Good afternoon Lorentaza,
Thank you for the clarification on your use. The DFF1-UHD is a Chirp Network sounder designed to interface with the NN3D, TZT, and TZT2 MFD's. The DFF1-UHD was not designed to be used as a bottom machine for really deep depths, 1100m is too deep for this product. It can be used to find Tuna fish for your intended use with the right transducer but I do not believe it will work to find bottom at 1100m. For that application I would recommend a different network fish finder like the DFF3. The DFF3 is a non-chirp network sounder that has the ability to use lower frequency and higher output power transducers (up to 3kw) which is a good combination to find bottom in deep water. For your application I would look at 2 or 3 kw transducers with a lower frequency range, like 28 or 38 kHz.
Kind Regards,
C-Bass