[Milsurplus] Hello Smart People: Output Network "L"

[David Stinson]

I learned the lazy-man's way (tinkering) just
how critical to PA stage efficiency and output
is getting the right value of "L" in the output network.
A single turn in a "Pi" net can make a large difference 
in how much you get out vs. how much you put in.  

While working on the RAAF AT5 transmitter,
I was getting 12 AM watts out in R/T, just as specified.
CW output was a little lower- about 35 watts.
But in AM I was seeing 100 mills into those two 807s.
That's 55 watts in for 12 out unmodded carrier... hmm.

The output for the AT5 is designed for 100 ohms
and normally feeds a tuner.  I was using, of course,
a 50-ohm load, feedline and wattmeter
(The original antenna connector is broken, so 
I've temporarily mounted an "N" connector there).

I got to thinking of my "lessons learned" while 
building "Old Fireball (1935 RK20 rig)" 
I dug-out a very short screw with course threads 
and "screwed" it between two turns in the PA output inductor- 
the turns between the two first vertical taps from 
the front of the coil- effectively removing a turn.
After re-tuning, I still have .100 mills on AM, 
but now the rig has 25 watts of clean, grid-modulated 
carrier out and on CW, 50+ watts.  

So, for the dozens of you smarter than me, 
here's the question:  
                              Why?

73 DE Dave AB5S

P.S. Australian folks:
If any of the AWA engineers still live, please tell them I'm 
going to have one to their health. These are neat radios.