A fellow ham had asked me whether I could program a couple of Motorola MTM700 tetra radios for him. To do so I could use my home made programmer. And it seemed I also had the sofware for the MTM700. So I was able to quickly read one of the radios. Nevertheless it’s quite hard to bring those old radios out of band. The workaround is to get a codeplug which is already out of band, edit it and upload it to the radio.

Another radio amateur was kind enough to send me a codeplug for the MTM700. But then a nasty issue popped up: the codeplug was for a MTM700, but for a lower / older firmware version of the radio. As different firmware versions can contain different functions, not only the firmware has a version number but also the codeplug itself. Different firmware versions can share the same codeplug version / structure, but not necessarily.

In this specific case the codeplug was suitable for radio firmware R020003317:
– R02: it’s Motorola MTM700 firmware
– 000: this is ‘clear’ firmware, so without TEA encryption
– 3317: this is the actual firmware version number

Unfortunately the radio contained a newer version: R020003357. And in this setup it was not possible to upload a ‘version 3317 codeplug’ to a ‘version 3357 radio’. There were two possible solutions. The easiest was a function in the lab CPS which translates a codeplug file to make it suitable for a newer firmware version. But in my case this function didn’t work at all. The next best option was to downgrade the radio to firmware version R020003317. After that downgrade I could then upload the corresponding codeplug.

It was just a tiny problem that this firmware version could not be found anywhere. But I had a file with R020003340 firmware, not an exact match but there was a chance that versions 3317 and 3340 shared the same codeplug version. It was a long shot, but bottom line was that this was the only option.

So first the radio had to get a downgrade from firmware 3357 to 3340. This starts by ensuring the firmware files are in the subfolder ‘sw’ in the Motorola directory. In this case these files had to be in the folder:
– R020003340.z19
– R020003357.z19

When starting the radio has to be off but connected to the power supply. First launch the CPS and connect the radio to the programmer. Then press the power-button of the radio for a few seconds. Nothing (visible) will happen, but a jumper wire in the programmer and pushing the power button will enable the programming mode of the radio. Next step is to select the item ‘Downgrade Phone’ in the ‘Tools’ menu of the CPS. The CPS then starts communicating with the radio the figure out if a downgrade is possible. This can take a couple of minutes while nothing happens at the screen. Finally a dialog shows up to confirm the serial port is available and a radio is connected.

After clicking ‘Continue’ the next dialog is shown to confirm the downgrade settings:
– select the target version under ‘Version Selection’
– ‘Subscriber Type Selection’ has to be set to ‘Clear’
– Leave ‘Downgrade Data Codeplug to’ unchanged
– disable both checkboxes at the bottom of the window

Finally click ‘Write’ to start the downgrade process. It’s extremely important not to interrupt this process. Before starting make sure data and power cables have been fitted tightly, don’t let the PC go into sleep mode and don’t do anything which could interfere with the downgrade as long as the process runs. This also includes the PC. Completion of the downgrade will be confirmed by a message box at the screen. Switch off the radio via the CPS using the red icon in the icon bar. This will be confirmed via a message box in the CPS as the radio still appears ‘dead’.

Now remove the programming lead and switch on the radio. It will boot normaly and during the boot sequence the new firmware version will be shown at the radio’s display: R020003340.

After the downgrade the codeplug for firmware version R020003317 can be uploaded to the radio. In fact the firmware version still aren’t equal, but the codeplug for version 3317 has the same version / structure than the codeplug for firmware version 3340. Before uploading the codeplug the radio has to be switched off again, the programming cable needs to be connected and with by firmly pushing the power button the radio has to be kicked into programming mode again. After uploading the codeplug the radio can be switched off using the CPS and the programming cable should be disconnected. After booting the radio the new (amateur radio) talkgroups can be used.

Generally the MTM700 is now ready for use in the amateur radio band. Except it now has a lower firmware version. For amateur radio needs this will probably have no consequences. But it looks more tidy to return to the firmware version we’ve started with. To do so the radio has to be connected to the programmer and put into programming mode. Via the CPS menu ‘Tools’ the item ‘Upgrade Phone’ starts the upgrade process. A similar window as in the downgrade procedure becomes visible. In the box ‘Version Selection’ now the higher firmware version is selected (R020003357). ‘Subscriber Type Selection’ is now also set to ‘ Clear’ and both checkboxes at the bottom remain unchecked. Then click ‘Write’ to start the upgrade process.

After this upgrade the radio still has its amateur radio codeplug, except the firmware version has been upgraded to 3357. After reading the radio again with the CPS the read codeplug edited and uploaded back to the radio. Unfortunately it can’t be saved. Probably the CPS performs a sanity check on the data and kicks out all frequencies above 430 MHz.