008 SDR Tutorial: How does Software Defined Radio SDR work under the Hood

The whole world goes wireless. And digital. One technology is right in the center of these two megatrends: Software Defined Radio or short: SDR. Do you know how it works? And how can you take advantage of it? If you do not want to take the time to watch Michael Ossmann's (Great Scott Gadgets) series, then this SDR tutorial is for you
Software-defined radio is a relatively new technology and was extremely expensive in the past. Then came this small USB dongle for 10$ and changed all. And other, more capable devices like the HackRF One for 300$ pushed this technology into the mainstream. Today, most modern radios used for example in Smartphones, in Amateur radio equipment, or Satellites are SDR radios. This is the reason for the tutorial.
I am a proud Patreon of GreatScott!, Electroboom, Electronoobs, and others.
#SDR #Tutorial #Electronics
Links:
HackRF one: amzn.to/3ei2gQn
Clones: bit.ly/2ZEe3Df or s.click.aliexpress.com/e/MnOHFW5w
RTL-SDR V3: s.click.aliexpress.com/e/B08cnKey
RTL-SDR Dongle: s.click.aliexpress.com/e/_9QvOSo (RTL2832U , R820T2 )
Pluto plus (better): s.click.aliexpress.com/e/_9G4To5
original Adalm Pluto: www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/adalm-pluto.html
SDR-Play: www.sdrplay.com/
Lime SDR: www.crowdsupply.com/lime-micro/limesdr
Ettus Research: www.ettus.com/
SDR Intro by M. Ossmann: kzbin.info/aero/PL75kaTo_bJqmw0wJYw3Jw5_4MWBd-32IG
SDR Software list: www.rtl-sdr.com/big-list-rtl-sdr-supported-software/
Qatar-Oscar 100 WebSDR: eshail.batc.org.uk/nb/
SD Card Image with SDR Tools (Buster):
Frank helped me again! drive.google.com/open?id=1lN8qQIzOLQnqVEXcgtGalGac2sKXoE9d
GNU Radio tutorial: wiki.gnuradio.org/index.php?title=Tutorials
The links above usually are affiliate links that support the channel (no additional cost for you).
Github: www.github.com/sensorsiot
My Patreon Page: www.patreon.com/AndreasSpiess
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[@jamesgoacher1606]

Those 1% of the facts informed me more about SDR than I have ever seen. And all with a Swiss accent. Thank you.

[@HB9BLA]

You are welcome!

[@matambale]

An RF engineer I worked with some years ago said that, "If you think negative frequencies can't exist, that's fine, but it means there are no positive frequencies, either." It is all relative: at any given frequency, carriers below are rotating in the 'negative' direction, at ever increasing rates with increasing frequency differences. Once you mix your carrier down to baseband, the lower carriers go 'negative'. We mix with two generated carriers at the same frequency, one of which is generated 90 degrees out of phase, so that we can retain the information necessary to determine positive and negative offsets relative to our carrier of interest (generating the complex values to which you referred). Edit: should note here that W2AEW has an excellent treatise on IQ modulation/demodulation in his video #170

[@HB9BLA]

Thank you for the additional info!

[@sarbog1]

Negative frequencies arise from a mathematical abstraction, complex numbers. It is very cool stuff that helps us understand radio... The actual magnitude and phase of a signal is found by multiplying it's complex representation by it's complex conjugate...

[@jordanheinemann6633]

I really appreciated this little explanation. I think something finally clicked when I read it. I've even taken classes on signals and systems, but too often the material is covered from a purely mathematical perspective rather than an intuitive one. I was disappointed when I clicked on your channel to find that you don't post videos yourself.

[@matambale]

Phase extraction is done by arc tangent, magnitude by the Pythagorean Theorem. Conjugate multiply can be used if you're working from a complex number as a reciprocal, as a first step.

[@dikcod]

Andreas, your videos are always very interesting and full of information. By the way, happy birthday and greetings from Milano

[@HB9BLA]

Thank you!

[@ImnotChuck.]

Thanks for assembling this information into a 27 minute video, and for the links to the sources. Very helpful.

