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CHIRP - Practically, What Do You Get?

Old 02-23-2012, 07:41 PM
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Default CHIRP - Practically, What Do You Get?

CHIRP is much more sensitive that the standard pulse sonar and works in much deeper water, but in the real world, what does it really get you if you are fishing in 1,000 feet or less? Either technology will show baitfish or gamefish in the water column. It appears that CHIRP, instead of showing a mass of fish, will provide some separation showing individual fish. I am not sure that is overwhelmingly useful as you are going to put your bait in the middle of the mass anyway.

Does CHIRP show a lot of fish that otherwise wouldn't show up on a pulse fishfinder because they are too close to the bottom or a wreck? Does it show flounder lying on the bottom or on rubble or a wreck? What else shows up that you wouldn't see if you are just using regular pulse sonar?

I am just trying to figure out specifically and practically what it provides over traditional pulse sonar.
Old 02-23-2012, 08:24 PM
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Simply this.. improved performance over the traditional tone pulse system in regards to every sonar paramater.

Detection of targets within inches of the bottom, finer bottom detail..even at greater depths.
Finer target separation and great resolution...far less noise under difficult water conditions.

And most importantly...the ability to search and display targets across an entire bandwidth rather than just one specific frequency such as in a traditional sonar system.

Example: Covering from 28 to 210 kHz in a continuous sweeping pulse..rather than just a single 50 or 200 kHz pulse.
Many experienced commercial fisherman have long used tunable sonars & transducers....being able to choose a frequency to detect certain species is most helpful.
Chirp sweeping the entire band provides amazing variation and flexibility.

And add to that...

You can even use CHIRP transducers in a non CHIRP sonar system and gain vastly improved results as long as they are tunable sonar systems.
For example: You can use a CHIRP transducer with any tunable sonar such as the Furuno FCV295 or FCV1150.


CHIRP is certainly not needed nor applicable for every fishing condition or pocket book.
But for a new boat build this is certainly an option that should be considered.
A complete CHIRP system can be installed for under $5K.
Considering the total cost of a new boat build ...this is could be the portion of the dollars spent that really pays dividends.

Last edited by semperfifishing; 02-23-2012 at 09:00 PM.
Old 02-25-2012, 04:07 AM
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I am looking to better understand CHIRP as I select electronics for my center console. It is small, 22'. I plan to use it to scout bottom spots and fish when I am short handed. Depth of water never more than 300-400 ft realistically.

I have an older NavNet on my offshore boat. Happy with it and it still works well. I wouldn't hesitate to install Chirp sounder when the NavNet goes down, but is Chirp over kill for a 22' boat?

Last edited by RK-AL; 02-25-2012 at 04:08 AM. Reason: correction
Old 02-25-2012, 04:15 AM
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i have a bsm 2 with the nse12 on my 22 foot hewewscraft hard top.seamed like a good choice to me.
Old 02-25-2012, 02:01 PM
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It is a better technology, but what isn't clear is exactly what that means in real life fishing conditions in 50-800 feet of water. Specifically, what useful information will you see that you wouldn't have seen with a good, regular pulse sounder system such as a Furuno 585 with a 1K thru-hull transducer?

I can't find any information establishing that you get more than better definition of what you would see on a pulse system anyway and the ability to see down to 10,000 feet, which isn't necessarily a plus for most fishermen.
Old 02-25-2012, 03:05 PM
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Can someone point me in the direction of a real good description of the CHIRP sonar waveforms? As a retired radar engineer, I'm assuming it is not unlike the broadband radar which uses a FM/CWI which could also be referred to as "chirp" in the radar world.

The problem applying such techniques in water vs. radio frequencies above water is that water is not a "coherent" medium to transmit and receive through, but it should work OK. In other words, water distorts complex waveforms far more than air distorts radar waveforms. The basic principles should still apply.

