Subelement A: — Topic :
Question 6A386
Element 6 (Radiotelegraph)The total bandwidth of a transmitter using A-2 emission with a modulating frequency of 800 Hz and acarrier frequency of 500 kHz is:
Explanation
A-2 emission is a type of Amplitude Modulation (AM) where a carrier is modulated by an audio tone, which is then keyed on and off (often for Morse code, known as "modulated CW" or ICW).
For standard AM, the total bandwidth occupied by the signal is approximately twice the highest modulating frequency. In this case, the modulating frequency is a single tone of 800 Hz.
Therefore, the total bandwidth = $2 \times \text{Modulating Frequency}$
Bandwidth = $2 \times 800 \text{ Hz} = 1600 \text{ Hz}$.
The carrier frequency of 500 kHz determines the signal's position in the radio spectrum, not its bandwidth.
Options C and D are incorrect because 800 kHz and 1000 kHz are vastly larger than the bandwidth generated by an 800 Hz modulating tone and are closer to the carrier frequency itself, not the bandwidth. Option B, 1.6 kHz, is numerically equivalent to 1600 Hz, but 1600 Hz is often presented directly in this context.
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