           if (VfoClockOffset > MaxClockOffset)
             VfoClockOffset = MaxClockOffset;
 #if (DEBUG & DEBUG_ACT)
-          Serial.printf(F("calibrate_freq_action: vfo_RRight, after VfoClockOffset=%d\n"),
+          Serial.printf("calibrate_freq_action: vfo_RRight, after VfoClockOffset=%d\n",
                         VfoClockOffset);
 #endif
           break;
         case vfo_DnRLeft:
 #if (DEBUG & DEBUG_ACT)
-          Serial.printf(F("calibrate_freq_action: vfo_DnRLeft\n"));
+          Serial.printf("calibrate_freq_action: vfo_DnRLeft\n");
 #endif
           ++seldig;
           if (seldig >= MaxOffsetDigits)
             seldig = MaxOffsetDigits - 1;
 #if (DEBUG & DEBUG_ACT)
-          Serial.printf(F("calibrate_freq_action: vfo_DnRLeft, after seldig=%d\n"),
+          Serial.printf("calibrate_freq_action: vfo_DnRLeft, after seldig=%d\n",
                         seldig);
 #endif
           break;
         case vfo_DnRRight:
 #if (DEBUG & DEBUG_ACT)
-          Serial.printf(F("calibrate_freq_action: vfo_DnRLeft\n"));
+          Serial.printf("calibrate_freq_action: vfo_DnRLeft\n");
 #endif
           --seldig;
           if (seldig < 0)
             seldig = 0;
 #if (DEBUG & DEBUG_ACT)
-          Serial.printf(F("calibrate_freq_action: vfo_DnRRight, after seldig=%d\n"),
+          Serial.printf("calibrate_freq_action: vfo_DnRRight, after seldig=%d\n",
                         seldig);
 #endif
           break;

          if (VoltsCalibrate < MinVoltsCalibrate)
            VoltsCalibrate = MinVoltsCalibrate;
#if (DEBUG & DEBUG_ACT)
          Serial.printf(F("volts_calibrate_action: vfo_RLeft, after VoltsCalibrate=%d\n"),
                        VoltsCalibrate);
#endif
          break;

/* reboot the Teensy, invoking bootloader. */
void reboot(void)
{
  Serial.print("Rebooting ...");
  delay(500);
  _reboot_Teensyduino_();
}
