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by fsh 1599 days ago
Noise figure is a property of receivers, not sources. Signal generators don't have noise figures.

The MAX2870 synthesizer chip used in the project has pretty good phase noise specifications. I don't see any broadband noise above the background in the SDR trace shown in the article. The second harmonic is more than 30 dB down which is not bad at all. The only thing not looking that great is the spur close to 400 MHz.
1 comments
hughrr 1599 days ago
The noise floor of the measurement receiver is terrible though so you really don’t know what the true performance is here.
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fsh 1599 days ago
I don't see a resolution bandwidth in the plot. How do you judge the noise floor without that?
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hughrr 1599 days ago
RBW is fixed at 1.75MHz on the HackRF. But it's the measurement setup as a whole (that is the measurement receiver). The noise floor of this measurement is represented by the visible noise floor at -70dBm. That's a combination of a number of factors. Plus the HackRF has poor dynamic range and only 8 bits sampling which is quite terrible.
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