Posted by
Jim Brown-10 on
Dec 02, 2004; 3:33pm
URL: http://elecraft.85.s1.nabble.com/160-M-Harmonic-Problem-with-K2-100-Driving-TenTec-Titan-tp372264.html
I've recently been using a K2/100 to drive a Ten Tec Titan as a CW contest rig. I only
need about 25 watts drive to get 800 watts or more out of the Titan on most bands.
On 160 (and maybe on 80), the K2/100 goes into some sort of unstable condition that
causes it to overdrive the power amp and create a pretty strong second harmonic (a
ham from Wisconsin emailed me to alert me to it, and said I was about S6). Some
testing has isolated it to the K2, thanks to a hint from Bill, NY9H. The Titan is clean as a
whistle driven to full power with my TS850 into the same antenna.
I'm also seeing some hint of this when operating on 80, and need to investigate it
further. I really want to fix this -- the K2 is my favorite CW contesting rig, and I really
need its DSP to fight my local noise on 160.
Some troubleshooting thoughts.
1) On 160, my only antenna is an 80/40 trap that I must load as a long wire against a
radial system (I'm on a city lot, and that's the best I can do). This puts lots of RF in the
shack. I suspect this may be related, but maybe not. I also often load the antenna this
way on 80.
2) As I increase the drive from the K2/100, I hear instability as the control system shifts
from the barefoot K2 to kick in the K2/100 amp. I can also listen to the harmonic on the
850 and hear it increase from barely audible (with no antenna) to quite strong when the
rig goes unstable.
3) The K2/100 runs about as warm at 25 watts as it does at 100 watts.
4) There are times that the instability in the K2/100 will cause the overdrive light in the
Titan to come on, indicating more than 120 mA of grid current, even though the stable
tuning was more like 10 mA or less. This is clearly coming out of the K2/100. This
instability is happening with roughly 20-25 watts of drive from the K2/100 and 500 watts
out of the Titan. The Titan is working into a big Ten Tec tuner, and a VSWR that is 1:1. I
recently replaced all the fixed caps in the tuner with 6 kV parts.
5) I have observed some pin 1 problems in the K2, and have fixed one of them (at the
mic connector). Maybe I need to fix the one at the headphone connector too.
Any thoughts or experiences with any of this from the group?
Jim Brown K9YC
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