Tap into the rear accessory socket or the front microphone jack for Audio In (Modulation) and the external speaker jack for Audio Out.
: On most classic IC-M700 models, snipping or removing a specific diode opens the transmit matrix.
: Locate the control circuit feeding the Clarifier potentiometer on the front panel board. By changing the values of the series resistors flanking the variable resistor, you can increase the voltage swing delivered to the local oscillator (VCO) varicap diode. icom m700 mods
: Look for a row of small switching diodes (usually 1N4148 type) mapped to specific frequency programming lines.
Which do you have (e.g., original M700 with dial wheels, M700PRO, or M700TY)? Tap into the rear accessory socket or the
You can build a simple interface circuit using a couple of resistors and a transistor to match the 4-pin Icom tuner control plug to the start/tune signaling requirements of third-party tuners. Maintenance and Stability Tips
These capacitors form high-pass filters in the receive audio chain. By increasing their capacitance, you lower the cutoff frequency to approximately 80-100 Hz, allowing natural voice fundamentals and low-end richness to pass through. By changing the values of the series resistors
To make the radio more usable on amateur radio networks where operators might drift, you can increase the RIT range up to ±1.5 kHz.
For radios where the LSB BFO crystal and components are physically absent from the board—as some owners have discovered—the solution requires hardware installation. The circuit board includes space and pads for the LSB components, with approximately seven or eight parts needing installation. The service manual provides detailed instructions for tuning up the LSB BFO oscillator.
Since the original HM28 is rare, many modify the radio to use the HM114 .
Using modified marine radios on amateur bands raises important legal considerations. In the United States, a modified ham radio is generally illegal to use on marine bands except in emergencies, and marine radios used on amateur bands must be operated by licensed amateur operators with their station license prominently displayed. Conversely, a marine SSB radio can legally be used on amateur bands as long as it is not operated on marine frequencies. The rules require that amateur and marine operations remain separate, though they can share a common antenna.