Topband: Using Video Baluns on 160.

[Jim Brown]

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