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Comment by jcims | Hacker News Reader

Anyone in here have a LimeSDR? They look great on paper but I get a sense from what I’ve read that they can be a bit finicky to run.

Also I’m curious about the 1-bit recording. Is that a thing?

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1-bit recording is in fact a common thing for very noisy signals. You're actually aggressively over-sampling and using correlations over many samples (in time) to get the signal out from under the noise. I've only glanced over it, but this looks like a fun related article, but driving the opposite way (oversampling to get more effective bits) https://thecavepearlproject.org/2017/02/27/enhancing-arduino...

Fantastic article! I think i might be able to put this to use with a load cell project to ge a little more precision out if it.

Thanks! There is a lot on the site, I really liked:

https://thecavepearlproject.org/2015/01/29/a-simple-diy-unde...

> Also I’m curious about the 1-bit recording. Is that a thing?

Yes. This homemade GPS receiver uses a simple comparator (1 bit) to sample the signal (after amplification to get the noise floor over the decision threshold).

http://www.aholme.co.uk/GPS/Main.htm

> Also I’m curious about the 1-bit recording. Is that a thing?

I'm no expert, but sounds like what you'd do with sigma delta modulation[1]. Basically you use a 1-bit ADC (a simple threshold comparator), but sample at a rate much above the Nyquist rate. The idea is that for a given value of the source signal, the noise inherit in the recorded signal will make some samples register as 0 while others 1.

You then basically average samples to extract the signal you're after.

[1]: https://en.wikipedia.org/wiki/Delta-sigma_modulation#Oversam...

I have had access to a limesdr, bladerf, etc. They are finicky. They're great tools, but it took me a long time to go from toy examples to doing useful things with them.

Any suggestions for where to get started? I've had one sitting for a long while as I had some ideas but I've never done anything

Putting together a gnuradio pipeline to play radio stations or whatever signals you can find is rewarding. Especially when you can get the waterfall spectrogram working

I didn't do anything useful before I had to for work, and it took 10x as long as it should have. I'd suggest just taking some known working examples for fm radio, garage door openers, etc and working through them. It'll be painful, but with enough time and effort it'll happen. And it's sort of like makefile debugging-- the first ten times you have to do it it's excruciating, but after that it turns into just another task you know how to do.

https://greatscottgadgets.com/sdr/

I really second that set of articles. Great introduction.

FWIW there are frontend plugins for LimeSDR that will let it work with SDR# and other standard listening applications. Gnuradio can be extremely frustrating for just basic tinkering.

The software documentation for people new to it is awful. The hardware is probably great, but I've had such a hard time with mine.

It's not newbie friendly at all, and the people in HAM and SDRs don't know how to teach. It's all jargon that they never define or things just like "Oh do XYZ in this software" and that's an entirely non-obvious thing that's entirely undocumented with no tutorials.

A lot of SDR stuff is like you're a person wanting to drive to the store to get some ice cream so you can eat the ice cream. So they give you the blueprints.. to an auto factory. So you can build an auto factory. Which will then build a car. Which you can THEN drive to the store.

Hope there's still ice cream left by the time you get there.

If there's a silver lining, you do learn a lot whether you planned to or not (mostly about how much more other people know than you do).

I first dipped my toes into it with the RTL SDRs back when they were first 'discovered'. I got into listening to local police scanners but got tired of chasing peaks in the spectrum. So I learned a little bit about DSP, wrote a couple of little auto-tuner plugins for one of the more popular SDR applications, built a crude audio pipeline to demodulate the p25, but ultimately had a $1200 PC doing a bad job at being a $200 scanner.

I started to pick it apart more when some genius masochist builds an SDR scanner that does all of the above (including multi-vcos), but then snips out the audio files, tags them with the origin and makes them available for the world to listen via a nice clean web ui. Demoralized and defeated I just moved on to tinker with ADS-B.

Geesh, the nerve of some people. :D

I've got a LimeSDR-mini (which is more economical). If you're only interested in RX, you should definitely consider the cheaper RTL-SDR. I'm just starting to learn about SDR, and am far from sending anything. I wish I had gone with an entry-level device first.

I’ve got at least a dozen RTL’s strewn around the place lol. They are easy to use but once you hit some of their limitations you wind up wanting something more

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