Re: Type 519 -- Why 125 ohms?


Tom Lee
 

(Sorry if this is a duplicate -- my email crashed just after I hit 'send' earlier, and the post had not shown up upon restart)

Close -- the minimum-loss impedance for coax is about 77 ohms, which is why the video industry is based around 75 ohms. The impedance for maximum power handling (again, for coax) is around 30 ohms. The mean is about 50 ohms, which is why general-purpose rf plumbing is based on that value.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 5/13/2021 12:55, Göran Krusell wrote:
My memory tells me that the Germans in the 1930s (?) made calculations to figure out if there would be a certain characteristic impedance that would give you the lowest possible cable losses and found 60 ohm as the result. Or am I out in the blue?
Göran



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