2 Display Lamp Circuit
The regulated power supply circuit consisting of Q505, Q507, R508, R509 supplies
H from CPU (IC508) when LAMP key is pressed. Then it is applied to the base
of Q507, and the voltage of 3.5V is outputted from the collector of Q505. lt is fed
to each LED (D503~D506, D509,D511 ,D513,D514).
3 Reset and Backup Circuit
When the voltage of approximately 3.0V or more is supplied from the external (DC
jack, battery), the reset signal of "H" level is outputted from Reset IC (IC506), and
it is fed to CPU (IC508) Ping, then the CPU is reset. Until the clock (X502) of CPU
is stabilized, the reset signal is fed to CPU after it is delayed in C522 and R58l.
When the voltage from external is decreased to approximately 3.3V or below, the
voltage of Pin18 in CPU is changed from "H" level to "L" level, then the CPU enters
into the backup mode.
4 S (signal) Meter Circuit
4-1 L Band
The DC voltage of IC302 Pin16 is low when the signal is weak and high when the
signal is strong. This change of DC voltage is adjusted the level at the trim pot
(VR304), and led to CPU (IC508) Pin98, then displayed on the LCD as S meter
after A/D converting.
4-2 R Band
The DC voltage of IC301 Pin13 is adjusted the level at the trim pot (VR302), and
led to CPU (IC508) Pin99, then displayed on the LCD as S meter after A/D
converting.
5 Full-duplex Circuit
When the DUP key is pressed, in the receiving side Q317 is turned ON and the
audio signal supplied to audio amplifier is decreased. ln transmitting side Q510 is
turned ON, and the modulation signaf is decreased to prevent the howling.
6 X-Band Repeater Circuit
ln X-band repeater mode, Q323 is turned OFF, the audio Signal which is opened
the squelch is passed through the audio high-pass filter (Q313: L band, Q306:R
band), and the signal is applied to the other modulation circuit. Then the radio
enters into the transmitting mode.
7 DTMF
7-1 Encoder
The DTMF encoder is built in the CPU (IC508). The DTMF signal output from
Pin91 is adjusted its level at VR308, and amplified by the mic amplifier (IC310),
then fed to the varicap for modulation of each VCO.
Simultaneously the monitor sound is passed through AF circuit, and it is supplied
from the speaker.
7-2 Decoder
A part of the audio signal which is demodulated in IC301 , IC302 is fed to the DTMF
switch (IC501), then only the selected band audio signal is fed to DTMF IC (IC502)
Pin1. The supplied signal is judged whether valid or not by the signal judgement
circuit in IC502, and converted into 4-bit code, then supplied to IC508 Pin85.
8 Tone Squelch
8-1 Encoder
The tone signal supplied from Tone IC (IC504) Pin21 (67.OHz~254.lHz) is ad-
justed the level at VR307, and amplified n the tone amplifier (Q322), then applied
to the varicap for modulation of each VCO.
8-2 Decoder
A part of the audio signal which is demodulated in IC301, IC302 is fed to the tone
switch (IC504), then only the selected band audio signal is fed to tone IC (IC504)
Pin1.
When the signal is accord with the programmed tone frequency, "LO" is outputted
from IC504 Pin14, and it is fed to CPU (IC508) Pin74, then the squelch is opened.
7 |
ACEC
ALINCO
