Alinco_DJ-296T_serv.pdf

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1、CIRCUIT DESCRIPTION DJ-296T 1) Receiver System The receiver system is a double superheterodyne system with a 30.85 MHz first IF and a 455 kHz second IF. 1. Front End The received signal at any frequency in the 216.00 to 249.995 MHz range is passed through the low-pass filter (L2, L3, L8, C2, C9, C10

2、, C11, C62 and C189), high-pass filter (C56, C57, C58, C61, L22, L25 and D15), and amplified by the RF amplifier (Q9). The signal from Q9 is then passed through the tuning circuit (C12, C14, C65, C66, L19, L20, L21, D12, D13 and D14) and converted into 30.85 MHz by the mixer (Q10). The tuning circui

3、t is controlled by the tracking voltage from the CPU (IC9) so that it is optimized for the reception frequency. The local signal from the VCO is passed through the buffer (Q11), and supplied to the source of the mixer (Q10). The radio uses the lower side of the superheterodyne system. 2. IF Circuit

4、The mixer mixes the received signal with the local signal to obtain the sum of and difference between them. The crystal filter (XF1) selects 30.85 MHz frequency from the results and eliminates the signals of the unwanted frequencies. The first IF amplifier (Q8) then amplifies the signal of the selec

5、ted frequency. 3. Demodulator Circuit After the signal is amplified by the first IF amplifier (Q8), it is input to pin 16 of the demodulator IC (IC4). The second local signal of 30.395 MHz , which is oscillated by the internal oscillation circuit in IC4 and crystal (X2). Then, these two signals are

6、mixed by the internal mixer in IC4 and the result is converted into the second IF signal with a frequency of 455kHz. The second IF signal is output from pin 3 of IC4 to the ceramic filter (FL1), where the unwanted frequency band of that signal is eliminated, and the resulting signal is sent back to

7、the IC4 through pin 5. The second IF signal input via pin 5 is demodulated by the internal limiter amplifier and quadrature detection circuit in IC4, and output as an audio signal through pin 10. 4. Audio Circuit The audio signal from pin 10 of IC4 is compensated to the audio frequency characteristi

8、cs in the ADJUSTMENT DJ296T 1) Required Test Equipment The following items are required to adjust radio parameters: 1. Regulated power supply Supply voltage: 5 - 14 VDC Current: 3A or more 2. Digital multimeter Voltage range: FS = Approx. 20V Current: 10A or more Input resistance: High impedance 3.

9、Oscilloscope Measurable frequency: Audio frequency 4. Audio dummy load Impedance: 8 ohm Dissipation: 1W or more Jack: 3.5 mm 5. SSG Output frequency: 500MHz or more Output level: -20dBu/0.1uV - 120dBu/1V Modulation: AM / FM 6. Spectrum Analyzer Measuring range: Up to 2 GHz or more 7. Power meter Mea

10、surable frequency: Up to 500MHz Impedance: 50 ohm, unbalanced Measuring range: 0.1W - 10W 8. Audio voltmeter Measurable frequency: Up to 100kHz Sensitivity: 1mV to 10V 9. Audio generator Output frequency: 67Hz to 10kHz Output impedance: 600ohm, unbalanced 10. Distortion / SINAD meter Measurable freq

11、uency: 1kHz Input level: Up to 40dB Distortion: 1% - 100% 11. Frequency counter Measurable frequency: Up to 500MHz Measurable stability: Approx. +/- 0.1 ppm 12. Linear detector Measurable frequency: Up to 500MHz Characteristics: F lat CN: 60dB or more Note Standard modulation : 1 kHz +/- 3.5kHz / DE

12、V Reference sensitivity 12dB SINAD Specified audio output level: 200mW at 8 ohm Standard audio output level: 50mW at 8 ohm Use an RF cable (3D2W: 1m) for test equipment. Attach a fuse to the RF test equipment. All SSG outputs are indicated by EMF. Supply voltage for the transceiver: 13.8VDC 2) Adjus

13、tment Mode The DJ-296 does not require a serviceperson to manipulate the components on the printed-circuit board, except the trimmer when adjusting reference frequency and deviation. Most of the adjustments for the transceiver are made by using the keys on it while the unit is in the adjustment mode

14、. Because the adjustment mode temporarily uses the channels, frequency must be set on each channel before adjustments can be made. For instructions on how to program the channels, see the “DJ-296 INSTRUCTION MANUAL” which came with the product. In consideration of the radio environment, the frequenc

15、y on each channel must be near the value (+/- 1 MHz) listed in the table below. To enter the adjustment mode, set key lock and input 490217. Decimal point at 100MHz and 10MHz appears in LCD. (To release the mode, set key lock and input 490217.) Channel frequencies used in the adjustment mode Memory

