2 – Wireless Regulatory Domains

It is very important to understand the laws of your country, if you go outside of the legal power levels you can get into trouble so don’t do it!

In a terminal window type the following

tail -f -n 0 /var/log/messages

Now to check your card type quickly and simply just unplug the card and plug it back in and you should see some output like below:

1 - Unplug and checkYou can see plenty of information about your card here.

To set a regulatory domain on the card for example let’s say Ireland run:

iw reg set IE

2 - Setting regulatory domain

In the previous window where we left tail running on /var/log/messages you will see the following output showing you the card regulatory configuration has changed:

3 - Country code changed IEIf you try to set certain channels they may fail as they are used by different country’s, this is also the same for the power levels on the card itself and what you are aloud to operate at. An example of this is that I can set my card to a txpower of 20 Decibel-milliwatts (dBm) here in Ireland but if you were in the US you can set to 27 dBM and in Bolivia you can set 30 dBm. These power levels may be illegal and you cannot operate at these levels without a license.

Converting your dBm to milliwatts can be done with the following calculations

The power conversion of dBm to mW is given by the formula:
P(mW) = 1mW · 10(P(dBm)/ 10)

Which means:
1dBm = 1.258925mW

Now to calculate 20 dBm

P(mW) = 1mW · 10(20dBm/ 10) = 100mW

27 dBm

P(mW) = 1mW · 10(27dBm/ 10) = 501.18mW

30 dBm

P(mW) = 1mW · 10(30dBm/ 10) = 1000mW

You can see the difference in the above conversions is quite significant.


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