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out of band by modifying the .mdf file
there is another method of programming the radio out of band, it is a little more complicated than the method described above, but it will work just fine.
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.
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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.
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add channels by modifying the .mdf file
