what is the output power in rf(dbm) for wireless?

superminis2007 · #1 (**permalink**) 08-25-2006, 09:33 AM

Please specify the dBm(power outup) of each of the wireless standard shown at below:
1.IEEE 802.11a
2.IEEE 802.11b
3.IEEE 802.11g
4.IEEE 802.11n

*Please explain the formula of getting the dBm, if you know.
Thank you!!

NZLamb · #2 (**permalink**) 08-26-2006, 01:10 AM

The RF power varies between manufacturers and is typically 13-20 dBm (approx. 20-100 mW). Some high power cards are capable of supplying up to 26dBm (about 400mW). As far as I know the output power is not specified in the IEEE 802.11 standards.

Countries around the world also have different restrictions on maximum radiated power on the wireless bands so this is always worth checking with your local regulatory body. For example in NZ the maximum EIRP at 2.4 GHz (802.11b/g) is 4W.

Most manufacturers publish the maximum output power and receive sensitivity of their products in the specification sheets so this is a good place to look if you are after details on equipment you own or intend to use.

The forumlas for calulating between dBm and milliwatts are shown below. Remember that 0dBm is equal to 1mW. Sorry about the crappy formatting, the forum doesn't seem to support subscript.

Milliwatts to dBm

dBm = (10Log10(mW))

dBm to milliwatts

mW = 10(dBm/10)

superminis2007 · #3 (**permalink**) 08-26-2006, 01:55 AM

Let's say wireless specification is not stated, may i know how to get the wireless ouput power(rf) of certain wireless device, if i only know the input and output power?

Input: 100-200VAC, 50/60Hz, 0.5A
Output: 5VDC, 2A

*I would very appreciate it if formula provided.

dan · #4 (**permalink**) 08-26-2006, 10:03 PM

ah no not likely, DC/AC supply power has nothing to do with RF power.
what brand of gear is it? what band does it operate in?

superminis2007 · #5 (**permalink**) 08-28-2006, 02:07 AM

Actually the product that i refer to is IP camera. No wireless detail provides. What i know is it is running 802.11g. As far as concern, we can calculate the power output(dbm) of wirelessa antenna as long as we know the watt and ampehere.

NZLamb · #6 (**permalink**) 08-28-2006, 06:42 AM

If in doubt a safe bet is 15dBm (just over 30mW) as this is a very common figure for standard 2.4GHz wireless devices.

As Dan stated it is impossible to calculate the output soley based on the power supply; it has no bearing on the RF output of the device at all. The only way of finding the output power if it is not published is to connect an RF power meter or spetrum analyser to the antenna connector.