Furuno FCV-1200L Service Manual page 16

Receiving Circuit
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The Received signals both H and L frequencies are converted into 246.2 kHz (1 IF signal) by the
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first mixer circuit and then converted into 11 kHz (2 IF signal) by the second mixer circuit after
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amplified by the TVG amplifier circuit. The local carrier signals (1 LOCAL/ 2 LOCAL) for the
mixer circuit are generated by the MAIN board.
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The 2 IF signals named "TRX SIG H" and "TRX SIG L" are outputted to the MAIN board.
The amplitude of the receiver circuit is controlled by the TVG voltage (TRX TVG) which is also
generated by the MAIN board. The maximum amplitude of the receiver circuit is 46 dB.
3.3.3 MAIN Board (02P6269)
See the block diagram shown in figure 3.6.
Received signals ( TRX SIG H/L ) from the ES board are converted into digital signals by the A/D
converter "U64" and then converted into parallel data by the serial to parallel converter "U26".
The output of the U26, linear signal, is compressed into log signal by the linear to log converter
"U8" and then sent to the switching circuit composed by U9/U10/U11/U15.
In the switching circuit, the received signals, digital and log signals, from the internal transceiver
unit or the external transceiver unit, are switched according to the display mode selection and then
selected signal is sent to the master and slave Gate Arrays "U65/U66".
The slave Gate Array (U66) processes the signal (L) and then output it to the master Gate Array.
The master Gate Array (U65) processes the signal (H) and converts into R/G/B signals, the signal
(L) from the slave Gate Array(U66) is also converted into R/G/B signals by U65. The R/G/B signals
are sent to the display unit or the interface unit "IF-8000" from the connector CN1.
The Master Gate Array also generates the transmission data to the DDS (direct digital synthesizer)
and KPOM/KPOS to the KP Selector. When internal transceiver unit is selected in the "ES DRAFT
SETTING" menu, the KPOM and KPOS are supplied to each DDS circuit as KPIM/ KPIS. When
the external transceiver unit (ETR) is selected on the menu, the KPOM/KPOS named EKPO are
outputted to the ETR. Each DDS circuit generates transmission signals "TX1H/TX0H and
TX1L/TX0L" to each TX amplifier circuit and carrier signals "LOCAL 1 H and LOCAL1 L" to
each mixer circuit on the ES board.
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