Icom IC-F3063S Modulation Circuit Main Unit, Transmit Amplifiers RF Unit, APC Circuit RF Unit

The output AF signals are then passed through the Digital/ Analog switch (IC14, pins 12, 14) and applied to the AF mixer (IC9, pin 6) where the MIC signals and Tone signals are mixed with (while CTCSS/DTCS are in use) via the PM/FM switch (IC13, pins 12, 14).

The CTCSS and DTCS signals are generated by the CPU (IC18) and output from pins 89−91. The output signals are passed through the 3 registers (R263–R265) to change its wave form. The wave form changed CTCSS/DTCS signals are passed through the LPF (IC17, pins 1, 3) and the D/A converter (IC4, pins 21, 22) for level adjustment. The level adjusted CTCSS/ DTCS signals are then applied to the AF mixer (IC9, pin 6).

2/5 tone and DTMF signals are generated by the CPU (IC18) and output from pin 43. The output signals are passed through two LPF's (IC17, pins 8, 10 and pins 5, 7), then applied to the AF mixer (IC9, pin 6).

The mixed AF signals are output from pin 7 of the AF mixer (IC9) and passed through the D/A converter (IC4, pins 3, 4) for level adjustment (=deviation adjustment), then applied to the modulation circuit (D9) as the modulation signals. The modulation signals are also applied to the reference frequency oscillator (X1) via D/A converter (IC4, pins 11, 12) and AF amplifi er (IC21, pins 1, 4).

5-2-2 MODULATION CIRCUIT (MAIN UNIT)

The modulation signals from the microphone amplifier circuits are applied to the D9, and modulate the VCO oscillating signal by changing the reactance of D9. The modulated VCO output signal is buffer-amplifi ed by Q4 and Q6, then applied to transmit amplifi ers as a transmit signal via the TX/RX switch (D14 is ON, D15 is OFF).

5-2-3 TRANSMIT AMPLIFIERS (RF UNIT)

The transmit signal from the TX/RX switch (MAIN UNIT; D14 is ON, D15 is OFF) is amplified to the transmit output level by pre-driver (Q603), driver (Q602) and power (Q601) amplifi ers.

The power-amplified transmit signal is passed through the two LPF’s (L607, L608, C620, C622−C624, C664 and L606, C615−617) to filter off the harmonic components in the transmit signal. The fi ltered transmit signal is passed through the antenna switching circuit (D601 and D603 are ON), then applied to the antenna connector (CHASSIS; J1) via another LPF (L601−L603, C601, C602, C604−C606, C608, C609, C663).

5-2-4 APC CIRCUIT (RF UNIT)

The APC (Automatic Power Control) circuit stabilizes transmit output power to prevent the transition of the transmit output power level which is caused by load mismatching or heat effect, etc. The APC circuit also selects transmit output power from high, middle and low power.

A portion of the transmit signal is detected by the transmit power detector (D604, D605) to produce a DC voltage corresponding to the transmit output power level. The detected voltage is applied to the APC amplifier (IC601, pin 3). The transmit power setting voltage “T2” from the D/A converter (MAIN UNIT; IC20, pin 2) is applied to another input terminal (pin 1) as the reference voltage.

The APC amplifier compares the detected voltage and reference voltage, and the difference of the voltage is output from pin 4. The output voltage controls the bias of the drive (Q602) and power (Q601) amplifiers to reduce/increase the gain of these amplifiers for stable transmit output power.

The change of transmit output power is carried out by the change of reference voltage "T2," and the transmit power muting is carried out by the TX mute switch (Q606), using the “TMUT” signal from the CPU (IC18, pin 13).

5-2-4 OVER CURRENT DETECTION CIRCUIT (RF UNIT) The driving current of the drive (Q602) and power (Q601) amplifiers is detected at the current detector (Q604, Q605) by detecting the difference of voltage between both terminals of R623. The detected voltage "ISENS" is applied to the CPU (IC18, pin 47).

In case of the over current, the CPU outputs "TMUT" signal from pin 13 to TX mute switch (Q606) to stop the transmitting for protection of transmit amplifi ers (Q601, Q602).

5-3 PLL CIRCUITS

5-3-1VCO (Voltage Controlled Oscillator) CIRCUITS (MAIN UNIT)

A VCO is a oscillator which its oscillating frequency is controlled by adding voltage (lock voltage).

This transceiver has 3 VCO’s; RX VCO1 (Q1, D1−D4), RX VCO2 (Q2, D5−D8) and TX VCO (Q3, D10−D12). The RX VCO1 oscillates the 1st LO signals for 155 MHz and higher, and the RX VCO2 oscillates the 1st LO signals for 155 MHz and lower frequencies. And the TX VCO oscillates the transmit output signal.

• RX VCO1 and RX VCO2

The RX VCO1/RX VCO2 (Q1, D1−D4/Q2, D5−D8) oscillates the 1st LO signals. The output signals are amplified by the buffer amplifi ers (Q4, Q6), and applied to the 1st mixer (Q37) via TX/RX switch (D14 is OFF, D15 is ON) and LPF (L38, L39, C161−C164, C383, C384), to be mixed with the received signals to produce the 46.35 MHz 1st IF signal.

• TX VCO

The TX VCO (Q3, D10−D12) oscillates the transmit signal. The output signal is applied to the transmit amplifi ers via the buffer amplifi ers (Q4, Q6) and TX/RX switch (D14 is ON, D15 is OFF).

• APC CIRCUIT

	Q604, Q605
HV	Current						to the receive circuits
	detector		T5V
“ISENS”				Q603	Q602	Q601
				Pre-	Drive	Power		ANT
							LPF		LPF
	from TX/RX switch			drive	amp.	amp.		SW
				amp.					to the anntena
	(MAIN UNIT; D14, D15)
“T2”
	Q606	+	IC601
“TMUT”
		ALC
							D604	D605
		– amp.
							Power detecter

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