User's Manual

4. Transmitter

1) Transmitting AF

The AF signal from the microphone passes through a pre-emphasis circuit, is amplified

and filtered by a low-pass filter at IC6-A, B, Q5 and Q7. The resulting signal enters VCO

for direct modulation. (See figure 5)

2) CTCSS/CDCSS Encoder

The necessary signal for 38 CTCSS and 83 CDCSS encoder is generated by TO pin of

IC8 and FM-modulated to the PLL reference signal. Since the reference OSC does not

modulate the loop characteristic frequency or higher, modulation is performed at the VCO

side by adjusting the balance. (See fig.5)

Fig 5.Transmit AF and CTCSS/CDCSS

3) RF Amplifier

The RF signal obtained from VCO buffer amplifier is amplified by Q9. The amplified signal

is amplified by power amplifier Q3, Q8 and Q10 to generate RF power. (See Fig.6)

AMP

DRIVE AMP

FINAL AMP

Q10

ANT SW

D1 LPF

ANT

ANT SW

Fig.6 Final Module

4) Antenna Switch and LPF

The RF signal is passed through a low-pass filter network and a transmit/receive switch

(D1 and D2) before it is passed to the antenna terminal. D1 is turned on in transmit mode

and off in receive mode.