The Icom M710 Marine SSB and HAM Radio has a DB9 port on it that is technically called a NMEA port. Via a custom cable you can connect it to a standard PC Serial port and control the radio with software programs. I have been trying to make this cable and it’s not working. I’m hoping by spelling out what I’ve done I’ll either figure it out myself (via the famous Anders Samuelson Paper Engineer methodology) or one of you will notice my error and let me know what is wrong.

First off let me explain the environment a bit.

  • I know my M710 has been modified for HAM use. I have participated in HAM Radio nets (14300 MHz) and have used it across many bands for winlink.
  • When I have attempted to use the REMOTE port, I have enabled the RS-232 in the SET menu on the M710.

First off I bought a male to female DB9 Serial Cable. I then cut it, filleted out the wires and with my multimeter in continuity mode, I identified which pin\hole went to which wire. I verified both sides of the connections just to be safe. This picture shows the ports\pins and which numbers I used for them. If I did this wrong, then everything is wrong for sure.

NMEA Remote Control Cable for Icom M710

The ICOM end is based on this drawing from the ICOM M710RT Manual.

NOTE: I have an M710 not an RT. I am not 100% there is any difference in the pinouts. I assume not. The Manual is the only one available on the Icom Website.

Icom M710 Remote Pinout

Once I filleted out the wires and labeled them I then connected them as per the directions I have found on various web sites. Here’s how that is written:

M710, M700pro:

The 9-pin NMEA "Remote" connector (labeled "DSC" on some models) can be used for remote control of the transceiver mode and frequency with any controller type, by using an additional computer serial COM port. NMEA signal levels are a differential version of RS-232 voltage levels, approximately +8 and -8 volts. With appropriate wiring the "+" NMEA connections can be connected directly to a RS-232 serial port. (Note that the "-" input must be grounded as a reference, but do not ground the "-" output).

A cable to a standard PC serial port can be made up as follows:

ICOM 710 Computer serial port

(9-pin male) (9-pin female)
   NMI+ 5-----------3 TxD
   NMO+ 7-----------2 RxD
   NMI- 6-----------5 GND
   GND  9-----------5 GND

Icom m710 remote

Pc serial port

If you look at these two pictures and match the colored alligator clips you will see I’ve connected them as follows:

| REMOTE                  | Alligator Clip          | PC                      |
| 7                       | Yellow                  | 2                       |
| 5                       | Red                     | 3                       |
| 6,8,9                   | Green                   | 5                       |
| Shield                  | Black                   | Shield                  |

With this setup connected to the radio I can NOT control the radio with any software. I should mention I also have a clone cable (the DB9 to 1/8” jack cable) and I can use software via that port, but not all functionality is working and I’m hoping if I get the REMOTE cable working it will fix that.

Anyway, that’s all I think to share… if you see something wrong please let me know I’ve been going round and round on this for a quite some time.