Which of the following frequencies will cause an image response when mixed with a 14.255 MHz signal in a mixer with a 13.8 MHz VFO?

To understand why mixing a 14.255 MHz signal with a 13.8 MHz VFO (Variable Frequency Oscillator) produces an image response at 13.345 MHz, it’s essential to grasp the concept of mixing and how image frequencies work.

In a mixer, two signals are combined to produce new frequencies, specifically the sum and the difference of the original frequencies. The difference frequency is usually the one we want to receive, while the sum can lead to an undesired image response.

Here, when a 14.255 MHz signal is mixed with the 13.8 MHz VFO, the result yields two key frequencies: the sum (14.255 + 13.8 MHz = 28.055 MHz) and the difference (14.255 - 13.8 MHz = 0.455 MHz). Therefore, the difference of 0.455 MHz is the intended output frequency from the mixing process.

Now, regarding image frequencies, they are frequencies that can also mix with the oscillator frequency to produce the same difference frequency. The image frequency can be calculated as follows:

Image frequency = VFO frequency + difference frequency.

In this case, substituting in the values gives us:

Image frequency = 13.