SDR is great but how do you "decode" all the digital stuff? BROAD TOPIC - Page 1
Forum section: electronics / rf-microwave

author: raspberrypi
author_rank: Frequent Contributor
timestamp: November 24, 2016, 08:32:20 am
content: I have an SDRPlay and I see it can do almost anything RF. But my question: how do you "listen" to it? I realize that each digital signal is its own protocol, like to hear GSM cellular stuff thats its own program in of itself. So this is what I'm trying to figure out; how do you decode the HAM digital signals; what are they 1st and whats required? Most sites seem to skip alot of the steps you would do if it was your first time.How do you get your "program" to hear your SDR software? I downloaded the software to get the info from in coming flights where you can see an commercial airlines anti collision signal software but it can't talk to my SDR# or SDRUno software. I once had a program that piped it into a port, but once I installed it I lost all my sound, i.e. watching eevblog on youtube no longer had sound and not being able to get it to toggle off I had to completely unistall the soft ware. I'm on windows 10 and doesn't help to be legally blind. I also got a raspberrypi so I could use that as well but running into the same problems.Basically all I can use it for now is listening to HF audio stuff. The articles are either extremely basic like its just how to get started or extremely technical and they assume you have done this before and are just adding an additional feature like picking up weather data. In the mean time I have been able to make some really good antennas, I'm covered from 1MHz to 2GHz.Really want to use that tracking software that emulates looking out the cockpit of a live flight using the plans transponder thats in the 130 140 MHz range. Hak5 youtube channel covers the flight data stuff but for some reason they skip videos or hide them in their site.

author: borjam
author_rank: Unknown
timestamp: November 24, 2016, 09:06:23 am
content: There are many digital modes. So, depending on your interests, you will need a bunch of programs.A Swiss Army knife is fldigi. It supports many modes.http://www.w1hkj.comThe easiest to decode signals are probably the JT9 and JT65 modes. I suggest you to try WSJT-X on the suggested frequencies (14076 KHz on 20m, 7076 Khz on 40m).And this website can be helpful to identify signals:http://www.sigidwiki.com/wiki/Signal_Identification_GuideThese programs expect an audio device to receive the signal. If running both the SDR software and a digital mode program on the same machine, you need some kind of "virtual audio connection" to feed audio between them. I have no idea how to do that on Windows. But that's the key.

author: stfsux
author_rank: Contributor
timestamp: November 24, 2016, 01:05:31 pm
content: I would suggest GNU/radio but it's a bit messy to setup (easier with GNU/linux, there might be some pre-installed vm somewhere in teh internet).If you have any issue with hardware support, the easy way to process rf signal is to capture that signal and save it as an audio format (e.g. wav) then do your stuff.Quote from: borjam on November 24, 2016, 09:06:23 am+1, thats an awesome wiki!

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: December 04, 2016, 12:29:49 am
content: I have a question along the same lines as the OP, and my main hobby has turned to building SDR hardware and some cabling in software beyond the driver level to DSP code.Let's say I'm looking at a signal in a basic SDR program, I.e sdr#, sdruno, hell even gnu radio fft. How do I make educated guesses as to go about decoding? I know how to tell between AM based and FM mod but what about phased based, what characteristics are unique to any phased base mod? Next is it look, ook, ask, fsk, psk, QAM??? After you figure that out then you can use programs and math to figure out the symbol rate, if it's qam1,2,4 etc... But I never know where to start when looking at a signal, I just pipe it through every decoder I have and hope something sticks. Some times research gets the job done that is looking through local fcc data etc.. but that's not helpful for personal ism type devices, SATs, amateur tv and packet, etc. For example there's a constant 1240mhz broadcast about 3mhz wide and almost flat, as in a 10db rise horizontal for 3mhz the 10db fall back to the noise floor. I can only pick this up with a patch pointed within a few degrees at the exact right height. It's always there it always looks the same no one on Reddit seems to know what it is, maybe it's noise idk, but where do you start when research fails?

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 12, 2016, 11:46:01 pm
content: Quotethats rubbis. I try to decode different things now way!QuoteI think you mean ADSB who runs on 1090MHz?For Digital look for "DSD+". There is some Tread about Tetra Decoding onhttp://forums.radioreference.com/.There are a lot of application for Windows out there. The major problem is decode some unknown Signals where you have no clue what it can be.Quotehttp://vb-audio.pagesperso-orange.fr/Cable/Quotesame problem here. The officials here have an PDF File who show what kind of useage the Band have like Professional Radio.There could be any weird antique Radio System on.In my case i receive a lot of that.

author: borjam
author_rank: Unknown
timestamp: December 22, 2016, 11:43:22 am
content: Quote from: Lord of nothing on December 12, 2016, 11:46:01 pmIt's an amateur radio program with, of course, amateur modesIf you want something more exotic you can resort to Hoka or Wavecom (warning, no experience with either!) but get ready to shed hefty amounts of money

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 28, 2016, 01:57:07 pm
content: Radio Amateurs use also 4FSK try to decode that with fldigi. No way.The same with all other thinks.