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Functions and dialog boxes
Active menu: functions and dialog boxes
The Active menu offers parameters related to current views and data presentations provided by the ST90 system.
Bandwidth function
The Bandwidth function allows you to select the frequency range in the frequency modulated transmissions (pings).

About this manual
The purpose of this publication is to provide the descriptions, procedures and detailed parameter explanations required to allow for safe and efficient use of the ST90 system. The publication also provides you with a thorough understanding of the parameters and adjustments provided by the ST90 system.
Simrad ST90
Operating procedures
Maintenance procedures
User interface
Menu system
Functions and dialog boxes
- Main menu: functions and dialog boxes
  The Main menu is located at the top of the menu structure. It offers the most common functions for efficient use of the ST90 system. Unless you hide the entire menu system, the Main menu is visible at all times, even if you close the secondary menus.
- Operation menu: functions and dialog boxes
  The Operation menu allows you to control the operating mode, the recording functionality, and how the ST90 system transmits audio pulses ("ping") into the water.
- Display menu: functions and dialog boxes
  The Display menu provides basic functions related to the screen behaviour and presentation of the echo data. Use the Display menu to control the visual aspects of the system, and to show or hide various elements in the presentation.
- Setup menu: functions and dialog boxes
  The Setup menu provides basic functions related to the installation parameters and the communication with peripheral systems.
- Active menu: functions and dialog boxes
  The Active menu offers parameters related to current views and data presentations provided by the ST90 system.
  - TVG function
    TVG (Time Variable Gain) compensates for the loss of acoustic energy due to geometric spreading and absorption. This makes the targets with the same strength appear with the same intensity independent of their physical distance from the transducer.
  - Ping‑Ping Filter function
    The Ping-Ping Filter analyses the historical information from previous consecutive pings in order to remove unwanted noise and interference from the echo presentation.
  - Pulse Type function
    The Pulse Type function allows you to select the "shape" of the transmitted pulses ("pings"). Different shapes have different qualities. Which pulse type to use depends on the current environmental conditions, your range to the target(s) and the type and speed of the target(s) you are observing.
  - Bandwidth function
    The Bandwidth function allows you to select the frequency range in the frequency modulated transmissions (pings).
  - Frequency function
    Use the Frequency function to specify the centre frequency for the frequency modulated (FM) transmissions (pings) and the operating frequency for the continuous wave (CW) pings. You can change the frequency in predefined steps from a "start frequency" to an "end frequency".
  - Horizontal TX Sector function
    In a horizontal swath the ST90 system transmits with a maximum horizontal opening angle of 360 degrees. Use the Horizontal Tx Sector function to control the opening angle - and thus the size - of the horizontal search sector (swath). This is the physical area that is covered with each transmission ("ping").
  - Vertical TX Sector function
    The Vertical Tx Sector function is used to change the vertical opening angle in horizontal and vertical swaths.
  - Range Projection function
    The distance to a target located anywhere in the water column can be measured in two ways. This can either be the horizontal distance to the target (True), or along the tilt angle (Slant). The Range Projection function defines how this distance is measured.
  - AGC (Automatic Gain Control) function
    The AGC (Automatic Gain Control) function runs an automatic analysis of the echo strength. Based on this analysis the ST90 system maintains a proper dynamic range based on all the current echo values. This is done by automatically reducing the gain if you have reverberation and noise, or increasing the gain if the acoustical conditions permit it.
  - RCG (Reverberation Controlled Gain) function
    The RCG (Reverberation Controlled Gain) function removes unwanted reverberation from the bottom and or from the sea surface. It may however also remove scattered fish from the presentation.
  - Target Threshold function
    The ST90 system provides a bottom filter to reduce the sometimes powerful echo from the seabed.
  - Noise Filter function
    The Noise Filter removes unwanted acoustic noise from the display presentation. It reduces the interference from other acoustic systems (sonars and echo sounders), as well as the noise from the propellers.
  - Horizontal Scroll function
    The Horizontal Scroll function controls how fast the echoes shall travel across the Inspection view.
  - Vertical Reference function
    During operations in a vertical view you may wish to focus on the echoes in the upper or lower part of the view.Use Vertical Reference to hide a part of the view. The function is only available in the Vertical and Plane views.
  - Echogram dialog box
    The Echogram dialog box allows you to control the echogram presentation in the Inspection views. Two pages control the horizontal lines and the echogram type with applied TVG (time variable gain). One page controls how fast the echogram travels horizontally across the presentation.
  - Information Pane Options dialog box
    The ST90 system offers several information panes to provide additional and detailed data from the presentations. The information panes are opened and closed from the top bar. Several of the information panes are fitted with a Setup button. Select Setup to open the Information Pane Options dialog box. Use the Information Pane Options dialog box to change the operating parameters for the data provided in the information panes.
- Secondary functions and dialog boxes
- Pages in the Output dialog box
  A key function of the ST90 system is its ability to export data. The purpose of the Output dialog box is to collect all functionality related to data output in one easily accessible location.
- Pages in the Display Options dialog box
  The Display Options dialog box is used to specify basic settings for the sonar presentation.
- Pages in the Environment dialog box
  Environmental parameters such as salinity, sound speed and water temperature all play an important part to present accurate echo data. Use the Environment parameters to define these values. Depending on the current sea and weather conditions, you may need to change these values frequently.
- Pages in the Diagnostics dialog box
  The ST90 system is a computerized sonar. There are hardly any analogue circuitry, and the possibility of traditional troubleshooting is limited. In order to rectify this, a built-in software application is available to offer test and maintenance functionality. The Diagnostics dialog box controls the test and diagnose application that checks the performance of the ST90 system.
- Pages in the Installation dialog box
  Before you use the ST90 system you must set it up to communicate with the relevant peripherals. Use the Installation dialog box to set up all interfaces with external devices, and to set up basic parameters related to installation and operation. In most cases, you only need to do this once.
- Pages in the Echogram dialog box
  The Echogram dialog box allows you to control the echogram presentation in the Inspection views. Two pages control the horizontal lines and the echogram type with applied TVG (time variable gain). One page controls how fast the echogram travels horizontally across the presentation.
- Pages in the Information Pane Options dialog box
  The ST90 system offers several information panes to provide additional and detailed data from the presentations. The information panes are opened and closed from the top bar. Several of the information panes are fitted with a Setup button. Select Setup to open the Information Pane Options dialog box. Use the Information Pane Options dialog box to change the operating parameters for the data provided in the information panes.
Concept descriptions
Technical specifications
The technical specifications summarize the main functional and operational characteristics of the ST90 system. They also provide information related to power requirements, physical properties and environmental conditions.
Datagram formats
The ST90 system can send and receive information to and from several different peripherals. All transmissions take place as datagrams with data sentences. Each datagram has a defined format and length.
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Bandwidth function

