

Taking the Raspberry Pi 2 for a Test Drive with GNU Radio - andyjohnson0
http://www.rs-online.com/designspark/electronics/eng/blog/taking-the-raspberry-pi-2-for-a-test-drive-with-gnu-radio-2

======
morganvachon
This is one of the projects I had in mind for the RPi 2. I've already got the
RTL-SDR stick and it works great on my workstation, but having it portable
would be even better. I'm happy to see that the RPi 2 can handle the workload.
It will be interesting to see if the Pi can also handle trunk tracking.

~~~
AceJohnny2
How does one handle portable power for a RPi2? Does a normal USB Power brick
(as increasingly used to top up phones) suffice?

~~~
wlesieutre
Yup, if it charges a phone it should power a Pi.

[http://www.adafruit.com/products/1566](http://www.adafruit.com/products/1566)
is sold specifically for this purpose, and it has some interesting notes about
how it behaves (like output fluctuation when the battery is simultaneously
charging and providing power) that might be worth noting. If all you do is run
off a battery, then unhook the battery to charge it, you shouldn't have those
sorts of issues.

~~~
nearengine
500mA and up will charge a phone (assuming you're not also doing power-
intensive things on it), but you'll probably need 1-2A to power a Pi and a SDR
reliably.

~~~
wlesieutre
Ah, looks like power consumption west up. B+ listed 600 mA typ, 2B is 800.
[http://linuxgizmos.com/raspberry-pi-gets-quad-core-soc-
keeps...](http://linuxgizmos.com/raspberry-pi-gets-quad-core-soc-keeps-same-
price/)

~~~
nearengine
Yep! Plus the tuner card itself can use 200mA or so, and if you want to use
any other USB accessories they'll be drawing power as well. I unfortunately
have too much experience using "phone chargers" that had enough current to run
it 90% of the time, but under hard load would cause enough voltage drop on the
5V rail to reboot the Pi.

------
famousactress
Got my Pi 2 recently, and it's awesome how much snappier it runs. I've only
used them to spin up game console emulator appliances so far. Would love to
hear about projects among the HN crowd. I'd really like to use one for
something more interesting!

~~~
jlhonora
My wife's Hedgehog tweets how much he runs every night
([https://twitter.com/runhedgie](https://twitter.com/runhedgie)). Hooked up a
RPi NoIR camera, so a video is included in the tweet as well. All the code is
here: [https://github.com/jlhonora/iot](https://github.com/jlhonora/iot)

~~~
burningion
This is great! Thanks for sharing, I just got a bird feeder, this will be a
perfect starting point for shooting images.

~~~
jlhonora
Cool project! I guess that with the Pi2 you could do some basic image
processing to detect changes and then decide which footage is interesting.

------
misuba
What are some of the popular applications for SDR? I can't imagine it's all
pirate radio and such.

~~~
jff
Almost none of it would be pirate radio, since the most common one (RTL-SDR)
is receive-only.

You can use it to tune in 2m ham radio repeaters, or listen to broadcast FM,
or pick up weather radio transmissions, or track which aircraft are flying
overhead, or build a little yagi antenna and hear people talking via ham radio
satellite, or possibly listen to police radio depending on what your local
cops use

~~~
rickr
You shouldn't need a yagi to listen to ham sats (transmit you will). A good
external omnidirectional antenna should be fine.

In addition to the sats ISS always has at least one ham radio operator. They
sometimes man the radio and make contacts with hams. In addition to THAT
sometimes they operate SSTV (sending pictures via radio) that you would be
able to pick up. Very cool stuff!

Here's a good site to see where hamsats are:
[http://www.amsat.org/](http://www.amsat.org/)

------
Animats
Nice. Now the question is how accurately you can timestamp the ADS-B replies.
If you can timestamp them to within a few hundred nanoseconds, and have at
least three (preferably four) receiving stations networked, you can draw a
radar picture of your local airspace.

~~~
ghost91
The problem are the RTL2832U receivers. The sample rate is too low, 500ns
resolution with 2MSample/s is not enough. For this reason I cannot recommend
using the dvb-t sticks as ads-b receiver (the symbol rate is too high, compare
nynquist theorem).

Multilateration has already be done for ADS-B on large scale, but with
different receivers. There are receivers available[1] with nanosecond accuracy
(and gps time synchronization).

GPS synchronization isn't needed, by choosing other flight paths to provide
basic time synchronization between receivers.

[1]: <[http://radarcape.com/>](http://radarcape.com/>)

~~~
bigiain
There seems to be "a trick"...

[http://www.rtl-sdr.com/passive-radar-dual-coherent-
channel-r...](http://www.rtl-sdr.com/passive-radar-dual-coherent-channel-rtl-
sdr/)

(That's on my list of "things to experiment with one day...")

~~~
9600
Yep, that's been on my list for a while too! :o)

Btw, I just updated the blog post with a link to another post where I ran up a
GSM network on a Pi 2 equipped with a UmTRX transceiver.

[http://www.rs-
online.com/designspark/electronics/eng/blog/ru...](http://www.rs-
online.com/designspark/electronics/eng/blog/running-a-gsm-network-on-the-
raspberry-pi-2)

Given that UmTRX is dual channel, has a GPS locked clock and is much higher
performance is general, I'm thinking it might make for an excellent platform
for experimenting with passive RADAR!

Andrew

------
bayesianhorse
Am I the only one who thinks this could work as an early-warning system for
drone strikes?

~~~
mmagin
I'm guessing (those kind of) drones don't have mode-S/ADS-B transponders.

~~~
toomuchtodo
They do have radio emissions you could triangulate.

~~~
madez
Are you sure?

As far as I know they use satellite links. So I imagine they can avoid sending
signals towards earth. I also assume they use frequency hopping in a wide
range so it's harder to track.

~~~
bigiain
I dunno, it's a _long_ way to a satellite, and only a short distance to the
ground. Given the space/packaging constraints on a drone I wonder just how
directional it's uplink antenna could possibly be. (Although I'd bet the
satellite probably has a _very_ high gain antenna on board - which'd turn the
tables back in their favour...)

~~~
madez
Making a drone hard to detect is a major priority. They'll go great length to
ensure it's hard to track.

However, it'd be interesting to try it. Sadly there are not many drones where
I am currently.

------
tombot
What fun projects can I do with GNU Radio?

~~~
jfoutz
[http://gnuradio.org/redmine/projects/gnuradio/wiki/WhatIsGR](http://gnuradio.org/redmine/projects/gnuradio/wiki/WhatIsGR)

------
spacemanmatt
Gotta wonder if there are already communities sharing profile information for
recognizing various government agency employees/vehicles by SDR.

