Tuning sonar in Deep Water

Bayhouse

Furuno Super Fan
B275LHW in fairing block with TZT19F sounder. Also have a 165T-50–200 on the DFF3D connected to my other TZT19F. Tuna fishing in waters from 300' to 3000' in the mid-Atlantic canyons and trying to figure out how to best optimize sonar settings, tried some tips yesterday from either this site or another, can't recall. Here's what I did using the B275LHW:
  1. Set screen advance for 4/1 (trolling 6-7kts)
  2. Set to Dual Frequency @ 53 / 170 (preset)
  3. Set Clutter and manual gain on both freq to 0
  4. Turned Auto Range off and adjusted range for depth (generally ~1k')
  5. Dialed gain up until I began to see clutter, then added a little more gain on each freq
  6. Dialed clutter up to clean up the screen
  7. All other settings were either default or auto
My questions:
I now realize I probably should have been setting range for ~200'
Am I missing any steps or does anything above incorrect/incomplete?
Step #5, "seeing clutter" is a subjective, is it the first sign of anything on the display or is it meaningful returns?
Step #6, "clean up the screen" is also subjective - is it remove everything?

I tried various combos of the above but always felt that when I dialed clutter up it was removing any possibility for a return. When I had returns, It was generally in the top of the water column on the 200 side but it was more constant leading me to believe it was tuning error.

I don't really expect to see Tuna on the display, but would like to know more confidently where the bait is.

If you're reading between the lines, yes we got skunked on the trip but that's on the angler/boat/spread, not the sonar.

Really impressed with the equipment, I had bottom at over 1700'.
 
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At risk of stating the obvious, what happens when you use the auto fishing mode? I find it makes a good reference point for manual adjustments and is really pretty good. I don't agree with the 4/1 picture speed. Generally I stick with 1/1 or even 1/2. That will give you much better detail. When trolling in deep water, I will either manually set range to about 300 feet or use the market zoom to see the top 200-300 feet side by side with the whole water column.

Manually cranking up the clutter will get rid of far too man returns from bait. You have to leave some on the screen. And you should definitely be able to see returns from tuna.

I have different transducers. I find that with the B175H, for offshore trolling it seems to do better with fixed frequency. than in CHIRP. I was out today and ran it at 170Hz and it did a great job showing bait and fish.
 
Bayhouse,

You have the right transducer, the B275LH-W for the fishing pelagics. Here are a couple of recommendations that might help you in the detection of tuna within the 300-500 feet of the water column.

It's recommended to use both Low Frequency and High Frequency when you are fishing for Tuna, and once you locate those schools, then fine tune those frequencies that may display them better.

While you could adjust your TVG, but found that most Commercial Tuna Fisherman usually don't like to adjust this setting. So try adjusting the Range, then the Gain and finally the Clutter in this order.

Start with the Clutter setting at Zero, then adjust the Range for the depth that you want to be fishing in. Then you'll want to adjust the Gain until you start to see a little Clutter (typically with Blue/Green speckles). At this point, you'll then want to add a little more Gain, and then use more of the Clutter control to clean up the screen as needed.

Please let me know how those settings work for you..?

- Deep Blue.
 
Thanks Quitsa, appreciate the feedback. On Auto, the HF screen was all clutter and now I don't remember the LF. I'll have to play around with the marker zoom, not currently in my bag of tricks. I also need to read up on the picture speed.

One change I did make that seems to have made a huge difference is Transmit Rate. It had been in Auto mode, but when I set that to Manual 20, huge improvement.

Deep Blue, what you describe is exactly what I've been doing and last trip (with Transmit Rate in manual), it was like a whole different sounder. I'm learning more with each trip.
 
Following. I use auto until i dont trust it then go manual and only adjust gain.
I like this thread.
I will be out Thursday chasing tuna on the flats 150-300’ and using the above.
I have the same transducer with the DFF3D and a Sidescan.
 
@Bayhouse I have to agree, the best thing I have done with my sounder is to adjust the transmit rate from "auto" to manual and set it at 20 as well. Doing so seems to render the best-looking sonar picture. When running in manual mode, the expanded color range seems to render the best images when manually adjusting. I use the same process that deep blue laid out for manually adjusting my picture. One thing that I will note is that the clutter really only seems to make adjustments in increments of 10. Not sure why they don't just go from 1-10 on the clutter vs the 1-100 that you have to move a scale of 10 to see an adjustment.
 
Here are a few more setting for use with the TZT3 Fish Finder that should help TZT3 Operators. Just keep in mind that you may have to make a few adjustments for your specific fishery or operating depths:

Picture Advance: "1/1"
Bottom Range Shift Area: Set this to the operating water depth that you are fishing.
Color Erase: "0"
Interference Rejection: Usually set to "OFF". However, if there are signs of interference, then you'll need to adjust accordingly. Start with "OFF", then "Medium", then "High"
High Frequency TVG: "5" Keep in mind, less is more for this setting.
Low Frequency TVG: "5" Again, with this setting less is more...
Clutter: "0" This is where I start out slowly by adjusting this setting until the background noise goes away. The majority of the time, this setting can be somewhere between "10-20", but it can go as high as "30".
White Line: "OFF" Only use this if you are bottom fishing.
Transmit Rate Mode: "MANUAL"
Transmit Rate: "20"
Then I like to select a "BLACK" Background, this will help bring out any of those weaker fish targets.


When trolling, slower is better. Around 5-6 knots if possible.

Hopefully, you will find this information helpful..?
- Deep Blue
 
Thanks Deep Blue, I'm out tomorrow and will try your suggestions. Was out yesterday and thought we had things dialed in, but still couldn't get a bite (damn fishing). Adding a pic to show what we thought were fish in the upper water column (depth was over 1k). Fish marks, bait or clutter? I can't figure out what the LF display was marking...?

Starboard is B275LHW with tzt3
Port is 165-50-200-SS260 on DFF3D
 

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Thanks Deep Blue, I'm out tomorrow and will try your suggestions. Was out yesterday and thought we had things dialed in, but still couldn't get a bite (damn fishing). Adding a pic to show what we thought were fish in the upper water column (depth was over 1k). Fish marks, bait or clutter? I can't figure out what the LF display was marking...?

Starboard is B275LHW with tzt3
Port is 165-50-200-SS260 on DFF3D
Bayhouse,

That really looks like a school of baitfish to me. When you see stuff like that, take the opportunity to play with the adjustment of your Clutter and Gain, and see how those targets change...

- Deep Blue
 
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