# Forum

## eirp density

• I have been looking through the European regulations on frequency allocations, and have come across this statement:

Use of the frequency band 2400 ?¡é?€?¡° 2483.5 MHz is authorised for data transmission in
accordance with the frequency use defined in the standard EN 300 328. Maximum
permitted radiated power is 100 mW e.i.r.p. For broadband modulation techniques other
than FHSS, maximum permitted e.i.r.p density is 10 mW/MHz.

What is e.i.r.p density, as it seems to apply to OFDM modulation schemes? I assume in some way it converts to 100mW, but I can't figure out how.

• I don't have the v4 CWNA study guide...but I'm sure this is in the glossary somewhere... Just look up EIRP or Equivalent Isotropically Radiated Power. In short - this is the max "Power" radio transmission that can leave the antenna when adding the radio power, loss from cable (if any), gain that comes with amplifiers, etc. No matter how you chop it, the max you are allowed is 100mW. I'm sure the abbreviation here is simply just the way the document was written.

As a side note...keep in mind the country for each of these calculations. It can be quite easy to mix up which is which if you spend too much time digging through them all. Having said that, I'm pretty sure the CWNA exam is based off the U.S. standards and the FCC rules. However since it seems you from Italy, you'll have to familiarize yourself with the rules and regulations there when needed in the real world.

• Hi,

I believe that you will find that there are actually two limits that are in use, you have a total limit of 100mW which is a maximum. The EIRP density really applies if you have a smaller bandwidth so if you are using a 5MHz Signal you are limited to a strength of 50MHz by EIRP density, if you have a 20MHz signal the EIRP density would allow a strength of 200mW - but the 100mW total limit would kick in and so your signal would be limited to 100mW.

Does that help?

• Brett C. Escribi?3:

Having said that, I'm pretty sure the CWNA exam is based off the U.S. standards and the FCC rules. However since it seems you from Italy, you'll have to familiarize yourself with the rules and regulations there when needed in the real world.

The CWNA exam no longer has any region specific information on the test.

GT

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