General USB DVB-T
You can identify your device (and whether or not it is supported) from this list (just hit ctrl-F and look for your device). In case your device isn't listed it might already be supported by default, try this documentation.
Else copy the firmware for your card to /lib/firmware/ from here.
Then follow this guide.
The specific steps needed on Ubuntu are:
Get the required packages ($ means your home directory in the shell) (EDIT: '$' actually just means you're an unprivileged user; make sure to check your path. '~' signifies your home directory. e.g. bob@computer:~$ means you're logged in as bob (an unprivileged user) on computer and that you're currently working in your home directory):
$ sudo apt-get install git linux-headers-$(uname -r) build-essential patchutils libproc-processtable-perl
Fetch source code:
$ git clone git://linuxtv.org/media_build.git
Change to the directory created before:
$ cd media_build
Compile the code (takes some time):
Install the compiled code:
sudo make install
Restart your system.
Now you can start kaffeine and it should automatically detect your DVB-T tuner. If you don't have kaffeine installed you just need to: sudo apt-get install kaffeine Although kaffeine is a KDE app it will work fine on GNOME.