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Normally the difference between 50 and 70 is neglectable. If you really know that
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the source/load is exactly 50 Ohm (that means you have measured that) and you really know the other side is exactly 70 Ohm, only then it's worth do do the effort. build a transformer on ferrite material suitable for the frequency. You have to know that? the impedance increases with the square of the winding ratio. A 2 winding to 4 winding transforms your 50 into 200 Ohm. you will need a winding ratio of 1.25 for 50-70 ohm. At low frequency you may want a lot of windings, at high frequencies you need much less. Using whole windings that means that the lowest number of windings is 4 :5 This seems suitable up to 250 MHz approx with the right ferrite. But at these high frequencies parasitic? and L may jeopardize the impedances at both side, normally not a big problem, but you wantend to be accurate isn't it ? If it is narrow band, within the resonance band of an LC, you may use a capacitor step up construction?? (C1- C2 and L back to C1) If you connect 50 ohm over C2 you will have 70 ohm over C1+C2 if C2 = 0,25 x C1.? And the loop needs to be in resonance too. And your caps need to be 5% or better. Quite a challenge. Other may have even better suggestions. Gert On 1-7-2021 15:41, Zack Widup wrote:
I know. That's a problem in this application. Another possibility is a --
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