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Comment by jenowigner | Hacker News Reader

amazing project ! well done ! inspiring to see it this morning the youtube algo recommended it for me. I was thinking what would be a budget way of creating this ? maybe a $20 SDR instead of the hack rf , seems to be a waste of the hack rf to use it as a lamp :)) I think the way you did must have cost you over $1k. Thanks for the inspiration !

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Hackrf is defo overkill for this. I got it cause my initial plan was to cover the whole spectrum

You could probably do it with a cheaper SDR, but it would be slower

Total budget for this is around $1k

IIRC, a regular SDR dongle will not be able to process the full bandwidth of GHZ range.

I do think most people implementing something like this, especially in the exact way this one was implemented would really just be interested in the Wi-Fi ranges.

When I was doing wireless stuff we'd show customers the output of RF analysers to show that even with their wifi turned off their spectrum was packed full of noise.

Having a large viceral display of this would quickly enlighten them.

The $5 nrf52840 should be sufficient, it can scan 114 channels (from 2400-2514 MHz) several times per second, measuring the approximate RSSI.

You could not use that as an SDR to make a waterfall which is required in this case

You do not need a full SDR to make a waterfall. The nrf52840 can function as a coarse spectrum analyzer, because it lets you tune to any frequency within its range, and then measure the approximate received signal strength over a period of time[0]. I have tested this myself, and it works pretty well. The only downside compared to an SDR is that it can only listen to one frequency at a time, so it will sometimes miss short signals.

[0] https://docs.nordicsemi.com/bundle/ps_nrf52840/page/radio.ht...

I know it can switch frequencies, but I predict it wouldn’t make a very pleasing visualization if the updates are slow, but maybe you are right it would look fine for this implementation which is already far off from a waterfall

HackRF isn't a good SDR by any metric except for the date it came out.

What would a better alternative be?

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