UHF Transceiver NO LICENCE for CB channels required
128 Channel Capability
The IC-400PRO comes pre-programmed with the 80 UHF CB simplex and repeater channels. Up to 35 additional channels are available for monitoring frequencies in the 450MHz-500MHz band. Channel data entry is available through the front panel, or via optional PC programming kit.
Designed for the most extreme Australian conditions. Die-cast aluminium chassis and heavy-duty heat sink, impact resistant polycarbonate front panel incorporating 4W speaker for crisp clear audio, even in high noise environments. Industrial grade condenser microphone is supplied..
Super Sensitive Private Channels
The IC-400PRO is also compatible and fully approved for use on Licensed Land Mobile Services at 25W within the 450-500MHz band* at 12.5 or 25kHz when re-configured by an Authorised Icom Radio Dealer. * ACMA Licensed Users only.
Unique Repeater Scan
Our unique repeater scan function finds available repeater stations even while you are travelling. In addition, Group/Priority scan detects tagged channels, while also monitoring your priority channel.
Listen only to your own group ! Up to 51 user selectable CTCSS group codes are available for silent stand-by operation. DTCS is also available with private channels.
Selcall (Selective Calling)
Hear only the calls intended for you and see who called with SelCall ! The IC-400PRO comes with all popular CB and commercial 5-Tone Selcall formats, along with user selectable ID number set up. The last 10 caller ID's are stored for easy recall and up to 28 numbers can be preprogrammed with name tags for easy reference.
Easy-to-use and install
- Smart Ring and Automatic Transponder acknowledges if other Icom CB transceivers received your call or are within range.
- Touch pad controls and rotary volume dial
- Backlit LCD with 8 character alpha display and status icons
- Compact and light with front facing speaker and quality mounting kit for roof or console mounting
- Optional DIN size kit for in-dash installation
ANTENNA SWITCHING CIRCUIT (MAIN UNIT)
The antenna switching circuit functions as a low-pass filter while receiving and as resonator circuit while transmitting. This circuit does not allow transmit signals to enter the receiver circuits.
Received signals enter the antenna connector and pass through the low-pass filters (L1-L3, C1, C2, C6-8, C16). The filtered signals are then applied to the RF circuit passed through the 1/4 type antenna switching circuit (D5-D7).
RF CIRCUIT (MAIN UNIT)
The RF circuit amplifies signals within the range of frequency coverage and filters out-of-band signals.
The signals from the antenna switching circuit pass through the two-stage tunable bandpass filters (D8, D4). The filtered signals are amplified at the RF amplifier (Q2) and then enter other two-stage bandpass filters (D9, D10) to suppress unwanted signals. The filtered signals are applied to the 1st mixer circuit (Q3).
The tunable bandpass filters (D4, D8-D10) employ varactor diodes to tune the center frequency of the RF passband for wide bandwidth receiving and good image response rejection. These diodes are controlled by the CPU (FRONT unit; IC1) via the D/Aconverter (IC6).
The gate control circuit reduces RF amplifier gain and attenuates RF signal to keep the audio output at a constant level.
The receiver gain is determined by the voltage on the "RSSI" line from the FM IF IC (IC1, pin 12). The gate control circuit (Q1) supplies control voltage to the RF amplifier (Q2) and sets the receiver gain.
When receiving strong signals, the "RSSI" voltage increases and the gate control voltage decreases. As the gate control voltage is used for the bias voltage of the RF amplifier (Q2), then the RF amplifier gain is decreased.
1ST MIXER AND 1ST IF CIRCUITS
The 1st mixer circuit converts the received signals to a fixed frequency of the 1st IF signal with the PLL output frequency. By changing the PLL frequency, only the desired frequency will pass through a MCF (Monolithic Crystal Filter; FI1) at the next stage of the 1st mixer.
The RF signals from the bandpass filter are applied to the 1st mixer circuit (Q3). The applied signals are mixed with the 1st LO signal coming from the RX VCO circuit (Q13) to produce a 46.35 MHz 1st IF signal. The 1st IF signal passes through a MCF (Monolithic Crystal Filter; FI1) to suppress out-of-band signals. The filtered signal is amplified at the 1st IF amplifier (Q4) and applied to the 2nd IF circuit.
