
Welcome to the World of Software Defined Radio - robputt796
https://www.robertputt.co.uk/2016/12/04/welcome-to-the-world-of-software-defined-radio/
======
mmaunder
SDR is fun and the way of the future. I'd say we're getting close to a very
low cost SDR that also brings together usability and excellent RX/TX and
filtering capability. We're not there yet and so my Kenwood TS-2000 and Yaesu
857D and 817ND still kicks the butt of low cost SDR's.

You'll find as you set up the base station your focus quickly moves to
antennas. And then you become obsessed with antennas.

Definitely get into amateur satellites.
[http://amsat.org/status/](http://amsat.org/status/) Go get a cheap handheld
arrow dual band antenna with built-in diplexer to get started. I use
macdoppler and also Ham Radio Deluxe's Satellite module. They are Mac and
Windows respectively - I use them both for different things. Mostly I use
macdoppler to make the doppler corrections automatically on my Yaesu 817ND and
I use HRD for my TS-2000.

Also, build yourself a HF monoband dipole antenna tuned to 14.3MHZ and then
listen in to the ham band from 14.00 to 14.150 for digital/cw and from 14.150
to 14.300 for voice. It'll cost you about 20 bucks for the coax and a few
bucks for the wire. You don't need a balun if you're using low enough power
for TX.

If you want to be a bit naughty (this is HN afterall) google around and learn
about FLTSATCOM 7 and 8. It's an old US milsat that is basically an open
repeater. They're geosynchronous birds that are used for encrypted comms but
Brazilian criminal gangs periodically use them for free communication. They
build antennas out of spare parts and use down-converters/up-converters to
deal with the 250mhz frequency which is outside normal VHF/UHF. With your SDR
you can build your own cheap home depot antenna and listen in without a
converter. Just do absolutely not broadcast because you'll get arrested -
someone already has. You can sometimes pick up used special forces directional
portable antennas for a reasonable price on ebay for 250mhz.

I'm a radio amateur, callsign WT1J. If you're into this stuff and find
yourself able to TX on HF or satellite, drop me a line and we can set up a
schedule.

Mark.

~~~
comboy
I'm a noob and yeah antennas seem crucial. I wish there was some book I could
read on the subject or some recommended websites. Maybe HN can recommend
something. There are many tutorials how to build an antenna for specific
purpose, but I'd like to gain some basic understanding of how do you design
it.

~~~
jonah
Take a look at the _ARRL Antenna Book_

~~~
mmaunder
What he said. It's sitting on a desk next to me.

------
heywire
SDR has been an endless source of fun for me. I have a half a dozen different
rtl dongles hooked up to raspberry pis and my laptop at any one time. Most
recently I wrote a program to read the 900MHz broadcasts from my electric and
water meters [1]. I'm also using an existing program to monitor our gas meter
[2]. rtl_433 is another fun one [3].

[1]
[https://github.com/shaunhey/ea_receiver](https://github.com/shaunhey/ea_receiver)
[2] [https://github.com/bemasher/rtlamr](https://github.com/bemasher/rtlamr)
[3] [https://github.com/merbanan/rtl_433](https://github.com/merbanan/rtl_433)

~~~
robputt796
This is a super cool application for this, unfortunately our water meters and
stuff in the UK are very basic mechanical devices in most cases still which
sucks so none of this fun for me... This does remind me I probably should
check out a few other things though, such as ZigBee protocol on my home
automation stuff.

~~~
TickleSteve
The SMETS1 and SMETS2 smart meters that you will be getting soon will have
ZigBee.... but secured and tied down so although you will be able to sniff the
comms... everything will be encrypted.

...We're far too privacy and security conscious in the UK to allow plaintext
personal data go over the airwaves...

~~~
graystevens
Been meaning to look into the smart meters here in the U.K. after having them
fitted recently. I had horrible thoughts of it all being clear text, so it's
nice to know that no one can snoop on my gas and electric usage. I had assumed
they were at least working on the 2.4Ghz frequency as it'd dropped out a few
times due to interference with other kit.

~~~
TickleSteve
All comms are end-to-end encrypted, each meter has unique certifications and
keys and the data also tends to be stored encrypted on FLASH. The
certification also requires the standards authorities to view the source and
have strict guidelines on security, robustness, sanitisation of data, etc.

~~~
draugadrotten
> All comms are end-to-end encrypted... The certification also requires
> ...strict guidelines on security...

So what you're saying is that, in the UK, your water meter and electrical
appliances are required to have a higher level of security than your online
browsing is _allowed_ to have?

