Furuno CN-24 User manual

COLOR NET RECORDER
CN-24

C
9-52, Ashihara-cho,
Nishinomiya, Japan
Telephone: [phone]
Telefax: 0798-65-4200
Your Local Agent/Dealer
All ri
g
hts reserved.
PUB. No. SME-13010-A
CN-24
(
MAYA
)
FIRST EDITION : MAY 2001
Printed in Japan

CONTENTS
1.GENERAL.........................................................................................................1-1
1.1 POWER SUPPLY......................................................................................1-1
1.2 UPWARD AND DOWNWARD SOUNDING .............................................1-1
1.2.1 Sounding Rate ................................................................................1-1
1.3 DATA FORMAT FROM TRANSMITTER UNIT ..........................................1-2
1.3.1 SYNC Code ....................................................................................1-3
1.3.2Temperature Data ............................................................................1-3
1.3.3 Upward/Downward Sounding ..........................................................1-4
1.3.4 Depth Data ......................................................................................1-4
2.CIRCUIT DESCRIPTION ................................................................................2-1
2.1TRANSMITTER UNIT ..............................................................................2-1
2.1.1 Board Function ................................................................................2-1
2.1.2 Power ON/OFF Control ...................................................................2-1
2.1.3 Upward and Downward Soundings ..................................................2-1
2.1.4 Depth/Temperature Measurement (SEN Board) ..............................2-5
2.1.5 Signal Transmission (CONT-A, CONT-B Boards) .............................2-7
2.2 DISPLAY UNIT ........................................................................................2-10
2.2.1 Power Supply (POW 01P5727) .......................................................2-10
2.2.2 Receiver Board (AMP 01P5725) .....................................................2-12
2.2.3 Display and Signal Processor Board (DISP 01P5726) .....................2-12
3.CHECK AND ADJUSTMENT ..........................................................................3-1
3.1 DISPLAY UNIT CHECK ...................................................................... 3-1
3.1.1Self-Check ................................................................................
3-1
3.1.2 Power Supply Circuit (POW Board 01P5737) ................................
3-2
3.2 TESTING FUNCTION IN AIR ..............................................................
3-2
3.2.1 Testing Transmitter Unit and Display Unit with Receiving Transducer. 3-2
3.2.2TestinginAirwithoutParavaneReceiver........................................
3-3
3.3ADJUSTINGTRANSMITTERUNIT
.......................................................
3-4
3.3.1GainAdjustment..........................................................................
3-4
3.3.2 Depth Indication Adjustment.........................................................
3-4
3.3.3 Adjusting Transmission Frequency on CONT.B Board......................
3-5
3.4ADJUSTMENTOFDISPLAYUNIT.......................................................
3-7
3.4.1ColorMonitorAdjustment.............................................................
3-7
3.4.2 DISP Board (01P5726).................................................................
3-8
4.CHANGE OF SPECIFICATIONS .....................................................................4-1
4.1DISPLAYUNIT .................................................................................. 4-1
4.1.1 Range Unit, Sounding Range, Data Format, etc ............................
4-1
4.2TRANSMITTERUNIT ........................................................................
4-3
4.2.1 Sounding Range..........................................................................
4-3
4.2.2SoundingRate ...........................................................................
4-4
4.2.3SignalTransmittingPower ...........................................................
4-4
4.2.4AdjustmentMode
.........................................................................
4-5
5.PARTS LOCATION............................................................................................
5-1
5.1DISPLAYUNIT....................................................................................
5-1
5.2 TRANSMITTER UNIT (CN-2220)..........................................................
5-6
6.BOARD INTERCHANGEABILITY.....................................................................6-1
6.1DISPLAYUNIT.................................................................................... 6-1
6.2TRANSMITTERUNIT..........................................................................
6-2

7.CALIBRATION OF PRESSURE SENSOR........................................................
7-1
8. DISASSEMBLING/ASSEMBLING TRANSMITTER UNIT .................................
8-1
SPECIFICATIONS.................................................................................................
SPC-1
EXPLODED VIEW.................................................................................................D-1
MECHANICAL PARTS LIST..................................................................................
M-1
ELECTRICAL PARTS LIST.......................................................................................
E-1
SCHEMATIC DIAGRAM........................................................................................
S-1

1-1
1. GENERAL
This chapter describes the basic operations of the transmitter unit.Most of operations are
CPU controlled.
1.1 POWER SUPPLY
The transmitter unit is automatically powered by the pressure switch when it descends 10
m in the sea and turned off when it ascends to 5m deep point.
1.2 UPWARD AND DOWNWARD SOUNDING
The transmitter unit incorporates only one sounding transmitter/receiver circuit.The upward
and downward transducers are alternately connected to the circuit by the action of a relay.
1.2.1 Sounding Rate
Two kinds of sounding rates are used to improve coverage area.
Standard Rate ("LOW" setting)
Downward
Sounding
Upward
Sounding
The time "T" between the pulses depends on the sounding range setting in the
transmitter unit.
Fig.1.1 Upward and Downward Sounding in Standard Mode
High Rate ("HIGH" setting)
In this rate, sounding is performed three times within one cycle of transmitter operation with
standard rate.
Downward
Sounding
Upward
Sounding
Fig.1.2 Upward and Downward Soundings at High Rate

