the length of the transmit pulse. A shorter pulse provides more resolution
and helps prevent small objects (such as fish) from blurring together but
longer pulses will often provide more depth range in deeper water.
In Analog Time-Varying Gain mode
you must supply three different
values as already mentioned earlier
- The Transmit pulse Width, Surface
Gain and the gain Change Rate.
Basically the Surface Gain is the
value of gain to start the receiver
with and the Change Rate is a
measure of how fast you want the
gain to increase as a function of time.
In DSP mode, selecting Digital
Processor Type 1 or Digital
Processor Type 2 will result in your
having to supply only a single DSP
Gain value. The Transmit Pulse Width is automatically set by the Interface
Box depending on the selected DSP gain value and you have no control
over the transmit pulse width. The larger the DSP gain, the more digital
processing is applied to the received signal and weaker signals can be
recovered from the noisy return signal. The benefit is that you can see
objects in deeper water than using analog processing. The higher DSP
gains require wider transmit pulses which result in a loss of resolution in
more shallow water.
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