RTL SDR Dongles: Anomalous Frequency Domain Response

I have been experimenting with a cheap-and-cheerful SDR receiver containing an R802T2 front end and RTL2832U demodulator. My ultimate aim is to make a low-cost network and spectrum analyser, but before that it is necessary to understand the receiver’s strengths and limitations.

In an ideal world the receiver’s power-vs-frequency response would be flat, but inevitably that won’t be the case with such a low-cost device: it will need calibration. That calibration has revealed some strange quirks in the R802T2 RF front end frequency response, discussed below. While the anomalies don’t kill the idea of using the SDR dongle as a spectrum/network analyser, I would feel happier if their cause (and preferably cure) was understood.

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