2ND IF AND DEMODULATOR CIRCUITS (MAIN UNIT)
The 2nd mixer circuit converts the 1st IF signal to a 2nd IF signal. A double-conversion superheterodyne system improves the image rejection ratio and obtains stable receiver gain.
The 1st IF signal from the 1st IF amplifier (Q4) is applied to the 2nd mixer section of the FM IF IC (IC1, pin 16) and is then mixed with the 2nd LO signal for conversion to a 450 kHz 2nd IF signal.
IC1 contains the 2nd mixer, limiter amplifier, quadrature detector, active filter and noise amplifier circuits, etc. A tripled frequency from the PLL reference oscillator is used for the 2nd LO signal (45.9 MHz).
The 2nd IF signal from the 2nd mixer (IC1, pin 3) passes through a ceramic filter (FI2) to remove unwanted heterodyned frequencies. It is then amplified at the limiter amplifier section (IC1, pin 5) and applied to the quadrature detector section (IC1, pins 10, 11 and X1) to demodulate the 2nd IF signal into AF signals.
The AF signals are output from pin 9 (IC1) and are then applied to the AF amplifier circuit.
AF AMPLIFIER CIRCUIT (MAIN UNIT)
The AF amplifier circuit amplifies the demodulated AF signals to drive a speaker.
The AF signals from the FM IF IC (IC1, pin 9) are applied to the active filter circuit (IC16). The active filter circuit (high-pass filter) removes CTCSS or DTCS signals.
The filtered AF signals are output from pin 14 (IC16) and are applied to the de-emphasis circuit (R117, C378) with frequency characteristics of -6 dB/octave, and then passed through the analog switch (IC14, pins 1-3) and low-pass filter (IC5). The filtered signal is applied to the electronic volume controller (IC6, pin 9).
The output AF signals from the electronic volume controller (IC6, pin 10) are passed through the analog switch (IC14 pins 9-11) and are applied to the AF amplifier (IC15) and AF power amplifier (IC8) to drive the speaker.
RECEIVER MUTE CIRCUITS (MAIN AND FRONT UNITS)
• NOISE SQUELCH
The noise squelch circuit cuts out AF signals when no RF signals are received. By detecting noise components in the AF signals, the squelch circuit switches the AF mute switch.
Some noise components in the AF signals from the FM IF IC (IC1, pin 9) are passed through the level controller (IC6, pins 1, 2). The level controlled signals are applied to the active filter section in the FM IF IC (IC1, pin 8). Noise components about 10 kHz are amplified and output from pin 7.
The filtered signals are converted to the pulse-type signals at the noise detector section and output from pin 13 (NOIS).
The NOIS signal from the FM IF IC is applied to the CPU (FRONT unit; IC1, pin 53). The CPU then analyzes the noise condition and controls the AF mute signal via "AFON" line (D44, D45) to the AF mute circuit (Q35, Q36, D29, D30).
• CTCSS AND DTCS
The tone squelch circuit detects AF signals and opens the squelch only when receiving a signal containing a matching subaudible tone (CTCSS or DTCS). When tone squelch is in use, and a signal with a mismatched or no subaudible tone is received, the tone squelch circuit mutes the AF signals even when noise squelch is open.
A portion of the AF signals from the FM IF IC (IC1, pin 9) passes through the low-pass filter (IC16) to remove AF (voice) signals and is applied to the CTCSS or DTCS decoder inside the CPU (FRONT unit; IC1, pin 60) via the "CDEC" line to control the AF mute switch.
MICROPHONE AMPLIFIER CIRCUIT (MAIN AND FRONT UNITS)
The microphone amplifier circuit amplifies audio signals within +6 dB/octave pre-emphasis characteristics from the microphone to a level needed for the modulation circuit.
The AF signals (MIC) from the MIC jack (FRONT unit; J1) are amplified at the AF amplifier (FRONT unit; IC5) and applied to the MAIN unit via J2 (pin 28). The AF signal are applied to the limiter amplifier (IC5, pin 5).
The entered signals are pre-emphasized with +6dB/octave at a limiter amplifier, then passed through the analog switch (IC14, pins 2-4) and splatter filter (IC5, pins 2, 1). The output signals from the splatter filter are applied to the level controller (IC6, pin 9).
The deviation level controlled signals are then applied to the modulation circuit (D18) as the "MOD" signal after being passed through the analog switch (IC14, pins 9, 8).
