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Understanding Parallel to Series conversion
Hi All,
Please look at this in fixed font. I'm looking for understanding of a series to parallel conversion for antenna matching. I'm pretty sure I'm missing something, so point it out to me. This is in regard to a crystal radio, so the match is for a low impedance antenna to a high impedance tank circuit. The antenna: R=58 ohms C=1072 ohms at 1Mhz. The tank: L=240uh C=106pf Q = 1000 Tank Z =~1.5 Mohms Here's my understanding of what I think I'm reading. I put a matching capacitor in series with the antenna. Antenna-- -----R-----C--------Match cap-----tank------ground. and this is supposed to transform the circuit to this. ( Maybe better said, equivalent to this) l------------l l l Antenna--- R C LC---Tank l l l------------l ^ Ground I calculate an 18.5pf cap for the match, making the antenna look like 58R and 17pf. So this; Antenna-- -----58R-----270pf--------Match cap18.5pf-----1.5Mohms------ground. This converts to; l-----------------l l l Antenna---58R 17pf 1.5M---LC Tank at l l Resonance l-----------------l ^ Ground And I now have a 1.5 Mohms source feeding a 1.5 Mohm load. The purpose of which is to cause minimal loading of the tank by the antenna. I don't understand how adding a series capacitor makes a parallel conversion. What do I misunderstand or do just need to believe the numbers. Thanks, Mikek |
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