Impedance measurement & Law of Cosines

Nick Kennedy
 

Speaking of alternate approaches, there's an interesting and fairly simple technique for measuring both R and the absolute value of X.  I don't think it's anything new but I don't see it discussed much.  It can be done with simple diode detectors, but I wonder if log power chips (AD8307) would help or hinder?


I built a version several years ago helping a guy on a commercial project.  It could be pretty good if the values didn't get too extreme.  But I don't remember exactly what "extreme" was.


A working product with some explanations is VK5JST's Aerial Analyzer:


Aerial Analyser Details


A paper on the math an a simple example circuit is here:


http://www.kennethkuhn.com/electronics/impedance_measurement.pdf


I can't remember if the MFJ259B uses this technique or not.  Probably does.


73,


Nick, WA5BDU


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