However, for ham radio operations—especially when chasing weak signals or participating in roundtables—operators often want the Clarifier to affect both transmit and receive (acting as a VFO fine-tune), or they want to expand its tuning range.
Unlocking transmit capability outside the standard 2-23 MHz marine bands.
What is your for the mod (e.g., HAM band transmit, better audio, digital modes)? What is your technical comfort level with a soldering iron? Share public link
: Access the top section of the radio chassis and remove the shielding cover over the digital control circuitry. icom m700 mods
Unlocking the radio allows continuous transmission across the entire HF spectrum (typically 1.6 MHz to 23.999 MHz), giving you full access to all amateur radio bands (such as 80m, 40m, 20m, 15m, and 10m). The Diode Matrix Modification
Modifying the Icom M700 can bring several benefits, including:
Note: This guide focuses on legitimate, safety-first, and legal modifications for the Icom IC-M700 (marine VHF fixed station) to improve usability, reliability, and integration. Do not perform modifications that violate local radio laws, FCC/ITU regulations, or that alter the unit’s certified transmission characteristics (e.g., increasing transmit power beyond spec, changing frequencies, or bypassing required emission limits). Always consult a certified radio technician or Icom for repairs that impact RF circuits or safety. Use this guide only for permitted hardware, ergonomic, and software/firmware tweaks that do not change certified RF parameters. What is your technical comfort level with a soldering iron
Serious operators desolder the stock Murata ceramic filter and install a sharper crystal filter (such as a 2.4 kHz or 2.1 kHz filter). This drastically improves receiver selectivity during crowded contesting or weak-signal operations. 3. Adding an External VFO or Frequency Control
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Many Icom M700 units have a "hidden" mode that allows for easier programming and operation. The Diode Matrix Modification Modifying the Icom M700
The factory heatsink relies entirely on passive convection cooling. If you plan to use the IC-M700 for high-duty-cycle data modes, adding an active cooling system is mandatory to prevent thermal runaway.
For these units, two solutions exist. The simpler approach, if the hardware supports it, involves entering the radio's advanced configuration menu. On M700PRO units, pressing ENT and 2 simultaneously while powering on grants access to an advanced mode where LSB operation can be enabled.
The solution revolves around a single wire bridge. Examining the logic circuits section of the service manual reveals that IC1006 outputs mute signals for frequencies outside the marine bands to pins P40 and P41. These pins enable a voltage called "TMU" (presumably Transmitter Mute) via transistor Q1003. The schematics show a wire bridge, W1037, shorting the base of Q1003 to ground. With W1037 installed, the transistor is never engaged to release the TMU voltage, effectively muting non-marine frequencies. By cutting or removing W1037, the radio can transmit on all frequencies.
On standard M700 models, removing specific diodes lifts the factory frequency restrictions. For many versions, snipping or unsoldering Diode D15 (or a specific combination detailed in the service manual for your exact sub-model) resets the radio to general coverage transmit.