Filter measurements with RF noise source

I got my BG7TBL RF noise source to make some RF measurements. To make those measurements, I needed some instructions how to make them. I first started with filter measurements because I could make them with the devices I have. Two good tutorials for doing measurement are Measuring Filters and VSWR With RTL-SDR and RTL-SDR Tutorial: Measuring filter characteristics and antenna VSWR with an RTL-SDR and noise source. There are also useful video tutorials:

KF5OBS #33: Filter Measurement using Noise Source

Using the BG7TBL Noise Source to Characterize a HF Filter

Now to practical testing. In addition to noise source the other tools I used were RTL-SDR compatible USB DVB-T stick and Spektrum RTL-SDR Spectrum Analyzer Software. Spektrum software with my RTL-SDR stick gave quite nice results, even though RTL SDR Dongles have somewhat anomalous frequency domain response.

Testing results (measured about 170 MHz band pass filter, cheap surplus I do not have data for)


End verdict is that measurement works acceptably. Doing measurements on wide frequency range is quite slow (take tens of seconds for one scan) and there is quite limited dynamics compared to expensive commercial measurement tools like vector network analyzer or spectrum analyzer with tracking generator.

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