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Allied SX-190, Инструкция по эксплуатации

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Allied SX-190 Скачать руководство пользователя страница 19

3.3 

FIRST MIXER AND BANDPASS IF 

 
The output of the RF Amplifier is applied to the gate of the first mixer Q4. At the same time the 
output of the HFO coupled thru T4 is applied to the source of the first mixer. The two signals are 
mixed and their products are selected in the drain circuit of Q4. The circuit in the drain of Q3 is 
tuned as a bandpass circuit passing all frequencies between 2.920 MHz and 2.420 MHz. This is 
the frequency range of the 500 KHz bandpass IF. The transformers L8, 9 and Ll0 and their asso-
ciated components comprise the bandpass IF. The output of this IF is applied to the base of Q8, 
the second mixer. 
 
 
3.4 

SECOND MIXER AND VARIABLE FREQUENCY OSCILLATOR 

 
The second mixer combines the output of the bandpass IF with the output of the variable fre-
quency oscillator (VFO) to produce the 455 KHz IF. 
 
The VFO produces the required frequencies for tuning LSB, USB, CW and AM signals. Inductor 
T7 parallels capacitor VC6, in the frequency-determining network. The output frequency is low-
ered causing the VFO to tune from 3.375-2.875 MHz. 
 
The mixing products of the bandpass IF and VFO are selected in the collector circuit of Q8 (sec-
ond mixer). The output of the VFO is provided at the rear panel at J4. Here the VFO is isolated 
by emitter follower (Q10). 
 
 
3.5 

455 KHz IF DETECTOR CIRCUITS AND NOISE LIMITER 

 
Immediately following the 2nd mixer (Q8) are the mechanical Filters (MF1, MF2). Output from 
the MF1 is amplified by Q13 and connects to MF2 and is tuned by the three transformers T9, 
T10 and T11. The signal is taken from the secondary of T11 to be detected and used as the AGC 
voltage. 
 
The AM detector, diode D5, also gets its signal from the secondary of T11 and is coupled to the 
noise limiter (D4). This noise limiter only functions in the AM mode when its output is delivered 
through the function switch, on to the AF GAIN and to the 1st audio amplifier. 
 
The detection of CW & SSB signals is accomplished by D8, D9. Dl0 and D11. These four diodes 
comprise a balanced demodulator circuit. The audio is developed from the product detection of 
the incoming 455 KHz signal and the output of the BFO, which may come from the crystal con-
trolled SSB oscillator, and its output is delivered to AM preamplifier (Q17). The output of the 
AM preamplifier is coupled thru C79 to Function switch (SW3-d) to the AF gain control, VR3, 
and on to the 1st audio amplifier. 
 
 
 
 
 
 
 
 
 

-18- 

Содержание SX-190

Страница 1: ......

Страница 2: ...lt for 10 db S N ratio Sensitivity SSB CW Less than 0 5 microvolt for 10 db S N ratio Selectivity 4 KHz at 6 db down Visual dial accuracy 200 Hz Calibration accuracy Better than 500 Hz adjacent 25 KHz calibration points after indexing Stability Better than 500 Hz after warm up Image rejection More than 60 db Spurious rejection More than 50 db Rejection tuning More than 40 db Selection tuning 500 H...

Страница 3: ...r calibrating the dial readout to an accuracy of better than 200Hz The SX 190 is equipped with a crystal controlled Beat Frequency Oscillator BFO for the recep tion of USB LSB and CW signals Incorporated in its circuitry are AGC ANL and S meter functions The AGC Automatic Gain Control has been tailored to produce minimum audio output changes even with large variations of input signal levels ANL Au...

Страница 4: ...IVER CONNECTIONS If the SX 190 Receiver is to be used for receiving only and not as part of a system with intercon nections to an associated transmitter there are only a few required connections These connec tions are easily accessible at the rear of the receiver and their design permits permanent connec tions to be made in a neat manner Figure 1 2 page 5 illustrates the connections points at the ...

Страница 5: ...he black to negative It is impor tant to observe the polarity when using the receiver on 12 VDC 1 2 5 STD BY CONNECTIONS The STD BY jack is jumpered in factory to operate the receiver 1 3 INTERCONNECTIONS FOR USE WITH TRANSMITTER Figure 1 1 page 5 illustrates the interconnections required for using SX 190 Receiver with a transmitter The following paragraphs describe the required interconnections t...

Страница 6: ...INTERCONNECTIONS A Speaker jack G AC line cord B Line Tape output H Fuse C VFO output I HFO output D Ext std by J GND terminal E AC DC switch K 80 239 antenna jack F DC input jack FIGURE 1 2 REAR VIEW OF SX 190 5 ...

Страница 7: ...FIGURE 1 3 ATTACHING CABLE TO PHONE PLUG CONNECTOR FIGURE 1 4 INSTALLATION OF GROUND 6 ...

Страница 8: ...b Doublet Antenna A doublet antenna will give excellent results especially on amateur bands A 75 ohms balanced transmission line should be used as shown in Fig 1 5 2 Since the doublet antenna provides optimum performance only at a given frequency it should be cut to the length for the most often used band of frequencies The overall length of a doublet antenna can be determined by using the followi...

Страница 9: ...tch J 100 kHz Calibrator switch C Band switch K AF gain control D Main tuning knob L RF gain control E Dial skirt M S meter F Main dial N Q multiplier switch G Preselector O Rejection tuning H Preselector dial P Phones jack FIGURE 2 1 FRONT VIEW OF SX 190 8 ...

Страница 10: ...r Band C This an 11 position Band Change Switch to cover the international broadcasting bands from 3 5 to 18 0 MHz the 15 MHz standard frequency signal WWV and the 27 MHz CB band Tuning D E F This is the Main Tuning Knob One revolution controls a 50 KHz linear dial reading Each indi cation line on the knob indicates 1 KHz for frequencies between 3 5 and 30 0 MHz The dial skirt is held in place by ...

