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Building a software-defined radio from scratch

electronics.kitchen

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Re: Building a software-defined radio from scratch

#41

Post by turnip1979 »

gjkood wrote: post #38
krapht wrote: post #37

Earlier quoted context omitted.

Didn't like what's already out there? https://contextualelectronics.com/

Thanks for the link. I am interested in such a program but $29/mo for a hobby is too much at the moment. It would be great if there was a free community edition also. However its good to know that there are options. My primary concern with signing up for something like this, from a hobbyist perspective, is that these things add up and soon you will be bleeding money without generating any income to cover the expenses…

I was thinking 1 on 1 tutoring. There are already a lot of video resources out there. I wouldn't mind 30-50 bucks an hour for a consultation. Sort of like a fitness trainer for my electronics hobby.

Re: Building a software-defined radio from scratch

#42

Post by voltagex_ »

simcop2387 wrote: post #16
jaytaylor wrote: post #10

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 conversa…

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.

Re: Building a software-defined radio from scratch

#43

Post by userbinator »

simcop2387 wrote: post #16
jaytaylor wrote: post #10

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 conversa…

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?

Re: Building a software-defined radio from scratch

#44

Post by ben174 »

userbinator wrote: post #43
simcop2387 wrote: post #16

Earlier quoted context omitted.

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 conversa…

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?

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.

Re: Building a software-defined radio from scratch

#45

Post by xt00 »

Awesome project man. I do EE HW design for a living and this I can attest is a hard project. I have a bladeRF and use it regularly. One thing I try to instill in the people that work on my team is that the best attribute you can have and try to foster in your career is not giving up on hard things. So it's great that that is something you have.. To stick with this project for a long time and putting in the time to make it happen. MIT will be a challenge but I'm sure if you stick with it you will end up doing great. Go for something tough and glad you are coming to the US. I have to apologize for politicians that say we don't like foreigners. We do like foreigners and we need them. You will be a great addition to the many awesome people coming here to find there path to great success!

Re: Building a software-defined radio from scratch

#46

Post by tonmoy »

userbinator wrote: post #43
simcop2387 wrote: post #16

Earlier quoted context omitted.

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 conversa…

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!

Re: Building a software-defined radio from scratch

#47

Post by dbcurtis »

laobeylu wrote: post #29
bsder wrote: post #25

Earlier quoted context omitted.

> Are you kidding? That falls into the realm of superhuman. I've seen 20 year veterans blow a 100 grand and get half that far. I think even Woz would do a double-take. A high density BGA through an OSH Park board with a homebrew reflow oven and only 3 revs and a stainless stencil on only the last pass? Yeah, that's really quite good. You practically can't avoid making a mistake on a PCB of that complexity. There are…

That's actually sort of what I did. I didn't explain it to someone else, but went through it in my head, talking to myself explaining the design. Explaining it to someone else must be even better!

Yes, great work! I think of PCB design like golf -- low scores are better, but nobody hits a hole-in-one every time they tee up. 3 revs is shooting par for even simple designs, much less a complex RF design like this.

Having someone else look over the design is always useful. A healthy distrust of datasheets is always useful. But at some point, you have to ask yourself you have reduced the risk of errors enough that a couple of rework wires with get you through debug, at which point just go fab it. Blue wires tack-soldered on are a fact of life in prototyping. It is easy to obsess over PCB designs, but "fail fast" applies here, too.

Re: Building a software-defined radio from scratch

#48

Post by simcop2387 »

userbinator wrote: post #43
simcop2387 wrote: post #16

Earlier quoted context omitted.

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 conversa…

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 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.

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