Icom IC-705 + fldigi Setup Guide

Complete setup for Olivia and other digital modes on this QRP portable transceiver. The IC-705 is uniquely suited for portable digital operations with built-in USB audio, WiFi, Bluetooth, and GPS.

Quick Reference

USB ConnectionType-C (side panel) - single cable for CAT + audio
CI-V Address0xA4 (164 decimal)
Hamlib Rig Number3085
Baud Rate19200 (or Auto)
Power Output5W (internal battery) / 10W (external 13.8V)
Recommended Methodflrig + fldigi

1. USB Connection Overview

The IC-705 features a USB Type-C port on the side panel that provides:

  • CAT control via virtual COM port
  • Built-in USB audio codec for digital mode operation
  • GPS data output (via secondary interface)
  • All functions operate simultaneously over one cable

Key Advantage for Portable Operation

Single USB-C cable provides CAT control, audio interface, and optional GPS - perfect for QRP digital field operations like POTA and SOTA.

2. Driver Installation

Windows 11/10

  1. Download the official Icom USB driver from Icom America IC-705 Downloads
  2. Disconnect IC-705 USB cable before installing
  3. Run installer with administrator privileges
  4. Restart computer
  5. Connect IC-705 via USB-C data cable (not charge-only)
  6. Verify in Device Manager:
    • IC-705 Serial Port A (CI-V) - for CAT control
    • IC-705 Serial Port B - secondary port
    • USB Audio Device - for digital audio

Important: Use a quality USB-C data cable. Charge-only cables will not work.

macOS

No driver installation required for macOS High Sierra (10.13) and later.

The system will automatically recognize the serial port and USB Audio Device. Identify with:

ls /dev/cu.usbmodem*

Linux

No driver installation required - the Linux kernel includes built-in support.

Look in /dev/serial/by-id/ for two devices:

  • Device ending in if00 - CI-V rig control and audio
  • Device ending in if02 - GPS data output

Set permissions if needed: sudo usermod -aG dialout $USER

3. fldigi Configuration

Method 1: Using flrig (Recommended)

flrig provides superior rig control and automatically handles CI-V addressing.

Configure flrig:

  1. Download and install from W1HKJ flrig project
  2. Go to Config → Setup → Transceiver
  3. Select Icom → IC-705
  4. Set Device to your IC-705 serial port
  5. Baud Rate: 19200
  6. CI-V Address: 0xA4 (auto-entered for IC-705)
  7. Click Initialize

Configure fldigi:

  1. Go to Configure → Rig Control
  2. Select the flrig tab
  3. Check Enable flrig xcvr control
  4. Leave server as localhost:12345
  5. Click Save

Method 2: RigCAT (Direct)

  1. Download IC-705.xml
  2. Save to fldigi rigs directory
  3. In fldigi, go to Configure → Rig Control → RigCAT
  4. Select IC-705.xml
  5. Baud Rate: 19200
  6. Check: Use RigCAT, CAT command for PTT
  7. Click Initialize

Method 3: Hamlib

Hamlib Rig Number3085
CI-V Address0xA4
 
rigctl -m 3085 -r /dev/serial/by-id/usb-Icom...-if00 -s 19200 f

Audio Device Configuration

  1. Go to Configure → Soundcard → Devices
  2. Capture (RX): Select IC-705 or USB Audio Device
  3. Playback (TX): Select IC-705 or USB Audio Device
  4. Sample Rate: 48000 Hz (recommended)

4. IC-705 Radio Menu Settings

Connectors Settings (MENU → SET → Connectors)

SettingValueNotes
DATA MODUSBRoutes USB audio to radio in DATA mode
DATA OFF MODMIC, ACCKeeps mic enabled in non-DATA modes

CI-V Settings

SettingValueNotes
CI-V AddressA4Default; do not change
CI-V Baud RateAutoRadio matches software automatically
CI-V USB Echo BackOFFMust match fldigi config
CI-V TransceiveONEnables radio to broadcast changes

USB Audio Levels

USB MOD Level50%Adjust for proper ALC
USB AF Output Level50%Adjust for comfortable receive

Operating Mode

Set radio to USB-D (USB Data mode):

  1. Press MODE button
  2. Select USB then press DATA soft key

Advantage: Microphone is automatically disabled in USB-D mode.

Disable for digital modes: NB, NR, COMP, Notch Filter

5. Portable/Field Operation

Power Management

Power SourceMax OutputBattery Life
BP-272 (internal)5W~3 hours
BP-307 (optional)5W~4.5 hours
External 13.8V10WUnlimited
USB Power Bank5WRX and low-power TX only

Digital Mode Power Settings

  • Olivia: 3-5W is typically sufficient
  • PSK-31: 2-5W
  • FT8: 5W (efficient for weak-signal work)

Access power control: Press MULTI knob and adjust RF Power

Antenna Considerations

  • Use resonant antennas when possible (EFHW, linked dipole)
  • External tuner recommended: Elecraft T1, LDG Z-100, mAT-705
  • Note: IC-705 does NOT have built-in antenna tuner

WiFi Operation

The IC-705 supports wireless operation via WiFi using wfview software. Enable Access Point mode in MENU → SET → WLAN Set. Note: WiFi uses more battery than USB.

6. Common Issues and Troubleshooting

USB RFI/Interference on HF

  • Wind 6 turns of USB cable on FT114-43 toroid at radio end
  • Add clip-on ferrite at computer end
  • Use shortest practical USB cable
  • Keep USB cable away from antenna

No Audio to/from Radio

  • Verify radio is in USB-D mode (not regular USB)
  • Check DATA MOD is set to USB
  • Verify correct audio device selected in fldigi
  • Check USB MOD Level is not at 0%

PTT Not Working

  • Verify CAT command for PTT is checked
  • Check CI-V address is A4
  • Check CI-V USB Echo Back matches fldigi config
  • Try baud rate 19200 (most reliable)

High ALC During Transmission

  • Reduce USB MOD Level in 5% increments
  • Reduce computer audio output volume
  • Target: ALC at zero during Tune

7. Official Documentation

Pre-Flight Checklist

  1. USB driver installed (Windows) or verified (macOS/Linux)
  2. USB-C data cable connected (not charge-only)
  3. CI-V Address: A4, Baud Rate: 19200
  4. Radio in USB-D mode
  5. DATA MOD set to USB
  6. flrig or fldigi RigCAT configured
  7. Audio devices set to IC-705
  8. PTT test passed
  9. ALC at zero during Tune
  10. Ferrite chokes installed (for HF portable)
  11. Power: 3-5W (battery) or 5-10W (external)
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