[Elecraft] KPA1500 Operation on 6 Meters

[Ed G]

Folks,
     I am trying to understand some odd KPA1500 operation on 6 meters.  When setting the power output of my K3 to give varying amounts of drive to the KPA1500, I am seeing SWR as displayed on the KPA1500 changing by a significant amount depending on the drive level.  This is with the KPA1500 tuner bypassed. An LP-100A on the output of the KPA1500 is also used and displays the correct low SWR at all drive levels that I would expect to be seeing on the KPA1500 display.
     For example, with 5 watts drive from the K3, I see 1.3 SWR on the LP-100, and 2.5:1 on the KPA1500 display.  As I increase drive, the KPA1500 SWR display goes down proportionally, until I get to about 40 watts drive. At the 40 watt drive level, I am seeing a nice healthy 1600 watts output, and both the LP-100 and the KPA1500 are showing the same 1.3 SWR.  15 watts drive shows 1.3 on the LP100 and 2.0:1 on the KPA1500 display. So I am not sure why the SWR sensing and display in the KPA1500 is behaving this way?  I do not see this oddity on any other bands.
     I might also add that attempting to get the KPA1500 internal tuner to bring down the high SWR as seen on the KPA1500 results in a drop in SWR displayed on the KPA1500 to where SWR almost equals that on the LP-100, but using the tuner I would expect that to be even better.
--Ed—




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