If that is what CHIRP really is (which is why I'd like a link to a description) then CHIRP sonar would provide improved range resolution of targets underwater. If "pulse compression" is employed in sigpro, then it would also deliver gain and improved detection of smaller targets as well, similar to transmitting a more powerful ping.
Old 02-25-2012, 05:38 PM
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Originally Posted by capecuddy View Post
Can someone point me in the direction of a real good description of the CHIRP sonar waveforms? As a retired radar engineer, I'm assuming it is not unlike the broadband radar which uses a FM/CWI which could also be referred to as "chirp" in the radar world.

The problem applying such techniques in water vs. radio frequencies above water is that water is not a "coherent" medium to transmit and receive through, but it should work OK. In other words, water distorts complex waveforms far more than air distorts radar waveforms. The basic principles should still apply.

If that is what CHIRP really is (which is why I'd like a link to a description) then CHIRP sonar would provide improved range resolution of targets underwater. If "pulse compression" is employed in sigpro, then it would also deliver gain and improved detection of smaller targets as well, similar to transmitting a more powerful ping.
very hard to find facts - just marketing generalisations.

theres a video on utube showing the transmit going from low to high frequency at a steady rate. but i think the guy is just demonstating chirp principles not particularly what is in these sounders.

i for one would really look forward to and appreciate some expert technical analysis.
Old 02-25-2012, 07:06 PM
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Originally Posted by capecuddy View Post
Can someone point me in the direction of a real good description of the CHIRP sonar waveforms?

.
Here are a few selections to start you out.

http://themarineinstallersrant.blogs...g-what-up.html

http://www.mbari.org/data/mbsystem/s...rocessing.html

http://www.dsprelated.com/showmessage/72221/1.php

http://digitalcommons.uri.edu/dissertations/AAI9008849/

http://www.mstarlabs.com/dsp/sonar-chirp-signals.html

http://woodshole.er.usgs.gov/operati...onar_equip.htm

http://www.tritech.co.uk/products/chirp.htm

http://www.starfishsonar.com/technology/chirp.htm


Quote:
Originally Posted by Matt1
Maybe semper can jump in here and clarify. There is obviously a number of people who believe these CHIRP systems are for the blokes who have no idea how to use a sounder correctly and/or tune one manually! Do you believe this to be the case?

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

No, I am not of that opinion.
I think that CHIRP is an improved and advanced system in total.

Anyone currently using a traditional system is wise to stay with that system if it fits their style and needs.
Anyone who is undergoing a total re-fit or a new build should at least consider learning about CHIRP systems.
That is what my goal..to help provide technical information concerning all sonar systems.
Including CHIRP.
In that way one can make a choice based upon technical information rather than advertising hype.
An informed choice.

This is a superior system compared to a traditional tone pulse sonar.
If not so..why has every manufacture spent the last several years in costly development....just to give everyone something "user friendly" ?
No, this is a better system.
And it is a system..both CHIRP sonar and CHIRP transducer.

Lets start with just the CHIRP transducers. (I will cover the CHIRP sonar itself later)

All sonars are only as good as their transducers.
Traditional tone pulse sonars are still limited by high power requirement to gain depth , signal to noise ratio and transducer quality.

CHIRP uses only a fraction of the power required by traditional tone pulse units...but transmits more energy into the water.
Increased energy onto the target means greater return echo energy which leads to improved target resolution.
Add a superbly sensitive CHIRP transducer.....the gain in target separation and resolution is impressive.

CHIRP transducers have higher quality ratings... a Q of 3 and less .
The lower the Q the less ringing.

The increase in round trip sensitivity of a CHIRP transducer over a traditional transducer is pronounced.
I have customers who are blown away with the improvement from a B60 to a B260...that is an increase of 250 times round trip sensitivity on the low band and 50 times on the high side.
The CHIRP B265 is 1000 times more sensitive on the low side than the B60...120 times on the high side.
The CHIRP B265 is 750 times more sensitive than the traditional tone pulse B260 on the low side and 70 times more sensitive on the high side.

