[AMRadio] Low Power AM?


Jim Wilhite w5jo at brightok.net
Sun Nov 23 18:31:27 EST 2008


Ok I will ask the stupid question(s).  What is the purpose of a 
output (Pi, Balanced) network?  Is it not to transform the plate 
load impedance (everyone knows how to calculate this right?) to 
whatever the antenna presents to the output of the transmitter.  Is 
not the rated power calculated at 52 or 72 ohms?

So if you have a final that is looking into 35 ohms (say a vertical 
antenna) and you dip the plate, what happens?  Do you see 50 ohms 
anywhere?  Is the system matched?  Just what is happening?  What is 
the efficiency and HARMONIC suppression at this particular setting?

Anyone explain this to me?

Jim/W5JO





>I really did not say to maintain the dip with the load capacitor.
>
> When I tune the final of any Pi-network Tx I first set the dip 
> with the
> PLATE capacitor. Then I adjust the coupling with the LOAD 
> capacitor. And I
> always recheck the dip with the PLATE capacitor after making any 
> adjustment
> to the LOAD capacitor.
>
> And when I am done I DO RECHECK THE GRID DRIVE!



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