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VGS-1
IC57
O
O
I
I
Fig. 3 External device, pull-up resistor
■ AI Input Port
If input exceeds 100mVp-p, the input signal is clipped and
distortion occurs.
It is necessary to make setting so that no signals exceed-
ing 100mVp-p are input.
If the input level lowers, S/N decreases, so the maximum
input not exceeding 100mVp-p must be used.
■ AO Output Port
When recording is performed with a 100mVp-p input, the
playback output becomes an approx. 2.8Vp-p level.
If Prerecorded Voice is generated, the output is approx
2Vp-p.
Beat Shift Circuit
To prevent VGS-1 clock oscillation for the MCU (IC2) from
causing spurious reception to transceivers to which VGS-1 is
connected, the clock oscillator (11.0592MHz) has a beat shift
circuit with a transistor switch (Q1).
■ Beat Shift Circuit Off
Pin 94 of the MCU (IC2) goes Low level, Q2 turns off, and
Q1 turns on because a 5V bias is applied to its base. In this
condition, C10 is shorted, so the oscillation frequency is un-
changed.
■ Beat Shift Circuit On
Pin 94 of the MCU goes High level, Q2 turns on, and Q1
turns off because its base is pulled down to GND. In this
condition, C10 is connected in series to the crystal oscillator
and the oscillation frequency increases by approx. 150ppm.
CIRCUIT DESCRIPTION
External device
5V
Pull-up
resistor
5V
Pull-up
resistor
XTAL
67
IC2 94 pin
R17
PA1
High : Normal
Low : Shift
Fig. 4 Beat shift circuit
Amateur Transceiver Identification
The VGS-1 can be set as an amateur transceiver or a Land
Mobile Radio transceiver in the factory.
When it is used as a Land Mobile Radio transceiver, inter-
nal data in the VGS-1 is changed to suit the Land Mobile Ra-
dio transceiver, so it cannot be used as an amateur trans-
ceiver.
The VGS-1 set as a Land Mobile Radio transceiver can be
identified because the RV4 land on the PCB is at High level.
The default is Low level.
Accessory unit
Foil side view
RV3
RV4
Fig. 5 RV4
VGS-1
IC2
MCU
EXTAL
66
C10
X1
Q1
R19
5V
Q2
RV2
RV1
3
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