The CHIRP B265 is the same size as the B260 but 750 times more sensitive.
Twice as good and the same physical size would be bragging rights.

But 750 times better........thats impressive.


You cannot debate just CHIRP sounder technology vs traditional sounders.
One must also include comparison of CHIRP transducers. vs traditional transducers.
It's a total system...and with major advancements by way of the CHIRP sonar module and CHIRP transducers.
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Last edited by semperfifishing; 02-29-2012 at 08:00 PM.
Old 02-25-2012, 08:00 PM
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Originally Posted by RK-AL View Post

I wouldn't hesitate to install Chirp sounder when the NavNet goes down, but is Chirp over kill for a 22' boat?
I installed a full CHIRP system for a customer with a 20' boat who fishes fresh water lakes, the Ca Delta and a bit offshore.

He could never find halibut on sonar with any regularity..before..now he can.
He had great trouble finding sturgeon..not a problem now.
And he had real problems with landlocked King salmon...not now.

He is very happy.

Last edited by semperfifishing; 02-26-2012 at 01:01 AM.
Old 02-26-2012, 04:56 AM
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If I can't swing a GSD 26 intially, can I buy a TM265 and use it with the GSD 24 until I can move up?
Old 02-26-2012, 07:37 AM
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Originally Posted by Miss Sadie View Post
If I can't swing a GSD 26 intially, can I buy a TM265 and use it with the GSD 24 until I can move up?
Yes, you can use aTM265 with a Garmin GSD-24 but please read the conditions.

1. The TM265 is a dual transmission line and you must connect it first thru a diplex box.

2.At this time it is not known if the 50 kHz side of the TM265 will have any loss being used with GSD-24.
If you decide to do this contact Garmin support.

Airmar states:
http://faq.airmar.com/index.php?acti...irp+transdcuer

Note: This week Furuno is testing a 265 transducer with a FCV585 and will post results on its open forum how it compares to a traditional 260.
Old 02-26-2012, 09:09 AM
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Semperfifishing's statements are all on the money regarding the Chirp systems capabilities. I will post some screen shots here next week from a daytime sword fishing trip in 1500ft of water using the GSD 26 and the 3000w R599LH transducer. I'm finishing an article about selecting the right chirp transducer for various fishing scenarios, and boats.
Old 02-26-2012, 10:25 AM
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Thanks, semper for the great links.

In a quick look at the first two, the first confirms that CHIRP is the same technique as linear FM pulse compression in the radar world. It is also no surprise that Simrad features in the discussion, since they do employ similar techniques in their broadband radar as well.

The second link confirms the need to taper the signal processing "filter" applied to avoid ringing fore and aft of the compressed pulse. That ringing is referred to as range sidelobes and if large can create false targets, thus the need to taper the filter to avoid such sidelobe targets.

If you look back at my earlier note in this thread, I expressed concern about applying these radar techniques in underwater applications because they depend on constant speed of the waveform through water to its full extent and back again (the echo). While that is a piece o' cake in the radar world (speed of light is invariant) the speed of sound in water is variable and a function of temperature, salinity, pressure and currents/roughness. Not to worry, since we are really talking about just how far you can push the frequency bandwidth of the chirp waveform. The wider the bandwidth, the more the waveform will "slur" or "smear" due to sound speed variations and detract significantly from the gain and resolution vs. theoretical. The wider the bandwidth, the more the flatness in response of the transducer can enter into the fray.

Another encouraging thing is that in the world of fishing/boating, the range of operation is limited which also helps "hold up" the analogy to radar processing, since the shorter the range the less likely that the sound speed is distorted. In military applications, this is not the case and thus the use of linear FM chirp is of limited value.

Bottom line, the CHIRP claims that the techniques improve range (i.e., depth) resolution and sensitivity (due to signal processing gain in pulse compression) are reasonable and consistent with the same improvements in the radar world as long as the bandwidth of the chirp is not "too large" and the depth is not "too high". The wider the bandwidth and the deeper the range, the more bandaids that have to be applied in processing to "fix" the speed distortion (and processing power required to apply them!)

