Which signal is produced when the MSSR receiver mixes the 1090 MHz with the local oscillator from the receiver interface?

Which signal is produced when the MSSR receiver mixes the 1090 MHz with the local oscillator from the receiver interface?

• A. 60 Hz
• B. 60 MHz
• C. 1090 MHz
• D. 6 MHz

Answer: (B)

In a superheterodyne receiver like the MSSR receiver, mixing the incoming RF signal with the local oscillator creates two new frequencies: the sum and the difference. The system is designed to downconvert the 1090 MHz transponder signal to a specific intermediate frequency that the rest of the receiver can process. If the local oscillator is set so that the difference between the RF and LO is 60 MHz, then the downconverted signal that the receiver uses is 60 MHz. The mixer also produces a sum frequency at 2120 MHz, but that is filtered out or ignored in normal operation. Therefore the signal produced by the mixing process, the one the receiver uses for further processing, is 60 MHz.

In a superheterodyne receiver like the MSSR receiver, mixing the incoming RF signal with the local oscillator creates two new frequencies: the sum and the difference. The system is designed to downconvert the 1090 MHz transponder signal to a specific intermediate frequency that the rest of the receiver can process. If the local oscillator is set so that the difference between the RF and LO is 60 MHz, then the downconverted signal that the receiver uses is 60 MHz. The mixer also produces a sum frequency at 2120 MHz, but that is filtered out or ignored in normal operation. Therefore the signal produced by the mixing process, the one the receiver uses for further processing, is 60 MHz.