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Comment by jaytaylor | Hacker News Reader

I am curious; what would one actually do with this device once it is working?

This is a really neat sounding project.

With 56MHz bandwidth, a lot. You could record and analyze most 802.11 connections (typically 20MHz to 40MHz, except for newer AC hardware that can go to 160MHz).

You could also record the entire FM band in your area at once, all of it. Same with AM and a lot of other bands. It'd also probably work really well for recording things like fire and police bands, with trunking and being able to determine an entire conversation at a time that normally need 2 or more cheaper SDRs to record the trunk and then the channels. That would normally mean you'd probably miss some channels that are at the other end of what you're listening to. It'd also mean you can monitor the entire bandwidth of many of the ISM bands to determine what some misbehaving device is doing.

So many things that I'd love to do with it! I really want one now.

Probably overkill, but I'd love to have at least AM and FM into a box on my network which then splits it up and streams via RTSP+SDP.

Fun fact: The rtl2383 which RTLSDR is based on has an undocumented function to dump an entire DAB+ station (10+ channels) at once. Nothing can demux the resulting file and the DAB spec is overwhelming.

You could also record the entire FM band in your area at once, all of it.

I'm not very familiar with RF beyond the basics, but could you explain simply how does that work? Don't you need to tune into a specific frequency to receive a signal?

Basically a traditional radio would multiply a signal with the frequency you want to tune to and give you the resulting signal which is an audio signal. With an SDR, you can record the actual RF signal and then store/multiply whatever you want to. So you can store everything and later tune to any frequency using software later!

Basically what SDR lets you do (More properly the Quadrature Sampling Detector techniques they use) is record a large amount of radio bandwidth at once. So in this case I could record from 80Mhz to 136MHz. I'd have to then tune in to each frequency on the recorded data, but I'd have the entire spectrum there recorded to play it back later.

It's like recording a bunch of TV channels all at once, and then being able to go back and look at every channel at any given time in the recording.

The bigger issue with this particular device is that almost any antenna you use is not going to perform very well over such a large bandwidth, but that's a much nicer problem to have.

Yea, but if you record the whole spectrum then you can tune frequencies on the recording.

It's a bit like a color photo vs black and white. I don't know if that's a great analogy though.

SDR has a lot of applications in infosec, amateur astronomy, and other signal processing science applications. Check out Balint Seeber's talk at DEF CON 21.

https://www.youtube.com/watch?v=1bgC3AjCnA4

another talk: http://www.rtl-sdr.com/new-talk-by-balint-seeber-hacking-the...

Transmit or receive analog or digital information on just about any frequency : audio/voice (including multichannel), video, GPS, telecommunications, data transmission, synchronization, module configuration, etc. etc. etc.

Sky's the limit.

> Sky's the limit.

Until you get a bigger antenna ;-)

Isn't the FCC the limit?

How much transmitting can you do legally?

You could in theory run an entire GSM base station over it, or use it to recieve television, radio... or use it to mess with airplane communications.

The possibilities are virtually endless, the responsibility is yours alone.

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