Item
Correct Answer and Feedback
8.
A.
1 MHz
SID causes total absorption of all frequencies above about 1 MHz. (page 3-10,
para 2e(2)(b))
9.
B.
The critical frequency
For any given time, each ionospheric layer has a maximum frequency at which
radio waves can be transmitted vertically and refracted back to Earth. This
frequency is called the critical frequency. (page 3-4, para 1d(2))
3-15
SS0130
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