diff --git a/app/src/main/java/com/laseroptek/raman/ui/screens/main/MainViewModel.kt b/app/src/main/java/com/laseroptek/raman/ui/screens/main/MainViewModel.kt
index b5a5063..7a81810 100644
--- a/app/src/main/java/com/laseroptek/raman/ui/screens/main/MainViewModel.kt
+++ b/app/src/main/java/com/laseroptek/raman/ui/screens/main/MainViewModel.kt
@@ -825,7 +825,7 @@ class MainViewModel @Inject constructor(
         txPacket(READ_WRITE.WRITE, CMD.Q_SWITCH, qSwitch.value)
 
         // tx Guide Beam Write
-        txPacket(READ_WRITE.WRITE, CMD.GUIDE_BEAM, GuideBeam(value = guideBeam.value.toInt()))
+        txPacket(READ_WRITE.WRITE, CMD.GUIDE_BEAM, GuideBeam(value = getGuideBeamTxValue()))
 
         // tx DCD_GAS Write (DEFAULT VALUE)
         txPacket(READ_WRITE.WRITE, CMD.DCD_GAS, dcdGas.value.copy(status = 0x50))
@@ -834,6 +834,18 @@ class MainViewModel @Inject constructor(
         txPacket(READ_WRITE.WRITE, CMD.SPRAY_DCD, sprayDcd.value)
     }
 
+    // Guide Beam step mapping (0~10)
+    // 0 -> fixed 0
+    // 1~10 -> min~max range in 10 steps (10 -> max)
+    private fun getGuideBeamTxValue(): Int {
+        val step = guideBeam.value.toInt().coerceIn(0, 10)
+        return if (step == 0) {
+            0
+        } else {
+            guideBeamMin.value + ((step - 1) * (guideBeamMax.value - guideBeamMin.value) / 9)
+        }
+    }
+
     // Example: Emitting an event after a delay
     fun txPacketLoop() {
         viewModelScope.launch {