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GNU Radio

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Re: GNU Radio

#61

Post by yeetaccount4 »

brightball wrote: post #44
ggm wrote: post #2

Has always done a terrible job of selling itself. A $25 dtv receiver and a chickenwire antenna parabola and code your own satellite TV decoder, learn what radar guns emit, emulate a modem... maybe even shift to IR and do TV controls.. it's, latent in this stuff. But the frontpage doesn't take you there.

I am always shocked that radio isn’t core science curriculum in high school at this point.

Have you driven around town at noon? That’s when kids were getting out of school pre-pandemic. I just read this morning Kansas is so desperate for substitute teachers that they’ll take on teenagers without a single college credit. The public school system in many parts of the country is basically state funded daycare.

Re: GNU Radio

#62

Post by CamperBob2 »

syedkarim wrote: post #46
aatharuv wrote: post #45

Earlier quoted context omitted.

Any chance this is at least partially deliberate? If more people were to use GNU Radio, the manufacturers of said hardware would get sued until they were forced to lock down their hardware.

Do you mean manufacturers of RTLSDR devices? Those don’t need to be locked down (in the US), as they are receive-only devices.

Technically, the ECPA is still on the books in the US, prohibiting devices that can receive the old 800 MHz AMPS cellular band.

The ECPA was always a complete legal atrocity, and I don't think it's been enforced for many years, and cell phones no longer use NBFM or anything else that an unauthorized receiver can decode, but...

Re: GNU Radio

#63

Post by nousermane »

jcrawfordor wrote: post #43
geenew wrote: post #13

Earlier quoted context omitted.

Is it possible to use a laptop's built-in wifi antenna / wifi card as the hardware side of a gnu radio setup? That seems like it would be a nice cheap one-two punch for getting started. AFAIR wifi uses the public (unregulated) bands so there should be lots of interesting stuff on those frequencies beyond wifi signals.

WiFi adapters don't really expose this type of interface. WiFi adapters interact with the host computer by sending and receiving packets, the 802.11 framing and radio de/modulation is performed internally by the adapter. In other words, the host computer sees IP packets, not radio data. Some adapters (or really most adapters) provide some ability for the host to send and receive raw 802.11 frames but it's an infreque…

Very few consumer wifi cards expose raw IQ to host software, but such cards do exist:

https://wands.sg/research/wifi/AtherosCSI/

Re: GNU Radio

#64

Post by Jenda_ »

throway453sde wrote: post #27
RF_Savage wrote: post #15

Earlier quoted context omitted.

Due to it being a radio licenced by rule, the firmware in wifi devices is locked down tight. If it ware wide open FCC would revoke it's type acceptance. The only project that so far has managed to even partially use wifi hardware as a more generic SDR is nexmon[1] and even that is rather involved. Really cool project but not much heard since 2018. For just experimenting with modems across a noisy path one could just…

If i run linux can i modify the firmware? Also the regulations differ from country to country so this should be legal in some of the country.

I would suggest not starting in the 2.4GHz band, the protocols used there (wifi, bluetooth) are very complicated to understand. Get a rtl-sdr and start with something simpler: FM broadcast (my blogpost: https://www.abclinuxu.cz/blog/jenda/2019/11/gnu-radio-first-..., there is even an example capture you can download and replay, so you can start without the physical radio), police radio (both analog and digital), radiosondes, weather satellites, ISM stuff - temperature sensors, garage and car remote controls, airplane multilateration (https://github.com/mutability/mlat-server )… You can do lot of stuff even with the $10 rtl-sdr, for example I have used it for multilaterating TV and radio transmitters (thesis: https://jenda.hrach.eu/dipl.pdf, unfortunately "layman's explanation" is available only as a lecture in Czech). I know people are even building radioastronomy stuff and passive radars (https://www.rtl-sdr.com/passive-radar-dual-coherent-channel-...) with rtl-sdr.

Once you have basic understanding of the topic, you can get better hardware: AirSpy (the same features as rtl-sdr, but MUCH better signal-to-noise ratio and bandwidth) or bladeRF (costly, but probably the best radio you can get now). For example I'm now building a weather radar based on bladeRF. The bladeRF has a FPGA with open-source HDL, so you can mess even with absolutely lowlevel and bleeding edge stuff.

Going back to your original question:

Most cards load firmware from a file when they are initializing (check "dmesg|grep firmware", on my machine, for example, it says it has loaded /lib/firmware/rtl_nic/rtl8153b-2.fw), you are free to modify it. However, all (or maybe almost all) wifi cards have the format of the blob completely undocumented so it would be very hard to make a modification that would allow you to transmit/receive arbitrary signals. Something similar has been achieved with GSM phones (see OsmocomBB), but it requires very complicated reverse-engineering.

Recently, there was a wifi stack released for a SDR, so the other way around: https://www.nuand.com/bladeRF-wiphy/.

Re: GNU Radio

#65

Post by Jenda_ »

szopa wrote: post #9
ggm wrote: post #2

Has always done a terrible job of selling itself. A $25 dtv receiver and a chickenwire antenna parabola and code your own satellite TV decoder, learn what radar guns emit, emulate a modem... maybe even shift to IR and do TV controls.. it's, latent in this stuff. But the frontpage doesn't take you there.

What are some good resources to start playing with SD add an amateur?

