The transient voltage will destroy the input mixer stage if the spectrum analyzer, which will typically allow 30dBm (1W) or 136dBuV over 50 Ohm.
So the limiter is always required, but often not built-in. If you use a LISN without a built-in limiter, you may easily forget the limiter and damage the spectrum analyzer.
Note: The limiter can only work when combined with an attenuator. The our LISN’s use 10dB attenuation, which must be compensated for on your spectrum analyzer graph.
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