diff --git a/Usage-cautions.md b/Usage-cautions.md
index 332276f..5bd2a35 100644
--- a/Usage-cautions.md
+++ b/Usage-cautions.md
@@ -6,4 +6,8 @@ The LNA of HackRF is extremely sensitive, thus you need to notice the following
 # Monitoring range
 - The LNA of hackrf is physically between SMA port and radio front end
 - Thus, you shouldn't receive near high power transmitters, even if it's not in the range that you are monitoring.
-- For example: You are receiving FM radio at 100.00MHz, and there's a high power transmitter at 2.5GHz around you, the transmitter will still blow your LNA, if you set LNA/AMP too high and/or too near the transmitters,  even if 2.5GHz is not in the freq range that you are monitoring.
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+- For example: You are receiving FM radio at 100.00MHz, and there's a high power transmitter at 2.5GHz around you, the transmitter will still blow your LNA, if you set LNA/AMP too high and/or too near the transmitters,  even if 2.5GHz is not in the freq range that you are monitoring.
+
+# I suspect I damaged the LNA, how do i check?
+- Try listen local radio. Try with AMP on and off both. 
+- Try replay a **non**-rolling code <sub>(to prevent break the rolling sync)</sub> fob. Try with AMP on and off both. 
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