I was asked about this yesterday but I did not see my response show up. I used to operate TTY back in the 60s witha real TTY machine. A Model 15.
After returning to ham radio after a 30 year absense I heard about PSK31. I downloades WinPSK and gave it a try. I also read about making an interface with isolation transformers. I am a Heath collector. I decieded I could make a decent PSK interface using a Heath HD-15 phone patch. But I knew very little about the phone patch at the time I started. I bought a pair of small 500ohm to 8ohm audio transformers from Ocean States Electronics. I pulled the original transformers made to work with a phone line out and replaced them with the small audio tranformers. I removed the nulling circuit as it is not needed. I commected the Rx transformer with the 8ohm winding to the speaker and the 500ohm winding going to the sound card LINE IN. I used the switch on the HD-15 to connect the Tx output to either the speaker or the audio transformer. I connected the second transformer with the 8ohm winding connected to the computer speaker output. The secondary was connected to the Hi-Z and Lo-Z outputs to the Tx. Since I have a SB-401 I used the Hi-Z connected to the phone patch input on the SB-401. I don't like messing with the mic input. The HD-15 switch and level controls were connected pretty much like the original circuit. I have the VU meter connected to the output of the Tx level control. I can copy PSK QSOs that I cannot even hear. I am very impressed with this technology. It does not take much bandwidth and the cost of the software is right. Bob Macklin K5MYJ/7 Seattle, Wa. "REAL RADIOS GLOW IN THE DARK"
