User manual ICOM IC-21A

[. . . ] DO NOT apply an RF signal of more than 20 dBm (100 mW) to the antenna connector. This could damage the transceiver's front end. To upgrade quality, any electrical or mechanical parts and internal circuits are subject to change without notice or obligation. ORDERING PARTS Be sure to include the following four points when ordering replacement parts: 1. Quantity required <SAMPLE ORDER> 1140005990 S. IC MB15A02PFV-1 IC-21A MAIN UNIT 5 pieces 8810009610 Screw FH M2. 6×6 ZK IC-21A Bottom cover 10 pieces REPAIR NOTES 1. Make sure a problem is internal before disassembling the transceiver. [. . . ] Transmit 8 V for VHF band which is the same voltage as the 8V line controlled by the VT8 regulator circuit (Q19, Q22) using the "VTXC" line. Transmit 8 V for UHF band which is the same voltage as the 8V line controlled by the UT8 regulator circuit (Q20, Q23) using the "UTXC" line. Common 5 V converted from the HV line by the +5 regulator circuit (IC503). Common 5 V converted from the 5V line by the +5 regulator circuit(Q503, D504). The circuit is controlled by the power switch controller (Q502). Common 8 V converted from the 8 V line by the +8 regulator circuit (Q4). VCC 4-4-2 LCD DISPLAY CIRCUIT (CONTROL UNIT) The transceiver's LCD display employs 1/4 duty custom LCD which displays frequency, S-meter, TX power level, etc. The LCD display is controlled by the sub-CPU (IC6, pins 41­78) directly. 8V VT8 UT8 4-4-3 LCD AND KEY BACK LIGHT CIRCUIT (CONTROL UNIT) The sub-CPU (IC6) outputs +8 regulator circuit (Q1, Q3, D5) control signal from pin 2. The voltage from +8 regulator circuit is applied to the key back light circuit (DS13­DS18, DS20, DS23) and LCD back light circuit (DS22). The back light color is also controlled by the sub-CPU via the color control circuit (Q6, Q7). The back light has 3 colors (Umber, Green and Yellow). 5V 5VS VCO8 Common 8 V line which is selected by the SEL_SW circuit (Q6, Q8). The voltage is applied V_VCO8 to the VHF VCO (VCO board; Q3, D1, D2) and buffer amplifiers (VCO board; Q4, Q5). High : While transmitting (136­174 MHz) Outputs the DTCS filter select signal. High : While the DTCS signal is transmitting. I/O port for the serial data to the EEPROM (IC501, pin 5). Outputs the clock signal to the EEPROM (IC501, pin 6). Low : While the packet [PTT] switch is ON 20 UTXC 21 VTXC 58 22 DTCS_SEL Outputs the detector circuit mute signal. DET_MUTE High : While the detector circuit is muting. Outputs microphone sensitivity control MIC_SENS signal. U_VCO Outputs the UHF VCO control signal. High : The VCO circuit oscillates 320­999. 99 MHz signal. 24 25 ES_DATA ES_CK 62 63 26 P-PTT 65 27 28 Outputs the packet modulation muting P_MOD_MUTE signal. 98_DATA Input port for the HM-98's data signal. Input port for the connecting microphone detect signal. [. . . ] The IC-21A wideband receiver covers 118­173, 230­549 and 810­999MHz* as standard. Listen to your Amateur VHF/UHF bands, as well as aviation, marine, weather and other utility communications in a compact mobile package. * Excluding Cellular range. User friendly design The large multi-function tuning knob provides intuitive channel tuning or band hopping. The multicolor display lighting and backlit buttons adds a new `fun' dimension to operating the IC-21A. HM-133, remote control microphone The supplied HM-133 remote control microphone allows you to control almost every function of the IC-21A from the mic. Detachable front panel Limited installation space is no problem with the IC-21A. [. . . ]