hillman,
A typical fish finder will only one Transmit and one Receive for Low Frequency, or High Frequency. For example Low Frequency will be 50kHz and the High Frequency uses 200 kHz.
For the DFF1-UHD CHIRP Sounder, it also utilizes one Transmit and one Receive for the Low Frequency using a sweeping frequency 30-70 kHz. And for the High Frequency, its one Transmit and one Receive using sweeping frequency between 175-225 kHz
I hope this information is helpful..?
- Deep Blue