RadioBanter - View Single Post

Owen Duffy · September 1st 08, 08:25 AM posted to rec.radio.amateur.antenna

wrote in news:c2a78f6b-eded-4547-ae32-bc8ccd60e186
@m73g2000hsh.googlegroups.com:

Technically I would have to disagree with calling even a 1:1 balun the
same thing as a common mode choke. A CM choke is an EMI prevention

I suggest that a reasonable definition of a balun is any device that
facilitates or assists transition from unbalanced to balanced mode of
operation. That definition permits a wide range of devices that may have
characteristics suited to specific applications.

(Keeping in mind that an unbalanced feedline is often not ideal in
application, ie one where common mode current is exactly half of the
differential current, and a two wire open line is often not ideal in
application, ie where common mode current is zero.)

Most people naturally think of balance in terms of voltages wrt some common
reference, eg ground. It is equally legitimate, and often more appropriate
to the antenna / feedline scenario, to seek balance in terms of current, ie
to minimise common mode current.

Owen