Data Terminal And Peripheral Circuits; Microphone Key Input; Transmission Signals; Data Terminal Input/ Output Level - Kenwood TM-V71A Service Manual

6-3. Microphone Key Input

■ When the MC-59 (Supplied microphone) is used
The pulse is output from the CM terminal of the MPU to
the microphone. The MPU judges which key was pressed
from the number of pulses returned from the microphone.
■ When the MC-45 (Optional microphone) is used
The microphone UP/DOWN and function keys are
connected to the microprocessor analog input. The voltage
when a key is ON operates the corresponding function.
5M
CP952
R983
MIC PTT
R984
MIC UP
R985
MIC DW
MPU
IC918
Fig. 12 Microphone (MC-45) key input

7. Data Terminal and Peripheral Circuits

J607 (Data terminal) is the data communications terminal
on the rear of the transceiver. It handles transmission
control, data input/ output, and squelch signals.
There are two data communications modes: 9600bps
mode and 1200bps mode. 9600bps mode communications
are GMSK and G3RUH packet communications. Unlike with
1200bps AFSK, with this type of high-speed modulation,
frequency modulation is carried out after the digital base
band signals (rectangular wave) are passed through a band
IC801
J801
AF AMP
(SP1)
J802
(SP2)
ATT
Q816
PR1
PR9
SQC
PKS
1200bps
D607
PKD
D609
Limiter
9600bps
CIRCUIT DESCRIPTION
MIC
IC804
E VR
Q804 Q803 Q606
IC804
E VR
IC806
IC805
Cross
1/2
Point SW
Fig. 13 Transmission signals
TM-V71A/V71E
limiting filter. For 9600bps GMSK for example, compared
to 4800Hz signals (nearly sine wave signals passed
through a fi lter), the signals have a hissing sound like digital
modulation when listened to by ear. Different types of
modulation, such as GMSK and G3RUH, are distinguished
by the type of band limiting fi lter used.
Pin No. Pin name
bps switching
1 PKD Modulation input
Frequency shift
4 PR9
5 PR1
Table 2 DATA terminal input/ output level

7-1. Transmission Signals

Transmission modulation signals enter from PKD of the
data terminals (J607). The path to the modulation depends
on whether communications are set for 1200bps or 9600bps
mode.
For 1200bps mode, the transmission modulation signals
pass through the analog switch (IC803), and are input to
IC801 (Pin 6). The signals pass through the pre-emphasis
(Q801, Q802), are adjusted by the electronic volume, and
are input to the VCO.
For 9600bps mode, the transmission modulation signals
pass through IC803 and are amplified by the tone amp
(IC802). Signals are then adjusted by the electronic volume,
and are input to the VCO.
The frequency shift depends on the input signal level, so
there is an amplitude limiting circuit (D702, D703) to hold
the signal below 4 Vp-p to avoid extreme shifts. This circuit
ensures that the PKD signal does not go above 4 Vp-p and
there is no extreme frequency shift fl uctuation.
DE-EMPHASIS A
Q806 Q810
IC806
Cross
Point
Q807 Q811
SW
DE-EMPHASIS B
BEEP
IC805
1/2
DTMF
IC918
MPU
MUTE1
IC805
MUTE2
1/2
CTCSS Filter AMP
PRE-EMPHASIS MOD AMP
IC803 IC803
Q805 Q808
1/2
Specifi cation
1200bps 9600bps
40mVp-p 2Vp-p
3±0.5kHz 2.2±0.5kHz
Output level 500mVp-p/10kΩ
Always output during reception
Output level 500mVp-p/10kΩ
Not output when squelch off
IC486
FM IC (A)
IC666
Multi
SW
IC546
FM IC (B)
Q607
IC804
IC807
E VR
VCO
2/2
TCXO
9