Alinco DX-SR9 E Скачать руководство пользователя страница 5

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The input signal from microphone goes thru mic-gain pot the VR117 and is fed
to a low noise amp the Q180. At the mic terminal there is an 5V bias thru the
R109 for providing voltage to certain type of mics. The IC119A has the gain
(about 20dB) which is determined by the R492 and R512. When in FM mode,
the gain increases by about 35dB due to the R494 parallel to the R512 thru the
Q175, and by the C465 the lower cut-off frequency is increased thereby
activating pre-emphasis and limiter. When in SSB or AM, if the speech
compressor is turned ON, the gain increases by about 35dB due to the C460,
R487, and Q172, and the IC119:A works as a limiter. The C460 cuts off lower
spectrum portion and the audio quality becomes suitable for speech compres-
sion. The in FM, the gain is adequately obtained and there is no effect of
speech compression. If the FM sub-tone is activated, the output of the IC119:A
pin No.1 is voltage divided by the R499 and R509, and the sub-tone fed thru
the R509. The IC119:B is a low pass filter which works as a splatter filter when
in FM and a low pass filter when speech compressor is in use. The output is
either fed to PLL circuit for FM modulating, or to the IC105 for balanced
modulation. The output of the IC105 is muted by the Q178 when in CW or FM.

IC105 is the balanced mixer, and the carrier is suppressed in SSB mode. To
get more ratio or carrier suppression, the balance adjustment of VR102 and
VR103 are applied. The carrier is necessary in CW/FM/AM mode, so the input
of Pin7 is made unbalanced by applying the DC voltage to obtain the carrier.
By applying the DC in AM/FM mode, or by keying in CW mode, the balance is
broken to obtain the carrier wave. VR115 is used for the adjustment or carrier
level in AM/FM mode. VR118 is used for the adjustment of carrier level in CW
mode. In the AM mode, the DC and modulation is added simultaneously. In
SSB mode, the modulation is added by R488. In AM mode, D174 is DC-biased
and turned ON. Then the attenuator consisting of R488 and R443 or R523
limits the modulation.

The output of the IC105 goes thru a temperature compensating thermistor
TH101 and the D128 and is fed to bandwidth limiting I.F. filter. Pulling up
cathode of the D128 when in Tx (and L when in Rx) makes Tx/Rx isolation
better. When in SSB mode, the signal becomes DSB without the carrier.
Switching of the filters is done by the diode switching mentioned before. For
each respective mode, filters are used as follows.

SSB, CW, AM-NARROW FL102 (CFJ455K5) 2.4KHz/-6dB 4.5KHz/-60dB
CW-NARROW FL101

(CFJ455K8)

1.0KHz/-6dB

3.0KHz/-60dB

FM, AM

FL103 (CFW455G) 9.0KHz/-6dB 20KHz/-50dB

Having passed the filter, the signal passes thru a switching diode (D110), amp
(Q104), and the D108, and thru the second mixer in reverse direction of Rx,
making 71.75 MHz signal. The Q107 depends on CW keying that improves
isolation when CW key is up. An ALC voltage is applied on the second gate of
the Q104. Signals from 71.295MHz local oscillator and reverse heterodyne are
filtered by the XF102. The signal is amplified by the Q614 and is input to a
balanced mixer. (D111).

2) Transmitter

1. MAIN Unit

a. Mic Amp

b. Balanced Mixer

c. IF filter

d. IF Amp, Second Mixer

The first transmit mixer comprising of the Q103, Q108, L104 and L117 is a
balanced type mixer and input about 3dBm of local oscillator
(71.75MHz+TxFreq) to obtain the wanted frequency. The signal converted to
the wanted frequency by the first Tx mixer is passed thru an LPF to filter out the
local frequency and image components before it is input to the Tx preamp.

The Q105 is a wide band amplifier. It can put out high power with saturating
output of about + 13dBm and more than 20dB gain. Inserting attenuators on
both the input and output make it widen its range with more stability. The output
at the Transmitter First Mixer is about 0dBm when the transmitter power is
100W.

By keying, the Q165 is turned on to the base of the Q162 in the main unit is
pulled to Low which causes the collector to output a voltage. This output
controls all the circuit which operates by CW keying. The output of the Q162
collector goes thru the D180, IC105, VR103, and D126 and by applying a DC
voltage to the balanced mixer it unbalances the mixer and generates a carrier.
VR118 determines the CW waveform of rising edges and falling edges by
adjusting the carrier level in R525 and C488. At the same time, the Q159 is
turned ON to turn OFF the Q107 isolating in keying. The C428 makes the Q107
OFF duration longer than keying duration to avoid effects to the output
waveform. By the D180 a voltage is input to pin No.10 of the IC119:C, and by
the output from pin NO.8 the Q161 is turned ON and the D171 pulling the PTT
line down to Low brings the transmitter ON. The capacitors at the input of pin
No.10 of the IC119:C (C246, C247) determines transmit time delay after stop
of keying. The BK1, BK2, and BK3 are 3 bit break-in time constant voltages
which are combined by the combination of the R469, R470 and R471 as D/A
for obtaining 8 levels of voltage. When all of the BK1, BK2, and BK3 are low,
the status if full-break-in, when more than one of the BK1, BK2, and BK3 have
voltage the status is semi-break-in and the break-in time fastest when all of
them have voltage. When in full-break-in, each of the BK1, BK2, and BK3,
voltages are low hence the Q164 is OFF, making a very fast discharge
time-constant with the C431 alone. When either of several of the BK1, BK2, or
BK3 has voltage, the Q164 would turn ON and the C434 would be added
parallel to the C431 making the time-constant longer which determines the
delay time for semi-break-in. There are 7 levels of semi-break-in voltages out
of the BK1, BK2, and BK3, that is fed to the IC119:C as comparative voltage to
change the discharge time constant. Thus the time constant is the shortest if all
of the BK1, BK2 ,BK3 outputs voltage. When in AUTO-break-in, the output is
from BK1 only, and the comparative voltage for the IC119:C is controlled with
the output voltage of the IC119:D. The keying output when in AUTO mode is
output with each keying using the one-shot multi-vibrator comprising of the
IC120:A and B. Hence the average value of the IC120:A output voltage would
be proportional to average speed of keying. To obtain average voltage, the
R463 and C432, etc. are used for integrating, and the output is DC amplified by
the IC119:D whose output is used as comparative voltage for keying. The
D182 is for turning OFF when in AUTO mode; when AUTO is low, the voltage
charging the C432 is shorted and AUTO is stopped.