I would suggest these two as a crashcourse to the math that is used in SDR:

https://www.dsprelated.com/showarticle/192.php https://www.katjaas.nl/home/home.html

We are maintaining a long list with theory/math: https://brmlab.cz/event/dsp#zdroje , and engineering stuff: https://brmlab.cz/project/sdr/start#links . However, I agree it is rather difficult to get into the topic. I'm playing with SDRs for almost 10 years (increasingly "fulltime" lately), and we still need to employ a professional mathematician to help me with some advanced problems.

Re: GNU Radio

#66

Post by Jenda_ »

nereye wrote: post #14
szopa wrote: post #9

Earlier quoted context omitted.

What are some good resources to start playing with SD add an amateur?

https://pysdr.org/ is a good introduction to DSP/SDR using Python. Previous discussion on HN: https://news.ycombinator.com/item?id=24750588 . Ham Radio Workbench podcast on GNU Radio: https://www.hamradioworkbench.com/podcast/GNU-Radio . In terms of hardware, there is a large spectrum, from inexpensive RTL-SDR (receive only, ~$25), PlutoSDR (transmit and receive, $229, which PySDR covers) all the way to $x000+ for US…

There are also cheap SDR transmitters:

https://osmocom.org/projects/osmo-fl2k/wiki (repurposing a USB-VGA dongle as analog source)

https://github.com/F5OEO/rpitx (repurposing bitbang/PWM GPIO; we had weird problems with data corruption when we were trying to use it as a radio modem, but maybe you will have more luck)

https://bellard.org/dvbt/ (repurposing standard VGA card, but it's probably not worth it since fl2k is way better)

(beware that low quality of the transmitter usually means it will cause interference with other stuff. However, all of these have such a low power that if you will not use an amplifier, it will be OK, the interference will be probably undetectable outside of the room where the transmitter is)

Re: GNU Radio

#67

Post by throway453sde »

RF_Savage wrote: post #60
throway453sde wrote: post #27

Earlier quoted context omitted.

If i run linux can i modify the firmware? Also the regulations differ from country to country so this should be legal in some of the country.

You will not be able to modify the firmware blob just by running linux. Few years back there was danger of FCC de facto banning alternative router firmwares like openwrt to prevent tampering with the wifi cards firmware. This was the "only manufacturer signed firmware allowed" thing that thankfully was avoided. FCC's motivation in this is to prevent people from using too much power or certain frequencies. And as most…

You mean there are binary blobs without source code in the linux repo?

Re: GNU Radio

#68

Post by bobthebuilders »

throway453sde wrote: post #67
RF_Savage wrote: post #60

Earlier quoted context omitted.

You will not be able to modify the firmware blob just by running linux. Few years back there was danger of FCC de facto banning alternative router firmwares like openwrt to prevent tampering with the wifi cards firmware. This was the "only manufacturer signed firmware allowed" thing that thankfully was avoided. FCC's motivation in this is to prevent people from using too much power or certain frequencies. And as most…

You mean there are binary blobs without source code in the linux repo?

Yup. One of the reasons GNU has a deblobbed Linux build.

Re: GNU Radio

#69

Post by geenew »

RF_Savage wrote: post #15
geenew wrote: post #13

Earlier quoted context omitted.

Is it possible to use a laptop's built-in wifi antenna / wifi card as the hardware side of a gnu radio setup? That seems like it would be a nice cheap one-two punch for getting started. AFAIR wifi uses the public (unregulated) bands so there should be lots of interesting stuff on those frequencies beyond wifi signals.

Due to it being a radio licenced by rule, the firmware in wifi devices is locked down tight. If it ware wide open FCC would revoke it's type acceptance. The only project that so far has managed to even partially use wifi hardware as a more generic SDR is nexmon[1] and even that is rather involved. Really cool project but not much heard since 2018. For just experimenting with modems across a noisy path one could just…

For future reference, this[0] is a good get-started guide to getting a signal from the microphone, outputting a signal to the speaker, and some basic signal display / waveform generation.

For my own use (on windows 10), I used the following device names for the microphone / speaker: Microphone: "Microphone Array (Realtek High Definition Audio)" Speaker: "Speaker/HP (Realtek High Definition Audio)"

Specific names on windows can be found in the Control Panel > System > Sound (as of the date of writing)

[0] https://www.youtube.com/watch?v=pTqaSCXTSqY

Re: GNU Radio

#70

Post by pabs3 »

geenew wrote: post #13
ggm wrote: post #2

Has always done a terrible job of selling itself. A $25 dtv receiver and a chickenwire antenna parabola and code your own satellite TV decoder, learn what radar guns emit, emulate a modem... maybe even shift to IR and do TV controls.. it's, latent in this stuff. But the frontpage doesn't take you there.

Is it possible to use a laptop's built-in wifi antenna / wifi card as the hardware side of a gnu radio setup? That seems like it would be a nice cheap one-two punch for getting started. AFAIR wifi uses the public (unregulated) bands so there should be lots of interesting stuff on those frequencies beyond wifi signals.

There are some cards with open source firmware, you might be able to modify it to do something like that.

https://github.com/chunkeey/carl9170fw/ https://github.com/qca/open-ath9k-htc-firmware http://netweb.ing.unibs.it/~openfwwf/

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