Gosh

[https://en.wikipedia.org/wiki/Encryption_ban_proposal_in_the...](https://en.wikipedia.org/wiki/Encryption_ban_proposal_in_the_United_Kingdom)

~~~
TickleSteve
hehe... effectively, yes, oh the irony....

You have to consider tho, that the smart meters don't operate on the public
internet, its all on a proprietary WAN (government specified).

There are many, many wacky design decisions regarding the UKs smart metering
design but they do at least make an effort regarding security and robustness.

------
edejong
If you like SDR, you should definitely have a look at GNU Radio Companion
(GRC) [1]. A nice introduction into the methods of GRC is given by Michael
Ossmann [2], which is really worth checking out.

[1]
[http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioC...](http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion)
[2] [http://greatscottgadgets.com/sdr/1/](http://greatscottgadgets.com/sdr/1/)

~~~
heywire
I can't recommend those videos enough, great stuff!

~~~
trapperkeeper79
Pardon me, what videos?

~~~
awqrre
[http://greatscottgadgets.com/sdr/1/](http://greatscottgadgets.com/sdr/1/),
probably...

------
w8rbt
___" I’ll be honest I have always thought radio related stuff is a bit of a
strange and boring hobby, the electronics side fine, but sitting and chatting
to people in a slow and often poor quality conversation didn’t really seem
that interesting to me"_ __

\---

You can send data over radio links and do other very interesting things... All
without using a network! Just two nodes transmitting and receiving data via
antennas at the speed of light. You don't have to talk at all. A lot of people
don't get this when they think about radio.

Radio is not just old, retired guys talking about health problems on VHF/UHF
repeaters. Rather, it's a world-wide network, that has no infrastructure
dependencies, transmitting data at the speed of light.

~~~
mmaunder
What many people don't realize is that right now, as you're reading this,
you're probably using radio. Either wifi or 4G cellphone. Seems like an
obvious statement, but RF engineers have done such a great job at making IP
over the air reliable with 802.11X and 4G/LTE that we can forget about the
fact that we're using it.

The problem with this though is security. We tend to focus as security
engineers too much on stuff riding on top of IP and forget about the
underlying layer 1 protocols. And so that's for me what makes radio really
interesting - especially dark corners that haven't been looked at for some
time because they've been forgotten about.

~~~
comboy
If you have proper security on a higher abstraction layer you don't care at
all how the data gets transmitted, who can listen to it or modify it.

~~~
jonah
Note that on the Amateur frequencies, it's illegal to "Obfuscate" your
transmissions. You can't even use coded language.

~~~
comboy
Didn't know that. Surely some people tried steganography? Or is there too much
noise to try something like that? (and thanks for the antenna book
recommendation)

~~~
pjc50
That would count as "obfuscation".

~~~
comboy
It's really hard to prove steganography if you are hiding encrypted data
(which looks like noise if it's properly encrypted)

------
deutronium
I really wish there were cheaper Tx capable SDRs, as they look like a lot of
fun! The cheapest ones I've seen at the moment seem to be around $200 hackrfs
from aliexpress.

~~~
heywire
While not SDR, there are some cheaper alternatives if you're just looking to
mix code and radio transmitting.

[1]
[https://www.adafruit.com/products/3076](https://www.adafruit.com/products/3076)
[2]
[http://www.ebay.com/itm/162086931088](http://www.ebay.com/itm/162086931088)

~~~
deutronium
Yeah that's a good point I've got a module which uses
[http://www.silabs.com/products/wireless/EZRadioPRO/Pages/si4...](http://www.silabs.com/products/wireless/EZRadioPRO/Pages/si446x.aspx)

The chip itself covers 119–1050 MHz, but the modules I have, have filters on
to allow only narrower ranges.

~~~
heywire
I got excited there for a second, I thought you linked the Si468x, which I
have been thinking about tinkering around with. It is just a receiver, but it
does HD radio which interests me for some reason (it certainly isn't the audio
quality :))

------
tmescic
A fun way to use one of these is to decode images sent from weather
satellites. We built a system to decode images from a Russian Meteor-M2
satellite by using a RTL-SDR, home made antenna and GNU radio (image gallery :
[http://meteor.amphinicy.com/](http://meteor.amphinicy.com/)). Unfortunately,
we are located in the city center with a lot of RF noise and interference so
images are not as clean as they could be.

------
buserror
Funny that, I've played all week-end with a RTL stick[0], and a £30 'weather
station' thing from amazon[1]. Using rtl_433[2] it took no time at all to be
able to receive what the sensor pods are sending over, it's really pretty
cool!

I've also ordered some 433mhz wall/light switches, I hope to be able to
receive/transmit and log all of that stuff, from what I can see, with a bit of
tweaking you can integrate quite a few vendor's kit, and even integrate it
with amazon Alexa for voice control.

Also started to 'explore' the spectrum using gqrx/gnuradio, I can see how it
could become addictive :-)

[0]:
[http://www.ebay.co.uk/itm/152142033580](http://www.ebay.co.uk/itm/152142033580)

[1]:
[https://www.amazon.co.uk/gp/product/B00SIZZBDK](https://www.amazon.co.uk/gp/product/B00SIZZBDK)
[ whoops sorry went up in price, cyber week is over :( ]

[2]: [http://www.rtl-sdr.com/using-rtl-sdr-rtl_433-decode-
various-...](http://www.rtl-sdr.com/using-rtl-sdr-rtl_433-decode-various-
devices/)

------
qwertyuiop924
...You can totally listen in to HAMs using RTL-SDR. 10m, 6m, 2m, 1.25m, 70cm,
33cm, and 23cm all fall within the ranges mentioned.

As much as the HAM radio is traditionally an HF affair, the easiest to obtain
licence (Technician class) actually pretty much only allows for VHF and UHF
transmission. Not only that, but even among Generals and Extras, 10, 6, and 2
are very popular, especially for local communication (usually through a
repeater), whereas HF is more commonly used for DXing.

You can even listen in to APRS, which is message stream that carries a lot of
interesting data (mostly GPS stuff, but you'll catch a few text, email, or
general messages through it every once in a while).

