[Elecraft] KPA-1500 Efficiency As A Function of Input Power

[charles at k5ua.com]

Thanks for the replies.

Upon further testing, I have found that the efficiency of the KPA-1500 
is varies greatly with driving power.  The following table illustrates 
the relationships between exciter power, voltage, current, 
power-in(voltage x amps), power-out, efficiency, and dissipated power. 
The following test was made with the KPA-1500 into a dummy load and 
readings from the KPA-1500 utility software.

(Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) 
(Dissipated Pwr)
   10w     29a     52.7v     1528w       375W        375/1528 = 24.5%     
1205w
   15w     37a     52.7v     1950w       620w        620/1950 = 31.7%     
1335w
   20w     43a     52.6v     2262w       861w        861/2262 = 38.0%     
1413w
   25w     47a     52.6v     2472w      1060w       1060/2472 = 42.8%     
1451w
   30w     51a     52.6v     2682w      1227w       1227/2682 = 45.7%     
1420w
   35w     53a     52.5v     2782w      1380w       1380/2782 = 49.5%     
1412w
   40w     55a     52.5v     2887w      1497w       1497/2887 = 51.9%     
1382w
   45w     56a     52.5v     2940w      1600w       1600/2940 = 54.4%     
1313w
   50w     57a     52.5v     2992w      1703w       1703/2992 = 56.9%     
1315w
   53w     59a     52.5v     3097w      1825w       1825/3097 = 58.9%     
1306w

The remarkable thing is that DISSIPATED POWER appears to be relatively 
constant from 375w output through 1825w output.  This implies the 
KPA-1500 will need to dissipate nearly the same amount of heat at low 
power output as at high power output, if I am interpreting the data 
correctly. I would like to know from Elecraft if this is normal 
behavior.

Charles  K5UA