3 ms·

> 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

> 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.

_whiteCaps_ 3y ago
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.
- H8crilA 3y ago
  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? :)
  - darkclouds 3y ago
    > 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? :)
    - _whiteCaps_ 3y ago
      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.
      - darkclouds 3y ago
        The RaspberryPi is very versatile. https://forums.raspberrypi.com/viewtopic.php?t=27922#p248364 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?
    - H8crilA 3y ago
      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, ...
      - darkclouds 3y ago
        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 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%20WiFi%20Radar%20for%20Human%20Sensing%20Using%20A%20Stand-Alone%20Access%20Point.pdf 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.
        H8crilA 3y ago
        > 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.

_whiteCaps_ 3y ago

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.

H8crilA 3y ago
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? :)
- darkclouds 3y ago
  > 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? :)
  - _whiteCaps_ 3y ago
    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.
    - darkclouds 3y ago
      The RaspberryPi is very versatile. https://forums.raspberrypi.com/viewtopic.php?t=27922#p248364 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?
  - H8crilA 3y ago
    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, ...
    - darkclouds 3y ago
      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 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%20WiFi%20Radar%20for%20Human%20Sensing%20Using%20A%20Stand-Alone%20Access%20Point.pdf 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.
      - H8crilA 3y ago
        > 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.