Building a software-defined radio from scratch
electronics.kitchen
electronics.kitchen
One question: If you had to start over on this project, what would you do differently? (I am going to guess you would go straight for a six-layer board rather than 4 to simplify layout...)
P.s. it says you are a student. If you want to earn a side income giving virtual classes on PCB design, etc. you'd make a decent side income. Just an idea :p
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 am blown away that someone your age can master all the expertise needed to implement this. This is very very non-trivial work indeed. At your age I could have put together some silly receiver/transmitter electronics based on schematics copied from an Elektor magazine. But this is mind blowing.
Wishing you the best. You have a great future ahead.
The project is on Github: https://github.com/FreeSRP Reddit discussion: https://www.reddit.com/r/electronics/comments/4uic5r/sdr_pla...
He's selling a small batch of these for $350 apiece - calling it now, he's going to be very successful in his career.
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 simply too many details buried on too many datasheets and one of them is going to drop.
If you have the time, the best thing I have found for catching mistakes is to have a design review. Even if the person doesn't understand electronics, the fact that you have to walk through every part and explain it to somebody means that you will catch some really stupid things.
However, if you're good and the board isn't too expensive, it's often cheaper just to fab the board. You're time is worth something, and you can be designing something else while the PCB is being fabbed.
https://en.wikipedia.org/wiki/Rubber_duck_debugging
Personally I use a cat. Its Steve-Jobs-like attitude seems ideally suited for the task.
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.
I actually cut my teeth on Python learning GNURadio.
This is a really neat sounding project.
https://www.youtube.com/watch?v=1bgC3AjCnA4
another talk: http://www.rtl-sdr.com/new-talk-by-balint-seeber-hacking-the...
Sky's the limit.
Until you get a bigger antenna ;-)
How much transmitting can you do legally?
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.
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.
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?
It's a bit like a color photo vs black and white. I don't know if that's a great analogy though.
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.
The possibilities are virtually endless, the responsibility is yours alone.
1. What are your plans for it? Aside from high altitude balloons.
2. Do you plan to turn this into a sort of "shield" add on?
3. What will you work on after this project is done?
Well, I'm currently working on a new version that I'm hoping to sell. I also still need to work on the software.
This won't be an addon, but the next revision will include an expansion header so you can add addons. Should be pretty neat to make an LCD+battery pack "shield" so you can use the SDR as a stand-alone spectrum analyzer.
What I'll actually use it for: I built it because I wanted to learn more about signal processing and the different protocols that common devices use, so I'll be tinkering with all those protocols.
No idea what I'll do after this, maybe that LCD addon I was talking about?
This is a really nice write up of an impressive project!
I don't think you can do high frequency RAM lines with hand etched boards or BGA escape routing without vias, but two layer prototype boards are pretty cheap these days.