A great way to make qso's is by using your computer. Even a simple 486 with a soundblaster-16 will work fine.
The interfaces as drawn below does not guarantee 100% isolation to avoid damage to your transceiver. Best is the use of 1:1 audio transformers like used in old 9k6 modems.
For RTTY i use the program MMTTY by Zakanaka.
For SSTV i use JvComm32. This also supports the FAX mode.
For PSK31 i use WinPSK version 2.22
A simple connection is as follows;
Connecting a Yaesu FT-100 CAT interface to your computer RS 232 connector:
Save out money and get a free MAX232 as a sample via www.maxim-ic.com
The datasheet for the MAX232 can be downloaded here: max232.pdf
Programs for CAT control with the FT-100 are TRX manager and FTBasic.
Digital modes can be heard on;
SSTV:
80 m 3730 - 3740 kHz call : 3730 kHz
40 m 7040 - 7045 kHz ,, : 7045 kHz
20 m 14225 -14235 kHz ,, : 14230 kHz
15 m 21335 -21345 kHz ,, : 21340 kHz
10 m 28660 -28700 kHz ,, : 28680 kHz
2 m 144500 kHz ,, :144500 kHz
RTTY:
80 m 3580 - 3600 kHz call : 3580 kHz
40 m 7035 - 7045 kHz ,, : 7040 kHz
20 m 14080 -14100 kHz ,, : 14080 kHz
15 m 21080 -21150 kHz ,, : 21080 kHz
10 m 28080 -28150 kHz ,, : 28100 kHz
PSK31:
1838.0 kHz
3580.0 kHz
7035.0 kHz
14070.0 kHz
18100.0 kHz
21070.0 kHz
28080.0 kHz
144.6 MHz