Standard Horizon Eclipes DSC GX1000S, Руководство по обслуживанию

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8
Circuit Description
Transmitter
The voice from the microphone is passed through the
CNTL Unit to the microphone amplifier
Q1001
(
LM2902PW
) on the MAIN Unit, a pre-emphasis network,
limiter (IDC: instantaneous deviation control), and low-
pass filter network, the audio is adjusted for optimum de-
viation level.
The voice or DSC (Digital Selective Calling) encoded sig-
nal from the low-pass filter network
Q1001 (
LM2902PW
)
is applied to the VCO Q1019 (
2SK210GR
) which oscil-
lates at the fundamental transmit frequency with direct
frequency-modulation using varactor diode
D1010
(
1SV214
). The modulated signal is amplified by the buff-
er amplifier Q1018 and Q1017 (both
2SC5006
), then
passed through the diode switch D1006 (
DAN235U
) to
drive amplifiers Q1008 (
2SC5006
) and RF power ampli-
fier module Q1014 (
S-AV37A
).
The RF energy then passes through antenna switch D1003
(
L308CCB
) and low-pass filter (LPF) consisting of coils
L1001 & L1002 and capacitors C1003, C1011, & C1024, and
finally to the antenna connector.
RF output power from the RF power amplifier module
Q1014 (
S-AV37A
) is sampled by C1014 and C1021 and is
rectified by D1002 (
1SS321
). The resulting DC is fed
through Automatic Power Controller Q1007 (
RT1N441U
)
to RF power amplifier module Q1014 (
S-AV37A
), thus pro-
viding positive control of the power output.
Generation of spurious products by the transmitter is min-
imized by the fundamental carrier frequency being equal
to the final transmitting frequency, modulated directly in
the transmit VCO. Additional harmonic suppression is
provided by a low-pass filter consisting of coils and ca-
pacitors, resulting in more than 80 dB of harmonic sup-
pression prior to delivery of the RF energy to the antenna.
DSC Encoder/ Decoder
Encoder
The DSC (Digital Selective Calling) encode signal which
D/A converted in the 8-bit MPU
Q2004 (
UPD78F0395GC
)
on the CNTL Unit is fed through the low-pass filter Q1001
(
LM2902PWR
) on the MAIN Unit to the VCO Q1019
(
2SK210GR
).
Decoder
A portion of the demodulated signal from the FM IF sub-
system IC
Q1029 (
TA31136FNG
) is passes through the
low-pass filter Q1037 (
2SC4154
) to the DSC Decoder IC
Q1034 (
NJM2211M
). The decoded DCS signal delivered
to the 8-bit MPU IC Q2004 (
UPD78F0395GC
) on the
CNTL Unit.
1050 Hz Weather Alert Decoder
The 1050 Hz Weather Alert signal from the buffer ampli-
fier
Q1033 (
2SC4154
) is applied to 8-bit MPU IC Q2004
(
UPD78F0395GC
) on the CNTL Unit.
MPU
Operation is controlled by 8-bit MPU IC Q2004
(
UPD78F0395GC
) on the CNTL Unit. This MPU uses a
18.432 MHz crystal X2001 for the system clock. IC Q2003
(
PST597CN
) resets the MPU when the power is on.
EEPROM
The EEPROM Q2006 (
BR24L08FVT
) on the CNTL Unit
retains TX and RX data for all memory channels, prescal-
er dividing, IF frequency, local oscillator injection side,
and reference oscillator data.