Страница 11: ...m a local station may overload the receiver causing distortion and a resultant decrease in sound level K This is the volume control Turn to the right in a clockwise direction to increase vol ume and to the left to decrease volume S Meter Readings M The S Meter provides a means of measuring the relative strength of incoming signals Relative readings are only correct when the RF GAIN control is full...

Страница 12: ...ity with which signal will be received will depend upon proper readjustment of the various controls Function Switch to SSB upper or lower for reception of SSB and CW and to AM for AM reception When pulse type interference hampers AM reception switch FUNCTION to AM ANL Band Set this switch to the desired band RF Gain Set this control for maximum sensitivity Full clock wise position AF Gain Adjust t...

Страница 13: ... then be adjusted on either side of the center for desired pitch Signal Sideband Operation For SSB reception the dial should be turned very slowly Excessive signal strength during SSB reception may make demodulation difficult In such cases decrease the RF GAIN by turning this control to the left Smooth demodulation will then be possible Control settings for sideband reception are virtually the sam...

Страница 14: ...e broadcast stations operate are found in the two upper bands of your receiver The majority of shortwave broadcast stations operate within certain internationally assigned groups of frequencies or bands For your convenience a list of the shortwave bands which offer best reception has been provided TABLE 3 Since shortwave reception varies with the time of day season of the year and with weather con...

Страница 15: ...ing to other bands Q MULTIPLIER The Q multiplier operates in all modes CW AM and SSB to null unwanted signals with a deep 40 dB notch or peak the desired signal while sharpening receiver selectivity to help you pick the signal you want out of the noise The selector switch has off reject and select positions A tune control allows you to move the peak or null throughout the receiver bandpass When ce...

Страница 16: ... 2 LOCATIONS OF EXTRA CRYSTAL AND CAPACITOR FIGURE 2 3 CHART OF EXTRA CRYSTAL FREQUENCY VS CAPACITOR VALUE FOR 3 5 10 MHz RANGE FIGURE 2 4 CHART OF EXTRA CRYSTAL FREQUENCY VS CAPACITOR VALUE FOR 10 0 30 MHz 15 ...

Страница 17: ... 16 ...

Страница 18: ...apacitor that tunes the gate and drain of the RF amplifier as well as the gate of the first mixer Q4 The required tuning range of these circuits is obtained by switching an appropriate value of induc tance in parallel with the PRESELECTOR tuning capacitor and its associated coils T1 T2 T3 The complete range of 3 5 30 MHz is covered by 2 tuning ranges of the PRESELECTOR and by 11 ranges of the crys...

Страница 19: ...he bandpass IF and VFO are selected in the collector circuit of Q8 sec ond mixer The output of the VFO is provided at the rear panel at J4 Here the VFO is isolated by emitter follower Q10 3 5 455 KHz IF DETECTOR CIRCUITS AND NOISE LIMITER Immediately following the 2nd mixer Q8 are the mechanical Filters MF1 MF2 Output from the MF1 is amplified by Q13 and connects to MF2 and is tuned by the three t...

Страница 20: ...an oscillator providing the necessary frequency to the bal anced demodulator for the beat between the 455 KHz IF signal In the LSB position of the Func tion switch X13 is in the circuit producing a frequency of 456 5 KHz In the USB position X12 produces a frequency of 453 5 KHz X Crystal 3 8 AGC AND S METER CIRCUITRY Signal voltage is coupled from the primary of T11 to AGC detector D6 and D7 The A...

Страница 21: ...er amplifier transistor Q18 And every 100 KHz harmonic is supplied thru C80 Q19 and Q20 are multivibrators to oscillate at 25 kHz It is also connected to buffer ampli fier and to C80 3 11 POWER SUPPLY The power supply of the SX 190 has the advantage of operating from 120 VAC 60 Hertz or 12 VDC without any internal wiring changes 3 11 1 AC POWER SUPPLY Transformer T13 steps down the voltage from th...

Страница 22: ...SCHEMATIC DIAGRAM OF RF AMP 21 ...

Страница 23: ...SCHEMATIC DIAGRAM OF BUFFER AMP SCHEMATIC DIAGRAM OF CALIBRATOR 22 ...

Страница 24: ...SCHEMATIC DIAGRAM OF VFO SECTION 23 ...

Страница 25: ...SCHEMATIC DIAGRAM OF I F AMP SECTION 24 ...

Страница 26: ...SCHEMATIC DIAGRAM OF POWER SUPPLY 25 ...

Страница 27: ...Variable Frequency Osc Q10 2SC372 Variable Frequency Osc Emitter Follower Q11 2SC372 Q Multiplier Inverter Q12 2SC372 Q Multiplier Q13 2SC372 2nd IFAmp Q14 2SC372 2nd IF Amp Q15 2SC373 AGC Amp Q16 2SC372 BFO Q17 2SC373 AF Amp Q18 2SC373 CAL Buffer Amp Q19 2SC373 25khz Multivibrator Q20 2SC373 25kHz Multivibrator Q21 2SC372 100kHz Calibrator Q22 2SC971 Regulator Q23 2SC373 AF Amp Q24 2SC735 AF Driv...

Страница 28: ... 1S188 AGC Detector D 7 1S188 AGC Detector D 8 18188 Product Detector D 9 18188 Product Detector D10 1S188 Product Detector D11 1S188 Product Detector D12 FR 2 Rectifier D13 FR 2 Rectifier D14 ZB1 10 10V Voltage Regulator D15 FR 2 Temperature Compensator TH 1 M 10K Temperature Compensator TH 2 M 10K Temperature Compensator 27 ...

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