[TowerTalk] Measuring Common Mode Choke with Anritsu VNA

Avery Davis wb4rtp at mindspring.com
Sun Dec 31 18:12:56 EST 2017

Just measure the common mode choke just like a simple inductor, i.e.,
ignore the center conductor of the coax with which it is wound.  Set the
measurement to S11, and the format to Smith Chart.  Connect the braid of
one side of the choke to the coax center of Port 1, and the braid of the
other side of the choke to the coax outer of Port 1.  Set the start and
stop frequencies to the band of interest.  You can use the marker
feature of the VNA to read out the specific complex impedance at any
frequency.  If you are not familiar with reading a Smith Chart, you will
need to find a tutorial on this.  Also, you should study a manual or
tutorial on the specific model VNA you have.  Ideally, you would
calibrate the measurement using calibrated open, short and precision
termination, but for a choke the factory default settings should be
reasonably close. 
Avery, WB4RTP

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