DWEdit is pretty useful and fun once you get used to it, shouldn't be too hard to setup.
1. Download the DWEdit program from Bill's site
http://www.subguru.com/downloads.html , iirc, I think the DWEdit program that I'm most familar with is the "Ludger Styra's Dangerous Waters database editor" (a few scroll-lengths down). Should be an independent program that stands alone.
2. To take a look at the database, active that program and open up the object.eod file in the DangerWaters/Database folder, this should have all the platform stats of the game that are accessible to modding
3. To see the platforms, open up the "object dialog". This is the list of all the ingame, including the playable, platforms. Use the filter option to select the platform type that your interested in seeing (i.e. unselect all the other platform types accept what you want to see only, and push "apply filter")
4. To see which active sonar that that platform is using doubleclick on an individual platform in the list. The sensors that that platform is toting should appear in the "sensor slots" list at the bottom left hand corner, the platforms active sonar should be included in the list somewhere, but may not be obviously named. For example, in LW 3.02 the 688i's active sonar is called "688i MF active (BQQ-10 Act). That should tell you the name of that platforms active sonar.
5. To see the stats of each active sonar sensors open up the "Sensors Dialog" Menu from the main menu. (looks like a satellite dish). You can use to "Filter" option to select only "Active" sensors (i.e. deselect all of the other sensor types in the upper left hand corner list except "active" and push "apply filter". These should be all the active sonar sensors in the game that were referenced in the sensor slots list on the "object dialogs"
6. By doubleclickin on a particular active sonar its stats should appear. The frequency of the active sonar should in the "Sonar frequency max" box iirc.
You should be able to view and modify each and ever active sonar frequency in the database with the method above. Hope that helps (or at least makes sense