Icom M700 Mods May 2026
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
The Icom IC-M700, originally a 150-watt marine HF SSB radiotelephone from the 1980s
, has become a popular project for amateur radio enthusiasts due to its robust build and low cost on the second-hand market. While powerful, its original firmware and hardware are strictly tailored for marine use, necessitating several modifications to make it a versatile amateur station. Frequency Expansion and Control
The most fundamental modification is enabling the radio to transmit outside of its factory-set marine bands (MARS/CAP and Amateur Radio expansion). Transmit Enable Jumper icom m700 mods
: Transmit on all covered frequencies (1.6 to 23.999 MHz) can be enabled by ensuring W37 (W1037) on the Logic Board is installed/soldered. Memory Lockout
: To allow programming for Banks A and B, which are often locked, W33 (W1033) should be removed. VCO Retuning
: Coverage can be extended into the 10-meter and 11-meter bands (above 24 MHz) by editing the internal SRAM contents and manually retuning the VCO. Keyboard Restoration
: If the 10-key numeric buttons are non-functional, toggling switch on the Matrix board can often restore them. Memory and Logic Upgrades
The IC-M700's native 48-channel limit is a significant bottleneck for modern amateur use. SRAM Expansion
: Advanced hobbyists have developed boards to expand memory from 48 to 480 channels The DSC upgrade requires a hardware modification and
. This involves modifying the RAM board that stores channel data; since the CPU constantly reads from this SRAM during power-on, external microcontrollers or larger SRAM chips can be interfaced to cycle through multiple memory banks. Split Mode Modification
: For faster channel programming, users have added toggle switches to disable the default "SPLIT" behavior, which otherwise requires separate TX/RX frequency entry even for simplex operation. Audio and Interface Enhancements
Marine radios are optimized for voice punch rather than high-fidelity or digital mode compatibility. Old HF Marine radio for Ham Radio: IC-M700 : r/HamRadio
Stock M700 audio is optimized for marine voice—often too bassy for ham radio.
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. Conclusion The Icom IC-M700, originally a 150-watt marine
The stock M-700 is designed for voice communication—specifically USB (Upper Sideband) for long-range marine traffic and DSC (Digital Selective Calling) for distress.
However, the rise of digital modes (FT8, Pactor, Winlink) and the needs of cruisers necessitated a change.
The "Data" Mod: Operators often open the radio to allow LSB (Lower Sideband) operation. While rarely used for voice at sea, LSB is critical for amateur digital protocols.
The ICOM M700 (and its variants like the M700PRO and M700TY) was designed for marine use on ITU channels. For amateur radio operators, its stock frequency coverage is limiting. This guide covers the most popular, proven modifications—from simple jumper changes to advanced filter upgrades.
⚠️ DISCLAIMER: Modifying your ICOM M700 may void any remaining warranty, violate laws if done improperly (e.g., transmitting out of band), and requires technical skill. Always check your local regulations. Proceed at your own risk.
The M700 contains electrolytic capacitors in the power supply and audio sections that are now 20-30+ years old.
Symptoms of failure:
Modification:
