RFID system components, such as readers (110) and tags (120, 220), communicate by a reader (110) transmitting waveforms that encode a calibration symbol and a divide ratio. Tags (120, 220) include a processor (652) to determine a backscatter link period result by dividing a count value representing the calibration symbol by the divide ratio and adding an adjustment. Tags (120, 220) modulate a backscatter waveform that includes symbols using a link period determined from the result.