Standart HX290U, Руководство по обслуживанию

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6
2.2.6 Squelch Circuit
A portion of the audio signal output from pin 9 of second
IF IC QH04 is input to a band-pass filter consisting of
CH23, RH22,CH30,RH14, CH21, CH22, RH12 and
RH13. Noise elements are extracted from the audio signal
by the band-pass filter and input to pin 8 of QH04 as the
noise signal. The noise signal has approximately 40 kHz
elements only amplified by a noise amplifier built into
QH04 to generate the squelch signal. This squelch signal
is converted into a DC signal by the noise wave detector
built into QH04 and then output from pin 14 of QH04.
Refer to figure 2-4 for a description of the squelch on and
off operation.
2.2.7 Tone Decoder
A portion of the audio signal output from pin 9 of second
IF IC QH04 is input to tone detector circuit built into base
band IC QM01 as the tone signal.
At this point, if the QM01 detects a match between the
input tone signal and the transceiver's tone signal setting,
output signals from pins 22 of QM01 is input to pin 69 of
microprocessor QL02. And the high level signal is output
from pin 65 and 66 of QL02. (Refer to figure 2-4) The high
level signal is input to AF mute switch QM02, causing it to
turn on. This causes an audio signal to be output from
internal speaker EL01.
2.3 Transmitter Block
2.3.1 Microphone Amplifier
Audio signal is input to the microphone amplifier built into base band IC QM01 and amplified by approximately 47 dB. QM01
has a built-in pre-emphasis circuit (6 dB/oct frequency characteristics), and the high-frequency components of the audio
signal are boosted and modulated. Also, the frequency elements 3 kHz and above are eliminated by low-pass filter built into
QM01 to limit the bandwidth. Refer to figure 2-5 for a description of the microphone mute switch QM09 operation.
(Approx. 47 dB amp)
(6 dB/oct)
8 2
73
Microphone
NL01
Base band IC
Audio signal
PTT switch
Microprocessor
QV04
2SK1875(V)
QL02
QM01
AK2342A
VCO TX
ON
OFF
QL02 Microphone mute
Pin 73 Hi output
Pin 73 Lo output
Mic mute switch
QM09
2SK1830
Figure 2-5 Microphone amplifier circuit block diagram
2.3.2 Pre-amplifier / Power amplifier
Refer to figure 2-6 for a description of circuit operation.
Pre-amplifier QT01, QT02 amplify the approximately 1
mW transmission signal by 17 dB to approximately 50
mW. The transmission signal is further amplified by
approximately 4 W by the power amplifier QT03.
2.3.3 Tone Encoder
Serial data output from pins 78, 81, 82 of microprocessor
QL02 is input to the base band IC QM01. QM01 then
outputs the tone signal specified by the serial data from
the microprocessor.
Antenna switch
QT04-HVU131
QT05-HSC277
L.P.F.
PLL buffer amplifier
QP08
2SC5005
TX/RX switch
QP09
DAN235E
Pre-amplifier
QT01-2SC5005
(19 dB amp)
(17 dB amp)
(0 dB amp)
4 W
VCO TX
QV04
Power amplifier
QT03
MODEL QT03
HX290UKA131 M68732(HM)
HX290UKA191 M68732(UL)
HX290UKA181 M68732(SL)
HX290UKA111 M68732(L)
1 mW
50 mW
VCO buffer amplifier
QV07
2SC5005
(0 dB amp)
0 dBm
1 mW
1 mW
QT02-2SC5227
Figure 2-6 Transmission circuit block diagram