On Sun, 25 Dec 2005 22:24:20 GMT, Cecil Moore wrote:

Owen Duffy wrote:
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).

Please reference "Baluns: What They Do and How They Do It" by W7EL.
VSWR causes impedance transformation. Impedance transformation
varies the impedance. Baluns work better with some impedances than
they do with others. Therefore, VSWR can cause balun malfunction
accompanied by feedline radiation.

Your example depends on the (mis)behaviour of a component (the balun)
external to the feedline as a vital link in the asserted relationship
between high VSWR and feedline radiation (both properties of the
feedline itself).

As you describe it the balun was not suited to the application, and it
is the interaction of the unsuited balun in the whole topology that
gives rise to feedline radiation.

In addressing the suitability issue, you could:
- change the environment external to the balun until the balun was
suitable; or
- replace the balun with one that suits the external environment.

If the balun were replaced with a balun that was effective, then
feedline radiation would be reduced sufficiently, without needing to
reduce the high VSWR on the feedline.

Excessive feedline radiation is not a necessary outcome of high VSWR,
high VSWR does not, of itself, cause feedline radiation.

If high VSWR does not, of itself, cause excessive feedline radiation,
then finding the root cause of feedline radiation means looking beyond
the myth that high VSWR feedlines radiate.

Owen
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