I'll keep reading but CHIRP sounds pretty good to me. I don't fish yet (spent the first season of retirement trying to stay off the sandbars and pointed between the ATON's and trying to keep at least some gelcoat on my hull after docking) so radar, GPS and VHF/DSC/AIS has been of more interest.

This is another example of why I tend to express the opinion that Simrad seems to be the guys driving the marine electronics industry from an R&D perspective. Between 4G radar and the BSM-2, these represent military techniques applied to commercial use. Simrad was most recently connected to Kongsberg Defense in Norway. Raymarine had its connection to my old Big Red, but it is longer ago and more constipated by export restrictions in the US. Now they are playing catch-up.
Old 02-26-2012, 04:19 PM
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Originally Posted by capecuddy View Post
Bottom line, the CHIRP claims that the techniques improve range (i.e., depth) resolution and sensitivity (due to signal processing gain in pulse compression) are reasonable and consistent with the same improvements in the radar world as long as the bandwidth of the chirp is not "too large" and the depth is not "too high". The wider the bandwidth and the deeper the range, the more bandaids that have to be applied in processing to "fix" the speed distortion (and processing power required to apply them!)
Based on this and your related experience and knowledge, what are we likely to see with a CHIRP system that we wouldn't have seen with a traditional sonar/ fishfinder system? Performing more efficiently and at lower power is a good thing overall and may justify going this route for an entirely new system, but people with existing boats need more to justify a full system upgrade rather than just replacing parts that go bad.
Old 02-27-2012, 08:16 AM
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Originally Posted by Frank007 View Post
Based on this and your related experience and knowledge, what are we likely to see with a CHIRP system that we wouldn't have seen with a traditional sonar/ fishfinder system? Performing more efficiently and at lower power is a good thing overall and may justify going this route for an entirely new system, but people with existing boats need more to justify a full system upgrade rather than just replacing parts that go bad.
Finer ability to see that there are more than one target as opposed to one big blob.

Smaller objects at deeper depths.
Old 02-27-2012, 03:02 PM
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does the dopler effect come in to play as the boat mounted transducer rises and falls with the water movement ?

does it matter that the distance of target to transducer can be varying during the pulse given that the pulse length is long ?
Old 02-27-2012, 04:14 PM
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Originally Posted by semperfifishing View Post
I installed a full CHIRP system for a customer with a 20' boat who fishes fresh water lakes, the Ca Delta and a bit offshore.

He could never find halibut on sonar with any regularity..before..now he can.
He had great trouble finding sturgeon..not a problem now.
And he had real problems with landlocked King salmon...not now.

He is very happy.
Are you saying this technology can mark halibut on the bottom?
Old 02-27-2012, 04:42 PM
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Originally Posted by High Wire View Post
Are you saying this technology can mark halibut on the bottom?

Not directly on the bottom..they have to be off a bit.
Halibut are almost impossible to see except with tunable systems..but with CHIRP if they are there and moving around and of the direct bottom a bit they do show up.
But you will have excellent returns from even squid which many sonars do have problems with.

Last edited by semperfifishing; 02-27-2012 at 08:50 PM.
Old 02-27-2012, 08:38 PM
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It seems like, with CHIRP, you might see some fish near the bottom that you otherwise wouldn't see with a traditional pulse system but otherwise its doesn't seem to show you things you otherwise wouldn't see (just greater detail). It makes upgrading an existing system where the display isn't compatible with CHIRP harder to justify even if the added cost of CHIRP makes sense on a full install (new boat or much older electronics).
Old 02-29-2012, 08:37 AM
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Originally Posted by puppy View Post
does the dopler effect come in to play as the boat mounted transducer rises and falls with the water movement ?

does it matter that the distance of target to transducer can be varying during the pulse given that the pulse length is long ?
I doubt it.....motion is too small compared to ranges of operation.

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