ICOM M-700 Modification Report
The Icom IC-M700 (and its variant the IC-M700TY) is a legacy HF marine transceiver. While robust, it is an older analog radio. Most modifications performed today fall into two categories: restoration (bringing the radio back to spec) and expansion (enabling HAM band usage or replacing obsolete components).
⚠️ WARNING:
If you want the "perfect" amateur-grade IC-M700, here is your shopping list of modifications:
| Mod | Difficulty | Time | Benefit | | :--- | :--- | :--- | :--- | | MARS/CAP Unlock | Medium (Soldering) | 30 min | Transmit on all HF amateur bands | | Audio Coupling (C37/C133) | Easy | 15 min | Warm, clear receive audio | | Mic Bias & EQ | Medium | 20 min | Use modern condenser mics | | ALC Threshold (R28) | Medium | 30 min | Cleaner SSB output | | Noise Blanker Threshold | Advanced | 1 hour | Usable impulse noise reduction | | Arduino Digital Readout | Advanced | 2-3 hours | Digital VFO function | | Fan Thermostat Mod | Easy | 15 min | Improved thermal management |
🧪 Test: After mod, verify you can tune to 14.200 MHz in USB and transmit a low-power carrier into a dummy load.
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 DSC upgrade requires a hardware modification and may require professional assistance. Consult an authorized Icom dealer or a qualified technician for this mod. icom m700 mods
Safety Precautions and Warranties
When performing mods, be aware of the following:
Conclusion
(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. ICOM M-700 Modification Report The Icom IC-M700 (and
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. Part 7: Summary Checklist – The Ultimate M700
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
A common complaint among audiophiles and DXers (long-distance listeners) regarding the M-700 is the audio filtering.
The "Filter Swap": The stock ceramic filters in the IF (Intermediate Frequency) stages are chosen for durability and "communications grade" audio—essentially, intelligibility over fidelity. They are often slightly too narrow, resulting in a "pinched" or tinny sound.
Goal: Transmit on 160m through 6m amateur bands (1.6–30 MHz continuous).
Most M700s are software or hardware limited to marine bands. Here’s how to open them.
The Icom M700 is a legend. Built like a tank for the harsh marine environment, this 150-watt HF SSB transceiver was a staple on commercial vessels and cruising yachts for decades. While its rugged build and powerful output are still revered, the stock unit is showing its age—especially for amateur radio operators (hams) who acquire surplus units.
However, the digital age and a passionate community of modders have breathed new life into this classic rig. The right Icom M700 mods can transform this marine radio into a modern, versatile, high-performance ham transceiver. This guide explores the most valuable, safe, and effective modifications to boost frequency coverage, audio quality, and usability.
Disclaimer: Modifying electronic equipment requires soldering skills, knowledge of high-voltage circuits (the M700 has lethal voltages inside), and proper test equipment. The author assumes no liability for damage to your radio, your vessel, or your person. Proceed at your own risk.