On Thu, 22 Dec 2005 15:07:45 GMT, Cecil Moore wrote:

Owen Duffy wrote:
Lots of people operate feedlines at high VSWR by design, and they do
not necessarily cause TVI.

Here's one example where a high VSWR might cause more TVI.


Your example suggests a simplified method of analysing the
effectiveness of a balun in reducing common mode current under two
different load scenarios (that happen to have a transmission line
operating at different VSWR).

If the line length of your example was an even number of quarter
waves, then by your own analysis method, in the second case, the balun
with 50 ohm load and "3000 ohm choking impedance" would be more
effective at 12:1 VSWR than the flat line?

So that goes to the meaning of "high VSWR *might* cause more TVI".
Perhaps there is some other factor, and perhaps VSWR is not a root
cause at all.

There is nothing in what you have said that suggests to me that VSWR
is the cause of TVI (or feedline radiation in the more general case).

Owen
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