Trying to pick best combo for shrimp

[PolarMarine]

This application is for extreme detail for the following:
shrimp are up to 25-30 cm
50-100 fm depth
sometimes on structure

This is at the limit for 200kHz at 1kW traditional sounder and the B259 with DFF1 has not been showing any of this stuff. The low frequencies are too large of a beam angle to do any good. The best so far has been a DFF3D with 165T-B54. It appears to work well because of the narrow fore-aft beam width. The wavelength for resolution of these targets suggests higher frequencies would be best.

It have heard that CW would work better for depth penetration compared with CHIRP. I don't know which one would work best for detail at this depth. Does it make more sense to go with an R109 with narrow 4-6 deg beamwidth on a DFF3 as CW, or use with TZT3 and DI-AMP as CHIRP?

Here's a screenshot of what they look like with the DFF3D. Any input appreciated.

 

[Deep Blue]

PolarMarine,

You are indeed correct regarding the DFF3D's narrow fore-aft beam width, but the fixed 165kHz CW frequency should also figure in the detection of your shrimp.

Using the DFF3 and with it's Furuno free synthesizer (FFS) transceiver design, will allow you to select the operating frequencies to help find that "sweet spot" for a shrimping frequency when using the R109LH.

Also keeping in mind why that you would be increasing your TX power from 1kW to 2/3kW with the R109LH and this will only lead to an increase detection by one third. But because your are fishing around a 600ft depth, that shouldn't be much of a concern.

It's the R109LH's Frequency and Beam widths used for Low Frequency where the beam width is 19 degrees to 10 degrees for port-starboard, and the High Frequency beam widths at 8 degrees to 4 degrees port-starboard. The transducer’s fore-aft beam width is roughly between 10 degrees to 5 degrees (this is all depending what frequency is being used...) that are the main concerns for providing better Shrimp Detection.

- Deep Blue