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
|