Motorola Radius GM300 Image

Motorola Radius Programming in Windows with RSS and DOSBox

Starting Motorola's Radio Service Software

Now it's time to see if we did so far is correct. Let's start DOSBox and see what happens. You should see a welcome screen that tells you to push any button, and then the following screen below.
If you see this screen above, congratulate yourself! You have successfully configured DOSBox to run Motorola's Radio Service Software.

Now comes the part that just about everyone has trouble with . . . getting your Motorola Radius to communicate with your computer. Cheap programming cables, and too fast of a CPU speed (on your computer/DOSBox) are the main cause of this problem. We already discussed what cables worked for me. Now let's go over how to slow down the CPU speed.

Slowing Down the CPU Speed in DOSBox

While DOSBox is running, hold down the "Ctrl" key and press "F11" until the CPU Speed (displayed in the title bar) reaches somewhere around 191 cycles. If you went too far, hold down the "Ctrl" key and press "F12" to raise the speed back up. I was able to successfully program with a CPU Speed of up to 400 cycles.


Configuring and Testing the Motorola RSS

Now it's time to configure the RSS, and test the connection between your computer and your Motorola Radius.

    1. From the "Main Menu" of the Motorola RSS, press "F9" to get into the "Setup Computer Configuration Menu".


    1. Now press "F3" to go into the "PC Configuration Menu"


    1. You will need type in the "Default Path Names" on this screen.

Archive D:\ARCHIVE
Backup D:\BACKUP
Repeater D:\REPEATER

RIB . . . . . . . . . . . . . . . COM1

Note: If you are using COM2, make sure to change the "RIB" setting to COM2.
  1. Now press "F8" to save your settings.
  2. Press "F3" to preform a "COMM TEST". This is where you will find out if your computer and your radio will be able to communicate. Look to make sure you get the "Radio Communications OK" message. If you get any error messages, double check everything above, and make sure all the settings are correct.

Programming Frequencies, Tones, Offset, and the Time Out Timer

    1. If you are not at the Main Menu, press "F10" until you get there. Press "F3" to "GET/SAVE Codeplug Data".


    1. Now press "F2" for the "READ Radio" option.


You should see a screen that looks like the one pictured below.


    1. After that is complete, press "F10" and then "F4" to get to the "CHANGE/VIEW Codeplug" menu. Now press "F5" to get into the "MODE Configuration: Frequency, Squelch Type, and Codes" menu.


This is where you can change the frequencies, PL tones, offset, and time out timer.

Note: The "Tab" key will navigate you around in this menu, and "F4" will take you to the next channel settings.


    1. Change the settings to what you require, and then press "F10" twice to return to the "Main Menu".


    1. Now press "F3" and then "F8" to select the "PROGRAM Radio" option. A warning screen will appear. Press "F2" to continue programming your Motorola Radius.


This is the screen (below) that you will see when your Motorola Radius is programming.


  1. Celebrate! You have programed your Motorola Radius!
Notable Resources

45 Responses

  1. KK6JYT
    | Reply

    I have heard that turning the transceiver off and back on again (power cycle) just before attempting to initiate communication from the computer has helped, for some people.

  2. Joseph Neale
    | Reply

    I need a little help I have followed all the steps up to the comm test. I have tried the comm test and get ‘Accessing Serial Bus.” but it stays on that. I don’t get an error or anything else. I even tried reading the codeplug and got the same message. Reading codeblock does not come up. I even left it there for 10 minutes. I using a computer with Windows Vista Business. Thanks in advance for any help.

    • KK6JYT
      | Reply

      What cable(s) are you using? If you are using cheap cables that’s where you will get stuck. The only cable(s) that I have found to work are the ones mentioned in the article. If you have those exact cables, try changing the CPU cycles (probably up in your case being it’s an older Vista computer). Hope that helps.

      • Joseph Neale
        | Reply

        The cable is probably the problem. I did order a programming cablf withe the serial plug off of eBay but I think it was one of the cheaper ones. I clicked on the link for programming cables on your site and it sent me to one on Amazon that was sold out.

        • KK6JYT
          | Reply

          That really stinks! You will probably have to just do what I did and keep ordering different cables until you find one that works. Try to search for GM300 RIBless cable schematics if you are capable of modifying your current cable, or even better – build your own RIB and dumb cable. The RIB is a lot better way to go.

