Total posts : 45366
First, some housekeeping. There is another thread where the Transmitter Challenge is being discussed and this thread is about Class E circuits and is not the place to revisit the Challenge. Future posts in this thread regarding the Challenge will be removed.
Now, thank you Phil for your input on this. You and I appear to be on the same page regarding defining the transmitter efficiency except that I would not count the .MEAS in LTSpice as an actual measurement.
Measuring output power via the loading coil (and antenna system) current fails unless the Rcoil and Rground are known. It would be appropriate, in my view, to simulate an antenna system using your 30 pF and 30 ohm bench load whereby the effect of the loading coil R can be measured under replicable conditions.
I can measure the efficiency of my transmitter with the actual antenna system by using a current transformer at the transmitter output to measure the output current and simultaneously measuring the output voltage to circuit ground (which is also the antenna system ground). The measurements are made with a two channel scope and antenna resonance is set by adjusting the phase angle between V and I to zero. Having previously bench measured the antenna loading coil RF resistance and using the V and I output measurements to calculate the total load resistance the Rground + Rrad can be calculated by subtracting the coil R. Thus the actual power delivered to the radiator plus ground is known.
The 86% number agrees closely with the bench measurement of the transmitter efficiency using only a 29 ohm resistive load and no loading coil.
My transmitter with 100mW DC input delivers 86 mW measured at the input to the loading coil and the coil R is 18 ohms (from memory so it may be off a bit) and a typical total load R measurement is 40 ohms. The efficiency when the loading coil is included as part of the transmitter with these data is (Pout*(Rg)/(Rcoil + Rg))/PDCIN which equals 0.47 or 47%.
Some power is lost because this transmitter has an output filter but using the same numbers for Rcoil and Rg and 100% as the drain efficiency and no output filter the efficiency would be 55% but I have not measured this.