so, why doesn't Garmin/etc. publish these numbers? I understand that CHIRP can get better resolution of a potential fish but if two fish have the same dimensions but different densities can CHIRP help distinguish the species (within reason)?

Also, how well does this work as you go deeper?

We're using the Garmin GSD26 if that helps.

Thanks!
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Old 04-02-2015, 02:07 PM
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Originally Posted by gbrown2036 View Post
Is it true that specific frequencies are used to target specific fish species? Meaning certain fish will resonate better at various frequencies based upon their swim bladder density? If so, why doesn't Garmin/etc. publish these numbers? I understand that CHIRP can get better resolution of a potential fish but if two fish have the same dimensions but different densities can CHIRP help distinguish the species (within reason)?

Also, how well does this work as you go deeper?

We're using the Garmin GSD26 if that helps.

Thanks!
Most fisherman using tunable soanrs have used this technique for many , many years.

Each fisherman uses trial and error in his area and under his particular fishing paramaters..
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