Hi fnaumann,
The point is to be careful, my spectrum analyzer has a limit of 100mW at its input.
If you put a pickup antenna next to a mobile phone, you can get over this limit.
The phone transmits not only when you make a call, it does this just when it feels like it. :-)
But don't get paranoid, it's all about being careful with your measuring equipment.
The 10 0f 20dB attenuator at the input you start with during a measurement session normally makes the SA indestructible.
( if you ar not doin measurement on tranmitters!)
The field of an antenna connected to a transmitter decreases quadratically with distance.
So if the distance to a phone is 4-meters, and you double this to 8 meters, then only 1/4 is left.
The manufacturers of this kind of measuring equipment have to perform tricks to get a good noise number, good distortion value and then also have a "decent protected" input, it is not easy.
Greetings,
Bram