Icom IC-F5062, IC-F5063, IC-F5061 manual Transmitter Circuits

The processed AF signals from the base band IC (IC2) are passed through the AF mute switch (IC8, pins 3, 4) and D/A converter (IC6, pins 15, 16) for level adjustment. The level adjusted AF signals are amplified by AF amplifier (IC22).

The amplified AF signals are then;

-Output from D-sub 25 pin connector (CONNECT UNIT; J602).

or

-Buffer-amplified by Q49, then applied to connected micro- phone via FRONT UNIT.

or

-Applied to the AF power amplifier (IC21, pin 1) to obtain AF output power level, then applied to the internal/external speaker via external speaker jack (J7).

5-2 TRANSMITTER CIRCUITS

MICROPHONE AMPLIFIER CIRCUITS

The AF signals from the microphone (MIC signals) are filtered and level-adjusted at the microphone amplifier circuits.

AF signals from the connected microphone (MIC signals) are passed through (bypassed) the ALC (Automatic Level Control) amplifier (FRONT UNIT; IC505, pins 3, 5) via AF switch (FRONT UNIT; IC507, pins 1, 6/7), then applied to the microphone amplifier (FRONT UNIT; IC508, pin 3). The amplified MIC signals are output from pin 4, and applied to the MAIN UNIT.

The MIC signals from the FRONT UNIT are passed through the Int./Ext. MIC switch (IC23, pins 1, 6), and applied to the base band IC (IC2, pin 3) and processed.

SQUELCH CIRCUITS <NOISE SQUELCH>

The squelch mutes the AF output signals when no RF signals are received. By detecting noise components (30 kHz and higher signals) in the demodulated AF signals, the squelch circuit toggles the AF power amplifier ON and OFF.

A portion of the demodulated AF signals from the IF IC (IC5, pin 9) are applied to the D/A converter (IC6, pin 1) for level adjustment (squelch threshold adjustment). The level-adjusted AF signals are output from pin 2 and passed through the noise filter (IC5, pins 7, 8, R121−R124, C216 −C218). The filtered noise signals are amplified the noise components only.

The amplified noise components are converted into the pulse- type signal at the noise detector section, and output from pin 13 as the “NOIS” signal. The “NOIS” signal is applied to the CPU (IC14, pin 113), Then the CPU outputs signal “AFON2” signal from pin 15 to the AF power amplifier controller (Q51, Q52, D65), according to the “NOIS” signal level. The AF power amplifier controller toggles AF power amplifier (IC21) ON and OFF according to the “AFON” signal.

<TONE SQUELCH>

The tone squelch circuit detects tone signals and opens the squelch only when receiving a signal containing a matched sub audible tone. When the tone squelch is in use, and a signal with a mismatched or no sub audible tone is received, the tone squelch circuit mutes the AF signals even when the noise squelch is open.

• CTCSS/DTCS

A portion of the demodulated AF signals are passed through the active LPF (Q4, R45, R46, R47, R63, R64, C45, C46, C47, C71) to filters CTCSS/DTCS signal. The filtered signal is applied to the CPU (IC14, pin 64). The CPU compares the applied signal and the set CTCSS/DTCS, then outputs con- trol signal as same as “NOISE SQUELCH.”

• 2/5 TONE AND DTMF

2/5 tone signals in the demodulated AF signals are passed through the LPF in the base band IC (IC2) and output from pin 21, then applied to the CPU (IC14, pin 63) via tone amplifer (IC1, pins 8, 9), and decoded.

• BASE BAND IC BLOCK DIAGRAM

The applied MIC signals are amplified at the amplifier (TXA1), and level adjusted at the volume controller (VR1). The level adjusted MIC signals are applied (bypassed) the compressor section, pre-emphasis section, TX/RX HPF, de-scrambler, limiter, splatter, in sequence, then applied to another volume controller.

The compressor compresses the MIC signals to provide high S/N ratio for receive side, and the pre-emphasis obtains +6 dB/oct audio characteristics. The TX/RX HPF filters out 250 Hz and lower audio signals, the limiter limits its level and the splatter filters out 3 kHz and higher audio signals. The filtered MIC signals are level adjusted at another volume controller (VR2), and then output from pin 7 via smoothing fi lter (SMF).

The MIC signals from the base band IC are passed through the digital/analog switch (IC8, pins 12, 14), FM/PM switch (IC3, pins 13, 14), and applied to the AF mixer (IC1, pin

13)where the MIC signals and tone signals are mixed with. The mixed MIC signals are passed through D/A converter (IC6, pins 3, 4) for level adjustment. The level adjusted MIC signals are then applied to the VCO as modulation signals.

MODULATION CIRCUITS

The modulation circuits modulates the VCO oscillating signal using the modulation signals.

The MIC signals from the microphone amplifier circuits are applied to the D20 of TX VCO (Q19, D14, D17, D18, D20) as the modulation signals, and modulate the VCO oscillating signal by changing the reactance of D20.

The FM-modulated VCO output is amplified by buffer- amplifiers (Q22, Q29), then applied to the power amplifiers via D24 as the TX signal.

SIGNALING ENCODE

5/2-TONE, DTMF and CTCSS/DTCS signals are output from the CPU (IC14) and passed through the LPF (IC7) and level converter (IC6), then applied to the AF mixer (IC1, pin 13) and mixed with MIC signals. The mixed tone signals are passed through the D/A converter (IC6, pins 3,

4)for level adjustment. The level adjusted tone signals are applied to the both of TX VCO (Q19, D14, D17, D18, D20) and reference frequency oscillator (X1, pin 1) via the level adjuster (IC1, pins 1, 3).

BASE BAND IC (IC2)

TXIN	3	VR1	Com-	Pre-						7	MOD
		(HPF)	pressor	emphasis	Limiter	Splatter	VR2	SMF
	TXA1
				TX/RX	Scrambler/
				HPF	De-scrambler
RXIN	23	VR3	RX		De-					18
		(HPF)	LPF			Expander		VR4
					emphasis
	21 RXA1
SDEC										19
									RXA2 20		SIGNAL
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