Installation manual

System familiarization

850--160137 / A

3.4 Receiving

A great effort has been made to reduce unwanted noise to get

a clean and stable echo presentation. To achieve this goal the

sonar receiver has the following filtering possibilities:

BANDPASS FILTER

One hardware filter for each preamplifierwith a bandwidth of

1500 Hz to reduce interference and noise from signals outside

the sonar frequency.

FM CORRELATION FILTER

See description in paragraph 3.3.

AGC (Automatic Gain Control)

This control will automatically adjust the gain in the

preamplifier, dependent on the strength of the incoming echo

signals. The strength of the filtering can be selected in the

menu: OFF, WEAK, MEDIUM and STRONG. Note that the

AGCissensingtheechostrengthintheaudiochannel,anduse

this as a basis for adjusting all the receiver beams.

RCG (Reverberation Controlled Gain)

RCG is sensing the noise level (reverberation, propeller noise,

etc.),adjusting the gain individuallyforeach of the 64 receiver

beamstoeliminatethenoiseonthedisplay. Thestrengthofthe

filtering can be selected in the menu: OFF, WEAK, MEDIUM

and STRONG.

Note that scattered fish can be perceived as reverberation, so

therefore RCGshouldbeusedwithcareifscatteredschoolsare

to be detected.

PP FILTER

The sonar is equipped with a ping--to--ping filterwhich gives a

cleanandsteadypresentationbyreducingtheinterferenceand

noise. This filter compares the echoes from a selected amount

of transmissions (pings), and an echo has to be present in the

selectedamountofpingsinordertobepresentedonthedisplay.

The selection is made in the menu, with the following

possibilities:

OFF - filter switched off

WEAK - compares 2 pings

MEDIUM - compares 4 pings

STRONG - compares 8 pings

Note that in rough seas, when the beam easily can miss the

target in several pings, the PP filter should be used with care.