In article ,
"BruceM" wrote:

Do you want me to repeat all I wrote?
200 (ithink) is narrow for better bottom reading.
50 is wider & better for reading fish in area.
Both together will not be much dif that 50 on it's own.
On some sounders 50 will be limited in ability to go DEEP & read bottom. So
in deep water using both (dual) might increase bottom echo.
The main dif is your ability to use & read the sounder.
For the few bucks more, I reckon you should maybe get it & learn how to get
the maximum out of it.
BruceM

Actually your conclusions above are a bit missleading.
200 Khz will actually deliniate individual targets
much better than 50Khz due to it's higher frequency and
shorter wavelength. The Rule of Thumb for sonar is:
The higher the frequency the better resolution of targets.
The lower the frequency the deeper the signal can go.
200 Khz machines can't see down farther than 100 Fathoms
in most cases, but can resolve individual fish easily.
50 Khz machines can see down to 1000 fathoms but can't
resolve anything smaller than a cabin. North Pacific
Crab fisherman use 28 Khz machines so as to get excellent
bottom resolution at extreme depth, but they don't expect
to actually see anything other than the profile of the bottom.

Bruce in alaska
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