On 3/2/2011 5:06 AM, Bill Coleman wrote: > s much as I hate to contradict your expertise -- are you sure it is wise to > use such a low center frequency for AFSK RTTY? (Although it does more easily > fit the limited BFO range of the standard K2)
Many good RTTY operators use 915 Hz as the mark frequency because it's much easier to listen to. Distortion should be low if you are using a proper interface and adjusting audio levels properly. With the K2, that means an interface that includes a simple 20 dB attenuator (resistive voltage divider) between the sound card output and the mic input. The sound card output level should be set at least 6dB below its max output voltage, and the K2 mic gain should be set just below the point where output power starts to level off. To set the sound card output level with a scope, look at the waveform at the output of the sound card while sending tones from the RTTY program, increase level until you just begin to see clipping, then reduce the voltage by one half. If you don't have a scope, LISTEN carefully to the tones as you increase the level. At some point, the SOUND of the tones will get "brighter" or "harsh." That's clipping. Now, back off the level until it sounds "half as loud." That's where you want to run the sound card. This setup procedure works for ANY rig and ANY sound card, not only the K2. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
