[PVRCNC] KPA500 drive power

[Jim K4QPL]

At the monthly online meeting there was discussion of drive power for full output with comments saying more was often required. Interesting observations in 160m contest. The 1:1 resonant point on my inverted L is 1.853 and the KPA500 outputs full power 500 watts with 21 watts drive. That holds true as I go down the band with increasing SWR. However, at 1.807 SWR increases to about  2.75:1. At that point the amp does not do a high SWR hard fault but folds back the power to 300 watts. This isn’t gradual but an instant, discrete power reduction. I assumed this was protective when SWR hits the predetermined point so the handful I worked at the bottom of the band were at 300 watts. 
1. Check your SWR and if you can’t get full output with + - 20 watts you may be overriding this built in protection. 
2. Choose a 1:1 resonant point which gives you maximum use of the band. In my case for 160 I need to lower the center point to 1.845 or maybe 1.840 for full coverage 1.8–1.880 with normal drive. YMMV. 
Being aware of this firmware and being careful may save your amp an expensive road trip to Watsonville CA!
73,
Jim K4QPL 

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