Another part of Amatuer Radio that I enjoy is working Digital Modes. With the DSP in Sound Cards, you can now use software to decode and encode digital signals on your computer. There are several software programs out there that can do this. Many are free

To get started, you need to either build or purchase an interface between your radio and the computer. Commercial interfaces include:

Rigblaster - this is what I use. I prefer it as it lets me keep the mic connected so that I can do SSTV.
Rigblaster Nomic - The Rigblaster's little brother. This is what I started with.
MFJ Interfaces - I have not had any experiences with these interfaces.

If you want to build it yourself:

W5BBR's Page with some schematics on rolling your own.
Rascal Kit - Includes everything you need to build one.

Eham.net Reviews of commercial interfaces and kits.

Now that you have an interface between the sound card and the radio, you need software to do the decoding. My personal favorite is MixW:

Here is a screenshot of MixW. Here you can see multiple PSK31 signals on the left and an MFSK signal on the right.

This program can decode many modes including CW, BPSK31, QPSK31, FSK31, RTTY, Packet (HF/VHF), Pactor (RX only), AMTOR (FEC), MFSK, Hellschreiber, Throb, Fax (RX only), SSTV, MT63. MixW will interface with most radios. I built a level converter for my Icom IC746 which works very well with MixW. MixW also includes many other features that I have not listed here. Check out their homepage:

http://www.mixw.net

Other Software: