[Elecraft] [Bulk] Re: [Bulk] [K2] Loose screws on KPA100 Q1 and Q2

[Jim Brown]

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