No, MAX2771 cannot simultaneously receive L1 and L5 signals. There is only one synthesizer in the IC, so only one Local Oscillator frequency can be generated at any given time to down-convert either L1 or L5 frequency.
MAX2771
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The MAX2771 is a next-generation Global Navigation Satellite System (GNSS) receiver covering E5/L5, L2, E6, E1/L1 bands and GPS, GLONASS, Galileo, QZSS...
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MAX2771 on Analog.com
No, MAX2771 cannot simultaneously receive L1 and L5 signals. There is only one synthesizer in the IC, so only one Local Oscillator frequency can be generated at any given time to down-convert either L1 or L5 frequency.