A radio receiver for the HF band covers the frequency range 2 MHz to 30 MHz.
The first IF frequency is 3.0 MHz and the local oscillator is above the received signal frequency.
a. The HF receiver is used to receive DSB-LC AM voice signals with an RF bandwidth of 8 kHz. The first IF frequency is too high for a narrow band pass filter with a bandwidth of 8 kHz, so a second down-conversion stage is employed with a second IF of 455 kHz. What are the two possible frequencies for the second local oscillator?