[@HB9BLA]

Glad it was helpful!

[@TheHellfiremissile]

Many thanks. I have some simple (read as Cheap) sdr's in the bottom drawer which I fiddled with but little more. You've inspired me to have another look.

[@HB9BLA]

SDR has a lot of potential. But you need a project like balloon tracking to get a value out of it...

[@idarwin]

What a fantastic overview of SDR, very comprehensive! One minor note, the link to "The theory behind" doesn't seem to work.

[@HB9BLA]

You are right. This blog does no longer exist. So I had to delete the link.

[@tav9755]

Sir, this is a very comprehensive summary of SDR and a great help in selecting the gadget for the purpose.

[@HB9BLA]

Glad it was helpful!

[@stanrock01]

Up till this moment I never understood what the I and Q signals were. Thanks Andrew! I always watch your videos to the end..so you know they are the right length and you know how to suck me in :-)

[@HB9BLA]

Thank you for watching the videos to the end. Not everybody does it!

[@ssl3546]

This might be the best video you've ever done. In the late 1990s I worked on a military SDR that worked from 30 to 2000 megahertz. The documentation I wrote has a screengrab I got off the air of The Simpsons, decoded the I and Q channels in Visual Basic. Amazing you can get that for basically $10 now.

[@HB9BLA]

Yes, and only a few MHz short (up to more than 1.5GHz)... A wonderful time!

[@simoncollins6650]

A great summary thanks. I have several SDR’s I used the HackRF one a lot several years ago but ended up in the draw when I used the SDRplay this is very good. I have now bought the Portapack H2 and has given the HackRF a complete new life as a very handy portable SDR setup nice small screen and many built in decoders such as for ADSB Sondes with Maps SSB etc and great for bug hunts 😁, with all the usual facilities to Rx & transmit from touch screen controls . Thanks for the new channel G8HAM

[@HB9BLA]

This Portapack seems to be handy compared with a standard HackRF... Maybe it lands on my shopping list, too.

[@fotografm]

Thank you Andreas for such a clear explanation !

[@HB9BLA]

You are welcome!

[@NatesRandomVideo]

Great job Andreas!

[@HB9BLA]

Thank you!

[@onuryorutken5540]

Absolutely perfect. Internets biggest problem is noise and one probably gets lets say 5 unit of useful information after watching 100 videos but this video is alone giving 100 units of information. You can smell the detailed experience behind it. I believe sdr s will be everywhere in near future (already actually), can you imagine uploading your new key (car, home etc.. ) to your telephone ? Actually gsm transmitters use sdr and our phones use sdr, did you know NASA has managed to reset a satellite in space with a sdr equipment. Did you know you can make your own radio telescope with sdr? Using a 10 dollar device for all those things still amuses me. I love sdr and loved this video.

[@HB9BLA]

I have a long subscription list of quality creators and do not enter youtube via the home screen. Like that I can avoid a lot of crap;-)

[@DougHanchard]

Absolutely brilliant presentation. Technology has come a long way since GPRS (General Packet Radio Service) ⭐⭐⭐⭐⭐

[@HB9BLA]

And GPRS was not the beginning ;-). I hope we can play a little with this technology in later episodes…

[@DougHanchard]

@@HB9BLA This is true. AX.25 (X.25) data packet radio was first tested in 1978. Before then, the USAF experimented during the 1960s, a form of packet radio communications based on early development work that soon became known as ARPANET. It was developed and intended for aviation packet radio comms. R & D teams used 3450 / 5550 kHz and 5560 / 8900 kHz, in the 1960s using B-52s during Chrome Dome nuclear strike deterrent flights. These frequencies bands are still used by Transport Canada and FAA ATC over the Atlantic. Modern 1990s FM out of band was to be leveraged by many FM broadcast radio stations to embed one way digital radio data that's been possible since 1995. But it was never released by Delco radio (then part of General Motors. They were simply too early. ITU standards for Radio Data Service (RDS) development began in 1994, using 57 kHz subcarrier. As you know, Packet radio has been in use by amateur Ham Radio and MARS operators, (duplex) data comm radio's since 1978.

