About time varied gain

Time varied gain (TVG) is signal compensation that removes transmission loss effects from echosounder data. Transmission loss is two-way and is due to acoustic beam spreading and absorption in the acoustic medium. Signal compensation is applied by the echosounder or by receiver electronics through analog or digital signal processing. The desired result is that targets of the same size produce echoes of the same size, regardless of target range.

The important part is the last sentence above ...meaning (in 2d) a 2lb fish at 10ft and a 2lb fish at 30ft create the same size target on the 2d display (adjusted by software - even tho the 2lb fish at 30ft has less echo because it was farther away) ...

Rickie