Post by wa9zvf on Nov 12, 2017 19:24:25 GMT -5
I'm trying to measure the common mode impedance of a 1:1 balun. The manufacturer of this specific balun has documented the common mode impedance using an AIM 4170 and shows it on his website. I've tried to duplicate the result and I don't come close. I understand from reading some forum post from 2013 that stray capacitance can be a big issue. I've tried two methods. First I've used the "fixture" shown in the attached picture. I'm connected on the shield, with one connection on the input side and the other connection on the output. Basically like measuring an inductor. I've done a custom calibration. I've also used a 24 inch piece of coax and the same connection points. Again, I've done a custom calibration. My impedance curve shows a peak at 40m and then it drops off significantly and smoothly with increasing freq being down 3/4 of the way by 20m. The published and supposedly correct curve is broad with a max near 20 meters. So, my question is what is the proper way of measuring the common mode impedance of a 1:1 balun and what are the details that need to be paid attention to with the fixture/connection?
Bob, I suspect you are busy with your move but would very much appreciate it if you would weigh in with some detailed specifics.
Ray Mikula
WA9ZVF
Bob, I suspect you are busy with your move but would very much appreciate it if you would weigh in with some detailed specifics.
Ray Mikula
WA9ZVF
