I use a SCI-6 PC Sound Card Interface Kit from Unified Microsystems for digital modes and Winlink packet. Gary Sutcliffe, W9XT, makes a really good kit. It was well designed and inexpensive kit. The kit sells for $24.95 plus $7.00 shipping. I have built several sound card interfaces, but price wise this kit is hard to beat. This is because finding the needed parts is getting expensive and hard to find locally. If you have any soldering skills, this kit is fun and quick to build. It takes less than an evening to build with the great instructions that come with it. If you follow the guide and use good building techniques it will work the first time you hook it up. The only thing you need with this kit is the cables for your radio. Order this kit and get started with digital communications.