[@HB9BLA]

Thank you for the info about the history. I did not know it.

[@olpqay]

Alles Gute nachträglich zum Geburtstag, Andreas🥳

[@HB9BLA]

Danke!

[@temyraverdana6421]

Thanks, a wonderful lesson

[@HB9BLA]

You are welcome!

[@JosepsGSX]

I honestly thought SDR wasn´t going to be a subject I´d like or be interested in, as radios never caught my attention. I was very wrong. Probably I´ll have to skip the advanced topics in the channel, but this one lesson was fantastic. Thanks, Andreas.

[@HB9BLA]

Glad you liked it. The radios often are not very interesting, but the applications can be quite cool...

[@martinmckee5333]

I have an SDR specifically because I needed to debug an Arduino-like project that communicated with radio modules. I'm not interested in HAM radio specifically either, but SDR is so flexible that I view mine as just another piece of test equipment.

[@jstro-hobbytech]

I've never understood your fondness for great Scott. You're q much better person Andreas. There's something to learn from every video you make. I've seen gs boast and act like his viewers are plebs who can't afford the gear he has (gotten for free). When I was new to circuit based theory, his videos were among the worst I've seen rivaled only by Scott at defpom mumbling about topics that he couldn't properly explain. I respect gs credentials greatly but the person and the attitude not at all. You've never made a video I couldn't understand and have made some of the most profound comments on life in general that have moved me. Great Scott will advertise for anyone and competing companies while making some of the laziest content I've ever seen. Maybe it's just my mental ilness talking but I used to think this was a community only to see people get a bunch of subs and become lazy creators who shoehorn 3 ads into a single video. People like him make me realize that ill never even own a keysight tshirt, get free pcbs and a mill to make them. I give half my disposable income to charity, that's not to say everyone should but I never see anyone at the top do anything nice unless it benefits them. I'm recently 45 and plan to get an ee degree as I have over a year's worth of math credits that carry over from my degree. I've been coupled up in my house for a decade, scared to leave, scared to sleep, keep to myself except for charity donations and I'm lucky to have paid enough insurance to make more money than most people I know and I grew up with nothing so I believe we should take from life what we need and let no extra go to waste. I could live tax free until I'm 67 and be over ten years past where my long term investments mature but I'm determined to get back to work and do something I love. A lot of our peers are blessed in that they worked hard and gained a following on here but have zero job experience when this comes to an end. This will come to an end as technology and people's interests have evolved since we could bang out cobol on a dummy terminal over half a decade ago. Sadly content creator will not be considered Jon experience I suspect and it pains me to say because I care about people's livelihoods whether I like them or not as my opinion does not equate to wishing bad things upon someone. People shoukd be giving back more, especially in our space where a creator could say to keysighT, carvera, pcbway or whoever that they insist on them giving back to people who feel like they're invisible and can't get ahead. I don't give to receive but positive reinforcement is what creates communities, builds good will and people remember that stuff in the future. Every time I've gotten a new scope or other piece of gear I've donated the old one (much to my wife reminding me we're not rich). There's a few passions in life that keep me going; rescuing animals, helping people get started in this hobby we love, my family, practicing guitar as it's what I'm best at and a world class player (not a boast, there are millions of others like me) and I donate guitars and gear when I get new stuff. Just once I'd like to see someone help me help someone. I'd do anything to have a decent spectrum analyzer but I can't justify 3k for a cheap one after tax in Canada because of all the other things I have to pay for to get into rf. I have weird traits due to being a first responder with ptsd and when I meet people I warn them about things I do sometimes that (I've been in therapy forever dealing with) that I hate but no one ever tells me that I'm doing it and end up hating me instead of helping me and being honest. I'm going away soon for a 9 week inpatient program that costs an outlandish sum to try and not be so afraid anymore and be able to leave my house and go for walks and travel, get more involved helping people. I've tried and failed to commit suicide 3 times this past year because I felt bad for people having to put up with me. It's like I'm a broken circuit that works acceptably but there's no feedback loop of any sort letting me know how I'm doing. I could be spiteful and not budget for charity and get a crappy sa (which I need for making antennas) and never be happy with it or continue on trying to help people which is bred into me but I get no enjoyment from as I believe people should be able to find their passions in life and 250 from me is a small price to help them find it. What am I doing wrong brother, I live a clean an honest life yet I'll spend Xmas alone while my family celebrate the next street over because they disowned me over a mistake which didn't hurt anyone and I've apologized for a million times. I go weeks without anyone texting me sometimes and I wonder why. I have no enemies, I hold no grudges, I treat people the way I'd like to be treated, with respect I mean. Dad died when I was 10 and life has been hell ever since, I hope the next 35 years are better.

