The default 2d frequency for the HB DI units is 200kHz/455kHz ...
The US2 in the Terrova is designed for 83kHz/200kHz ...
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As Bob mentions, change the Connected Transducer selection under the Sonar tab to "HB+200/83" if your unit has this selection (not all DI models even have this possible selection) ..
And also as Bob mentions, you will lose DI function with the US2 because there is no DI piezo in the US2 xducer = The US2 is 2d (200kHz/83kHz) only ...
Rickie