If you want sharp photographs, you focus your camera tightly on your subject. Likewise, if you want sharp sonar images, check out the Raymarine DSM250 High Definition Fish Imaging sounder module and the L770D, a 7" color echosounder. This digital system's ability to separate closely spaced fish targets is amazing.
We compared the DSM250 and L770D to the integrated system's nondigital predecessor, the L760. The L760 is an excellent machine, but baitfish schools appeared on the screen as blobs, and fish blended into bottom structure. The DSM250/L770D combination clearly displayed individual fish within schools at all speeds, with no clutter. The key to its clarity is that the DSM250 sends out sonar signals at a high rate, constantly adjusting transmitter and receiver parameters so that closely spaced targets are reflected individually. Advanced software manages output power, noise suppression, and other variables while running at maximum gain to catch all returning echoes. A Raymarine engineer describes this system as "listening hard and being selective about what it displays."
Raymarine will upgrade your existing L760 or L1250 fishfinder to run with a DSM250 module. The upgrade costs $170 for the L760 and $300 for the L1250.
Price DSM250 $780, L770D $2,345 Contact Raymarine, 603/881-5200, www.raymarine.com