Question
What is the primary effect of extremely short rise or fall time on a CW signal?
Answer Options
- A) More difficult to copy
- B) The generation of RF harmonics
- C) The generation of key clicks
- D) More difficult to tune
Correct Answer: C
Explanation
When a Continuous Wave (CW) signal is generated, the amplifier must be rapidly switched on (rise time) and off (fall time). An abrupt, near-instantaneous switch results in a square-wave-like envelope which is rich in high-frequency sidebands that extend far beyond the necessary signal bandwidth.
This instantaneous switching (extremely short rise or fall time) is the primary cause of the undesirable effect known as the generation of key clicks. These key clicks appear as broadband splatter across adjacent frequencies, interfering with other users. To prevent key clicks, the keying waveform must be shaped to have a controlled, softer rise and fall time (shape factor).
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