          • Joseph Neale

            I haven’t gotten my new cable yet but I tried changing a couple of setting on my computer and not it is giving me “#7 INVALID OPP CODE” when I try to read the radio. When I just do the COMM TEST it gives me that error for a second then tells me Radio Communications good. Is there a setting that needs changing or do you know anything about that? Thanks for your help and Thank you for this site too.

      • jim
        | Reply

        I have had good luck building my own cables. A chunk of Cat 5, an RJ45 end and a DB 15 (or 9, depending on the rib).

  3. Joseph Neale
    | Reply

    Adding to my last comment I had switched it from COM1 to COM2 in all the settings above because it was giving me that at first when I switched it to COM2 that is when it wouldn’t do anything. I had forgotten what the error was because it flashed up too quick that is why I didn’t include it in my first question.

  4. AD0JA
    | Reply

    I am having the same issue as Joseph. I wonder if it’s the programming cable because I also got a cheap one off Amazon.

    KK6JYT – your reccomended cable is STILL out of stock on Amazon. Do you a have a different one to reccomended or does some one else know of one that ACTUALLY works?

    I don’t have the time (or knowledge) to build a cable.


    • KK6JYT
      | Reply

      Sorry, I do not know of one that is in stock and works. I will update the listing as soon as someone can verify a good cable.

  5. Clifford
    | Reply

    Same issues here as with others. Error 7. Dell E5500 w native com port, tried DOSBox, boot to DOS, etc. Only thing that worked for me was a Maxton model RPC-MM RIB-less cable loaned to me. Works perfectly. I just ordered this one as the photo shows same cable we shall see-

    • Clifford
      | Reply

      I got the above referenced cable today and it works perfectly.C

      • KJ4VOV
        | Reply

        I followed your advice and also was now able to program both of the radios I have with no problems or issues. This cable WORKS!

        (short URL to the cable on Amazon)

  6. Jack
    | Reply

    The multicable from KaWaMall works fine. The only problem I have had is getting it to save to my archive file. It says “Path does not exist”.

    • KJ4VOV
      | Reply

      If it’s the first time saving that file then that will pop up, since there’s no such file created yet. Go ahead and save it anyway and that will fix the problem.

      Another reason this can happen is the drive letter not being correct for how the drive was mounted. For example, if I mount my D: drive as the C: in DOSbox, I have to make sure the path I set corresponds to that and set the path as going to drive C:, not drive D: (because DOSbox will change it to the correct drive when it comes through).

  7. mike
    | Reply

    nice, i do the same via DOSBox for Radius GP300 (old type) via Homemade MAX232 Com/TTl programmer ( and it works fine on P4 2Ghz CPU.
    For GP300 with LCD and keyb, the sw R05.03.00 (r other versions ) does not work , i have 057 on the lcd when pressing 2 sidekeys and PTT at turning on the TRX. Do i need other sw for this GP300 2T/DTMF version? or other start-up keys to press ?? vy73
    mike on6jf

  8. AA1PR
    | Reply

    GM300.EXE illegal command is the prompt I’m getting

    • KK6JYT
      | Reply

      Try to change it to this:

      mount d c:\gm300.exe

      I updated the post.

  9. KJ4VOV
    | Reply

    First, my compliments on a great resource you’ve created here. Your work on it is much appreciated. Second, like many others here I’m also encountering the “Error #7 INVALID OP CODE” problem. The PC I’m using is one I built myself, specifically for amateur radio, so it does have a native serial port. The cable is from KJ6ZWL, as is the RSS software. Under Win 7 and the latest DOSbox I get the error flashing on the screen very briefly and then the “Radio Communications OK” message when testing the comms. Attempts to read the radio result in the same error displayed and failure. At the same time, in the DOSbox status window I’m seeing a serial port error that the RX buffer overflowed. This makes me believe the problem is a handshaking issue, that either the radio or the computer is not pausing when it should. I’ve tried experimenting with the handshaking (XON/XOFF, hardware, none) to no effect, but this was with DOSbox and RSS running, so changing the settings without exiting and restarting DOSbox may not have any effect. I’ll experiment further and report back. It would help a lot though to know what ALL of your port settings are set at, not just baud and FIFO. Regarding FIFO, Windows 7 advanced settings do no permit setting RX to zero. It uses sliders and RX is 1-14 (because that’s the size of the buffer in the UART chip) and the TX buffer is 1-16 characters. You can untick the checkbox, which would turn off the buffering completely, but that does not seems to have any effect on this problem (so far).

    • Brandon
      | Reply

      I’m having the exact same problem. Did you find a solution?

