Bill, I noticed in your last chirp images there were some nice arches. Why do our humminbird units not show good fish arches when using 200 kHz?
Forgive me for this being my first post (Troy knows me from other forums) ...
I feel I may be able to help some understand Troy's question quoted here ... Hopefully without getting to complicated ...
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All sonar systems have "trade offs" ...How effectively they can obtain "good echoes" without also getting the "bad echoes" ...
Xducers are rated (in part) by their own specific "Q" factor ...
The "Q" factor is a measurement of how long the piezo vibrates after the transmit cycle (called "ringing" - like a church bell resonates)... The lower the "Q" factor = the less the piezo vibrates after transmit ... Less "ringing" ...(this is one of the major factors of why Airmar xducers are more expensive ...they're designed for a lower "Q" factor = less "ringing"...)
These vibrations after the transmit can, in fact ... be "received" during the "listening" cycle ...and are then plotted as "noise" (or false echoes) on the display ...
Certainly a higher energy transmit (more wattage pulse) ...in a high "Q" factor xducer... Would just create more "ringing" ... Which is plotted as more noise (clutter or false echoes)...
CHIRP by technological reasoning (and by the capability of being able to use lower "Q" factor xducers) ... can put more energy into the acoustic signal ...without also creating more noise ...
There's more to CHIRP than just the lower "Q" factor xducer ... But that's the easiest part of the equation to explain ...
In a nutshell ...
To put the same amount of energy output into the 200kHz "tone burst" signal as is achieved in the CHIRP signal (with a lower "Q" factor xducer)...would create so much noise (..."ringing"...)...that the display would be one big mass of noise (clutter)....
So to answer your question Troy ...the CHIRP has better defined arches (than normal "tone burst" sonar)...because CHIRP (by design) is a much stronger acoustic signal ... Even out toward the edges of the sonar cone ...
Rickie
BTW ... All xducers have a rated "Q" factor (CHIRP or tone burst)...it's just that most "tone burst" xducers have such a high "Q" factor ... It's of no benefit to any brand to publish this spec ...
Rickie
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