diff --git a/libraries/Desktop/support/sitl.cpp b/libraries/Desktop/support/sitl.cpp
index 8e4d35c904..e2207ac1bb 100644
--- a/libraries/Desktop/support/sitl.cpp
+++ b/libraries/Desktop/support/sitl.cpp
@@ -157,8 +157,11 @@ static void sitl_fdm_input(void)
 
 }
 
+// used for noise generation in the ADC code
+bool sitl_motor_running = false;
+
 /*
-  send RC outputs to simulator for a quadcopter
+  send RC outputs to simulator
  */
 static void sitl_simulator_output(void)
 {
@@ -192,6 +195,10 @@ static void sitl_simulator_output(void)
 		// the registers are 2x the PWM value
 		pwm[i] = (*reg[i])/2;
 	}
+
+	// use pwm3 as a proxy for if the motor is running
+	sitl_motor_running = (pwm[2]>1200);
+
 	sendto(sitl_fd, (void*)pwm, sizeof(pwm), MSG_DONTWAIT, (const sockaddr *)&rcout_addr, sizeof(rcout_addr));
 }
 
diff --git a/libraries/Desktop/support/sitl_adc.h b/libraries/Desktop/support/sitl_adc.h
index a467a20b7f..95ee7038f5 100644
--- a/libraries/Desktop/support/sitl_adc.h
+++ b/libraries/Desktop/support/sitl_adc.h
@@ -8,10 +8,14 @@
 
 #include <stdlib.h>
 
-#define NOISE_BITS 4
+#define NOISE_BITS 8
 
 static inline float noise_generator(void)
 {
+	extern bool sitl_motor_running;
+	if (!sitl_motor_running) {
+		return 0;
+	}
 	float noise = ((unsigned)random()) & ((1<<NOISE_BITS)-1);
 	noise -= 0.5*(1<<NOISE_BITS);
 	return noise;