Reducing Bit Error Rate
Individual hotspots can require different offsets. If experiencing high (greater than 1%) Bit Error Rate (BER) with your radio, you can try reducing it by adjusting the RX Offset.
Set up Pi-Star with the MMDVM Host Configuration Mode you want to use. Be sure to apply changes for them to take affect.
Once your hotspot is working as it shoud, I suggest that you back up you Pi-Star configuration file and save it to your PC
The best way to work on this is to have Pi-Star open in two browser windows
Set up the first browser window to view the Expert Editor (http://pi-star/admin/expert/) - this is where you will make the adjustments. Click on MMDVMHost
Scroll down to the Modem section and find the RXOffset setting.
Set up the second window to view the Dashboard (http://pi-star/) so you can view your BER readings.
The easiest thing to do is to make calls lasting a few seconds to a Parrot talkgroup or reflector.
In the Expert Editor / MMDVM Host / Modem section adjust the RXOffset setting while making a parrot call and observe the readings. A BER of less than 1% is the target, preferably less the 0.5%.
Begin with +/-100 offsets, and see how that affects the BER. Be sure to to click on "Apply Changes" after each change you make before moving on to the next change.
Once you find the lowest BER with the +/-100-step offsets, repeat the process with +/-50-step offsets, and finally +/-10-step offsets until you find the lowest BER.
Repeat the process for each MMDVMHost Configuration Mode in which you're experiencing high BER, until you achieve the optimal BER in each one. If you can't find a good balance for the BER between the different modes, it may be better to use different hotspots for each different mode.
I highly suggest that you back up your Pi-Star configuration file and save it to your PC (deleting your previously saved file) for future use...
A more exact method to calculate offsets can be found at Hotspot Offset Calibration
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