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Trying to figure out conjugate impedance.

Crusher

Well-Known Member
May 12, 2007
841
389
73
Louisville, KY
I have built several amps and worked on many more. But I was sitting down one day thinking of how to figure out the conjugate output impedance of an amplifier. For instance say I wanted to combine 2 modules. How could I figure out what combined Zo is so that I can figure out a tank circuit to get it to whatever R(load) I want. I have lots of books that tell me about the tankcircuits, but nothing really says how to figure out what you are starting with. Unless you have a really nice network analyzer. Which I do not have laying around.

Thanks,
Crusher
 

You could always configure each module for 50 ohms output and then all you are left to deal with is two 50 ohm impedances combined to make one 50 ohm output. I know that commercial broadcast amp modules in high powered transmitters are done that way.Everything is normalized to 50 ohms all along the chain.
 
Yeah, I have done that. I was just wondering if I should take into account and inductive reactance for feed lengths and if using a ferrite/toroidal combiner if this plays a part. If so how would I figure this out or is this not necessary as long as i can keep leads down to a minimum. say like 2 50 ohm loads in parallel =25ohms, 3 in parallel = 16.66 ohms and 4 in parallel =12.5 ohms. But as I stated if using a 4 port combiner similar to motorola hybrid using 2 1" transformers. But I don't want to use a step up or step down transformer (I am still playing with that circuit). Would this strictly be resistance, or would I have to take into account any reactances or would that hardly be noticable at HF?
 

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