Even with the mod, the M700 is far from ideal for digital modes:
Turn the radio OFF. Hold down the MODE and SQL (Squelch) buttons simultaneously, then turn the radio ON. This typically enables the 10-key keypad for direct frequency entry.
These modifications unlock the radio's full potential by allowing it to operate outside restricted marine bands. Transmit Frequency Expansion (MARS/CAP):
Practical necessity sometimes drives modifications. The original HM28 hand microphone is no longer available, forcing owners to modify their radios to accept the HM114 replacement. This modification involves removing the top cover (12 screws), unplugging the HM28, removing the MIC board (3 screws), unsoldering J3, replacing it with a new connector (part #936-05432), and reassembling. The up/down buttons on the replacement microphone will not function after this modification.
Locate switch S1228 on the Matrix board and toggle it to enable the keypad functionality. 4. Audio Quality and Signal Processing Enhancements icom m700 mods
Unlocking transmit capability outside the standard 2-23 MHz marine bands.
Modifying radio equipment requires solid soldering skills and test equipment. Working inside electronic hardware can damage sensitive components through electrostatic discharge (ESD). Additionally, transmitting on unauthorized frequencies or exceeding legal power limits may violate national telecommunications regulations (such as FCC rules). Proceed at your own risk. 1. General Coverage Transmit Mod (Frequency Expansion)
Do you need the for the rear accessory jack?
In some versions, a trimmer potentiometer can be used to increase the power. Even with the mod, the M700 is far
For amateur radio use, the standard SSB ceramic filter can be broad, allowing adjacent channel interference to bleed through.
The frequency restrictions are governed by a diode matrix located on the board.
Enable the front panel 10-key numeric keypad for manual frequency entry. Location: The Matrix Board.
Look for a row of small switching diodes (usually labeled in the D1–D20 range depending on the specific board revision, such as the M700 vs. M700PRO). These modifications unlock the radio's full potential by
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
Adding an internal speech compressor can significantly improve your signal punch during SSB operations. Operational Tips for Ham Use
Find the Logic/Matrix board, typically located near the front shield panel.
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 microphone.
: Modifying a marine transceiver to transmit outside its type-accepted frequencies is perfectly legal for licensed Amateur Radio operators using the gear on ham bands. However, it is illegal to use a modified radio to transmit on commercial or unauthorized marine frequencies without proper maritime licenses.
