Icom IC-FR3000 manual Case of the 2/5TONE Signals, Case of the Dtmf Signals from Dialer IC

The filtered signals are applied to the limiter amplifier (IC3), and are then mixed with the DTMF signal from the CPU (IC33, pin 43) via the TX-signal filter (IC3, pins 8, 10, 12, 14). The mixed signals are applied to the splatter filter (IC4), and are then applied to the PA unit.

•IN CASE OF THE AF SIGNALS FROM THE ANTENNA CONNECTOR

The AF signals (received signals) from the antenna connec- tor (RX unit; J1) are applied to the buffer amplifier (IC9), CTCSS detector (IC29) and AF amplifier (IC6). The ampli- fied signals are applied to the D/A converter IC (IC25, pins 8, 9) to adjust a repeater AF level. The adjusted AF signals pass through the RPT AF mute switch (IC14), and are applied to the limiter amplifier (IC3).

•IN CASE OF THE 2/5TONE SIGNALS

The 2/5TONE signals from the CPU (IC33, pin 43) are applied to the mixer amplifier (IC3) via TX signal filter circuit (IC3, pins 8, 10, 12, 14).

•IN CASE OF THE DTMF SIGNALS FROM

DIALER IC

The DTMF from dialer IC (IC47, pin 14) are applied to the mixer amplifier (IC3) via the TX signal filter circuit (IC3, pins 8, 10, 12, 14).

•IN CASE OF THE CTCSS AND DTCS SIGNALS

FROM THE CPU

The CTCSS and DTCS signals from the CPU (IC33, pin 44) are applied to the TX-tone filter (IC4, pins 12, 14). The fil- tered signal are applied to the D/A converter IC (TX unit; IC5 pin 9) to adjust a tone level needed, and are then mixed with AF signal at the mixer amplifier IC (TX unit; IC6).

3-2-2 MODULATION CIRCUIT (TX UNIT)

The modulation circuit modulates the VCO oscillating signal (RF signal) using the AF audio signals.

The filtered signals from the LOGIC unit are applied to the D/A converter (IC5, pin 4) to adjust AF level. The adjusted signals are applied to the mixer amplifier IC (IC6, pin 1) with the CTCSS/DTCS signals.

The mixed signals are applied to the TX VCO circuit to mod-

•APC CIRCUIT (PA UNIT)

ulate the oscillated signal (TVCO unit; D5) and modulate the oscillated signal at VCO circuit (TVCO; Q1, D1–D4). The modulated VCO output is amplified at the buffer amplifier (Q1) and is then applied to the drive amplifier circuit on the PA unit.

3-2-3 POWER AMPLIFIER CIRCUIT (PA UNIT)

The power amplifier circuit amplifies the driver signal to an output power level.

The RF signal from the TX unit is applied to the pre-drive (Q4) to amplify the level needed at the power amplifier. The amplified signal passes through the attenuator circuit (R29–R31) and is then applied to the power amplifier (IC2).

The RF signal from the pre-drive (Q4) is applied to the power amplifier (IC2) to obtain 50 W ([IC-FR3100]: 25 W) of RF power.

The amplified signal is passed through a low-pass filter cir- cuit (L6, L7, L20, C1–C3, C48, C73, C98, C100) and APC detector (D2, D4, R7, R8, R20, R21, R25, R26, 58, R36, R37, C78, C79), and is then applied to the TX antenna con- nector (CHASSIS; J1).

Control voltage for the pre-drive (Q4) and power amplifier (IC2) comes from the APC amplifier (IC1, Q9, Q10) to obtain stable output power. The transmit mute switch (Q7, Q8) con- trols the pre-drive (Q4) and power amplifier (IC2) when transmit mute is necessary.

3-2-4 APC CIRCUIT (PA UNIT)

The APC circuit protects the power amplifier from a mis- matched output load and stabilizes the output power.

The APC detector circuit detects forward signals and reflec- tion signals at D2 and D4 respectively. The combined volt- age become minimum level when the antenna impedance is matched at 50 Ω, and the voltage is increased when it is mismatched.

The detected voltage is applied to the APC amplifier (IC1 pin 3), and the power setting “PCON” signal from the D/A con- verter (TX unit; IC5), controlled by the CPU (LOGIC unit; IC33), is applied to the the APC amplifier (IC1 pin 1) for ref- erence. When antenna impedance is mismatched, the

DRIVE

POWER AMP IC2

TX UNIT

Q4

ATT

LPF

VCC

DET

		APC	PCON
		CTRL	(TX UNIT; IC5)
	+9V		IC1, Q9, Q10
	SW
Q7, Q8
	TMUTE2		FWSWR
To IC33; pin 46 (LOGIC UNIT)
To IC33; pin 47 (LOGIC UNIT)
			RVSWR

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