Guys, I put up a new tribander.
I had a difficult time tuning it up so that CW/RTTY segments allowed full KPA-500 power without tripping w/o a tuner. It's OK that higher phone segments need a tuner. Part of the problem had to do with the differences seen between K3 and KPA-500 SWR's. Show below is a sample on 15M. The coax was taken off the back of the amp and plugged into the K3. Thus no cable length differences. The procedure was to tune up the antenna with the K3 so that the bottom end of the CW band was just under 2:1. Then use the amp. Zap, the amp trips thinking the SWR is 2.3:1. I thought it was something in the feedline shorting, arcs or bad traps. Not so apparently. The bottom line is the KPA-500 reads higher by as much as 0.4 in SWR. Yes different SWR meters read differently. However here, the result is that the amp will trip earlier than if one believed the K3 SWR. Truth is apparently hard to divine. There also is a power level dependence in the KPA-500 SWR. 200 ->500 watts increases SWR 0.2. The K3 shows no difference from 10-100 W. FINAL RESULTS AFTER ALL ANTENNA TRIMMING COMPLETE Freq K3 SWR KPA-500 SWR 21 1.7 1.9 21.025 1.4 1.7 21.06 1.1 1.3 21.100 1 1.1 21.2 1.2 1.6 21.3 1.5 2.0 I can't answer how the two compare into a dummy load. The point at 21.1 suggests the two would agree. I would like some understanding of this effect. I'm all for protection, but I'm not for over protection. 73 de Brian/K3KO ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2221 / Virus Database: 2441/5375 - Release Date: 11/05/12 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
