User guide

68 Chapter 6: Analyzing Spectrum Data
AirMagnet Spectrum XT User Guide
Figure 6-6: Spectrum Density graph
Viewing AP Signal Strengths Across Frequency Range
You can also display the signal strengths of APs selected from the AP List by SSID/Channel
on the left-hand side of the screen. The signal strengths of the selected APs appear in the form
of curves across the corresponding frequency range used by the APs. Notice that the selected
APs and their signal strength readings are color-coded with matching colors for easy
identification. See Figure 6-7.
Figure 6-7: Showing AP signal strength in Spectrum Density graph
The AP signal strength curves are based on WiFi data captured by the wireless network
adapter in use and may not completely match the spectrum plot. As shown in Figure 6-7, AP
signal strengths as represented by the colored curves appear higher than the maximum signal
strength shown in the Spectrum Density graph. This is because AP signal strengths (and the
curve representing them) are based on RSSI data captured by the external wireless network
adapter. While RSSI is usually calculated over a packet or averaged over multiple packets, RF
power as measured by the spectrum analysis engine includes packets and background noise,
plus RF silence in between the packets. For this reason, it is no surprise that the RSSI value
(the AP curve in this case) differs from the peak of the spectrum graph for the same AP.
Configuring Spectrum Density Plot Parameters
You can set or change the settings of the Spectrum Density graph the same way as you do
with the Real Time FFT graph.