I would like to add a small bit of information to the fine work Prairie Dweller [1] provided about digital modes in Amateur Radio.
One of the things that has kept me from exploring digital modes has been the requirement for a laptop or desktop system, generally running Windows. Firstly, I don’t do Windows. Secondly, two is one, one is none. How will you repair your laptop after TSHTF? How many laptops can you inventory? Do you have large enough Faraday cages?
Given the above, I would like to suggest creating your digital mode hardware setup, using a Raspberry Pi B+ (aka Pi 2) [2]. This quad core system is more than capable of running the FLDIGI software, where the original Pi struggled. Add a USB sound card, a 5V power supply, a connector cable for your specific Ham radio, and a few other minor parts… and you should be good to go. Googling search terms “raspberry pi 2 fldigi” will get you going. 73s and Happy DXing – RDG
HJL adds: You might also look at Raspberry Pi’s 7” touch screen [3] and case, which gives a really nice complete solution. I’ve been playing around with this setup, and it has some very interesting possibilities for the experimenter.