🎚 Calibration
When the radio «can't hear»: tuning the modem frequency by BER.
Cheap MMDVM modems almost always drift off frequency: the radio is right next to you, yet there's no link or data won't decode. The fix is calibration — tuning RXOffset/TXOffset down to the lowest BER. Here's how to chase zero step by step with the MMDVMCal utility, and what the BER and RSSI numbers actually mean.
It's important to grasp the cause and effect: if the hotspot logs are clean but the radio isn't receiving, the culprit is almost always modem frequency drift, not the server. A healthy BER is below 1%.
Hotspot «can't hear»: MMDVM frequency calibration step by step
Why the radio is right beside you yet there's no link: frequency drift on cheap modems, RXOffset/TXOffset and how to chase zero by BER.
CalibrationMMDVMCal step by step: calibrating the MMDVM modem
Full hotspot calibration with the MMDVMCal utility: DMR mode, frequency tuning, RXOffset/TXOffset and the BER test. Why it matters for receiving data on the DMRhub network.
CalibrationBER in DMR: what this number means and what's normal
BER is the bit error rate and the key indicator of hotspot health. What's normal (below 1%), why it climbs and how to lower it by tuning the frequency.
CalibrationHotspot RSSI calibration: the correct receive level
What RSSI means in MMDVM, why you calibrate the level table and how it affects the signal shown in the DMRhub portal's last-heard. Not to be confused with BER.
CalibrationTXLevel and RXLevel: MMDVM modulation level
The TXLevel/RXLevel parameters in MMDVM.ini set the deviation. How to dial in an even level without skew or distortion — and how it ties into BER and data reception.
CalibrationMMDVM.ini explained: a breakdown of the key parameters
MMDVM.ini explained: the key parameters, dangerous values and common hotspot config mistakes.
CalibrationTCXO and hotspot frequency accuracy: why the modem drifts
Why the modem drifts off frequency, what a TCXO is and how to fix the drift on HS_Hat/Dual_Hat boards.