DMR: Adjusting the offset by Al AF4FA

Most of the boards lately have required adjusting the offset to function properly on DMR. Many boards are shipped with a sticker on the bottom with the required offset.

These are usually pretty close. There is however a way to get this more exact and specific to your radio. Luckily there is a utility built in to Pi Star that enables you to tune your offset.

All it requires is pen and paper, a calculator and a little time.

Step one is to gain ssh access to your Pi. The easiest way to do this is go to “Configuration” then click “Expert” then “SSH Access” and log in with pistar and your password.

First, set your radio to 433.000mHz Talk Group 1 and Color Code 1 TS 1.

Next, use the command in SSH to start mmdvmcal “sudo pistar-mmdvmcal” then press “b” to start the BER tuning program.

1.Press the PTT on your radio for about 1 second. Then unkey.
2.If no BER response or a high response press the “F” key to raise the frequency and repeat step 1 until you get the smallest BER you can.

If you get to more than 1.5kc from the starting frequency without seeing a BER response or if the BER keeps increasing press “Q” and start the program over and press “f” instead of “F” and repeat steps 1 and 2 lowering the frequency until you get the smallest BER you can achieve.

At this point you can change the frequency step to a lower increment by using the ā€œZā€™ key and entering a lower step (50 or 25 or 10) and go back to step 1 to see how much lower you can get by using the “F” and/or “f” keys.

When you are satisfied with the BER then do the following.

However far off you are from the starting frequency of 433mHz is what your RXOffset should be set to plus or minus.