Out of band programming
To program frequencies outside of the rated bandsplit in the GM300 can be very simple, follow the listed steps:
Out of band by modifying the .MDF file
In the GM300.MDF file make a Checksum-16 of the whole file (the F12 option in Hex Workshop), in our case we ended up with 0x5D53 (RSS V 05.00), write this down, you might need it later.
Look starting at about offset 0x2AC, you should see something like:
The highlighted area contains all the possible bandsplits that a GM300 could be.
A single bandsplit entry looks like:
The bytes to take note of are:
05 00 = Bandsplit identifier (Note: the bandsplit identifier is at the end of the frequency list)
94 11 = 4500 in decimal, ie 450.0000 MHz
5C 12 = 4700 in decimal, ie 470.0000 MHz
Note there are 3 occurances of the strings 94 11 and 5C 12, the first set is the limits displayed in the Radio Wide menu (F4-F2). The second set are the TX limits for the radio. The third set are the RX limits for the radio (note that if the TX and RX limits are not set the same the RX limits are screwed up).
To figure out what hex to enter for your bandsplits you can either use the Base Convertor (in Hex Workshop), or use a calculator with a HEX --> DECIMAL conversion function.
If you are using a calculator enter your limit (ie 4400 for 440.000 MHz) and convert it to hex, you should get 0x1130. When you enter the data into the .mdf file you have to reverse the bits such that you would actually enter 0x3011 in the field you are changing.
If you are using Hex Workshop, launch the Base Converter utility and select "Intel Byte Order". Then, enter your desired frequency and write down the hex result.
You can then directly enter the hex result (0x3011) into the bandsplit field.
In this example we are changing the lower bandsplit of a 450-470MHz radio to 440-470MHz.
Save the new file (you might want to make a backup copy of the original if you haven't already.
Some of the RSS packages (we don't have codeplugs for everything, so we can't check them all) check the checksum of the .mdf file when you try and load a codeplug and return an error if the checksum of the .mdf file doesn't match the one stored in the program. Try running the RSS with the new .mdf file, if you don't get an error when you run the RSS and load a codeplug then you don't have to worry about the next step.
Correcting the .mdf File Checksum
If you get a corrupt .mdf file error then you will have to go back and correct the checksum in your edited .mdf file. Load the file back in your hex editor and make a Checksum-16 of the file. If you compare the new checksum
with the original one
You will find they are probably different.
The only way we have to correct the checksum of the file at this time is to keep editing bits and making Checksum-16 calculations until the edited file's checksum and the original match. You can either edit the Copyright statement or some of the model descriptions in the file. Just take one or a few of these insignificant bytes (some experimentation may be required depending on by how much the cheksum is out) and add or subtract a few bits of the numbers make a Checksum-16 of the file. You should notice the checksum has changed by the number of bits you added or subtracted. Keep going until the checksum's match.
Once the checksum's of the files match you should be able to run the RSS, load the codeplug, and enter the frequencies within your new bandsplits with ease.
Add channels by modifying the .MDF file
Search the .mdf file for your radio's model number. You should see something like (for a M33GMC29C2__):
Now, looking at the bytes after the model number, you will find the following:
The 0x03 is the bandsplit used by this model, you can find this in the bandsplit list discussed above.
The 0x10 is the number of channels in the radio. 0x08 = 8 ch, 0x10 = 16 ch, 0x20 = 32 ch, 0x28 = 40 ch.
Now, if you have a 8ch radio you can try bumping it up to 16, we've been told that it works fine (in fact, depending on what other options you use you might even get 17 channels).
You can take a 16ch radio all the way up to 40 ch (0x28) and it should work fine, any more than that and it does strange things (codeplug probably gets too full and wraps).
Another thing you will notice is that you can only have the first 16 channels in the scan list (if anyone finds a workaround, let us know).
Note: You will have to correct the checksum for the file as described above.
General Information
Look here for the pinout of the accessory connector for the 8 channel radio or 16 channel radio.
If you need a repeater interface cable to connect a couple of these radios together, look here.
Need to connect a couple of GM300 radios together? Here is a schematic of the R.I.C.K. to get you started. Order the service manual part number 6880901Z79 from Motorola. Note: If you try and print this schematic with your brower, it probably won't work. So, save the image and print it using a graphics program.
The GM300 Series are 9600 baud packet capable. They do need a minor modification though. For RX, its no big deal, just take RX audio from PIN 11 of the Accessory Connector and swing JU551 to the (A) position (Flat RX Unmuted). For TX audio, you will have to run a jumper to the junction of R223,C228,R222 on the RF board to inject the data (if applicable you may need to set the deiation pot in the radio to maximum). You might want to put a pot on your TX line somewhat like the setup Motorola uses (voltage divider) to adjust the deviation. It would be wise to do some measurements to make sure you have the deviation correct. You might also want run the RX and TX pins to the unused pins on the front mic connector after the mods are done.
This radio can decode and display up to 126 PTT IDs. But how, you ask, since it only has a 2 digit display? It encodes (in HEX) the first two numbers of the PTT ID. See below:
PTT ID���� GM300 display 007��������� 07 099��������� 99 105��������� A5 110��������� B0 120��������� C0
Good luck in adding scan to a GM300 8 Channel radio, tried it by editing the .mdf file, and the RSS just crashes when you try to load a codeplug.
GM300 RSS and the OpCode #7 Error
It seems that some radio's are very particular when it comes to programming voltages from the RIB. Try using a brand new battery fresh out of the package or use an external voltage source for the RIB and see what happens.
We have also heard of some people getting this error when trying to program the radio in a DOS box under Windows. When they use DOS only, it programs just fine. Not sure why anyone would even think of attempting to try and run RSS under Windows to begin with... you're just asking for trouble.
Another solution to getting rid of the error was to re-install the RSS
Even another solution was to use a backup copy of the .mdf file, in this case the error popped up after modifying the .mdf.
If you have any questions, email us and we'll try to help.