  10. Rick
    | Reply

    Thanks to all ““““good guys

  11. KJ4VOV
    | Reply

    Just an update to my previous post:

    I did what Clifford (above) did and ordered the same cable he did from Amazon. It arrived today and, with no other changes to the system, read and programmed both radios without a problem. Evidently there is a problem with some programming cables, even ones that aren’t cheap junk from Chine (mine was from KJ6ZWL – custom made) but this one from Amazon works beautifully!

  12. faisal
    | Reply

    i have error #2 aknowledge how to fix it

  13. Gino Faucher
    | Reply

    I read code plug sm50 Radius. I used win 8.1 or win 10, dosbox and Tripple-lite cable usa-19sh. I didn’t meet any problem. No power cycle needed. When I used prolific usb serial cable, I had to power cycle between read/write code plug.
    Thanks for your advices on this blog.

  14. KG5GBR
    | Reply

    if your going to use it very often..just build a DOS computer from an old 486 etc……you can also change cables and do EF JOHNSON…DO IT RIGHT AND YOU DON’T NEED BOOT DISKS!…….

  15. KG5GBR
    | Reply

    I have maxtrac lab, gm300/m120, sm50/120, and one of the ef Johnson rss,,all on an old 486….works great….had to go old school to get the hard drive right, but now just turn it on and program!!!!

  16. Gleiber PU4GMC
    | Reply

    TKS so consegui Programar um GM 300 gracas as sua dicas

  17. Mitch
    | Reply

    I appreciate the shout out :).
    73s! KF5RRX.

  18. K5CG
    | Reply

    Thanks for the post!

    TIP: Once you figure out the CPU speed that works for you it can be saved into the configuration file in the cpu section:

    cycles=fixed 191

  19. Ryan
    | Reply

    I am Getting “no acknowledgment” when trying to read my radio. Running windows 10 with dos box. any ideas

  20. Jeff
    | Reply

    Hello Michael:

    I am using DOSBox on my Windows computer. I have a known working RIB box. I’m trying to read a Radius M208. I also have the correct RSS ver R07.20.01. I have DOSBox configured to use COM1. DOSBox starts my RSS perfectly. I use the CNTRL F11 and F12 keys to adjust the CPU to about 275. Now when I run the COM TEST it responds perfectly with RADIO ACESS OK. Now when I go to read the radios codeplug I get the status bar and the computer attempts to read the radio but after a minute or less I start seeing Overrun RX errors on my DOSBox window. After reading about Overrun RX issues I tried playing with the FIFO buffers by first turning it off, by adjusting for various settings, and still get the overrun errors on RX. I also set the COM1 port to 2400 baud, 8, N, 1.

    Not sure what else to try. Can you send some light on what else I might need to do?

    Thanks for any help!



    • KK6JYT
      | Reply

      Try adding rxdelay=200 to your [serialports] section in the DOSBox configuration file. Increase or decrease the number if 200 doesn’t work to see if it helps.

      rxdelay: How long (milliseconds) to delay received data if the interface is not ready. Increase this value if you encounter overrun errors in the DOSBox Status Window. Default: 100

  21. Jeff
    | Reply

    Thanks for the suggestions Michael, I will try them out.


  22. Jeff
    | Reply

    Thanks Michael!

    I set the CPU to 191 cycles and added the “rxdelay=200” and I am now able to read the codeplug! Just wrote new codeplug to radio and checked out radio with service monitor, ALL GOOD! I really appreciate you taking the time to respond so quickly. I was going to give up when I decided to send you the e-mail with my issue, sure glad I did!

    Thanks again,


    • KK6JYT
      | Reply

      Excellent! Glad I could help.

    • Juan
      | Reply

      Hi, where exactly did you paste the rxdelay=200? I’m having similar problems programming the GR300.

      • KK6JYT
        | Reply

        In the DOSBox Options file. The file name will be something like “dosbox-0.74.conf”. Read the section above labeled “Configuring DOSBox to Run Motorola RSS” to see how to get to that file.

  23. Steve
    | Reply

    Getglitched seems to have gone 🙁 cannot find the software to program a GM900

  24. Les
    | Reply

    I can read the codeplug but I get error 58 and have had no luck on fixing it….. Any Help on this ?

    • KK6JYT
      | Reply

      The error might be because the model number is for an 8 channel but there are 16 frequencies programmed and it is confusing the software. You may have to use a hex editor to make it look like a 16 channel. Check out this link –

Leave a Reply

Your email address will not be published. Required fields are marked *