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WebSDR – Internet-connected Software-Defined Radios

websdr.org

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Re: WebSDR – Internet-connected Software-Defined Radios

#51

Post by 6312783123 »

deltasepsilon wrote: post #29

For those interested in SDR, there was recently a discussion here on signals identification [1], and some months ago a discussion of NXP's new LA9310 ADC chip for radio applications [2]: [1] https://news.ycombinator.com/item?id=37869534 [2] https://news.ycombinator.com/item?id=35325165

Sadly the LA9310 DSP instruction set is considered highly proprietary[1] by the manufacturer, NXP. So I'll give this one a miss, and choose a FPGA based SDR instead. Some of the FPGAs even have a completely open-source toolchain, that has been developed by reverse engineering the bitstream format.

1. https://news.ycombinator.com/item?id=35357451

Re: WebSDR – Internet-connected Software-Defined Radios

#52

Post by lormayna »

squarefoot wrote: post #49
lormayna wrote: post #46

Is there any good open source software for WebSDR? I am living in a very noisy area from RF standpoint, but my parents are living in a better position. So I was thinking to install a SDR and a Raspberry and use them as remote SDR

If you don't need the web interface and your usual desktop SDR software supports rtl-sdr tcp mode, you can easily set up a small board that calls rtl-sdr with the appropriate parameters so that it will wait for a remote connection from the above software, not unlike what happens with WebSDR, but you would be using your usual desktop SDR application which would be native and much more snappy than a web browser. Here's…

Ah yes, good suggestion. I forget about it. I have a mini whip antenna that I can place on the roof.

Re: WebSDR – Internet-connected Software-Defined Radios

#53

Post by hoppyhoppy2 »

desertraven wrote: post #20

This is a cool project. I bought both a HackRF and an Ettus USRP B210 years ago for playing with. I am yet to actually do anything of interest! Anyone want to share anything cool they’ve done in the SDR world?

I run a local Fire/EMS scanner feed for my county so people can listen in without a scanner or SDR of their own. It uses a bunch of directional antennas in the attic for best reception (I can't put up a giant mast antenna) connected to a bunch of Nooelec rtl-sdr dongles.

Unlike a traditional scanner which only monitors one frequency at a time, if two things are happening simultaneously then you hear them both. This would be annoying or unlistenable in a busier area, but in my area it works fine.

Re: WebSDR – Internet-connected Software-Defined Radios

#54

Post by ale42 »

gregsadetsky wrote: post #31

I’d love to decode some radio signals - just to go through the “motions” and try my hand at it. Is something like an AM radio signal decoding relatively easy to understand? What about FM? And NTSC? Is the python code clear-ish? Complicated? Full of math I’m not appreciating? Thanks! Ok… it’s not exactly trivial: https://pysdr.org/content/rds.html#fm-demodulation

There's for example SDR++ (https://www.sdrpp.org/), which has lots of plugins to decode specific types of signals, or SDRangel (https://www.sdrangel.org/), which has quite some digital signal decoders built-in.

Re: WebSDR – Internet-connected Software-Defined Radios

#55

Post by mpalfrey »

nullpage wrote: post #35

University of Twente in the Netherlands has a great websdr[1] running some custom hardware that can tune into pretty much the entire shortwave spectrum. I've spent countless hours tuning in to various European radio stations and broadcasts (you can even pick up the odd number station if you are on the right frequency and get lucky with timing). [1] http://etgd1.ewi.utwente.nl:8901/

Have used this for number stations in the past. It's great - amazing what you can still find on shortwave.

Re: WebSDR – Internet-connected Software-Defined Radios

#56

Post by 1317 »

mikewarot wrote: post #38
nomel wrote: post #23

Earlier quoted context omitted.

> but you need to hunt down EMI sources, before you can properly use it. Do you have any recommendations for doing this? I have some source that interferes every 11 seconds for a second or so. It causes packet loss with my wifi (2.5 and 5GHz), and makes my bluetooth game controllers really frustrating to use, since input are missed every time it does it. I assume it's in the microwave range. I'm familiar with RF test…

You could get an rtlsdr dongle cheap and use it as a spectrum analyzer. There are command line utilities for that task in with the drivers online.

they don't go up to the 2.4/5Ghz range though, they max out at about 1.7

Re: WebSDR – Internet-connected Software-Defined Radios

#57

Post by mikewarot »

1317 wrote: post #56
mikewarot wrote: post #38

Earlier quoted context omitted.

You could get an rtlsdr dongle cheap and use it as a spectrum analyzer. There are command line utilities for that task in with the drivers online.

they don't go up to the 2.4/5Ghz range though, they max out at about 1.7

Yeah, but it seems he's got a broadband noise source, likely the 2.4 Ghz is a harmonic of something that is within their range.

Re: WebSDR – Internet-connected Software-Defined Radios

#58

Post by leesalminen »

nullpage wrote: post #35

University of Twente in the Netherlands has a great websdr[1] running some custom hardware that can tune into pretty much the entire shortwave spectrum. I've spent countless hours tuning in to various European radio stations and broadcasts (you can even pick up the odd number station if you are on the right frequency and get lucky with timing). [1] http://etgd1.ewi.utwente.nl:8901/

This link is pretty famous in some “conspiracy theorist” circles, specifically those interested in “Skyking”.

Skyking is a military radio transmission protocol, believed to be command-and-control in nature. Some believe there to be a correlation between the length of the encoded message/how many times the operator says “Skyking” and the DEFCON level/how close the US is to blowing shit up.

Re: WebSDR – Internet-connected Software-Defined Radios

#59

Post by pid-1 »

gregsadetsky wrote: post #31

I’d love to decode some radio signals - just to go through the “motions” and try my hand at it. Is something like an AM radio signal decoding relatively easy to understand? What about FM? And NTSC? Is the python code clear-ish? Complicated? Full of math I’m not appreciating? Thanks! Ok… it’s not exactly trivial: https://pysdr.org/content/rds.html#fm-demodulation

AM in particular is quite intuitive as you can study the modulation visually. IMO it's the "everyone could have invented that" modulation technique.

FM is built on a simple idea, but it has more involved maths.

Analog television signals are way more complex IIRC.

Re: the lib you linked - libs used to deal with radio signals is made by people who have studied signal processing and comm systems formally so you will see lots of jargon and advanced maths like Fourier Analysis. However, you most likely can build something shittier yet working by yourself by understanding the fundamentals of how those signals are encoded, modulated and transmitted.

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