On 5/7/2012 5:31 PM, ZR wrote: > ince those TV baluns share a common ground they are likely not > transformers and more likely a simple 4:1 autotransformer making it > useless for common mode.
Rick Karlquist has correctly described the so-called "baluns" we're talking about here, which are intended to carry baseband analog video, and to break the path for AC-power-related leakage currents that result when a video source feeding a video display are plugged into the power system at widely separated power outlets. That leakage current is the same thing we hear as hum and buzz in an audio system -- it's low frequency audio -- but analog video also includes components down to 60 Hz (vertical sync) and, as Rick noted, even slowly modulated DC. Put simply, this type is a broadband transformer. This discussion emphasizes why the word "balun" should be removed from our technical vocabulary -- it is used to describe many very different things, all of which seem to be viewed as a magic box that no one understands. Let's call them what they are -- transformer, common mode choke, transmission line matching section, and so on, so that we can work toward actually understanding what they are, what they do, and how they do it. 73, Jim K9YC _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