[@danadkin8652]

I use SDR as part of my QO100 setup. Another to receive and upload my weather station onto aprs. Another for tracking radiosondes, and im halfway through building a RX_TX ensemble transciever. Looking into adding a sdr to my FT991 to add a panadapter. Go fun and interesting.

[@HB9BLA]

I added a "panadapter" to my 7300 which was quite easy because it already provides cat signals. But mostly the waterfall on the rig is ok for me. Of course I use a Pluto plus for my QO-100 (with an ethernet connection to the roof)

[@wei48221]

Awesome!!

[@HB9BLA]

Thanks!

[@nnd18571]

Nice countryside in Switzerland :)

[@HB9BLA]

Thank you!

[@serych]

One of your greatest videos! Thanks! And your Swiss accent is perfect as usually. :-) 73! Jakub, OK1SE

[@HB9BLA]

Glad you think so!

[@DAVIDGREGORYKERR]

All SDR receivers/transceivers use ADC to digitize the the incoming signal into data then process it using High School Mathematics then convert the resultant data back to audio using a DAC.

[@HB9BLA]

You forgot the most important stuff: The transmit and receive it on RF

[@henkoegema6390]

Very interesting. 73, PA2HO

[@HB9BLA]

Thank you!

[@grahamtanner1066]

Very interesting, and I learned a few things from the video. Why no mention of the Airspy series of SDRs?

[@HB9BLA]

Because there are many SDR receivers and I do not own an Airspy...

[@Andy2e0ree]

Fantastic show thanks for sharing brother de 2e0ree

[@HB9BLA]

Thanks for coming!

[@thomasyamaguchi6434]

Consider to learn more on the SDR

[@HB9BLA]

Good idea!

[@user-pm1yz5zv4v]

Hi, can we use a SDR Rx radio to accurately measure the FM frequency deviation. ie. as a deviation meter to check the transmitter drive level? any thoughts? thanks regards Nigel ZL2SEA

[@HA7DN]

As a freshmen in the HAM club, I was tasked to give an exercise to the (not-yet-joined) newbies about SDR, from the basics to the point where we made an FM receiver from scratch using an RTL-SDR and some C code. I have to congratulate you for cutting down the math, because this topic is very math-heavy (but also I think one can only understand the beauty of it if he/she also understands the math). Anyways, I might have scared the newbies a bit with the half-a-blackboard equations, but also told them not to ever try to learn it, only care about the first/last lines...

[@HB9BLA]

I do not think math is needed. And the chance you scare them, and they are no more interested in the topic is high :-(

[@HA7DN]

@@HB9BLA to be fair, this HAM club mostly gets fresh members from a technical university (and mostly EE and CE), so in fact they should already know the math, but not seen it in use. I do not, however, agree with the "no math is needed" point. Yes, no math is needed to plug in an RTL-SDR and listen to stations, but to build anything you will need it - even just to make some simple receiver in GRC, you have to understand how do IQ signals work.

[@chuxxsss]

Morning mate, I need a cheap SDR for my weather station. We don't get nice ID card here. Are we calk this i or J notation. 4 + j10? Had a old SDR TV tuner, but it just doesn't show on Linux.

[@HB9BLA]

I use the RTL-SDR dongles from Aliexpress. They are widely supported and relatively cheap. i or j: I do not care too much ;-)

[@maximus6884]

Caribourite is also an excellent device based off HakRF but works as a header for RPI. Its made for educationa purposes. So the code is based off python and is so easy to understand.

