Alinco DJ-X3, Service Manual, Page: 4 / 35

4
The 2nd Mixer
The input signal and the 2nd local signal is added or subtracted at mixer IC4,
and switched to FM/AM receiving side or WFM receiving side at D24 or D25 .
FM/AM
At FM/AM receiving side, the crystal filter XF1 selects the signal of 38.85 MHz.
The signal is amplified at the 1st IF amplifier Q22 after the adjacent signal is
eliminated.
WFM
At WFM receiving side, the band pass filter selects the signal of 38.85 MHz.
The signal is amplified at the 1st IF amplifier Q22 after the adjacent signal is
eliminated.
4. IF
FM/AM
The amplified signal at the 1st IF amplifier Q22 is supplied to pin 24 of IC6 for
demodulation. The signal of 12.8 MHz from the IC 1 reference buffer output is
multiplied by 3 at Q17, then mixed with the signal added to pin 1 of IC6 in the
mixer circuit inside IC6 to be converted into the 2nd IF signal of 450 kHz. The
converted 2nd IF signal is output from pin 3 of IC6.
FM
The output signal from pin 3 of IC6 is input to pin 7 of IC6 after the adjacent
signal is eliminated at the ceramic filter FL2. The 2nd IF signal input to pin 7 of
IC6 is demodulated at the limiter amplifier and quadrature detection circuit
inside IC. Then the signal is output from pin 12 of IC6 as an AF signall.
AM
The output signal from pin 3 of IC6 is input to pin 5 of IC6 after the adjacent
signal is eliminated at the ceramic filter FL2. The 2nd IF signal input to pin 5 of
IC6 is output from pin 13 of IC6 as an AF signal after AM is detected inside IC.
Also reverse AGC is added to the 1st IF amplifier Q22 by AGC amplifier Q25
and the gain is controlled to get the normal audio output even though the input
signal is fluctuated.
WFM
The output signal from pin 3 of IC6 is input to pin 7 of IC6. The 2nd IF signal
input to pin 7 of IC6 is demodulated at the limiter amplifier and quadrature
detection circuit inside IC, and output from pin 12 of IC6 as an AF signal.
5. Squelch
The AF signal is output from pin 12 of IC6 and input to pin 19 of IC6. The
input signal is output from pin 21 of IC6 through the noise filter amplifier
and rectifying circuit. The rectified signal is supplied to the A/D port of
microcomputer IC1. Then the microcomputer IC1 judges the signal to
control ON/OFF of audio output.