[Elecraft] KPA1500 Solution to the efficiency problem?

[Roger D Johnson]

It occurred to me that the KPA1500's built in tuner might be of
some help.

Here's my reasoning. If we decrease the drive power to lessen
the output power but keep the same voltage, the amplifier wants
to see a higher load impedance.

Here are the results of some quick tests:

Base line is the amp set for 1000 watts output and eff is 44%

I the set the tuner so the amp "sees" a load of 60 Ohms (actually)
58 Ohms with the values of L and C available. Eff went up to 53%!

I then set the tuner to present a 70 Ohm load (actually 68 Ohms).
Eff went up to 59%!

This was into a dummy load. I realize that, if you're using the tuner
to match an antenna, this could be very complicated.

If Elecraft could figure some way to give us a choice of voltages
for differing power levels, this problem would go away.

73, Roger