Icom’s new M803 Marine SSB Radio began shipping in early 2020 and is a terrific radio for use with Sailmail. It supports the latest DSC standard, incorporates Icom’s latest SDR radio designs, and also includes GPS (internal or external) and provides that data for position reporting. Any of the SCS modems are supported.

Connection is similar to Icom’s previous marine radios, with audio and control cables commecting radio to modem: One for the audio signals and a second cable for radio frequency control. While the M803 has the same “ACC” connector as the earlier M802 and M710/700pro radios, it is not compatible and a different cable is needed for the AF/MOD connector. Here are the details:

Modems: Any of the SCS Pactor modems including the DR-7400 or DR-7800 Pactor-4 modems, the PTC-IIIusb Pactor-2 modem, and any of the earlier PTC-II modem-series.

Cables: The audio cable is Farallon #9098 (2M, or 9099 for 4M). This is a new cable for the M803 (details below). Connect this from the modem’s “Audio” (“Main Audio” for the DR-7800) to the radio’s “AF/MOD” connector and plug the 8-pin DIN plug into the radio’s “ACC” connector (for 12V power).  The 9090 cable used on most Icom radios for the “ACC” connector cannot be used. The audio level settings should be 900/1200 for FSK/PSK respectively. Airmail’s “autoset” function has been updated and works well for the M803.

Frequency Control: The radio’s “REMOTE” frequency-control connection is via a standard RS232 serial port and can be connected to the modem with a Farallon #8083 cable (2M, or 8084 for 4M). Connect this from the modems “Control” connector to the radio’s “REMOTE” connector. Alternately use a standard serial cable from a computer serial port (or USB/serial adapter) to the radio’s REMOTE port (9-pin male-female). The M803’s Remote-ID is 20, and the baud rate is 4800 (avoid the higher rates).

Ferrites: It is important (with any radio installation!) that ferrite chokes be installed at each end of both cables from the modem to radio, and also at both ends of the USB cable from computer to modem (does not apply with a bluetooth connection). The ferrites should be located near each end, use a small cable-tie to prevent them from sliding down the cable. It is also a good idea to add a cable-tie around the ferrite itself to make sure it stays closed. The recommended ferrites are Type-31 material from Fair-Rite.

Modem setup: The only setup required is for a PTC-IIIusb/DR-7400/DR-7800, if you want it to power-on with the radio (and of course you do): Set Dip Switch #1 on the back of the modem to the DOWN position to power on automatically when the radio is powered on. 

Radio settings: Check the following settings in the radio’s setup menu. To change a setting press the radio’s MENU button , then use the arrows or the big knob select the setting and press the “enter” (ENT) key, then repeat for each sub-menu:

• MENU > Configuration > Remote > Interface: Select RS-232C. Leave baud rate set to 4800 bps. Verify that MOD is set to AF/MOD.
• MENU > Configuration > GPS > Internal GPS: Verify GPS, GLONASS and SBAS are set to On if using the external GPS antenna (see below).  
• MENU > Configuration > GPS > External GPS: If an external GPS is connected via the BNC connector then verify the baud rate: 4800 for most connected GPS receivers, 38400 for a connected AIS receiver.
• MENU > Radio Settings > Auto Tune: Select ON (assuming the AT-140 Icom auto-tuner is used). 

Other notes: The M803 has a Noise Reduction feature (under Radio Settings menu), it is recommended to leave this off for radio email– the modem has its own digital signal processing. Similarly leave the NB Level (noise-blanker) setting at minimum, and leave the RF-Gain setting set to max (9). Also use high TX-power mode (soft-key menu)– reducing transmit power will slow the connection.

Position Reporting: The M803 needs to be connected to a GPS in order for the DSC distress function to work– either using the radio’s internal GPS with a connected antenna, or (same as the M802) via the GPS-Data BNC connector from an external GPS. Where the M802 kept this data to itself, the M803 transmits the GPS data (from either source) via the REMOTE connector to the computer where Airmail (ver 3.5.054 or later) will pick it up.

What this means is that once GPS is connected to the radio for DSC, Airmail can update your lat-lon whenever Terminal window is opened, and Position Reports are updated automatically. Multiple formats are available including MarineTraffic to continue your AIS track offshore, CruisersCafe for Yotreps-style updates, and Sailblogs for a comprehensive tracking/blogging site.