So far, the instantaneous bandwidth of conventional digital real-time spectrum analyzers is limited to a few GHz, a limitation set by the clock jitter of the analog-to-digital converters, and by the processing capabilities in real time of digital electronics. Here, we propose a simple analog architecture of RF spectrum analyzer based on photonic frequency-shifting loops. It utilizes only compact commercial telecom components, a single CW laser, and slow electronic resources (10 MSa/s). The probability of intercept is 100%, the instantaneous bandwidth reaches 16 GHz, and the spectral and temporal resolutions are respectively equal to 160 MHz and 50 μs.