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Appendix G – Site Survey Tool (SST)
The Site Survey Tool will display three graphs:
a. The main scan graph (large rectangle in the lower half of the display) indicates the activity of each
frequency channel in three ways. The bar in light blue is the mean energy of all 7 antennae and may have
multiple scans of data averaged together. The red bar indicates the peak energy discovered at any one of the
7 antennae and could represent the peak of the current scan or previous scan depending on the "window
size selected (the default is 10). Lastly there is a black bar that indicates the red peak is historical or recently
active. Normally the "Mean" RSSI (receive signal strength indication) will be -123 dBm across the channel
band.
b. The smaller rectangular antenna display in the upper center of the GUI shows the activity on each of the
7 antennae for a single channel. The channel of interest is highlighted by moussing over the channel of
interest on the main display and left clicking to select the channel. A yellow highlight box is drawn around
the channel of interest and the text in the upper right of the screen will display "Selected Channel: XXX (NN
Scans)" If the user has selected more than 1 scan and the application has had enough time to collect more
than one scan, then the display will indicate the following: Light blue shows the "mean" RSSI value for each
antenna over the completed number of scans; the red show the peak value obtained over the specified
number of scans; and finally the black bar shows the value of the current scan.
c. The hexagonal direction display in the upper left corner of the GUI displays a top view of the ODU antenna
array. The ground lug on the ODU aligns with the aft direction of the install. When a channel is selected in
the main display the red and blue spots provide an approximate direction back to the source of the detected
signal. This direction plot is based on a calculation of relative signal strengths of the 7 antennas.
In Figure 27 a single scan has completed in a nearly noise free environment. Channel 130 has been selected in
the main display and both the "Mean" and "peak" maxima are seen on antenna 2 with slightly lesser amounts
detected on antennas 1 and 3 while all the other antennae stay near the -123 dBm noise floor of the receiver.
The direction display shows the probable direction of the detected signal. Since the display shows only a few
discrete active channels, the signals are known to be in-band and are most likely real Iridium down links.
Figure 27.
Reading the SST Graphs
The SST output can tell the installer much about the potential RF environment of the ODU's location during
the test. It should also be noted that two or three scans will add to the knowledge about the RF environment
58
Iridium Pilot Land Station Installation Guide
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