The Bandwidth function allows you to select the frequency range in the frequency modulated transmissions (pings).

How to open

Open this function from the Active menu.

Description

Each frequency modulated transmission ("ping") from the ST90 system consists of a frequency sweep around the centre frequency. The difference between the lowest and the highest frequency in each transmission is referred to as bandwidth. The centre frequency in each transmission is chosen with the Frequency function. The chosen bandwidth will spread equally to both sides of the centre frequency.

Example:

If the chosen operating frequency is 17 kHz, and you set the bandwidth to 2 kHz, the frequency range in each transmission starts on 16 kHz and ends on 18kHz.

The bandwidth function does not apply to CW (Continuous Wave) transmissions.

Tip:

You can adjust the bandwidth to very low values. These values will reduce the resolution in the beam direction, but also increase the range. Some users find it useful to use a smaller bandwith to reduce noise.They will typically use it to remove propeller noise from other vessels in the vicinty.

Move the cursor to either side of the button to change the setting. Observe that the background colour changes. Select [-] on the left side or [+] on the right side to choose the requested setting. Select the middle of the button to open a small menu with the available options.

Related functionality

Frequency function

Use the Frequency function to specify the centre frequency for the frequency modulated (FM) transmissions (pings) and the operating frequency for the continuous wave (CW) pings. You can change the frequency in predefined steps from a "start frequency" to an "end frequency".

Open this function from the Active menu.

Pulse Type function

The "shape" of the transmitted pulse is controlled using the Pulse Type function.

For each pulse type, you can select Short, Medium or Long. These options define the pulse duration. This is the current duration ("length") of the transmitted pulse.

Open this function from the Active menu.