How about one that does PSK31? The Warbler series kits from SmallWonderlabs work great. They're basically fixed frequency rigs on the most popular PSK31 watering holes. http://www.smallwonderlabs.com/ Of course, you'll need to have some kind of a portable computer with you. You can pick up old laptops that will do fine for little money, and the new Netbooks are pretty affordable. Here's a homebrew PSK rig that uses a PDA - http://kd1jv.qrpradio.com/PSKTX/SIMPLEPSKTX.HTM If you don't want to use a PC, here's a standalone PSK31 terminal you could use with a Warbler: http://www.nue-psk.com/ 3-4 watts of PSK31 on 20 meters with a halfway decent portable antenna will make contacts all over the country.