[Amps] Effects of load Z mismatch?

Jim Kearman jkearman at att.net
Mon Jan 9 15:56:47 EST 2006


 
> Loading an amplifier heavier than where maximum output occurs helps to 
> keep the operating region in the more linear portion of the load line. 
> In other words heavier loading helps keep the operation down below the 
> upper curve of the load line where flat topping starts to occur, but at 
> the expense of some efficiency.

Thanks. If I understand correctly, loading more heavily presents a lower impedance to the anode(s), and also incidentally reduces network Q. As a CW op, my main concern is efficiency and minimizing harmonics. It was difficult for me to feel confident that I was correctly calculating the required load impedance for my 4CX800As. Now I see that by making the load C large enough, I'll have the flexibility to match a wide range of plate Zs while maintaining adequate network Q. Having enough loading C only becomes a problem on 80 and 160, but this amp will be used only on 160-80-40, so getting those numbers right was critical.

73,

Jim, KR1S
http://kr1s.kearman.com/




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