Question
Why is it not legal to transmit a 3 kHz bandwidth USB signal with a carrier frequency of 14.348 MHz?
Answer Options
- A) USB is not used on 20-meter phone
- B) The lower 1 kHz of the signal is outside the 20-meter band
- C) 14.348 MHz is outside the 20-meter band
- D) The upper 1 kHz of the signal is outside the 20-meter band
Correct Answer: D
Explanation
This question tests your understanding of amateur band limits and emission bandwidth. The 20-meter amateur band extends up to 14.350 MHz. Upper Sideband (USB) transmissions create a signal whose bandwidth is primarily above the carrier frequency. For a 3 kHz wide USB signal centered on a 14.348 MHz carrier, the signal occupies the frequency range from 14.348 MHz up to 14.348 MHz + 3 kHz, which is 14.351 MHz.
Since the maximum frequency limit for the 20-meter band is 14.350 MHz, the upper 1 kHz (14.350 MHz to 14.351 MHz) of the signal would extend beyond the legal band edge. Therefore, transmitting this signal is a violation of the amateur service rules. This highlights the importance of setting your transmitter’s carrier frequency far enough below the band edge to ensure your entire signal remains within the legal frequency privileges, especially with sideband modes.
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