Cecil Moore wrote:

The latest QEX has an article by k9la: "The Impact of Load SWR
on the Efficiency of Power Amplifiers". The amplifier is designed
to drive a 50 ohm load and simulated measurements were made for
8 reflection coefficients of 0.333 with phase angles in 45 degree
increments.

One thing I don't understand. When driving a 100 ohm load, the
drain current is 33 amps and the efficiency is 62%. When driving
a 25 ohm load, the drain current is 12 amps and the efficiency
is 83%.

The amp is a Class E/F design from Jan/Feb 2004 QEX. Why would
the drain current fall when the load is decreased from 100 ohms
to 25 ohms?

How has the QL changed as a function of load? How has the power output
changed from 110 to 25 ohms load? Have you calculated the effective load
lines for the amplifiers?

We need a lot more information.

I don't subscribe to QEX so I don't have the circuit available.