The Icom IC-M700 is a classic marine HF SSB transceiver that has become a favorite for modifications, particularly by amateur radio operators looking to adapt its robust marine build for ham use about.gitlab.com Popular Modification Categories Frequency Expansion:
Most mods focus on "unlocking" the radio from its 48 factory-programmed marine channels to allow full coverage across the HF bands. Audio Quality Improvements:
Users often report "off" audio in used units, leading to mods that replace poor-quality third-party microphones (like 1970s telephone elements) with modern high-fidelity ones to restore clarity. Digital Mode Adaptation:
Adding DIN plugs or custom leads to the rear of the radio allows for interfacing with Pactor Modems or other digital communication methods. Power and Lock-out Mods: Specific technical tweaks like the IC-M700D lock-out disable
and general power modifications are documented to improve operational flexibility. "Interesting Report": Restoration Hazards
A notable "interesting report" from the community highlights the risks of buying used M700 units. One restorer found that a previous owner had replaced the original microphone with a 1971 vintage rotary telephone "T1" carbon element, which severely degraded signal quality. This serves as a warning that used marine gear often contains decades of "jury-rigged" repairs that must be reversed for proper operation. Key Resources for Step-by-Step Guides
A central repository for M700 power and frequency unlock guides. Elliott Liggett's GitLab
A modern repository documenting mods to make the radio more user-friendly for ham radio, including video demonstrations. about.gitlab.com Are you looking to perform a specific modification, such as frequency unlocking interfacing for digital modes IC-M700 Mods - Elliott Liggett - GitLab
Icom M700 Mods: Enhancing Your Marine Radio's Performance
The Icom M700 is a popular marine radio used by sailors and boaters worldwide. While it's a reliable and feature-rich device, some users may want to explore modifications to enhance its performance, functionality, or compatibility with specific accessories. In this article, we'll discuss some common Icom M700 mods, their benefits, and provide a step-by-step guide on how to perform them.
Common Icom M700 Mods
Pre-Modification Checklist
Before attempting any mods, make sure to:
Step-by-Step Mod Guides
Here are brief guides for each mod:
A common failure point in the IC-M700 is the incandescent bulbs behind the LCD display and meter. They run hot and burn out, making the radio unreadable at night.
Modification:
The IC-M700 typically uses tube (valve) finals (often 6JS6C or similar sweep tubes). Solid-state versions exist but are less common. icom m700 mods
Maintenance/Modification:
The M700’s fan is loud and often runs continuously.
The DSC upgrade requires a hardware modification and may require professional assistance. Consult an authorized Icom dealer or a qualified technician for this mod.
Safety Precautions and Warranties
When performing mods, be aware of the following:
Conclusion
Modifying the Icom IC-M700 (and its variants like the M700PRO and M700TY) is a popular project for amateur radio operators looking to repurpose these rugged marine transceivers for ham use. Core Performance & Frequency Modifications
MARS/CAP & Wideband Transmit: To unlock transmission across all covered frequencies, locate the Logic Board and ensure jumper W37 (W1037) is installed. If it has been cut to restrict the radio to marine bands, simply solder it back together. Memory & Programming Lockout:
To enable programming of banks A and B (which are often locked out), ensure jumper W33 (W1033) on the Logic Board is not installed.
If your 10-key buttons are unresponsive, check switch S1228 on the Matrix Board to toggle their functionality.
SRAM Memory Expansion: The standard IC-M700 has 48 memory channels. Advanced users can expand this to 480 channels using a custom SRAM expansion board that replaces the original memory.
Split Mode Toggle: You can install a physical switch to disable "Split Mode" behavior. This makes programming much faster for simplex operation by removing the need to enter transmit and receive frequencies separately. Audio & Interface Improvements
Microphone & Speech Processing: Modifying the microphone gain and adding a speech compressor/processor can significantly improve signal punch for DX contacts.
Pactor Modem Integration: For digital modes like Sailmail or Winlink, you can add a dedicated interface lead. This typically involves tapping into the internal PTT, Line In, and Line Out lines to provide a DIN plug output for a Pactor modem.
Internal Tuning Power: If using an external non-Icom antenna tuner, you can adjust the tuning power level (factory set at 10W) between 5 and 20 watts by adjusting R247 on the Main Board and R19 on the RF Board. Quick Reference: Icom M700PRO "Soft" Mod
Unlike the original M700, the M700PRO often supports a button-press modification to enter an "extended frequency mode": Turn the radio OFF.
Hold the MODE and SQL buttons simultaneously and turn the radio ON. The Icom IC-M700 is a classic marine HF
This unlocks the 10-key keypad for direct frequency entry across ham and marine bands. Essential Resources
Elliott Liggett's GitLab Repository: Contains the most comprehensive technical write-ups, schematics for SRAM mods, and instructions for user-friendly ham conversions.
Mods.dk - Icom M700 Section: A central archive for power modifications, lockout disables, and various service bulletins.
