Welcome to the World of Software Defined Radio (2016)

[qubex]

DVB-T type devices such as the one referred to in this article are indeed remarkably flexible but keep in mind that they are only able to receive. In my case, that quite rapidly exhausted my curiosity.

I'm now eagerly awaiting delivery of a LimeSDR (https://www.crowdsupply.com/lime-micro/limesdr), one of several hacker-friendly radio peripherals that can both receive and send (in the LimeSDR's case, in full duplex mode) because of course having a transceiver is a whole different ball-game. GnuRadio can serve as the logic of both receivers and transmitters.

Of course depending on country, frequency and transmitted power you may require licences to operate.

[superkuh]

>In my case, that quite rapidly exhausted my curiosity.

I've been exploring the world of radio emissions with rtlsdr since 2013 (http://superkuh.com/rtlsdr.html) and I'm still finding plenty of new things to do.

IMO, the newest cool stuff with rtlsdr are computational hacks to align multiple non-coherent receivers in time to do distributed direction finding and the like.

[ptero]

I recently read here that a Raspberry Pi can be turned into an SDR transmitter by attaching a wire to a pin. On paper, the specs look impressive (for a $20-$30 device), but I would love to know the RF quality of the resulting waveform.

I cannot find the discussion, but the info is here: http://www.rtl-sdr.com/tag/rpitx/

[technofiend]

What exhausted mine is the fact broadcast digital FM radio in the US is protected by patent and license encumbered encoding schemes, so there are no open-source decoders for GNU Radio and derivatives.

[brian-armstrong]

I got a Lime and I've not really had a great experience with it. You can't actually receieve HF with it unless you desolder an inductor. Also mine has a HUGE DC bias which introduces a ton of noise and basically cuts the usable bandwidth in half, if not more. Sadly I think these things were overhyped and/or ran into design issues that keep them from living up to the promise

[robputt]

Yeah, I get that feeling too, but the problem is the licensing and stuff... The good news is I get my send and receive fix from LoRa and The Things Network, still has legislation you must abide by like duty cycle and power limits, but doesn't have the headache fo being a HAM.

[anfractuosity]

That micro limesdr looks very tempting. Also someone on /r/rtlsdr mentioned PlutoSDR which is also in a similar price range. I need to start to save up!

[nextlevelwizard]

Sending capability (at least here) requires amateur radio license. It is technically illegal to even own transmit capable equipment without a license and you can operate it only under supervision of licensed person.

[trishmapow2]

SDR and RF in general has always felt like black magic for me, but the availability of cheap hardware and wife software selection makes this accessible to everyone. For newcomers I recommend the RTL-SDR subreddit, plenty of great resources. My latest venture is a jam and replay attack on keyless entry systems eg vehicles, project page is here: https://github.com/trishmapow/CC1101-FSK

[bjt2n3904]

Not gonna lie. As a radio guy, our terminology is messed up. My favorite though is using superlatives.

Low Frequency (LF), Medium Frequency (MF), High Frequency (HF).

You'd think that maybe HF is WiFi, but you gotta remember these terms were invented back in the early days of radio. HF is between 3 and 30 MHz.

You have Very High Frequency and Ultra High Frequency, but that only takes us to 3 GHz. 5 GHz Wifi is technically SHF -- or Silly High Frequency.

But we also refer to these frequency bands in terms of MHz, or if we feel like it, wavelengths. Since radio signals travel (effectively) at the speed of light (m/s), we can multiply Hz (1/s) by a distance and get wavelength. (c = f * l). 144 MHz then is the 2 meter band, or VHF as we call it.

Confused yet? Wait until we start talking about baseband and I/Q signals!

[mberger]

  availability of cheap hardware and wife software selection

If only that was true... ;)

[payne92]

For a device that can transmit as well as receive, consider HackRF: https://github.com/mossmann/hackrf/wiki

It's been out for a while.

The newer option is LimeSDR, which just shipped: https://www.crowdsupply.com/lime-micro/limesdr

(Note that you need to comply with all local laws regarding transmitting).

[TKinNC]

There is a glaring error at the beginning of this article under the "things you cannot do with SDR."

"Listening in on the conversations of Ham operators."

In the US at least, there are many VHF/UHF Ham bands easily received by SDR. I use an Airspy on Mac OS X, and although the software is terrible, there is plenty to listen to.

[codazoda]

I was thinking / wondering the same. Many new HAM operators get handheld radios that use the 144MHz (2 meter) and 440MHz (70 cm) bands. Both of these seem to be within range of this device. You can also build a dipole antenna for these frequencies for a few dollars. That would allow many of us to listen to repeaters in our local area. RepeaterBook.com (or the mobile app) is a good resource for listing repeaters near you.

I haven't had time to write much detail about this but here's an antenna I built recently. A quick google search will bring up dozens of other designs.

https://www.joeldare.com/topics/amateur-radio/#gift-card-dip...

[mikestew]

Maybe they were thinking HF (High Frequency), which is what's used for long distance/international contacts and what many people think when they think "ham radio". AFAIK the USB stick receivers can't receive HF. But that's a hardware limitation, not SDR limitation. There exist SDRs that can do HF, they just don't cost $15.

[KGIII]

This thread could use this link:

http://websdr.ewi.utwente.nl:8901/

Basically, it is an SDR for multiple users and an online interface. It's RX only, of course. More options are available at websdr.org but the above is my favorite.

Caution, it can be a huge time sink.

[coin]

> mhz

Should be written using the proper SI prefix, MHz. There's a huge difference between the milli (m) prefix and mega (M).

[bosky101]

Relevant...

Listen to Radio from around the globe

http://radio.garden/live/ (drag the map to tune in)

[lioeters]

This is really wonderful, thank you for the link. I'm enjoying now a radio broadcast from..Malawi. The diversity of voices around the world, the ease of moving and focusing on stations - one of the best things I've seen on the web.

[codazoda]

Is there a similarly priced and sized SDR that can both receive and transmit?

Having received my ticket recently, I'd love to try some digital ham radio modes without spending a fortune.

[billh]

There is the LimeSDR Mini that is currently being croudfunded[1]. For $140 USD you would be hard pressed to find anything like it that would give you full duplex across that frequency range. I own the full size LimeSDR device and it has been a great piece of hardware for playing around with.

1. https://www.crowdsupply.com/lime-micro/limesdr-mini

[rwmj]

Not that I've seen. There exists SDR hardware for transmitting, but all seemed to start at multiple $100's. In any case note that you will almost certainly need a license to transmit on most interesting frequencies and power levels.

Edit: "ticket" = license?

[senatorobama]

Why are SDRs for TX when you can get a SoTA radio in a smartphone for < $10?

[jballanc]

...wrong thread...

[mnarayan01]

If anyone's confused, parent is presumably intended for https://news.ycombinator.com/item?id=15302267.

[lima]

Wrong thread :)

[dogruck]

Reminds me of this ye old project at MIT http://www.sds.lcs.mit.edu/SpectrumWare/home.html