A superheterodyne receiver has an intermediate frequency (IF) of 455 kHz. The local oscillator runs above the operating frequency. To which frequency should it be tuned to receive a signal on 3.54 MHz?

In a superheterodyne receiver, the local oscillator (LO) mixes with the incoming radio frequency (RF) to produce a fixed intermediate frequency (IF). The formula used depends on whether the LO is tuned above or below the operating frequency. Since the problem states the local oscillator runs above the operating frequency, we must add the IF to the desired receive frequency. First, convert the IF to MHz: 455 kHz is 0.455 MHz. Next, add this to the receive signal frequency: 3.54 MHz + 0.455 MHz = 3.995 MHz. If the LO ran below the signal frequency, you would subtract 0.455 MHz instead.