[Elecraft] K3S IMD Questions

[Jerry Moore]

Thank you Jim,
  I'd expect if my signal was being overdriven that someone would tell me so
I could fix it *shrug*.  
Anyway... I think this has been covered pretty well. 
Thanks for all the responses. 
Jer

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim
Brown
Sent: Monday, August 31, 2015 11:14 PM
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3S IMD Questions

On Mon,8/31/2015 10:04 AM, Yngvi (TF3Y) wrote:
> Even though I'm personally most interested in CW I wonder if there is 
> any recent two tone SSB tests that's been published?

I've published some SSB bandwidth measurements using pink noise as
excitation. Because pink noise contains all frequencies, the spectra
resembles music and speech, and is dynamic, it excites IMD in a manner
comparable to speech.

http://k9yc.com/P3_Spectrum_Measurements.pdf

http://k9yc.com/FTDX5000_Report.pdf

So far, I've measured only a few rigs using pink noise, but of those I've
measured, I've seen very little difference between them.

On the air is a very different story -- it's VERY common to see distortion
on SSB signals in the form of both upper and lower sidebands on audio peaks.
Because it is present in both sidebands, I strongly suspect it's caused by
power amps that are over-driven, or poorly tuned, or improperly biased. We
hear it as splatter (sometimes as wide as 10-20 kHz), and see it on the P3
and horizontal lines corresponding to audio peaks.

73, Jim K9YC


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