You can use the DFF1-UHD as a single channel sounder. However, the DFF1-UHD module will on transmit on these following frequencies of: 30-70khz & 175-225kHz
You must do the follow these steps for it to be used with only one transducer connected:
• A 100-ohm 10-watt resistor must be added across the unused LF or HF channel.
• When using only one transducer, Bottom Discrimination and ACCU-FISH will not work as both modes need both the frequencies to function properly.
• The DFF1-UHD should be programmed to use a B-265 transducer and the Orange TID wire should not be connected. :noway
If you wire the B175L Transducer (40-60kHz) to the Low Frequency side of the DFF1-UHD, and then wire the B175HW Transducer (150-250kHz), for the High Frequency side. You should be okay for having both the Low Frequency and High Frequency capability on the DFF1-UHD.
But remember that this setup isn't the same as having a B265LH Transducer that CHIRPs at 42-65 kHz for Low Frequency or 130-210 kHz for the High Frequency. Also keep in mind that the use of those B175s Transducers won't provide you with any of the ACCU-Fish or Bottom Discrimination functions.