🚧 Project Status: In Progress 🚧
Documented by:
A comprehensive repair and modification documentation repository for the Icom IC-706 MkIIG multi-band amateur radio transceiver. This project archives hands-on repair procedures, common failure modes, performance modifications, and factory service documentation for one of the most popular mobile/base station radios in amateur radio.
What's Inside:
- ✅ Real-world repair documentation
- ✅ MARS/CAP out-of-band modification guide
- ✅ Factory service manuals and schematics
- ✅ Photo documentation of repairs
📡 73 to all hams! This repository serves the amateur radio community by preserving repair knowledge for a legendary transceiver.
Frequency Coverage:
- HF Bands: 1.8 - 54 MHz (160m through 6m)
- HF 60m (With MARS/CAP mod)
- VHF: 144 - 148 MHz (2m)
- UHF: 420 - 450 MHz (70cm)
Operating Modes:
- SSB (USB/LSB phone)
- CW (Morse code)
- RTTY (Radio Teletype)
- AM/FM (Voice)
Power Output:
- HF/6m (SSB): 100 watts
- HF/6m (AM): 40 watts
- 2m: 50 watts
- 70cm: 20 watts
Key Features:
- All-mode, multi-band transceiver
- AH-4 antenna tuner for auto tuning
- DSP (Digital Signal Processing)
- Compact mobile/base station design
- Detachable front panel for remote mounting
- Several filter options to enhance performance
All manuals are publicly available from Icom and archived here for convenience:
Instruction Manual - User guide, basic operation, menu settings
Service Manual - Schematics, alignment procedures, component locations
Operating Guide - Complete menu layout with button combinations
Factory Instability Fix - A modified version of the Icom-issued repair bulletin for 15/17m instability
Also see Releases for file bundles
What is MARS/CAP?
- MARS: Military Auxiliary Radio System
- CAP: Civil Air Patrol
- Enables transmit capability outside amateur radio bands
- Required for 60m ham band operation
- Current ARRL Frequency Band Chart chart
- 12/2025 FCC update announcement
Modification Details:
- Extends transmit range beyond ham bands
- Used for emergency communications
- Documented step-by-step procedure
- Reversible modification
⚠️ Legal Notice: 60m is legal for hams to operate on a secondary basis due to updated rules. Operation in the 60 meter ham band (5.3 - 5.4 MHz) was allocated after the production of this radio, which is why the out-of-band MARS Mod is perfect for this radio.
My First IC-706 - Original HF/VHF model installed in my truck. Note only 10W FM on VHF and lack of UHF coverage compared to the MkIIG.
Current IC-706 MkIIG - HF/VHF/UHF tri-band transceiver with improved features and UHF capability.
Key Differences from Original IC-706:
- ✅ UHF (70cm) band coverage added
- ✅ Improved receiver performance
- ✅ Enhanced DSP capabilities
- ✅ Better spurious emission suppression
- ✅ Upgraded firmware features
- ✅ Increased VHF-Hi (144) power
RF Testing Configuration - IC-706 MkIIG connected to Bird 43 wattmeter and 100W dummy load for power output testing and alignment verification.