Icom M700 Service Manual: Available on the Icom Japan Support site, this is necessary for identifying board locations like the Logic and Matrix boards mentioned above. IC-M700 Mods - Elliott Liggett - GitLab
(and its successor, the M700PRO) is a legendary marine HF transceiver prized by mariners and amateur radio operators alike for its rugged construction and 150W output. While originally designed for marine SSB channels, a few key modifications can transform this workhorse into a versatile HF rig for the ham bands or specialized data use. 1. Transmit Frequency Expansion (MARS/CAP Mod) The most common modification for the
is "opening up" the transmitter. In its stock configuration, the radio often limits transmission to marine bands.
The Jumper Fix: To enable transmit on all covered frequencies (approximately 1.6 MHz to 23.999 MHz), check the Logic Board for jumper W37 (W1037).
If the jumper is cut or missing, the radio may be locked to marine channels.
Action: Solder the jumper (or a wire bridge) back together to unlock general frequency transmission.
Limitations: While this mod covers most HF bands, reaching the 10-meter band (28 MHz) typically requires more complex hardware modifications beyond a simple jumper. 2. Memory and Programming Unlocks
Some regional versions of the M700 have locked memory banks (A and B) to prevent users from accidentally overwriting critical marine frequencies.
W33 Jumper: To allow full front-panel programming of banks A and B, ensure that jumper W33 (W1033) on the Logic Board is NOT installed.
Keypad Issues: If your 10-key keypad isn't responding, look for switch S1228 on the Matrix board. Toggling this switch can often restore keypad functionality for field programming. 3. Digital Modes and Pactor Integration
Modern operators often want to use the M700 for FT8, Winlink, or Pactor. Because the M700 lacks a modern "Data" port, custom cabling is required.
Audio Interfacing: Modifications often involve tapping into the internal PTT (Push-to-Talk), Line In, and Line Out lines to create a DIN plug interface for a PC or Pactor modem.
Microphone Upgrades: Newer modifications include adapting the 8-pin connector to accept high-quality dynamic microphones or XLR inputs, which can significantly improve audio punch in difficult conditions. 4. Mode and Power Adjustments
AM Emulation: The M700’s AM mode (A3H) actually operates as upper sideband with a carrier. It provides a robust, "loud" signal that is well-suited for broadcasting on non-marine frequencies. CTCSS (Continuous Tone-Coded Squelch System) Modification
Power Output: While rated at 150W PEP, internal adjustments (usually found in the service manual) can fine-tune the ALC (Automatic Level Control) to ensure you aren't overdriving the final amplifiers during data operation. Comparison: IC-M700PRO ICOM--IC-M700-user-manual.pdf - QRZCQ
Page 3. SECTION 1 SPECIFICATIONS. GENERAL. Frequency Coverage: Receive. Transmit. 1.6MHz ~23.9999MHz. 2.0MHz - 2.9999MHz. 4.0MHz ~ IC-M700 - Single Sideband Radiotelephone - ICOM Canada
The Icom IC-M700 is a classic marine HF transceiver that has become a popular project for amateur radio enthusiasts due to its robust build and low second-hand cost. While originally locked to marine bands, several modifications can unlock its full potential for ham radio use. Core Functionality Modifications
These "jumpers" on the internal logic board control the radio's primary operating restrictions.
MARS/CAP (Transmit Unlock): To enable transmission on all covered frequencies (roughly 1.6 MHz to 23.9 MHz), ensure that jumper W37 (W1037) on the Logic Board is installed. If it has been cut, resoldering it restores full coverage.
Memory Bank Unlock: To allow programming of banks A and B (which are sometimes locked out), jumper W33 (W1033) must be removed.
Keypad Activation: If the front-panel 10-key buttons are unresponsive, toggle the small switch S1228 located on the Matrix board. Advanced Amateur Radio Mods
For those looking to go beyond basic frequency unlocks, advanced hobbyists have documented more complex upgrades:
SRAM Expansion: The standard 48-channel memory can be expanded to 480 channels via an SRAM expansion mod, making it more practical for storing numerous amateur bands and nets. Mode & Audio Upgrades:
Speech Processor: Adding a speech compressor improves talk power during SSB operation.
LSB Addition: While most marine operations are USB, some regional versions (like those in Australia) may have LSB removed; it can often be restored with internal switch and wiring adjustments.
Digital Interface: By constructing a custom interface box for the microphone socket, users can connect the M700 to a PC for digital modes like FT8, SSTV, or Pactor. Microphone Compatibility
The original HM-28 microphone is often missing or damaged. Because it is no longer manufactured, a common mod involves adapting the radio to accept the newer HM-114 microphone.
Replace the internal connector J3 on the MIC-C-UNIT with a compatible 8-pin connector (#936-05432).
Route the HM-114 cord through the existing side hole and solder it to the new connector.
Note: The up/down buttons on the HM-114 will not function after this mod. Operating Tips for Modified Units IC-M700 Mods - Elliott Liggett - GitLab
The M700 uses a Phase-Locked Loop (PLL) with programmable dividers. Jumpers on the main PLL board (often labeled the "PLL Unit" or "Frequency Unit") set the frequency limits. By changing diode or jumper configurations, you override the marine band limits.
Older M700s drift like a lost buoy on a cold morning. Install a Temperature Compensated Crystal Oscillator (TCXO) module. Remove the stock 30 MHz crystal oscillator and drop in a 1 ppm TCXO unit (available from Icom dealers or eBay). This is critical for 10m and 15m operation.