Is SDR technology a way for me to listen to a large group of stations or even the entire FM band at once?
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3$\begingroup$ yes. So, what's your question? $\endgroup$– Marcus MüllerCommented Feb 26, 2018 at 15:40
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$\begingroup$ There's a previous question about this but I can't find it. $\endgroup$– Phil Frost - W8IICommented Feb 26, 2018 at 17:59
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$\begingroup$ close: ham.stackexchange.com/questions/9510/… $\endgroup$– Phil Frost - W8IICommented Feb 26, 2018 at 18:02
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$\begingroup$ I am trying to find a replacement for a SB7 Spirit Box that scans through the FM band, at different ms settings, forward or backwards, to pick up spirit voices. Sometimes I only pick up a word or two, but seldom a whole sentence, because it keeps changing stations as it sweeps. I thought if there was a way to listen to many stations at the same time (actually the white noise between each local station), I would have a better chance of capturing entire sentences. Just trying to think outside the box, and not have to rely on just the SB7 Spirit Box. $\endgroup$– Rick CallahanCommented Feb 26, 2018 at 21:19
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$\begingroup$ I've seen wideband receivers (and tape recorders) used for this, in an attempt to hear through static. The SB7 is a scanner with the purpose of generating white noise sound energy that can be modulated by very small signal sources like ghosts. It is a bit like watching a TV screen tuned to a channel without a station and trying to discern shapes. SDRs are difficult to set up as scanners. And white noise is easy to generate by other means. So if you want the SB7 functionality so be it. White noise circuits are much simpler. No radio technology necessary. $\endgroup$– SDsolarCommented Apr 1, 2018 at 4:23
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1 Answer
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Yes. To actually do it, you need:
- SDR receiver hardware with (slightly more than) 20 MHz bandwidth to capture the entire FM broadcast band.
- A computer, fairly powerful (definitely not a Raspberry Pi or such).
SDR software which can be configured to actually do this. Many receiver programs are focused on receiving a single signal; my own ShinySDR can do multiple but not as efficiently as a purpose-built program.
The likely place to start to make this actually happen would be to use GNU Radio, a framework for making SDR applications. GNU Radio's polyphase channelizer can efficiently separate all the FM channels since they are conveniently equally spaced. You will also need something to do with the hundred separate channels other than playing them all at once (unless that mess is what you wanted).
answered Feb 26, 2018 at 17:13
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$\begingroup$ Notice that Kevin is absolutely right, to capture the whole FM broadcast band, (where I'm, that's 87.5 to 108 MHz), you'd need a 20 MHz of bandwidth – but the 2.4 or so MHz of a ~ 10$ RTL-Dongle would probably be a start, wouldn't they? You could even use multiple of them at once. So, I'd propose you just get one of these via amazon or ebay or rtl-sdr.com or nooelec or so, and then just start with gqrx or something. You can move on to the GNU Radio Tutorials later. You will definitely be having fun! And even if you didn't,your losses might be tolerable. $\endgroup$ Commented Feb 26, 2018 at 22:26