• Is there a forum dedicated to wireless hardware?
• What is WEP and should I use it?
• What is the relationship between dBm and milliwatts

Wireless Networking Forum

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by graffixx
last modified: 2003-08-29 17:50:42

WEP, or Wired Equivalent Privacy, is used to secure your Wireless Network in a fashion similar to a regular Ethernet Network by Encrypting all data sent across the Wireless Network. If your Network or Access Point supports it, you should enable it to keep prying eyes off your data and network. Most Access Points support 48-bit (also referred to as 64-bit) encryption, while some support the more advanced 128-bit Encryption.

NOTE:
Be aware that using WEP on your Wireless Network can have a minor performance/throughput hit negatively, but is usually small and worth the added Security.

For information on how to enable WEP (or to find out if your Access Point supports it), visit your Equipment Manufacturers Website or visit any of the following links:

Webopedia.
Wireless-computer-networking

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by chrisf8657 edited by graffixx
last modified: 2003-01-12 14:42:46

A: The units of dBm and milliwatts are used quite a bit in communications and wireless. Both are units of RF power. There seems to be a lot of confusion between the two. Watts (or milliwatts) is a linear unit, while dBm is a logarithmic unit. Confusing the two can really make for interesting results. Recently, a WRT54G wireless router was described as outputting 84 dBm. Obviously, mW was the desired term, since 84 dBm equals 250 Kilowatts! One should really avoid being anywhere near a 250KW RF transmitter! Here is simple description of the two terms.

0 dBm in the RF world is arbitrarily defined as 1 mW of power (.001W). From this, we get:

dBm = 10 * log(mW) (Note: power is in mW, not Watts!)
mW = 10 ^ (dBm/10)

Both of these can easily be calculated using the Windows Calculator in Scientific mode. Or, for the lazy, try this site: »www.aerialix.com/calculators/dbm···ion.html

Here is a simple cross reference, including some commonly found values for wireless, and all 1 dB increments from 20 to 30 dBm. Remember, for all practical purposes, every 3 dB is a doubling/halving of power, and every 10 dB is an order of magnitude difference.

-10 dBm = 0.1 mW
0 dBm = 1.0 mW
10 dBm = 10 mW
17 dBm = 50 mW
19 dBm = 79 mW

20 dBm = 100 mW
21 dBm = 125 mW
22 dBm = 158 mW
23 dBm = 200 mW
24 dBm = 250 mW
25 dBm = 316 mW
26 dBm = 400 mW
27 dBm = 500 mW
28 dBm = 631 mW
29 dBm = 794 mw

30 dBm = 1 Watt
40 dBm = 10 Watts
50 dBm = 100 Watts
60 dBm = 1000 Watts ...etc.

Some of the above numbers are approximated for clarity; 26 dBm actually equals 398.107 mW.

Hint: to quickly find some other unlisted value, say 12 dBm, look up the wattage for 22 dBm and divide by 10 (pwr = 15.8mw). Likewise, for 32 dBm, one would multiply the wattage by 10 (pwr = 1.58W).

Use the term "dBm" when referring to any absolute power level; never just "dB." e.g. "This router has 23 dBm of output power."

The phase, "This outputs 25 dB" is technically meaningless, although most will interpret this to mean 25 dBm.

The term "dB" is a relative term only; such as, "This router has 5 dB more output power than that Access Point." This is somewhat analogous to percent, where one does not say, ”This sweater cost me 70%”, but you can say, “I saved 70% on this sweater.”

Let's keep those terminators straight!

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by caesarv edited by SYNACK
last modified: 2005-09-06 17:28:47