That's correct and I knew that. ?I only ran the test because Farhan asked me to. ?I was quite surprised that he would be thinking the adjustment would change the third. Harmonic.
After I posted those results I re-adjusted the bias properly and even harmonics are now in the noise floor as they should be.
Jim
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On Mar 1, 2019, at 7:34 PM, jim via Groups.Io <
ab7vf@...> wrote:
Bias on Push-pull finals will NOT change 3rd harmonic ..Balanced the 2nd harmonic will go away (mostly)...Odd harmonics won't null, even ones will
Jim
On Friday, March 1, 2019, 12:34:22 PM PST, Gordon Gibby <
ggibby@...> wrote:
Thanks for running that test! Sad to say that the bias and drive did not cure the issue ??
I am trying to raise finances to go buy a spectrum analyzer myself, and then I¡¯ll actually put a bit of miniature coax to the outboard relay board that I built and find out if my early successful ?tests are confirmed. ?
Certainly the filters can always be improved if that is the issue. ?
Gordon
On Mar 1, 2019, at 22:30, Jim Sheldon <
w0eb@...> wrote:
Yes, I know Gordon, but changing the bias and dropping the drive did not have enough effect on the harmonics on 80/40 to eliminate the problem.? The lowest LPF needs a sharper upper cutoff frequency in order to get rid of them.? Beyond my expertise.
Jim
Jim Sheldon