Test Equipment Shown:
- Bird 43 Thruline Wattmeter
- 100W dummy load with optional -30 dB sample port
- Coaxial jumpers and adapters
Not Shown:
- Power supply (13.8V DC @ 23A)
Electrical Repairs:
- Power cycling failure (in progress)
- Out-of-band MARS/CAP modification
- Receiver cooling fan mode modification (in progress)
Known Issues:
- Screen polarizer failure (in progress)
- Receiver instability on 15/17m (modified factory bulletin)
icom-706-mkiig/
├── docs/ # Documentation and manuals
│ ├── manuals/ # Factory Icom PDFs (publicly available)
│ │ ├── IC-706MK2G_IM.pdf # Instruction Manual
│ │ ├── IC-706MK2G_SM.pdf # Service Manual
│ │ ├── IC-706MK2G_OG.pdf # Operating Guide
│ │ └── ic706mk2g_instability_reva.pdf # Factory fix bulletin
│ ├── OOBMod # Folder for the OOB mod
│ │ └── OOBmod.tex # Out-of-band mod guide (LaTeX-generated)
│ ├── pwrRepair/ # Folder for the power repair
│ │ └── pwrRepair.tex # Power Cycling Repair (-COMING SOON-)
│ ├── rxFanMode/ # Folder for the RX fan modification
│ │ └── rxRanModeMod.tex # RX Fan Mode Modification (-COMING SOON-)
│ └── screenRepair/ # Folder for the screen polarizer repair
│ └── screenRepair.tex # Screen Polarizer Repair (-COMING SOON-)
├── img/ # Photos and diagrams
│ ├── ic706.jpg # Original IC-706 photo
│ ├── ic706mkiig.jpg # IC-706 MkIIG photo
│ ├── TestSetup.jpg # RF test configuration
│ └── ... # Other pictures for the documents as needed
└── README.md # This document
For Repairs:
- Soldering station with temperature control
- Multimeter (digital preferred)
- RF test equipment (optional but recommended)
- Dummy load (appropriate wattage)
- Wattmeter (Bird 43 or equivalent)
- Spectrum analyzer and/or service monitor (for advanced work)
- Icom service manual (included in this repo)
- Basic electronics knowledge
For Modifications:
- Same as repair tools
- Understanding of FCC regulations
-
Browse Documentation:
- Start with the Instruction Manual for basic operation
- Reference Service Manual for schematics and alignment
-
Identify Your Issue:
- Check known issues section
- Review factory bulletins (instability fix)
-
Follow Repair Guides:
- Use documentation in
/docs/folder - Reference photos in
/img/for visual aid
- Use documentation in
-
Test and Verify:
- Always RF test with dummy load first
- Verify power output on all bands
- Icom America - Official manufacturer site
- Icom Service Bulletins - Factory updates
- Antenna Theory - Antenna design resources
- Smith Charts - RF impedance matching
Power Supply:
- Use 13.8V DC @ 23A minimum
- Heavy gauge wire (10 AWG or larger)
- Keep leads short to minimize voltage drop
- Add ferrite chokes for RFI suppression
Antenna System:
- Use AH-4 Auto tuner
- AH-4 Comes weather proof with quality coax for outdoor use.
- Find a long whip antenna and connect to the AH-4
- Works great in my truck with this Breedlove QD Ball Mount and their Stake Pocket Bracket
- This setup will tune on 80m - 10m with very low SWR.
- Add any other dual-band antenna for VHF/UHF FM operation if needed.
This is an ongoing documentation project. Contributions welcome:
- 📝 Additional repair procedures
- 📷 Photo documentation of your repairs
- 🐛 Error corrections in documentation
- 💡 Performance improvement tips
- 🔧 Alternative repair methods
How to Contribute:
- Fork the repository
- Add your documentation to appropriate folders
- Include clear photos with descriptions
- Submit a pull request
Amateur Radio Operation:
- Valid amateur radio license required for transmission
- Must operate within authorized frequency allocations
- Part 97 rules apply to all modifications: Frequency Band Chart
- In this case, we want to enable the 60m (5.3 - 5.4 MHz) Band since it is already a Part 97 Radio.
MARS/CAP Modifications:
- Out-of-band transmission requires FCC authorization
- This recently happened (again) in 2025 with the allocation of the 60m band since the production of this radio began.
- It's up to the operator to verify they are operating within specifications.
- Radio contains high voltage circuits
- Disconnect power before servicing
- Discharge capacitors properly
- Use appropriate power levels
- Use ESD protection when handling repairs
- Ground technician(s) to ESD mat to a household 120VAC NEMA 5-15 or 5-20 outlet using adapters
- Ground ESD mat and adapters to wall outlet.
Documentation: Open source, free to use and distribute.
Manuals: Factory Icom PDFs are publicly available and archived here for convenience. All rights reserved by Icom Inc.
Modifications: Follow all applicable FCC regulations. The author assumes no liability for modifications or improper use.
Radio Operator: Joel Brigida (ADolbyB)
LinkedIn: Joel Brigida
Questions? Open an issue, please. Or just call me.
Preserving Ham Radio Knowledge. One Repair at a Time.
73 de ADolbyB 📡
