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HB Greg, sonar cycles, pixels, chart and boat speed

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rnvinc:
Here is a what I hope to be a "reasonable" explaination of this "burst of energy" that Greg speaks of..(and of which I, and others, have always blanket labeled the "ping"...)

Copied from an interesting read at thehulltruth forums in a thread discussion about CHIRP technology....(this is a long and growing read...and mostly over my head...but it has tidbits of info that really help understand "pulse lengths" and their effects on resolution of the sonar image..)
http://www.thehulltruth.com/marine-electronics-forum/506221-chirp-sounders-fish-finder-explained.html

Quote: Recall that traditional sounders send a single tone pulse (usually 50 or 200 KHz) and listen for the return signal. The length of the pulse determines the resolution of the system looking down. Hence, the smaller the pulse, the better or finer our ability to separate targets (e.g. fish). On the other hand, the pulse also determines the power injected into water. So the longer the pulse the better. As an example, if I have a 1 millisecond pulse (1/1000 sec) and I have 500 watts in my sounder, the actual net power in the water is 0.5 watts. If I keep the transmission power fixed, then my only option for more power to combat losses due to depth, is to increase the pulse length. But if I did that, I would lose resolution. Clearly then there is conflict in traditional sounders between wanting to have enough power to get a reasonable signal back and wanting it to be short enough to tell objects apart.

Rickie

promapper:
Thanks Rickie.  A good explanation.  I don't suppose multi beam has any relationship to this forum as I believe it is low frequency and limited to high resolution data for bathymetry.  It is a neat system though.

Philip Brown:

--- Quote from: promapper on June 08, 2013, 12:40:23 PM ---Thanks Rickie.  A good explanation.  I don't suppose multi beam has any relationship to this forum as I believe it is low frequency and limited to high resolution data for bathymetry.  It is a neat system though.

--- End quote ---

So.... 7 years later, I chime in to say that this is really cool!!!   It also provides some context as to why Humminbird now offers CHIRP, and how and why CHIRP can give you the best of both worlds, at least to some extent!

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