Quote:
Originally Posted by The Kid
Q1: Higher kHZ means you can read down into deeper water beyond 200 ft depending on finders. Although the band circumference becomes thinner.
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That is actually kinda incorrect.
Sonars work with pressure waves or what we consider sound. khz is not describing power but the frequency, pitch or osculation of the sound wave used by the transducer. Essentially the transducer sends out sound then draws it's picture by what returns in the form of an echo. So a transducer acts like a speaker and mic both sending out sound and receiving and logging the reflections or echo returns.
A 200khz or 200,000 cycles per second sound wave gives lots of detail because it sends a lot of waves out per second there is a lot to reflect back but the trade off is that lower frequency sounds carry farther and therefor can give detail from a greater distance.
It's like the rumble of thunder: the further from the storm you are the less crack you hear and the more rumble, or like in a parade where with a marching band you always hear the drums first as they march toward you.
Humans perceive various frequencies of sound waves as various pitch. Musical notes correspond to precise frequencies or hertz. The higher the frequency the higher the note. We can hear sound from 20hz to roughly 20,000 hertz or 20 khz. Sonars use pitches we can not hear, though other animals like whales and dolphins can hear some of the lower frequency sonars.
200khz is standard for shallow water sonars as it gives you good detail in shallow water, lower numbers give you less detail but higher penetration, so the more expensive finders have numerous lower KHZ settings for fishing deep.
For instance a furuno FCV1100 has six khz settings preset for 6000 to 16 feet at 28/38/50/88/107/200kHz
Back on topic the DSI finders are using 455/800 kHz capable transducers. Think of them as supper high pitched sonar. The idea is they should give incredible detail. I have not used one but the science makes sense as these higher frequencies send double to four times the amount of compressed sound in waves per second than a standard 200khz transducer.
More waves means more waves reflected back per second and more data for the finders transducer to pick up and create an image with. Bottom line these finders have more reflected data to work with, and depending on how it's interpreted that should give a much clearer picture of what's down there when in shallow water then traditional 200khz sounders.
The trade off is they do not go as deep. Check the numbers the DSI units are only rated for 250 feet. I'd say that is a little too specialized for me.
No doubt these will be ideal for shallow water bass fishing in freshwater where they rarely fishing in water deeper then 60 feet. My question would be how well do they do in say 100 to 150 feet of water, where I like to fish for Yellows and need to see squid on the bottom.
I also like to go deep occasionally and fish rockfish at 300+ feet. Even at 200khz my current sounder can see them, the DSI I units won't work for fish that deep..
If I was making finders I'd make a dual frequency 200khz 455khz unit that could read to say 400ft but still give more detail in shallow water, but I don't see that on the Lowrance menu.
Jim