Re: KPA500 PA current

Posted by ANDY DURBIN on Aug 04, 2019; 6:48pm
URL: http://elecraft.85.s1.nabble.com/KPA500-PA-current-tp7654248p7654260.html

"This is the effect of not being able to obtain perfect components. It is easy to forget that the toroid cores used for the inductors vary, as do the windings and capacitors. There will be variances because of this which will be different from KPA to KPA. They are set up for best case operation, but then as components age things will change. As it is, the design is outstanding. With efficiencies greater than 50%, the designers did a super job!"

Jack,

I understand that there will be variation between different KPA500.   However, 2 owners have reported that 20 m stands out as being less efficient than other bands.  I was asking if that is typical of all KPA500.   I don't really expect to get an answer though as I doubt many owners have test data as comprehensive as mine.

I just did a spot check on 20 m and, despite my line voltage being down to 118.1 V with the high air conditioning load in the area,  I saw 60% efficiency with load R 51 X 0.4:

PA voltage=58.9
PA current=13.8
PA input=812
RF out=490
PA diss=322
PA effic=60

Of course this is not typical of normal operating conditions.

73,
Andy, k3wyc





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