diff --git a/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/defaults.parm b/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/defaults.parm
index 8ff4570cbf..d5fa305db6 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/defaults.parm
+++ b/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/defaults.parm
@@ -1,3 +1,5 @@
 # setup for LEDs on chan9
 SERVO9_FUNCTION 120
 NTF_LED_TYPES 257
+# Default VTX power to on
+RELAY_DEFAULT 1
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef-bl.dat b/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef-bl.dat
index 1516669eea..201ffc4df0 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef-bl.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef-bl.dat
@@ -36,6 +36,8 @@ define HAL_LED_ON 1
 # default to all pins low to avoid ESD issues
 DEFAULTGPIO OUTPUT LOW PULLDOWN
 
+PC5 VTX_PWR OUTPUT HIGH
+
 # Add CS pins to ensure they are high in bootloader
 PA15 FLASH_CS CS
 PB12 MAX7456_CS CS
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef.dat
index af7cea3919..104343420c 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/MambaH743v4/hwdef.dat
@@ -146,6 +146,10 @@ PB1  TIM3_CH4 TIM3 PWM(6) GPIO(55)
 PC8  TIM8_CH3 TIM8 PWM(7) GPIO(56) BIDIR
 PC9  TIM8_CH4 TIM8 PWM(8) GPIO(57)
 
+# VTX Power control - should be high at startup to ensure power
+PC5 VTX_PWR OUTPUT HIGH GPIO(81)
+define RELAY2_PIN_DEFAULT 81
+
 # Motor order implies Betaflight/X for standard ESCs
 define HAL_FRAME_TYPE_DEFAULT 12