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10 AirPcap User’s Guide
Settings
The AirPcap N adapter
Is Selected.
Extension Channel
Drop-down List for
AirPcap N
The AirPcap N adapter
Is Selected.
Extension Channel
Drop-down List for
AirPcap N
Figure 2: AirPcap N and Extension ChannelSetting
The Basic Configuration box contains the following settings:
• Channel: The channels available in the Channel list box depend upon
the selected adapter. Since channel numbers 1, …, 14 in the 2.4GHz
and 5GHz bands overlap and there are center frequncies (channels)
that do not have channels numbers, each available channel is given by
its center frequency. Where applicable, the BG or A channel numbers
are also given. All of the channel center-frequencies supported by the
selected adapter will be made available in the Channel list. The
bandwidth of each channel is 20MHz.
• Extension Channel: For 802.11n adapters, one can use the Extension
Channel list create a “wide” channel. The choices are -1 (the
preceding 20MHz frequency band), 0 (no extension channel), or +1
(the succeeding 20MHz frequency band). The channel of the
additional frequency band is called the extension channel. The
Extension Channel list box lets you choose a valid extension channel
(above or below) for a given channel (See Figure 2). Not all channels
have above and below extension channels. For example, BG channels
1, 2, 3, and 4 do not have a -1 (below) extension channel. The reason
is that the center frequencies of the primay and extension channels
need to be separated by 20MHz. So if 4 were the primary channel,
channel 1 (which is the lowest BG center frequency) is only 15 MHz
below channel 4.
• Capture Type: 802.11 frames only, 802.11 frames plus radio
information (See
Radiotap), or 802.11 frames plus the Per-Packet
Information (PPI) header (See Downloads for the current PPI