Re: KX1 Please need help with T/R thump

Posted by Jerry W7ANM on May 25, 2011; 1:55am
URL: http://elecraft.85.s1.nabble.com/KX1-Please-need-help-with-T-R-thump-tp6395259p6401119.html

Thanks for your thoughts Don.

I checked the STL and It's been at 2. The thump does not really change much on any setting of the STL. I also checked the components you suggested and Q2 and Q3 are installed correctly and in fact are J309s. R29 is also 22k and in the right place. Other associated components are correctly installed.

Rick KL7CW suggested an experiment for me to try. That was to connect a .02 to .1 cap across C9 to see if it made a difference. At first I tried a .1 and the thump was completely eliminated and changeover dead quiet but it made the T-R delay about a second long. (with Menu T-R set to 0). I next tried a .047 and that seemed to do the trick. I could still hear a very slight quiet "poof" at changeover and the T-R delay is slightly longer than before with the thump but still very acceptable. About the equivalent of setting the Menu T-R delay to 30 or 40. Definitely QSK not as fast as my K2 but I'm not sure the KX1 was ever supposed to be fast as the K2.

Still something not quite right? In theory the parallel cap shouldn't be needed but at this point maybe it's a case of component tolerance/anomalies? Any other ideas?

Thanks for all your help and suggestions.

73,
Jerry