Add back FEM LNA mode configuration for LoRa (#9809)

* Add back FEM LNA mode configuration for LoRa

* Update src/mesh/NodeDB.cpp

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/modules/AdminModule.cpp

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* copilot garbage

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: thebentern

src/mesh/NodeDB.cpp

@@ -568,6 +568,11 @@ void NodeDB::installDefaultConfig(bool preserveKey = false)
         true; // FIXME: maybe false in the future, and setting region to enable it. (unset region forces it off)
     config.lora.override_duty_cycle = false;
     config.lora.config_ok_to_mqtt = false;
+#if HAS_LORA_FEM
+    config.lora.fem_lna_mode = meshtastic_Config_LoRaConfig_FEM_LNA_Mode_DISABLED;
+#else
+    config.lora.fem_lna_mode = meshtastic_Config_LoRaConfig_FEM_LNA_Mode_NOT_PRESENT;
+#endif
 
 #if HAS_TFT // For the devices that support MUI, default to that
     config.display.displaymode = meshtastic_Config_DisplayConfig_DisplayMode_COLOR;

src/mesh/SX126xInterface.cpp

@@ -58,6 +58,10 @@ template <typename T> bool SX126xInterface<T>::init()
 
 #if HAS_LORA_FEM
     loraFEMInterface.init();
+    // Apply saved FEM LNA mode from config
+    if (loraFEMInterface.isLnaCanControl()) {
+        loraFEMInterface.setLNAEnable(config.lora.fem_lna_mode == meshtastic_Config_LoRaConfig_FEM_LNA_Mode_ENABLED);
+    }
 #endif
 
 #ifdef RF95_FAN_EN

src/modules/AdminModule.cpp

@@ -795,6 +795,17 @@ void AdminModule::handleSetConfig(const meshtastic_Config &c)
         }
 #endif
         config.lora = validatedLora;
+
+#if HAS_LORA_FEM
+        // Apply FEM LNA mode from config (only meaningful on hardware that supports it)
+        if (loraFEMInterface.isLnaCanControl()) {
+            loraFEMInterface.setLNAEnable(config.lora.fem_lna_mode == meshtastic_Config_LoRaConfig_FEM_LNA_Mode_ENABLED);
+        } else if (config.lora.fem_lna_mode != meshtastic_Config_LoRaConfig_FEM_LNA_Mode_NOT_PRESENT) {
+            // Hardware FEM does not support LNA control; normalize stored config to match actual capability
+            LOG_WARN("FEM LNA mode configured but current FEM does not support LNA control; normalizing to NOT_PRESENT");
+            config.lora.fem_lna_mode = meshtastic_Config_LoRaConfig_FEM_LNA_Mode_NOT_PRESENT;
+        }
+#endif
         // If we're setting region for the first time, init the region and regenerate the keys
         if (isRegionUnset && config.lora.region > meshtastic_Config_LoRaConfig_RegionCode_UNSET) {
 #if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN || MESHTASTIC_EXCLUDE_PKI)