User guide

802.11g ERP-OFDM
Identify 802.11g ERP-OFDM by looking for a flat top.
The flat top of OFDM signatures are under 20 MHz
wide.This is the same signature for 802.11a OFDM.
The second image is a more typical representation of
what ERP-OFDM looks like in the 2.4 GHz band.
802.11n 2.4 GHz 40-MHz ERP-OFDM
802.11n OFDM 802.11n APs with data rates of
300mbps use channel bonding, which appear as two
802.11g ERP-OFDM signatures bonded together.
Notice how the 40 MHz wide 802.11n access point
goes beyond Wi-Fi Channel 6? There is not enough
room in the 2.4 GHz public ISM band for two co-
located 802.11n access points using channel bonding.
802.11n does not imply that the width of the AP
transmitter will always be 40 MHz. In most cases, 40
MHz transmissions appear in bursts when an APs
throughput exceeds the capabilities of 802.11g ERP-
OFDM.
You can see the bursts in the waterfall view very
easily. 802.11a/g/n typically shows abrupt edges, due
to the dBm drop on each side of the signatures.
Adjacent Channel Interference
Your Wi-Fi may be on the same channel as other
wireless APs. There are 11 channels in 2.4 GHz, but
only three that don’t overlap (1, 6 and 11 in the U.S.).
Page: 16 - Chanalyzer Pro 1.0.12.0407