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CHIRP Power

Old 02-26-2012, 02:05 PM
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Semper:

Like many folks here on THT I am very interested in CHIRP and had read everything I can find on the subject. Your comments, discussions and links have been very informative and are very much appreciated.

I do however have a question concerning CHIRP power. If I understand things correctly Tone Burst sonar does to a large degree depend on power (600W, 1000W, 3000W, etc) to increase target definition and range and that CHIRP uses bandwidth and frequency scanning to accomplish greater target definition and increased range.

What I don’t understand is where CHIRP power fits into the equation. Let’s assume for the sake of this discussion that the B265 uses 100W of power (A totally fictitious figure). What would happen if you increased the power to 200W or 500W? If nothing is gained are we to assume that once the minimum power requirements of a system are met then the system has reached its maximum capability?

If increasing power does not increase the capability of CHIRP then it appears that the easiest or only way to increase capability is to add elements i.e. B265 = 7 & 1, R109 = 15 & 1 and R509 = 24 & 1 – more elements = more money = more capability. Is this true?

If each of the CHIRP manufactures are using the same transducers and power is not a factor than it would appear that the way each manufacturer processes and displays the transducer signal would determine which one would be “The Best”. Would this be a fair assessment?

Now if Furuno would get off its ass and release a stand -alone CHIRP system I think a lot of us would be happy campers.
Old 02-26-2012, 03:11 PM
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This is the same issue for radar as for sonar. The issue is not just power.....it's power applied over time, aka energy.

Chirp waveforms transmit at some nominal power (fill in your favorite) for more milliseconds than the so-called tone burst sonars. It comes down to watt-seconds, not just watts. The tone burst may boast lots of power (watts), but cop out on the duration of the power burst (watt seconds). Chirp, similar to BR/3G/4G radars, transmit a coded pulse over a longer period of time, usually at less peak power, but then run signal processing algorithms to package up those extra seconds of watts into more "energy on target".

More power is mostly always a "good" thing, but for a particular waveform design, it may stress the heck out of transmitter components. A transmitter that can deliver a modest level of power for a much longer TIME will carry the day.

Chirp transducers need to be capable of delivering the acoustic punch across a wider range of frequencies and do it at a fairly constant power level across the band.

Using chirp waveforms that get long in time to help drive energy-on-target start to cause a longer blind spot beneath the boat similar to minimum range in radar. I'll be interested to see if anyone decides to do FM/CW like the 3 and 4G radar waveform to enable the use of "chirp-like" waveforms right up to the props.

Think "Energy"....it's the new "Power"!!
Old 02-26-2012, 03:18 PM
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CHIRP and power....

Traditional tone pulse systems have this drawback.
To get target resolution one must use a higher frequency as a shorter pulse gives the best results.
But, with a short pulse length you are limited in depth as there is not enough energy in a short pulse to obtain adequate depth.

Lower frequencies in a tone pulse system can put far more energy into the water but the longer pulses do not have good target resolution.
Traditional sonars have a single carrier frequency and fire just a single pulse per duty cycle.

But with CHIRP, the frequency within the burst is changed..swept.. though the duration of the transmission, from one frequency to another.
Thus you may have a bandwidth of from 28 to 600 kHz for example.
So instead of a single tone burst at a set frequency ...CHIRP fires across an entire bandwidth producing far greater continued energy into the water but at a total of less energy required.

This is a simplified explanation but in a nutshell: CHIRP does produce far great depth and detail with only a fraction of the power required in traditional tone pulse systems.

And CHIRP utilizes a higher performing transducer...A CHIRP B265 for example.. has 750 times more round trip sensitivity than its tone pulse B260 counterpart.
And correct..the number of elements in a CHIRP transducer are its key requirement for different levels of performance.

Link to posting on CHIRP transducers:
http://www.thehulltruth.com/marine-e...o-you-get.html


The key here is this..one needs to actually take a ride on a CHIRP equipped boat..and few are currently out there.
Seeing is believing....and hands on use will make a believer of many of those in doubt.
This time next year that situation will have dramatically been changed as CHIRP is a major part of sonars future.

