[Elecraft] Data mode and filters

[Jim Brown]

On Mon,5/11/2015 8:39 PM, Joe Subich, W4TV wrote:
> IMD is not an issue with CW or FSK (or JT65/JT9 for that matter) - they
> are modes designed to work with saturated (class C) amplifiers. IMD is
> a real issue with SSB when you separate out all the other junk caused
> by bad ALC, excess IF gain and excess *audio* processing.

Not true, Joe. Both CW and FSK involve 100% modulation of a carrier by 
square waves. That's why rise time and shaping of the keying signal 
matters. That's what Elecraft changed when they cleaned up their FSK a 
year or two ago. That's why some rigs click a lot wider than others. 
Compare the keying spectrum with the unkeyed steady carrier.

Further, EVERY component of audio excites IMD, depending on the relative 
strength of all of the thousands of components. It is NOT to over 
processing audio -- the distortion of excessive processing and 
overdriven audio happens at baseband (audio) and in the audio chain.

I don't buy your complaints about my PSK31 measurements. It has never 
been my practice to drive amplifiers into saturation.

73, Jim K9YC