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8. READ the instructions of test equipment thoroughly before connecting equipment to the transceiver. Icom, Icom Inc. and are registered trademarks of Icom Incorporated (Japan) in the United States, the United Kingdom, Germany, France, Spain, Russia and/or other countries.
Chassis unit *: IC-F24/F25 only • • REMOVING THE MAIN UNIT (IC-F24/F25) REMOVING THE MAIN UNIT (IC-F24S/F25S) 1 Unscrew 2 nuts F, and remove the top plate G. 1 Remove the switch connector O. 2 Unsolder 1 point H, and remove the earth plate.
SECTION 4 CIRCUIT DESCRIPTION The RF signals from the bandpass filter are mixed with the 4-1 RECEIVER CIRCUITS 1st LO signals, where come from the RX VCO circuit via 4-1-1 ANTENNA SWITCHING CIRCUIT the BPF (L12, L38, C49, C304, C305), at the 1st mixer cir- The antenna switching circuit functions as a low-pass filter cuit (Q3) to produce a 46.35 MHz 1st IF signal.
4-1-5 AF AMPLIFIER CIRCUIT • CTCSS AND DTCS The tone squelch circuit detects tone signals and opens the The AF amplifier circuit amplifies the demodulated AF sig- squelch only when the receiving signal contains matched nals to drive a speaker. subaudible tone (CTCSS or DTCS).
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4-2-4 APC CIRCUITS 4-2-2 MODULATION CIRCUITS The bias current of the drive (Q8) and power (Q7) amplifiers The modulation circuit modulates the VCO oscillating signal are controlled by the APC circuit. (RF signal) using the audio signals from the microphone. The AF signals from the D/A converter (IC8, pin 3) change The APC circuit (IC2, D1, D30) protects drive and power the reactance of varactor diode (D18) to modulate the oscil-...
4-3-2 VCO CIRCUITS 4-3 PLL CIRCUITS The VCO circuit contains a separate RX VCO (Q14, D16, 4-3-1 PLL CIRCUIT D22) and TX VCO (Q13, D17, D21). The oscillated signal A PLL circuit provides stable oscillation for the transmit fre- is amplified at the buffer amplifiers (Q10, Q12) and is then quency and the receive 1st LO frequency.
4-6 PORT ALLOCATION 4-4 OTHER CIRCUITS LED CONTROL CIRCUITS 4-6-1 D/A CONVERTER IC (IC8) The LED control circuit is composed of the CPU (IC13), Port LED driver (Q32) and LED (DS1). Description number name The CPU outputs “RLED” and “TLED” signals from the pins Outputs the modulation balance level 42 and 43.
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4-6-2 CPU (IC13) Port Port Description Description number name number name Input port for the transceiver’s RLED Outputs receiving LED control signal. TEMP internal temperature detecting Outputs transmitting LED control signal. TLED signal. Input port for the detect signal BATV for connecting battery pack’s OPT3 voltage.
SECTION 5 ADJUSTMENT PROCEDURES 5-1 PREPARATION When adjusting IC-F24/F25/S, the optional CS-F14 ADJ (Rev. 1.0 or later), JIG cable (see the illust ADJUSTMENT SOFTWARE below) and OPC-478 (RS-232 type) or OPC-478U (USB type) are required. CLONING CABLE REQUIRED TEST EQUIPMENTS...
5-2 CONFIGULATION LIST FOR ADJUSTMENTS - IC-F24/F25 - [US2]=USA-02, [GE2]=GEN-02, [EU2]=EUR-02, [US3]=USA-03, [GE3]=GEN-03 FREQUENCY (MHz) FREQUENCY (MHz) SETTING CONDITION SETTING CONDITION [US2], [EU2], [US2], [EU2], [US3], [GE3] [US3], [GE3] [GE2] [GE2] Set TX power to Low1. Set DTCS code to 007.
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SINAD meter JIG cable To [SP] (see page 5-1) Speaker (8 Ω) IC-F24/F25/S (JIG CABLE ( SP + ) (SP − ) (GND) 3-conductor 3.5(d) mm plug OPC-478/U JIG cable To IC-F24/F25/S [SP] jack (CLONE) 5 - 3...
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(PC SCREEN EXAMPLE NOTE: The above screen is an example. Each transceiver has its own specific values for each setting. 5 - 4...
5-3 SOFTWARE ADJUSTMENTS (TRANSMITTING) Select the operation using [↑] / [↓] keys, then set specified value using [←] / [→] keys on the connected computer keyboard. MEASUREMENT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION PLL LOCK • Operating CH : CH2 (*CH1) "...
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5-3 SOFTWARE ADJUSTMENTS (RECEIVING) • Select an operation using [↑] / [↓] keys, then set specified value using [←] / [→] keys on the connected computer keyboard. MEASUREMENT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION CTCSS/DTCS 1 • Operating CH : CH10 (*CH1) Connect the FM deviation ±0.68 kHz DEVIATION...
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