DON'T CUT THE CABLE! The installation instructions for the DS 500X (see page 34) and for most other fishfinders prohibit cutting the cable attached to a multi function transducer (sonar, temperature and boat speed sensors). A few words of explanation of the prohibition may be useful. The cable likely contains a number of   very small diameter individually insulated stranded wires that carry data from the speed and temperature sensors in the transducer, plus a shielded pair that serves the sonar transducer element. A boat owner might be successful in splicing the small diameter wires in the cable that carry data from the temperature and speed sensors, however successfully splicing the shielded pair is a major challenge. Conveying the power necessary to excite the sonar transducer requires voltage pulses that can exceed 4,000 volts. Maintaining the integrity of the shield can be difficult. Ensuring that the resulting splices will properly resist the marine environment is problematic. If the cable is too long, coil the excess in a figure 8 in an out of the way place. If more cable is needed, buy an extension cable already fitted with end connectors.

Today's high tech fishfinders provide what may be the easiest way to find fish other than by draining a lake. And the new line-up from Raymarine may be among the most advanced examples of this technology. The 400, 500, and 600x series provide a level of performance in the fully automatic mode that often exceeds what even an experienced operator can achieve with manual manipulation of the controls. A significant component of each unit is the Digital Signal Processing (DSP) technology Raymarine introduced a little over a year ago in the 1000 watt DSM 250 black box sonar.

I tested the middle range unit, the compact (only 5.9 x 6.4 x 3 inches) DS 500X. All three units use identical electronics, sonar transducers and control interfaces, differing only in display screen size and in the case of the 600X the overall shape of the case. This manual provides an illuminating insight to design and operation of units. It explains each of the menu selected operational settings available for a function and then concludes by recommending that the system be used in the default, AUTOMATIC mode. This reflects the fact that the DSP supported system logic provides a level of performance in the automatic mode superior to what a typical user can achieve with manual control of the operating parameters. Some experienced fishfinder operators, with substantial experience in making the control tweaks needed to get the best from more conventional equipment may find the idea of running in automatic difficult to accept. However the same confidence building process that has allowed experienced stick shift jockeys to accept and appreciate microprocessor controlled automatic transmissions in high performance cars will find that running in the automatic mode exacts no performance penalty. A similar level of automatic operation superiority can be found in other DSP enabled marine electronic devices such as weatherfax receivers and HF radio transceivers. New users of these Raymarine DSP enabled fishfinders should relax and let the box do the thinking.

The 500X presents the processed sonar information on a 5-inch diagonal color TFT LCD screen. I found the brightness and contrast of the image on the display sufficient for use in direct sunlight. Data visibility in a variety of lighting conditions is assured by the provision of ten steps of screen backlighting brilliance plus a choice of 6 color pallets with three background colors. As with all LCDs used in bright sunlight reflections from the user's clothing can enhance or detract from the clarity of the on screen image. (Wearing a dark color shirt can be a real help, until the development of intensely bright and intensely expensive color screens for aircraft, cockpit crews often wore black bibs to minimize distracting reflections.)

The 500X has three information pages, the primary fishfinder page, a temperature graph page and a navigation data page. The navigation data page is active when the system is connected to a NMEA 0183 source of navigation data. The basic fishfinder page display choices include a single data display window or a vertically split display plus a selectable narrow vertical "A" scope window. The split display shows sonar data from both the 50 and 200 kHz transducers, with the 200 kHz data on the left. Water temperature and battery voltage information may be superimposed on the screen in either digital or analog plus digital form. The various menu screens can be shown as a transparent overlay on the screen, keeping sonar data visible even when making changes in the system settings. The temperature page display consists of a 60-minute histogram plus selectable readouts for boat speed, log and trip distance, battery voltage and water depth. The navigation page presents position, speed and course over ground, waypoint position, time to go, range and bearing plus time, date, water temperature, battery voltage and depth, plus an alarm clock. (A feature likely suggested by the wife of the designer, tired of having the family fisherman show up late for dinner.) The process of customizing the various display pages is easy to learn.

The frequency of the transmitted sonar pulses can be manually set to either 50 kHz or 200 kHz, to a dual manual mode transmitting at both frequencies or in the recommended automatic mode where the frequency choice is software driven, based on the information extracted from the returning sonar echoes. The display screen is split vertically when dual frequency pinging is in use.

The zoom menu selections are off, full screen or a split screen with the zoom feature active in one of the two windows. The zoom level choices are 2, 3 or 4 times magnification. The zoom modes are automatic, ensuring that bottom details are always kept in view or manual, allowing arbitrary positioning of the zoomed area.

The system's hunt mode provides automatic search for the bottom when the system is operating in the auto range mode. If the auto frequency mode is selected the system will repeat the bottom finding process using the other frequency to ensure that optimum sonar results are obtained.

The Raymarine DS 400,500,600 products are clearly among the most advanced sonar fish finding systems available and with street prices of about $450, $650 and $850 respectively, (with transom mounted transducers) they provide excellent value. We do wonder a bit about the approximate $200 price premium charged when a thruhull transducer is required.

Contact: Raymarine, www.raymarine.com.