~~~
mmaunder
Yes that's about right. For technician's 2 meters and 70cm are by far the most
popular. Just tune into a local repeater using a $50 handheld and you can chat
all day. You can also use echolink and IRLP to chat world-wide via your local
repeater or even connect to a repeater from your smartphone or PC.

------
devereaux
I will leap as soon as I can get something like the
[https://xtrx.io/](https://xtrx.io/) with a mini PCIe interface or expresscard
interface. I want to do the processing on my laptop without the limitation of
a slow bus.

Also I would love some solution to nicely expose the ufl connectors.
expresscard would seem a better choice to me that mini PCIe, to connect
antennas on the side of the laptop or the back of the desktop when using a
PCIe to expresscard adapter.

~~~
gravypod
I could only dream of having this in my thinkpad able to do some cool mesh
networking/APRS strait in my machine.

------
fosco
Think this bookmark of an intro to SDR is appropriate

[https://www.youtube.com/watch?v=kWfU1G3Jq4w](https://www.youtube.com/watch?v=kWfU1G3Jq4w)

------
Tempest1981
How do Ham radio operators feel about SDR? (In general)

Do they think it's interesting and cool, or do they reject it for being
different and inferior vs. more expensive and sensitive equipment?

~~~
w8rbt
It depends on who you ask.

The younger generation who have ECE/CS degrees love SDR. So does the military
and the commercial/corporate radio industry. Some of the older generation
frown upon SDR as voodoo magic with too many computer/network dependencies.

There is a general distrust (among older hams) of computer/network technology
and especially anything that depends on a non-human (computer program) to
modulate or demodulate a message.

For example, you can send Morse Code with a Carrier Wave and a simple switch
(on and off) that you built from wood scraps and copper. You don't need an
external thing (program, software, device, etc.) to do that for you. So there
are less dependencies and in general it is much simpler to reason about and
use. When the shit hits the fan, you want simple, reliable things.

The problem is, most humans don't know Morse Code. So they can't decode a
message anymore. Thus the reliance on computers and software.

The efficiency gains are hard to argue with as well. You can do things with
SDR that would be impossible or far too costly in hardware... Like
resurrecting and communicating with a 36 year-old satellite [http://www.rtl-
sdr.com/rebooting-isee-3-usrp-software-define...](http://www.rtl-
sdr.com/rebooting-isee-3-usrp-software-defined-radios/)

~~~
qwertyuiop924
Pretty much. There's a lot of people doing cool stuff over the radio, but the
conventional wisdom is that if it wouldn't work in an emergency, you can't
rely on it. So while you can rely on computers somewhat, be prepared to jump
on SSB/CW/FM in the worst cases (ie, you only have power for your radio,
nothing else).

And relying on the internet for _anything_ is an absolute no-no, at least
among the emergency people.

------
jonah
I just got my Ham license a couple weeks ago and picked up an updated version
of the SDR dongle he's using a few days ago[0][1]. I've just started playing
with it but even if you're not that into radio, it's worth $20 and a couple
hours with to explore the invisible radio frequency world around us.

[0] Be sure to get one with a TCXO (Temperature Compensated Crystal
Oscillator) which reduces frequency drift.

[1] His link actually goes to the newer, improved, Mini 2+.

------
mindentropy
I am interested in using a SDR for exploring the PHY in software. This
includes having to sniff the GSM, bluetooth etc. I have a Nooelec SDR USB
dongle but I am yet to experiment with it. I have used to listen to FM radio
and that's it.

I am thinking of starting decoding FM radio by myself to understand the
basics.I do not want to use GNU radio except for better understanding. I would
like to learn and have an understanding of things from scratch so that I get
an intuitive feel when I am developing sniffers. Is this a good way to start?
I really love wireless protocols but have worked from link layer upwards and
would love to understand wireless PHY implementations.

------
periodicfunc
For those interested in ADSB#, I believe it was renamed ADSB Spy and is now
included with SDR# available at airspy.com.

SDR# has a bit of a messy history and at one time was completely open source
but was later closed after some dispute between the developers (to the best of
my knowledge).

If you look hard enough you can still find the source code of the older
versions of SDR# and ADSB# which is handy if you want to learn how they work,
although its all C# .NET and there is some wild stuff going on to try and
squeeze enough performance out of the code. This is where I started learning
though being a .NET developer, and from there moved on to GNU Radio and now
learning C++.

Fascinating subject.

------
gerryk
I have been through a number of SDRs - Softrock, RTLSDR, HackRF, and more
recently I have a Red Pitaya ([http://redpitaya.com/](http://redpitaya.com/))
and am ICOM 7300
([http://www.icomamerica.com/en/products/amateur/hf/7300/defau...](http://www.icomamerica.com/en/products/amateur/hf/7300/default.aspx)),
which is a traditional looking radio with SDR at its core.

The flexibility offered by doing all the work in software is ground-
breaking... really only limited by imagination.

------
mrkgnao
Apparently antirez is a radio enthusiast.

[https://github.com/antirez/dump1090](https://github.com/antirez/dump1090)