[@HB9BLA]

I did not know CaribouLite but of course, I own a HackRF. I will probably focus on Gnu Radio Companion for the SDR education because I think it is easier to understand for non-programmers. But Python is a good choice for the rest...

[@maximus6884]

@@HB9BLA ofcourse! GNU Radio is amazing! I think it makes a lot of sense to use Python with GR. I heard we can develop OOT modules with python and make our own demodulators. Coo stuff.

[@DavidMishchenko]

Is it possible to hack SDRs to bypass the Mixer or set the Local Oscillator to 0 Hz to use them as crude oscilloscopes?

[@HB9BLA]

If you have an ADC with the needed speed you do not need a mixer.

[@yvesinformel221]

At 21:08 for the SDR play, frequency range start at 100Khz not 1 Khz

[@HB9BLA]

You are right. My mistake.

[@yvesinformel221]

let say I want to use SDR for a high quality FM receiver, does it make any difference to choose a cheap vs an expensive unit. expansive unit have larger banwith (you can record more at once), more bits ( more bits enable you to receive lower and higher strench signal without overloading), so the difference would be after the ADC (my guess is that the ADC is important for lower conversion error ie distortion)?

[@HB9BLA]

The ADC is the expensive part and defined the bandwidth as well as the dynamic Range of the SDR receiver. The rest is software (and a bit filtering for strong signals)

[@planker]

Good Show. I have purchased the Nooelec Nano three months ago I'm not sure why. I have SDRSharp on the PC and had a few tests. It works, now what?

[@HB9BLA]

That is often the question. I try to start the other way round, but I am not always successful, too.

[@peterdambier]

Trying to mess with my Yaesu FT-4X for CW. Now I know why I did not see 455 mHz. No Way. 73 Peter DL2FBA

[@HB9BLA]

The problem is that you probably will not find anybody doing CW on FM... (I do not own such a device and assume it is FM only)

[@peterdambier]

@@HB9BLA it is FM only. Normally I could inject a BFO at 455 kHz but this thing has got no decent IF - a YAESUed BAOFENG SDR.

[@tompodgorski3598]

Very interesting movie. What will be the best solution to work on QO 100 HackRF or Adalm Pluto? Many colleagues work on the latter platform. What to choose?

[@HB9BLA]

I had the Adalm Pluto and recently changed to the Pluto Plus because it has built-in Ethernet. I never saw somebody using the HACKRF for that purpose.

[@tompodgorski3598]

@@HB9BLA TNX Andreas see you in QO100 Best 73 Tom SQ6PNT 👍

[@danstahlberg]

Thank you for a very good overview video, I almost understand the Q/I-signal now. Almost :) Do you have any link to the IMSI catcher software? /SM0YWD Dan

[@HB9BLA]

No, I am not interested in this topic :-(

[@silvio2402]

What do you think about the cheap HackRF One clones from China? Can they at least be used or are they complete garbage? Thanks!

[@HB9BLA]

I have one and it works. But I bought it years ago. Check also if an Adalm Pluto or a Pluto Plus is an alternative. I use them for my satellite project. Important is that your software has the drivers.

[@DAVIDGREGORYKERR]

A Stereo ADC/DAC should work what about sample at 88200Hz

[@HB9BLA]

Maybe. We do not use stereo with SDR stuff. And our bandwidth is usually quite small (3kHz)

[@DAVIDGREGORYKERR]

@@HB9BLA I meant a dual channel ADC chip and possible a DAC chip as you have to sample both the I/Q signals do you for processing before converting back to analogue.

[@lemd49]

Nice radio amateur licence in CH. Here in EA land we get a pdf that we need to print and cut out ourselves…

[@HB9BLA]

True, it is nice. But till last year it costed 120 Euro per year. And now still 45…

[@zyghom]

@21:07: 0.1MHz in Switzerland is 1kHz - wow ;-)

[@HB9BLA]

You are a very good viewer ;-)