MODULATION CIRCUIT (MAIN AND FRONT UNITS
The modulation circuit modulates the VCO oscillating signal (RF signal) using the microphone audio signals.
The AF signals from the analog switch (IC14, pin 8) change the reactance of varactor diode (D18) to modulate the oscillated signal at the TX VCO circuit (Q14, D17). The modulated VCO signal is amplified at the buffer amplifiers (Q11, Q10) and is then applied to the drive amplifier circuit via the
T/R switch (D14).
The CTCSS/DTCS signals from the CPU (FRONT unit; IC1, pins 22-24) are passed through the low-pass filter (FRONT unit; IC5), and mixer and splatter filter (IC5), and are then applied to the VCO circuit.
DRIVE AMPLIFIER CIRCUIT (MAIN UNIT)
The drive amplifier circuit amplifies the VCO oscillating signal to the level needed at the power amplifier.
The RF signal from the buffer amplifier (Q10) passes through the T/R switch (D14) and is amplified at the drive amplifier circuit (Q8). The amplified signal is applied to the power amplifier circuit.
POWER AMPLIFIER CIRCUIT (MAIN UNIT)
The power amplifier circuit amplifies the driver signal to an output power level.
The RF signal from the drive amplifier (Q8) is passed through the low-pass filter circuit (L18, L43, C89, C90, C92, C380, C381, C510) and applied to the power module (IC3) to obtain 25 W of RF power.
The amplified signal is passed through the antenna switching circuit (D2), low-pass filter and APC detector, and is then applied to the antenna connector.
Control voltage for the power amplifier (IC3, pin 2) comes from the APC amplifier (IC2) to stabilize the output power. The transmit mute switch (D28) controls the APC amplifier when transmit mute is necessary.
APC CIRCUIT (MAIN UNIT)
The APC circuit protects the power amplifier from a mismatched output load and stabilizes the output power.
The APC detector circuit detects forward signals and reflection signals at D1 and D11 respectively. The combined voltage is at minimum level when the antenna impedance is matched at 50 Q, and is increased when it is mismatched.
The detected voltage is applied to the APC amplifier (IC2, pin 3), and the power setting "T2" signal from the D/A converter (IC6, pin 22), controlled by the CPU (FRONT unit; IC1), is applied to the other input for reference. When antenna impedance is mismatched, the detected voltage exceeds the power setting voltage. Then the output voltage of the APC amplifier (IC2, pin 4) controls the input current of the power module (IC3) to reduce the output power.
PLL CIRCUIT (MAIN UNIT)
A PLL circuit provides stable oscillation of the transmit frequency and receive 1st LO frequency. The PLL output compares the phase of the divided VCO frequency to the reference frequency. The PLL output frequency is controlled by the divided ratio (N-data) of a programable divider.
The PLL circuit contains the TX/RX VCO circuit (Q13, Q14). The oscillated signal is amplified at the buffer amplifiers (Q11, Q12) and then applied to the PLL IC (IC4, pin 8) via the low-pass filter (L32, C298, C299).
The PLL IC contains a prescaler, programable counter, pro-gramable divider and phase detector, etc. The entered signal is divided at the prescaler and programable counter section by the N-data ratio from the CPU. The reference signal is generated at the reference oscillator (X2) and is also applied to the PLL IC. The PLL IC detects the out-of-step phase using the reference frequency, and outputs it from pin 5. The output signal is passed through the loop filter (R97/C147, R95/C146), and is then applied to the VCO circuit as the lock voltage.
If the oscillated signal drifts, its phase changes from that of the reference frequency, causing a lock voltage change to compensate for the drift in the oscillated frequency.
VCO CIRCUIT (MAIN UNIT)
The VCO circuit contains a separate RX VCO (Q13, D16) and TX VCO (Q14, D17). The oscillated signal is amplified at the buffer amplifiers (Q11, Q10) and is then applied to the T/R switch circuit (D14, D15). Then the receive 1st LO (Rx) signal is applied to the 1st mixer (Q3) and the transmit (Tx) signal to the YGR amplifier circuit (Q9).
A portion of the signal from the buffer amplifier (Q11) is fed back to the PLL IC (IC4, pin 8) via the buffer amplifier (Q12) and low-pass filter (L32, C298, C299) as the comparison signal.