A receiver (Rx) analog frontend (AFE) for wireless sensor nodes is investigated and presented, whose dc power consumption is significantly lower than the state-of-the-art. The incoming radio frequency (RF) signal is amplified and filtered passively using an off-the-shelf surface acoustic wave (SAW) resonator. A small active circuit integrated in GlobalFoundries 22 nm fully depleted silicon on insulator (FD-SOI) technology provides gain required for oscillation, leading to a switched injection-triggered oscillator (SITO), and performs energy detection and sampling. On-off keying (OOK) modulated signals in the public 434 MHz band can be received with a bit rate of up to 66 kbps (measured). The AFE is supplied from 0.3 V and 0.8 V and is bit-level duty-cycled. The measured AFE performance is: input sensitivity (bit error rate (BER) ≤ 1E-3) of - 94 dBm and input 3 dB bandwidth of 133 kHz at a dc power consumption of 2.8 pJ per bit, corresponding to 28 nW at 10 kbps bit rate.