1-2
The receiver receives signals within the range in use at the first sounding, and it receives
signals between 0 and 20 meters at the second and third soundings in both upward and
downward directions. Generally, the blind zone occurs in short range due to the beam
shape and rare transmission rate. The high transmission rate can reduce the blind zone
and increase the number of reflection from the target.
Refer to the figure below.
Fig.1.3 Sounding Area (Standard versus High)
The received signals obtained by these three soundings are processed as follows in the
transmitter unit.
a) 0 - 20m:The received echoes obtained from the three soundings are compared and
the strongest echo is picked up and sent to the display unit.
b) more than 20m: The received echoes obtained from the first sounding are sent to the
display unit.
1.3 DATA FORMAT FROMTRANSMITTER UNIT
The data sent from the transmitter unit to the paravane receiver consist of upward and
downward sounding signals, sync code, temperature and depth data, and catch sensor
data (option).Transmission sequence of these signals are shown in Fig.1.4.
Fig.1.4 Data Format
There are two SYNC codes, DN SYNC and UP SYNC, and (2) depth data is divided into
two parts, MSB and LSB.
Detects target one time Detects target three times

1-3
1.3.1 SYNC Code
The synchronous signal consists of 32bits binary coded data.
The DN SYNC code is attached to the beginning of each transmission cycle to enable the
display unit identifying the signal. The coded pulses enable to reduce the effect of noise
along the transmission line to the paravane receiver.
The S/N ratio becomes maximum when the number of bits is 2n -1 (n: integer), 31 bits out
of these 32 bits are actually used in the display unit. Fig.1.5 shows the 32 bits code data.
Fig.1.5 SYNC Code (DN SYNC)
The UP SYNC signal inserted before the catch monitor data consists of 15 bit binary code
data and is used to stabilize the oscillation line of the upward sounding picture on the
display unit.
For the modulation of the sync codes, the FS (Frequency Shift) modulation is employed; "1',
and "0" are modulated at frequencies which are different by 1kHz each other, as shown
bellow.
Code/Frequency
Transmission Frequency 0 1
33 kHz 33 kHz 34 kHz
40 kHz 40 kHz 41 kHz
50 kHz 50 kHz 51 kHz
1.3.2Temperature Data
The water temperature is indicated by the time interval from the left edge of the
temperature data region to the temperature signal (15 bit H/L code). The temperature data
region is allocated next to the DN SYNC code.
Fig.1.6 Temperature data region
Depending on the temperature, the time from the left edge varies.
Temperature signal (15 bit H/L code)

1-4
Note: In actual processing, the temperature data expressed by 9 bit binary number is
divided into two parts, the lower 5 bits and the upper 4 bits, and the temperature data
region is also divided into two sections. The time interval from the left edge of each section
to temperature signal indicate the value of the lower 5 bit or upper 4 bit number. This
configuration enables to shorten the length of the temperature data region.
Fig.1.7 Temperature data region
1.3.3 Upward/Downward Sounding
The received echo signals are transmitted to the paravane receiver with
frequency-modulated form.
The echo signals received by the upward/downward sounding circuit are converted into 4
bits binary data which represent 15 stages signal level and then converted into FM signal
by the V-F converter.
1.3.4 Depth Data
Like the water temperature measurement, the detected depth is indicated by the time from
the left edge of the depth signal area to the depth signal (15 bit H/L code). However, to
shorten the length of the depth signal area, the depth data is divided into two parts (upper
6 bits and lower 6 bits) and inserted into the pause areas of downward and upward
sounding periods.See Fig. 1.8.

1-5
Fig. 1.8Transmitter unit timing chart (range: 80/80 m and sounding rate: high)

2-1
2. CIRCUIT DESCRIPTION
2.1TRANSMITTER UNIT
2.1.1 Board Function
Refer to the block diagram shown in figure 2.1. The transmitter unit consists of five PC
boards.The table below shows the major functions of each PC board.
Board Major Functions
TRS. A 01 P5742 1) Generates upward/downward sounding TX signals.
2) IF amplifier, mixer, and detector of received signals.
3) TVG control of received signals.
4) A/D conversion of received signals.
TRS. B 01 P5743 1) Power amplification of upward/downward sounding TX signals.
2) RF amplification of received signals.
SEN 01 P5744 1) Depth/water temperature measurement.
CO NT. A
01P5740 1) Control of transmitter, receiver and signal transmitter circuits by CPU.
2) Acquisition and processing of A/D converted received signals.
3) Power amplification of signal transmitted to paravane receiver.
CONT.B 01P5741 1) D/A conversion and frequency modulation of signals transmitted
toward paravane receiver.
2) A/D conversion of depth and water temperature signals for
acquisition by CPU.
3) Presetting of transmitter unit operation mode.
2.1.2 Power ON/OFF Control
When the transmitter unit reach at 10 m deep in the water, the pressure switch is turned on
and activates the + 5 and 15 V regulator on the CONT A board. And the transmitter unit
starts functioning automatically. When the transmitter unit rises above 10 m, the pressure
switch is turned off, and the transmitter unit stops functioning.
2.1.3 Upward and Downward Soundings
Transmitter Circuit
The transmitter circuit for upward and downward soundings are incorporated onTRS.
A and TRS. B boards. For the 75 kHz transmission, the 1.2 MHz signal generated by the
CPU on the CONT A board is frequency-divided by 16 to 75kHz and 1.4 MHz generated by
a crystal oscillator on the TRS.A board is divided by 8 to 175 kHz.
These 75 kHz or 175 kHz clock signals are applied to the succeeding gate circuit, where it
is gated by 0.2ms long TSMT pulse from the CPU, and then sent to the power amplifier.
The power amplifier amplifies the transmission signals to 100W and sent to the sounding
transducer via the output transformer and the T/R circuit. The T/R circuit links the
transducer to the transmitter circuit during transmission and to the RF amplifier during
reception. Relay K1 selects the transducer for upward or downward sounding and is
controlled by the CPU via the UP/DN CONT circuit.
Figure 2.2 and 2.3 show the transmitting waveform and TSMT signal.