[Elecraft] KPA500 Power In Digital Modes

[Jim Brown]

On Mon,11/10/2014 4:59 PM, mcduffie at ag0n.net wrote:
> Full linearity is needed for these modes to keep IMD under control.

Huh? "Full linearity" would be zero distortion. ALL amplifiers have some 
amplitude distortion. See ARRL test results for a sample of current 
products. 2-tone IMD in the range of -30dB is pretty common.

In the link I just posted, look at the occupied bandwidth of the K3 
driving a KPA500 to full power, and to a few dB less power, then compare 
to the K3 driving a triode tube amp to legal limit. The IMD sidedbands 
are clearly visible, even with a CW signal -- remember that a CW signal 
is a carrier amplitude modulated by a square wave. The square wave has 
harmonic content (as a function of its rise time and shaping), so it 
produces IM.

73, Jim K9YC