9
7. 1050 Hz Weather Alert Decoder
A portion of the signal from an FM IF subsystem IC
Q1031
(
NJM2591V
) passes through a low-pass filter
Q1037
(
2SC4617-R
) to the amplifier
Q1038
(
2SC4617-
R
). The amplified signal is delivered to the Schmitt In-
verter IC
Q1016
(
SN74LVC3G14DCT
) to obtain the
weather alert tone pulse. The microprocessor
Q1032
(
µPD78F1167GC
) watches this pulse to count the weath-
er alert tone frequency.
8. Miscellaneous Circuits
8-1 MPU
Operation is controlled by a microprocessor
Q1032
(
µPD78F1167GC
). This microprocessor uses a 9.8304
MHz crystal X1002 for the system clock. This micropro-
cessor includes a reset circuit.
8-2 EEPROM
The EEPROM
Q1036
(
BR24L64F-W
) retains TX and RX
data for all memory channels, prescaler dividing, IF fre-
quency, local oscillator injection side, and reference os-
cillator data.
8-3 PTT circuit
The PTT switch for the internal microphone is connect-
ed to pin 5 of microprocessor
Q1032
(
µPD78F1167GC
),
so that when the PTT switch is closed, pin 5 of
Q1032
(
µPD78F1167GC
) goes “low”. The microprocessor
Q1032
(
µPD78F1167GC
) disables the receiver by dis-
abling the 5 V supply bus at
Q1012
(
UMD5N
) to the front-
end and FM IF subsystem IC
Q1031
(
NJM2591V
). At the
same time,
Q1011
(
UMD5N
) activate the transmit 5 V
supply line to enable the transmitter.
Circuit Description
Содержание HX851
Страница 1: ...1 SERVICE MANUAL Floating Marine Transceiver with GPS HX851 EM031N95C 16 9...
Страница 4: ...4 Exploded View Miscellaneous Parts Note...
Страница 5: ...5 Block Diagram...
Страница 6: ...6 Block Diagram Note...
Страница 10: ...10 Circuit Description Note...
Страница 18: ...18 MAIN Unit Note...
