Finally Tune but Eff is no were near 75%

[KA6VKP]

I got the High Band Version. Took about an hour in assembly. It took me a week in tuning..
I could not get any better than 4.5 watts, and 58% Eff. 10m its 48% regardless of tuning. It was a pain to get the Notch on 56mhz (2nd Harmonic or 28mhz for 10m). If I knew a way, to measure the input impedance looking into the LPF, maybe I could tune it better (Dip the Current hi hi).



Is there a better way to tune the low pass and impedance matching?

I'm guess the transistor impedance is Z= (VCC*VCC)/ 2*Po. So 5W @ 12.00V would be 14.4 ohms.

So, how do I go about measuring the input impedance of the LPF with a Nano VNA?

Is there a measurement on how well the low impedance is transformed into 50 ohms?
Im using Logmag on the NVNA, but the output is 50 ohms not 14.40 ohms.