I am active on PSK31, MFSK16, RTTY, & SSTV. I really like MFSK16 due to its low signal strength abilities. And, using your soundcard, (I use a Soundblaster 16 with a PII 66), there is so much versatility with the HF digital modes and ease of interfacing. I am using a home made interface to get audio to an from my older Kenwood TS-120S, and running about 25-50 watts. The antenna's at KE0VH are dipoles.
I am using Hamscope software, offered by Glen, KD5HIO, and is freeware . I use the MMTTY  software for RTTY, which interfaces to Hamscope for RTTY functions. I really like the X-Y scope and automatic tuning functions this software provides. And, I use the MMSSTV software for Slow Scan TV. Both are written by JE3HHT, Mako. All of his software is offered for free.

I have rebuilt my home made interface for setting up digital modes to HF and VHF radio's using the keying circuit that I posted about a year or so ago, and mostly junk box parts.
I wanted to be able to switch in and out two microphones, one balanced and a D-104, the computer in and out, plus an HF and VHF radio. Also, in this setup my interface has a small 12 volt 1.25 amp "wall wart" power supply "built in" to provide auxiliary power for another radio, scanner, or to power my TNC if I am using it. All is ugly construction but it works well, and is now in operation at KEØVH.
I am using the Hamscope free software offered by Glenn KD5HIO and also have a link to that software on my digital webpage. I had a lot of interest in my last post and want to make the information available in better form with much easier access here on Hamuniverse.com than on my web site at www.geocities.com/ke0vh.
I will be glad to respond to any and all e-mails where there is interest in building one of these that will both save money and be fun. Commercial units are great and offer a lot of features but this is easy, quick, and shouldn't present any problems to anyone who can handle a soldering iron. Plus, it is very affordable.

Schematic notes:
To view my schematic as one page you will need to go to the website:
http://www.expresspcb.com/ and download the free program to read it.

The schematic format has been changed here for this project page and broken down into sections for much faster downloading than having to download the program above and then waiting for me to send you the schematic.
E-mail me for more information and the original schematic at:
ke0vh@qsl.net

See the broken down (4 part) schematic here

My station uses a Kenwood TS-120s, and an Alinco DR-110 for the radios at this time. This design is based upon those radios. My comptuer is a P-II 66 mhz with a standard Soundblaster card. This design could be adapted to just about any situation. There is a 1:1 audio transformer on the soundcard speaker out to the interface and I run the HF/VHF audio out to an audio mixer for isolation and recording convenience, simply because I had it available. Again, feel free to email me for the complete schematic and if I can be of any assistance if you decide to try to build your own.
Below are some pictures of the finished project and the four part schematic for you to use as you see fit. You may save them to your computer by just right clicking on each and saving to a file of your choice on your hard drive for later viewing.....