What frequency range is occupied by a 3 kHz LSB signal when the displayed carrier frequency is set to 7.178 MHz?
A. 7.178 to 7.181 MHz
B. 7.178 to 7.184 MHz
C. 7.175 to 7.178 MHz
D. 7.1765 to 7.1795 MHz
LSB, or Lower Side Band, is a transmission mode where all of the transmitted signal exists to the “left” or on the “lower side” of the center or dial frequency. The image above shows a signal with both sidebands. The “lower” is on the “left” and that’s a good way to remember it if it gives you trouble.
If the center frequency is at 7.178 MHz, and its 3 kHz wide (a typical LSB signal) then the signal exists C. from 7.175 to 7.178 MHz. We simply took the 3 kHz and converted it to MHz, which is .003 MHz, and subtracted that from the center frequency.