~~~
lorenzhs
Yes, and contrary to the article it has a google maps display, too. Try
"./dump1090 --net --interactive" and open localhost:8080. Would be neat if it
could query some API to find out the flight's origin and destination, etc
(flightradar24 maybe? do they have an API?)

~~~
jburgess777
The web interface on the dump1090 fork shipped by FlightAware has links to
lookup flight information for each aircraft:

[http://flightaware.com/adsb/piaware/build](http://flightaware.com/adsb/piaware/build)

Google started blocking the mechanism used by the dump1090 map display. It
might work if you have used it previously but not for new users:
[http://discussions.flightaware.com/ads-b-flight-
tracking-f21...](http://discussions.flightaware.com/ads-b-flight-
tracking-f21/dump1090-google-maps-not-displaying-publicly-t37546.html)

The FlightAware fork now uses an OpenLayers map instead:
[https://discussions.flightaware.com/ads-b-flight-
tracking-f2...](https://discussions.flightaware.com/ads-b-flight-
tracking-f21/announcing-piaware-3-t37681.html)

~~~
lorenzhs
Thanks for the link, that looks nice! I used dump1090 for the first time this
weekend and simply ran it from localhost, it worked fine.

------
partycoder
On Linux there's Cubic SDR (among others).
[http://cubicsdr.readthedocs.io/en/latest/](http://cubicsdr.readthedocs.io/en/latest/)

Make sure to use it with a supported device. The device in the article is
supported I think (by the SoapyRTLSDR module).

------
madengr
I have a KiwiSDR going here on the HF band:

[http://64.136.200.36:8073](http://64.136.200.36:8073)

Also wrote a GNU Radio based scanner that will work with the SDR dongles:

[https://github.com/madengr/ham2mon](https://github.com/madengr/ham2mon)

------
gbtw
The University of Twente SDR is pretty neat too:
[http://websdr.ewi.utwente.nl:8901/](http://websdr.ewi.utwente.nl:8901/)

------
phkahler
Can't you decode OTA TV? I know GNU radio was doing that years ago, but not in
real time yet. I would think that's possible now.

~~~
mcpherrinm
The cheap RTL_SDR dongles are actually sold as OTA TV tuners. It's how I watch
TV.

~~~
mcpherrinm
Edit: Apparently I'm wrong, and the DVB-T decoding is actually done in
hardware.

[https://www.reddit.com/r/RTLSDR/comments/368s1n/how_does_a_d...](https://www.reddit.com/r/RTLSDR/comments/368s1n/how_does_a_device_with_32mhz_of_bandwidth_decode/)?

Nonetheless, you can receive TV with a higher-end SDR, ala
[https://medium.com/@rxseger/receiving-atsc-digital-
televisio...](https://medium.com/@rxseger/receiving-atsc-digital-television-
with-an-sdr-76b03a863fea)

------
metaphor
Snapshots depict sub -100dBm noise floor...on a $21 DVB-T receiver...mkay,
sure.

------
BuuQu9hu
[https://www.crowdsupply.com/lime-
micro/limesdr](https://www.crowdsupply.com/lime-micro/limesdr)

~~~
gerryk
I look forward to seeing some end-user reviews of this device when it finally
ships. I realise that there are plenty of pre-production reviews, but I
believe that the final version will have broader matching networks,
facilitating better sensitivity on HF and low VHF.

------
photogrammetry
Strange that he couldn't find ADSB# - I used it just a few months ago. Perhaps
it's been merged with another repository. If he wants the zip I used for
installation I can send it to him, just give me an email address.

