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Figure 29.
4. Figure 29 indicates a very good installation with a minimal noise environment. 100 scans were collected
(2.7 hours of data) and a few interesting observations can be made.
a. First there are three evenly spaced "blue" peaks at the aforementioned channels 24/25, 125 and 226. As
noted above these happen to be "self noise" caused by the harmonic of an internal clock and are expected to
be present on all installations, but they are a good example of how CW or continuous wave interference will
appear on a multiple scan plot.
b. Second, during this nearly three hour scan, no dynamic activity was seen in the lower portion of the
Iridium band. This lower portion of the Iridium band is shared spectrum that we avoid using during normal
operation. There are times during natural disasters when the lower portion of the band is active, however,
so your plot may differ. Dynamic activity is defined as a red peak in excess of -115 dBm while the mean value
remains close to the -123 dBm receiver noise floor on a multi scan plot.
c. Finally, as seen in Figure 30, channel 60 through 251 show a lot of dynamic activity with the peak indication
showing considerably large signals while the mean values hover near -123 dBm. This display is just showing
a 2.7 hour history of active channels the ODU could see and could have used.
Figure 30.
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Iridium Pilot Land Station Installation Guide
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