Tone Squelch Circuit - Alinco DJ-G1T Service Manual

5) DTMF Circuit
1. Encoder Circuit
2. Decoder Circuit
6) Tone Squelch
Circuit
1. Encoder Circuit
2. Decoder Circuit
Each of the oscillation frequency of VC01 and VC02 is as follows.
Oscillation Frequency
138.85MHz~170.845MHz
VC01
170.85MHz~204.845MHz
134.575MHz~169.57MHz
144.00MHZ-147.995MHz
(TTX)
(E TX) 144.00MHz-145.995MHz
VC02
450.85MHz~460.845MHz
399.15MHz~419.145MHz
419.15MHZ-449.145MHz
384.575MHz~484.57MHz
(E)
The CPU has the DTMF encoder. The column signal is output from Pin98,
and the row signal is output from Pin99. The DTMF signal is determined
corresponding to the combination of the column and row. DTMF signal is
passed through variable resistor for modulation adjustment, and input to the
modulation terminal of VCO unit via the splatter filter.
The detected signal from IC301 is input to the DTMF decoder Pin2 of IC402.
When the tone squelch decoder decodes the input tone signal frequency as
the programmed frequency, the decoded data is output from P inll, 12, 13
and 14 processed in the CPU IC401.
The 4-bit digital codes are output from Pin 34, 35, 36 and 37 of CPU and
converted into the mimic sign wave with the R437 and R440. The sign wave
is input to the low-pass filter (R435, R436 and C419), AF amp Q313, and via
the active low-pass filter (Q314, R359, R360, R363 and C364), input to the
modulation terminal of VCO unit. 39 selectable tone frequency waves are
provided.
The tone decoder unit EJ-16u is option. The detected signal from Pin 12 of
IC301 is input to the Pin15of IC701 in the EJ-16uvia CN302. When the tone
squelch decoder decodes the input tone signal frequency as the pro­
grammed frequency, "high" signal is output from Pin9. When the tone
squelch decoder does not decode the input tone signal frequency as the
programmed frequency, "low" signal is output from Pin9, and it is input to the
CPU. Consequently the audio signal is controlled by CPU.
Tune Varicap
108.00MHz~ 139.995MHz
140.00MHz~173.995MHz
420.00MHz~429.995MHz
430.00MHz~449.995MHz
450.00MHz~479.995MHz
800.00MHz~999.99M Hz