Icom M700 Mods <ORIGINAL ◉>

Have a unique M700 mod? Share your experience in the comments below!

The Icom IC-M700, a legacy marine HF transceiver first sold in 1984, is a popular candidate for modifications to make it suitable for amateur radio use. Because it was originally designed for maritime service, its standard features often lack the flexibility required for ham radio operation. Core Functional Modifications

These mods focus on unlocking the radio's hardware potential for broader frequency use:

MARS/CAP & Frequency Expansion: To enable transmit capabilities across all covered frequencies (roughly 1.6 MHz to 23 MHz), ensure that jumper W37 (W1037) on the logic board is installed; if cut, it must be soldered back together. Expanding coverage to the 10-meter band typically requires further board-level adjustments.

Memory Expansion: The stock radio is limited to 48 channels. Specialized mods, such as an SRAM expansion, can increase this capacity to 480 channels.

Programming Unlocking: To allow programming of memory banks A and B, ensure that jumper W33 (W1033) is not installed. If the 10-keypad is unresponsive, toggle switch S1228 on the Matrix board.

Split Mode Toggle: A common modification involves adding a switch to disable "split mode" behavior, which facilitates faster channel programming for amateur use. Audio & Performance Upgrades icom m700 mods

Microphone & Speech Processing: Users often modify the microphone gain or add a speech compressor to improve signal punch on SSB. Modern replacements like the HM-180 8-pin microphone are frequently used to replace aging EM-101 models.

External Reference Injection: For those requiring high frequency stability (e.g., for digital modes), boards like the Leo Bodner reference injection board can sometimes be adapted to override the internal oscillator with an external source.

RFI & Noise Reduction: External kits, such as the Palomar Engineers RFI Kit, use ferrite chokes on the DC power and antenna lines to reduce the noise floor and suppress interference. Reference Resources

For detailed schematics and step-by-step instructions, these repositories and sites are frequently cited by the community:

Elliott Liggett's GitLab: Contains a technical write-up and SRAM schematic for the memory expansion and jumper mods.

Mods.dk: Hosts a collection of over 100 Icom modification documents, including specific guides for the M700's power and lock-out settings. Go to product viewer dialog for this item. Have a unique M700 mod

HM-180 8Pin Microphone Speaker Mic for ICOM IC-M700 IC-M710 IC-M600 Radio | Made in China | Clip

Description: NEW HM-180 replace old model EM-101 Hand Microphone For IC-M700 IC-M710 IC-M700PRO IC-M600 (equal EM-48 or HS-50 mic, Go to product viewer dialog for this item.

Hm-180 8pin Microphone Speaker Mic For Icom Ic-m700 Ic-m710 Ic-m600

Description: NEW HM-180 replace old model EM-101 Hand Microphone For IC-M700 IC-M710 IC-M700PRO IC-M600 (equal EM-48 or HS-50 mic, Let's MOD the Icom IC-9700 for Big Jim!

Modifications for the Icom IC-M700 marine HF transceiver focus on expanding transmit frequencies, increasing memory capacity, and enhancing digital mode capability. Key hardware changes include installing jumper W37 for MARS/CAP access and removing jumper W33 for expanded channel programming. For a detailed list of modifications and schematics, visit IC-M700 Mods on GitLab. IC-M700 Mods - Elliott Liggett - GitLab

A common complaint among audiophiles and DXers (long-distance listeners) regarding the M-700 is the audio filtering. The "Pseudo-CW" Mod: Some hams wire a small

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.

The M700 has a spot on the main board for an optional mechanical or crystal filter (often a Murata CFJ455K or equivalent). Many surplus units have an empty slot.

How to do it:

The "Pseudo-CW" Mod: Some hams wire a small SPST switch to the filter board. When flipped, it swaps the 2.4 kHz SSB filter for the 500 Hz filter. This lets you use the radio for CW with the clarity of a dedicated contest rig.

The M700 relies on convection cooling. For contesting or FT8 (high duty cycle), it gets scorching hot.

The M700 has no built-in narrow CW filter, making weak-signal work difficult.