HomeHomebrewHelp Needed – Icom M710 Remote Control Cable

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 remotePc serial port

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


Alligator Clip











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.


Help Needed – Icom M710 Remote Control Cable — 10 Comments

    • OK, I disconnected #8 on the Remote side from the clip and taped it off. The SW that works via the clone port still doesn’t work via the REMOTE. I rebooted and stuff in between just to be safe… this is making me feel like something is wrong with the remote port. I wish I knew how to connect to that remort port with PUTTY or another terminal applicaton so I could elminate more variables (i.e. the software). Just connecting to COM2 doesn’t yield anything at all.

      • Show us a picture of the backside of the m710 and indicate which connector you are using. Also take a good close up of any intact factory labels.

          • I think that is a picture of the front side of the main unit of an Icom M710RT. Around the back side of this main unit is where you will find the NMEA db9 connector. It is important to note what hardware version you have. General, Marine or gmdss to make sure you are plugging into the correct connector. I assume you are trying to utilize HRI’s Cat controls including CAT Tx and combine modulation and AF on one cable.

          • Tom this is exactly what I needed. Someone to challenge all my assumptions.

            This radio was already installed in my boat when I bought it. The Face place
            says M710, but you are correct, crawling in the locker the main body does say
            Model: M710RT on it!

            The M710RT manual shows the front side RS-232C connector being used to connect
            to a PC. I’m not sure how that works because it doesn’t work with any software I
            can find. This is the port I had been using.

            On the backside of the main body there is another DB9 connector and this is
            where my pactor is connected. I disconnected that, and connected the cable I
            made and now HRI can control the radio. The Speaker and Dimmer do not work, but
            the Transmit but does which did not work via the clone port (the 1/8″ jack).

            I was hoping I could use the PC or the Pactor without re-cabling each time. I
            guess I’ll need an A/B DB9 selector switch to make the happen.

            I’m still dumb founded as to how that other RS-232C port is for PC control, as
            shown in the M710RT manual. They did at one time sell a proprietary SW for the
            rig, must be what it was for.

            Thanks a lot Tom you were a huge help!

  1. Hi sorry to trouble you i was wondering if you could point me in the right direction to download the software you use to control the m710rt via pc and also recommendations as far as cable connections are concerned.
    thank you very much
    kind regards

    • Pretty sure I replied to you in email already. But all the softare for the M710 is in the Icom M710 Yahoo Group I started. The group is ver low volume but full of folks who can and will help you out. As for the cable. I mad emy own and that is outlined here on the site. You can ask about buying a premade cable in the group.

  2. Control cable for Icom IC M710.
    Can I use a “null modem” (9 pin female-female RS-232) ready made cable.?

    • Sorry I’m so long in replying. No. Its a custom cable. You can buy one online. I didn’t have that option when we were living in Mexico. We could though find the cable at Sterns in Mexico (equivalent of Radio Shack).