16、Channel Channel function Frequency 1 Reference frequency adjustment 223.5 MHz 2 High power adjustment 223.5 MHz 3 Low power adjustment 223.5 MHz 4 Minimum frequency sensitivity adjustment 215 MHz 5 Medium frequency sensitivity adjustment 223.5 MHz 6 Maximum frequency sensitivity adjustment 240 MHz 7

17、 S-meter ( 1 ) adjustment 223.5 MHz 8 S-meter ( FULL ) adjustment 223.5 MHz 9 Deviation 223.5 MHz 10 DTMF ( 1 ) test 223.5 MHz 11 DTMF ( D ) test 223.5 MHz 13 Tone 88.5Hz test 223.5 MHz 15 DCS code 255 test 223.5 MHz 16 Tone burst test 223.5 MHz 17 Aging (Not required to use ) 223.5 MHz Reference Fr

18、equency Adjustment 1. In the adjustment mode, select channel 1 by rotating the main tuning dial. 2. Press the PTT key to start transmission. 3. Rotate TC1 on the Main board until the value on the frequency counter matches the one displayed on the LCD. High Power Adjustment 1. In the adjustment mode,

19、 select channel 2 by rotating the main tuning dial. ( “L” at the upper-left of the display disappears). 2. Hold down the PTT key to start transmission. 3. While watching the reading of the TX power meter, set the output power to the value closest to 5 W by rotating VR3 on Main board. Low Power Adjus

20、tment 1. In the adjustment mode, select channel 3 by rotating the main tuning dial. (“L” appears at the upper-left of the display). 2. Hold down the PTT key to start transmission. 3. While watching the reading of the TX power meter, set the output power to the value closest to 0.8 W by rotating the

21、main tuning dial. 4. When the PTT key is released, the output power at that time will be stored as the low power setting. Minimum Frequency Sensitivity Adjustment 1. In the adjustment mode, select channel 4 by rotating the main tuning dial. 2. Adjust the minimum frequency sensitivity to the best tun

22、ing by rotating the main tuning dial, while F appears after the FUNC key is pressed. Medium Frequency Sensitivity Adjustment 1. In the adjustment mode, select channel 5 by rotating the main tuning dial. 2. Adjust the medium frequency sensitivity to the best tuning by rotating the main tuning dial, w

23、hile F appears after the FUNC key is pressed. Maximum Frequency Sensitivity Adjustment 1. In the adjustment mode, select channel 6 by rotating the main tuning dial. 2. Adjust the maximum frequency sensitivity to the best tuning by rotating the main tuning dial, while F appears after the FUNC key is

24、pressed. S-meter (1) Adjustment 1. In the adjustment mode, select channel 7 by rotating the main tuning dial. The S-meter will show a single star. 2. Enter “0” dBu (EMF) with the transceiver tester. 3. Press the F key. The transceiver beeps indicating the new setting has been stored successfully. S-

25、meter (FULL) 1.In the adjustment mode, select channel 8 by rotating the main tuning dial. The S-meter will show all six stars. 2. Enter “+20”dBu (EMF) with the transceiver tester. 3. Press the F key. The transceiver beeps indicating the new setting has been stored successfully. Deviation 1. In the a

26、djustment mode, select channel 9 by rotating the main tuning dial. 2. Input a 50mVrms, 1KMz signal with your transceiver tester through the external microphone jack. 3. With the tester, put the transceiver in the transmission mode. 4. Rotate the VR1 on the printed-circuit board of the transceiver un

27、til the deviation is set to 4.5KHz. DTMF (1) Test This function is only for checking the DTMF code, not adjusting it. 1. In the adjustment mode, select channel 10 by rotating the main tuning dial. 2. Press the PTT key. DTMF code “1” is automatically sent and you will hear the monitoring tone from th

28、e speaker. 3. Check the deviation with the transceiver tester. DTMF (D) Test This function is only for checking the DTMF code, not adjusting it. 1. In the adjustment mode, select channel 11 by rotating the main tuning dial. 2. Press the PTT key. DTMF code “D” is automatically sent and you will hear

29、the monitoring tone from the speaker. 3. Check the deviation with the transceiver tester. Tone 88.5Hz Test This function is only for checking the tone encoder, not adjusting it. 1. In the adjustment mode, select channel 13 by rotating the main tuning dial. 2. Press the PTT key. An 88.5Hz tone is aut

30、omatically sent. 3. Check the deviation with the transceiver tester. DCS Code 255 Test This function is only for checking the DCS, not adjusting it. 1. In the adjustment mode, select channel 15 by rotating the main tuning dial. 2. Press the PTT key. A 255 DCS code is automatically sent. 3. Check the

31、 deviation with the transceiver tester. Tone Burst Test This function is only for checking the tone burst, not adjusting it. 1.In the adjustment mode, select channel 16 by rotating the main tuning dial. 2. Press the PTT key. A 1750Hz tone burst is automatically sent. 3. Check the deviation with the