Last edited by semperfifishing; 02-26-2012 at 04:54 PM.
Old 02-26-2012, 03:46 PM
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Is this longer blindspot under the boat, longer than a tone pulse and how big is this blindspot likely to be compared to the tone pulse?

If this is true are you going to lose performance in the upper water column?
Matt
Old 02-26-2012, 03:56 PM
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Originally Posted by Matt1 View Post
Is this longer blindspot under the boat, longer than a tone pulse and how big is this blindspot likely to be compared to the tone pulse?

If this is true are you going to lose performance in the upper water column?
Matt
"Blind spots"..are result of cone angle more than anything else.

With a CHIRP system you have a continually changing cone angle.
For example: The CHIRP B765 will have a cone width from 9 to 15 degrees on the High end and a cone of 40 to 21 degrees on the low end.

At 10' below the boat the cone width is 7' wide.

And you have superb performance in the upper water column. Even the B265 has a cone of 25 to 16 degres on the low end.
And the B265 has 1000 times more round trip sensitivity than a P66.

CHIRP will not lose performance in any part of the water column ....it dramatically gains performance.


Simply select the transducer that best fits your fishing conditions.

Last edited by semperfifishing; 02-26-2012 at 04:47 PM.
Old 02-26-2012, 04:54 PM
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Gil:
Let me apologize if I am not communicating very well. I fully understand what you said in your reply and in previous posts about the difference in how Tone Burst and CHIRP transducers work and I fully realize that the emerging CHIRP systems give greater target definition and depth than Tone Burst. I also know you don’t buy CHIRP transducers by power, i.e. output watts.

But I still would like to know where power fits into the CHIRP equation, hence my question;

“What I don’t understand is where CHIRP power fits into the equation. Let’s assume for the sake of this discussion that the B265 uses 100W of power (A totally fictitious figure). What would happen if you increased the power to 200W or 500W? If nothing is gained are we to assume that once the minimum power requirements of a system are met then the system has reached its maximum capability?”

If I am correct the power for the transducer comes from the sonar unit. For the sake of discussion let’s say you have three sonar units A, B, and C from different manufactures and each one is connected to an identical CHIRP transducer which requires X amount of power to operate. Let’s further ASSUME sonar A puts out X power, B puts out 2X power and C puts out 3X power. Are you saying that all three systems will operate the same and that the additional power output of B and C will not result in greater performance? Don’t you see a time in the near future when CHIRP gets more main stream and the advertising toads get into the picture that we will see “My unit is more powerful than your unit” advertising?

My question is more of a hypothetical question and has very little practical value other than “Inquiring minds just want to know”. Thanks for putting up with me and OBTW since “The only substitute for cubic inches is more cubic inches” my mind is keeps telling me “More watts is better”

SB
Old 02-26-2012, 05:12 PM
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No need to apologize....this is a new playing field and the rules and boundaries are indeed different.
Very different.

Let me state this as clearly as possible.

In CHIRP ...power is the least ....and I mean the very,very,very least of what the end user should be concerned about.
Power is a term that is important only with traditional tone pulse systems...not CHIRP.

Think of it this way.

One singer is on the stage at Carnegie Hall.
One single voice...at a normal and pleasant level.
To fill the auditorium with overwhelming sound...he would have to really,really raise his volume..or more "power"..

Now add 3000 singers..
3000 voices all singing at the same normal pleasant level .
Carnegie Hall would be filled with sound..and yet no one needed to raise their voice to do so..it was the whole group together.
More combined energy.
The same with CHIRP.

What will separate one CHIRP manufactures system from another?
Not power......perhaps slick advertising slogans, fancy coined phrases and terminology .
Plus the catch of the day proudly held on high.

It's worked before.

Last edited by semperfifishing; 02-27-2012 at 12:02 PM.

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