Alinco Dj-296t Circuit Description Manual

							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, 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 circuit 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
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 selected 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 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 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 characteristics 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. 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              Measurable 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 frequency: 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:         Flat 
                          CN:                  60dB or more 
Note 
•  Standard modulation :    1 kHz +/- 3.5kHz / DEV 
•  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) Adjustment 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.  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 frequency 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 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       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 Frequency 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, 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 Adjustment 
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 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 tuning 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, while 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 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-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 adjustment 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 until 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  
the 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 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 automatically 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 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 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         TX: 222.000 – 224.995MHz
                         RX: 216.000 – 249.995MHz
Mode                     F3E (FM)
Channel steps               5, 10, 12.5, 15, 20, 25, & 30KHz
Memory channels           160 channels + 1CALL channel
Antenna connector          BNC (50 ohm unbalanced)
Frequency stability          +/- 5 ppm
Microphone input impedance  2K ohm nominal
Power supply requirement     7.0 to 16.0 V DC (negative ground)
Current drain (at 13.8 V DC)   1.2 A (typical) Transmit high at 5W
                          200 mA (typical) Receive at 280mW
                          50 mA (typical) standby
                          20mA (typical) Battery save on
Usable temperature range     -10 to +60 degrees C (14 to 140 dgrees F)
Dimensions                56 (W) * 124 (H) * 40 (D) mm  (with EBP-50N)
(Projections not included)     2.2” (W) * 4.88” (H) * 1.57” (D) inches  (with EBP-50N)
Weight                    Approx.375g (13.2oz)  (with EBP-50N)
DTMF                    16 Buttons Keypad
Sub audible Tone (CTCSS) encoder/decoder installed (39tones)
Sub audible Tone (DCS) encoder/decoder installed (104codes)
  
TRANSMITTER
Output power              Approx. 4 .5W EBP-50N installed
                         Approx. 5 W 13.8 V DC
                         Approx 0.8 W (LOW)
Modulation system          Variable reactance frequency modulation
Spurious emissions          Less than -60dB
Max. frequency deviation     +/- 5KHz
  
RECEIVER
Receive system            Double conversion superheterodyne
Intermediate frequencies     1st 30.85MHz / 2nd 455kHz
Sensitivity(12dB SINAD)    Less than -12.0 dBu (0.25uV)
  
Selectivity                -6 dB : 12KHz or more
                        -60 dB : 26KHz or less
Audio output power        280 mW (typical with an 8 ohm load)
                        200 mW (8 ohm 10% THD)