[Amps] AL-80B questions

[Steve Thompson]

Tom W8JI wrote:
>>OK, probably a stupid question. Are we sure that the 
>>tuning point with minimum input capacitance is actually 
>>tuned to 50MHz, and not 100MHz, with the stage acting as a 
>>power doubler?
> 
> 
> A doubler with that conduction angle should have well under 
> 10% efficiency, but I suppose it is possible the 6 meter 
> tank is hitting two or more frequencies at once. That was 
> one thing that crossed my mind. 
That was my thought at first - harmonic load phase angles (or a load 
line if one exists) could have a big effect in a hard driven amplifier.

Another thought (much easier in a picture). Plot a grph of Po/Pi for the 
high efficiency/high load resistance case. The line goes up, then bends 
over and the gradient decreases with increasing Pi. Superimpose a plot 
for the low efficiency tuning point - the line goes up at a lower angle, 
but is straighter and goes on for longer. There will be a point where 
the two lines cross, same Pi, same Po, one gives better linearity, the 
other better efficiency.

Doug - can you run some numbers for the low anode/high grid current 
tuning position?

Steve