Raymarine 465 GPS Receiver User Manual


 
36
Operating Instructions
Choosing a Frequency
We said that the FishFinder uses sound waves to “see” through the water
under the boat. The “frequency” is a measure of how fast the sound
waves change or “vibrate.” The FishFinder uses sound waves with two
different frequencies – 50 kHz and 200 kHz. Apelco uses these two
frequencies because each is better for a particular purpose:
50 kHz frequency
Scans a wide area
Penetrates water well, good for deep water
200 kHz frequency
Scans a narrower area, but produces a more detailed view
Good for seeing fish near the bottom or fish close together
Better for use in very shallow water
“Dual” frequency (both 50 kHz and 200 kHz at once)
Has the advantages of both frequencies
Good depth penetration
Good detail in display
Using the “Dual 50 kHz” setting, the display is produced using the
signal from the 50 kHz beam, with additional information from the
200 kHz beam.
Using the “Dual 200 kHz” setting, the display is produced using the
signal from the 200 kHz beam, with additional information from the
50 kHz beam.
If you are using one of the dual frequency settings, you can get some
useful information from the fish symbols. If the fish is spotted by the
narrow 200 kHz beam, the fish symbol will be black or filled-in. If a fish is
detected by the wide 50 kHz beam, the symbol will be hollow.
When the unit is first turned on, it is set to use the Auto frequency
feature. When set this way, the unit begins by using the 200 kHz
frequency. If the bottom depth increases to more than 250 feet (or 50
fathoms or 80 meters), the unit will automatically switch to the 50 kHz
frequency. If the unit cannot find the bottom, it will try both the 200 kHz
and the 50 kHz frequencies. The unit will then use the frequency which
finds the bottom first.