Can I set Tx power too high?

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Problem :

I have a high power WiFi card (AWUS036NH) which is capable of tx powers as high as 33 dB.
Recently I’ve, ehm, accidentally, changed the corresponding regulatory domain to allow up to 40 dB.

Now when I bring the interface up, iwconfig claims that tx power is 40 dB which is impossible.

So my question is this: What is the real tx power when it says 40 dB? Does it actually try to transmit at 40 dB or does it go to max (33 dB) power? Or does it module the power (in this case by 34 resulting in 6 dB) or something completely else?

And most importantly: Can this damage the card?

Obviously I could set the regulatory domain to max of 33 dB and fix this but I have other wireless cards with lower output (namely AWUS036H and TL-WN722N) which also go to the max power allowed by the regulatory domain.

And if this is an issue, how do I fix it? I’ve tried adding up iwconfig wlan0 txpower 33 or wireless-txpower 33 to /etc/network/interfaces in the wlan0 section but the interface still starts at 40 dB.

Solution :

Any changes to force the hardware to operate upper than the normal levels can damage or at less reduce the hardware’s time life.

One good question is if the OS is really setting AND recognizing the tx power according the configresults.

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