Retrogram rtl-SDR – a radio spectrum analyzer for your terminal | Hacker News Reader

Retrogram rtl-SDR – a radio spectrum analyzer for your terminal

github.com

77 pointsthcipriani22 comments

It looks like a direct fork from retrogram~plutosdr, and it itself is a hack from Ettus UHD RX ASCII Art DFT code for ADALM PLUTO [1]. This version seems to support the RTL-SDR dongles that already exists.

[1]PLUTO SPECTRUM ANALYZER USES COMMAND LINE:

https://hackaday.com/2021/11/15/pluto-spectrum-analyzer-uses...

How long will this forking continue until someone ports it to Soapy SDR? :)

A command-line waterfall would be awesome.

I just started getting into SDR. This is some interesting work in this space, unfortunately there isn't a lot of development to make exploring this space easier.

If you're looking for interesting signals to receive, check out:

  * NOAA satellites in the 137MHz range
  * APRS packets on 144.390MHz
  * ISS and other amateur radio satellites around 435MHz

For the satellites, I really like GPredict as it can drive SDR programs.

ISS, TEVEL, SO-50 are often active.

Thanks for this! I am actually just getting into sdr stuff as well and always appreciate any pointers or things like this.

Yeah, the other consistent signals you can get are the Marine VHF and WX stations around 156MHz.

If you're really into programming + RF, check out the M17 codec project.

SDR is a tool, like a hammer.

If you have a nail to hammer in, SDR will help you do it. Having a hammer and not knowing what to do with it is either boring or breaks glass.

There's a lot of interesting things in the spectrum, and the RTL-SDR costs only $50-$100. I don't see why not just buy it and then figure out what to do with it. Poor analogy.

> There's a lot of interesting things in the spectrum

What I want is something to steadily sweep its whole spectrum and give me a "heat map" of all the signals it picks up. I've got dozens of PDFs and saved pages of interesting bands and don't see much except FM broadcast radio stations and the local airport when I go looking.

You're going to have trouble covering 50M to 2GHz with a single antenna. Sounds like yours is working well for 80MHz - 120MHz.

You should see some stuff around 433MHz like garage door remotes. Same with 900MHz. But again you need the right antenna for it.

Also, if you don't have one already, an FM bandstop filter might be helpful, as the FM stations will often overpower the dongles.

You can cover lots of strong signals with any basic (inappropriate) antenna. And if you want something cheap that tunes then get a telescope dipole, and set the length correctly (and maybe also polarization). In either case, height / clear line of sight is much more important than a good antenna.

But I'd start with the most basic question - is your antenna even outside of the building? :)

> But I'd start with the most basic question - is your antenna even outside of the building? :)

Why not monitor electrical interference inside the home? You could work out when your dishwasher has finished, the different parts of a washing machine program, vacuum cleaner, when the kettle is switched on and off, the fridge/freezer, tv, hifi, lights.

You can learn alot about peoples home life and their patterns just from picking up electrical interference of devices. Who needs to hack CCTV to see inside someone's house? :)

I interviewed at a startup building a product that was doing exactly that. Well, it was a sensor on the mains power but same idea.

The RaspberryPi is very versatile.

https://forums.raspberrypi.com/viewtopic.php?t=27922#p248364

What does it take to make an antenna of sorts?

Now who trusts their operating systems?

Because he is just starting, so it will be a lot easier to pick up the many usual signals that exist pretty much everywhere. Like broadcast, police/emergency radio, pagers, aircraft comms or data, satellites, HF communication, ...

They might be in an otherwise radio silent part of the world though. And how hard is it recording the electrical interference of a device from the same room and then from other rooms, to establish the variability of its electrical "interference/signal" properties?

Knowing about the Theremin, a Russian electrical instrument invented in 1919, is similar to walking around a house with mains electricity is an audible example of the interference in our homes which we interact with. https://www.youtube.com/watch?v=-QgTF8p-284

Could even do human detecting wifi signals. https://discovery.ucl.ac.uk/id/eprint/10103371/1/Passive%20W...

If someone can detect multiple wifi signals, the are effectively inside a phased array radar system.

> They might be in an otherwise radio silent part of the world though

> Could even do human detecting wifi signals

I can confidently say that you have never tried to do anything with radio.

I've experienced it, because I have FE(II,III) in me, so have you.

https://web.gps.caltech.edu/~jkirschvink/pdfs/JoeMicrowave.p...

https://ui.adsabs.harvard.edu/abs/2019AGUFMGP23B0794P/abstra...

https://www.pnas.org/doi/10.1073/pnas.1613349113#:~:text=In%....

Still confident or have you spent too long on your mobile phone that you cant remember?

The quieter you become, the more you are able to hear.

That's a great statement. The're about 32$ each, 42 with a basic antenna kit.

https://www.aliexpress.us/item/2251832753237163.html

Sure, you can tap stuff with a hammer, and then get bored. If you want to listen to FM radio, an actual radio is cheaper and gets better reception, if you want to listen to walkie talkies, a scanner is better, or getting a cheap baofeng or a similar radio is even cheaper and works better. Yes, you can play with getting satellite images, but in the end, you look at weather reports online.

The great power of SDR is, that you can capture signals to your PC, so if you're eg. reverse engineering a temperature sensor, you can use the tool to get the signal onto your PC. Then you're done with the first tool and need a few other tools to do all the other parts (demodulating and getting binary data, finding what each bit/byte does, what sequence is used for what, how the checksum is calculated, etc.

I mean sure, it's fun to play with for a few hours, but after you've listened to the local taxi frequency and tried to get some satellite data, you get bored and put it in a drawer somewhere.

This is how people end up with drawers full of dusty Arduinos and Raspberry Pi's :-)

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