32、transceiver tester. Aging Perform this aging test only when necessary. 1. In the adjustment mode, select channel 17 by rotating the main tuning dial. The transceiver automatically repeaters transmission for a minute and reception for another minute. SPECIFICATIONS DJ296T GENERAL Frequency coverage T

33、X: 222.000 224.995MHz RX: 216.000 249.995MHz Mode F3E (FM) Channel steps 5, 10, 12.5, 15, 20, 25, one amplifier (pins 5, 6 and 7) is composed of pre-emphasis and IDC circuits and the other (pins 1, 2, and 3) is composed of a splatter filter. The maximum frequency deviation is obtained by VR1 and inp

34、ut to the cathode of the varicap (D3) of the VCO, to change the electric capacity in the oscillation circuit. This produces the frequency modulation. 2. Power Amplifier Circuit The transmitted signal is oscillated by the VCO, amplified by the pre-drive IC (IC1) and drive amplifier (Q4), and input to

35、 the final amplifier (Q2). The signal is then amplified by the final amplifier (Q2) and led to the antenna switch (D2 and D5) and low-pass filter (L2, L3, L5, C2, C9, C10, C11, C24, and C189), where unwanted high harmonic waves are reduced as needed, and the resulting signal is supplied to the anten

36、na. 3. APC Circuit Part of the transmission power from the low-pass filter is detected by D7, converted to DC, and then amplified by a differential amplifier. The output voltage controls the bias voltage from the source of Q2 and Q4 to maintain the transmission power constant. 3) PLL Synthesizer Cir

37、cuit 1. PLL The dividing ratio is obtained by sending data from the CPU (IC9) to pin 2 and sending clock pulses to pin 3 of the PLL IC (IC2). The oscillated signal from the VCO is amplified by the buffer (Q5 and Q37) and input to pin 6 of IC2. Each programmable divider in IC2 divides the frequency o

38、f the input signal by N according to the frequency data, to generate a comparison frequency of 5 or 6.25 kHz. 2. Reference Frequency Circuit The reference frequency appropriate for the channel steps is obtained by dividing the 12.8 MHz reference oscillation (X1) by 2048 or 2560, according to the dat

39、a from the CPU (IC9). When the resulting frequency is 5 kHz, channel steps of 5, 10, 15, 20, 25, 30 and 50 kHz are used. When it is 6.25 kHz, the 12.5 kHz channel step is used. 3. Phase Comparator Circuit The PLL (IC1) uses the reference frequency, 5 or 6.25kHz. The phase comparator in the IC2 compa

40、res the phase of the frequency from the VCO with that of the comparison frequency, 5 or 6.25kHz, which is obtained by the internal divider in IC2. 4. PLL Loop Filter Circuit If a phase difference is found in the phase comparison between the reference frequency and VCO output frequency, the charge pu

41、mp output (pin 8) of IC1 generates a pulse signal, which is converted to DC voltage by the PLL loop filter (C69, C70, C80, C88, R44 and R48) and input to the varicap (D3) of the VCO unit for oscillation frequency control. 5. VCO Circuit A Colpitts oscillation circuit driven by Q3 directly oscillates

42、 the desired frequency. The frequency control voltage determined in the CPU (IC9) and PLL circuit is input to the varicaps (D3). This change the oscillation frequency, which is amplified by the VCO buffer (Q5) and output from the VCO unit. 4) CPU and Peripheral Circuits 1. LCD Display Circuit The CP

43、U turns ON the LCD via segment and common terminals with 1/4 the duty and 1/4 the bias, at the frame frequency is 112.5Hz. 2. Display Lamp and Key Lamp Circuit When the LAMP key is pressed, “H” is output form pin 42 of the CPU (IC9) to the bases of Q19, Q24 and Q25. Q19, Q24 and Q25 then turn ON and

44、 the LEDs (D17, D18, D20, D21, D22 and D23) light. 3. Reset and Backup When the power form the DC jack or external battery increases from Circuits 0 V to 2.5 or more, “H” level reset signal is output form the reset IC (IC11) to pin 33 of the CPU (IC9), causing the CPU to reset. The reset signal, how

45、ever, waits at 100, and does not enter the CPU until the CPU clock (X3) has stabilized. 4. S (Signal) Meter Circuit The DC potential of pin 8 of IC5 is input to pin 1 of the CPU (IC9), converted from an analog to a digital signal, and displayed as the S-meter signal on the LCD. 5. DTMF Encoder The C

46、PU (IC9) is equipped with an internal DTMF encoder. The DTMF signal is output from pin 10, through R179 and R180 (for level adjustment), and then through the microphone amplifier (IC8), and is sent to the varicap of the VCO for modulation. At the same time, the monitoring tone passes through the AF circuit and is output form the speaker. 6. CTCSS Encoder The CPU (IC9) is equipped with an internal tone encoder. The tone signal (67.0 to 250.3 Hz) is output form pin 9 of the CPU to the varicap D4 of the VCO for modulation.