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.
Summary of Contents for Eclipes DSC GX1000S
Page 4: ...Exploded View Miscellaneous Parts 4 Note ...
Page 5: ...Block Diagram 5 ...
Page 6: ...Block Diagram 6 Note ...
Page 14: ...14 MAIN Unit Note ...
Page 24: ...24 Note MAIN Unit ...
Page 31: ...31 ...
