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Richard Clark · September 4th 08, 05:18 AM posted to rec.radio.amateur.antenna

On Wed, 3 Sep 2008 16:14:23 -0700 (PDT), wrote:

Let me put it this way (again very simplifed): How do you explain a
residential 208V power source where you have 120 V from line 1 and
line 2 to ground but 240V with respect to each other.

I have explained it and I see nothing in your query that changes any
particular. Multiple phases compounds the complexity, it doesn't
change first principles. The terminology and usage have been long
established and I have described everything by those conventions.

I cannot think of a simpler way to express
this although I expect to see many statements (you can't equate 60Hz
to RF!). Yes you can; a transformer operates as a transformer in the
same wayat any frequency providing you design it properly for the
frequency of interest.

RF transmission line transformers DO NOT HAVE TO employ squared turns
ratios linked through magnetic flux. The purpose of successful BalUn
core designs is to isolate input from output, not to perform magnetic
coupling. Hence the topic of choking being so tightly conjoined with
RF Z transformation.

Modern BalUns, by this design, exhibit far wider bandwidths of
operation than would be exhibited by traditional flux linked
transformers. More so, the cores used for modern BalUns would roast
in a millisecond under those traditional flux linked conditions where
they can easily pass huge amounts of power differentially, and
suppress Common Mode currents.

The two design principles are vastly different, but serve the same
goal and employ the same terminology: both being called
"transformers." One very obvious confounding example to flux linkage
is the halfwave coaxial BalUn that is fed in parallel and loaded in
series to transform the unbalanced line input from 50 Ohms to the
balanced load output of 200 Ohms. No cores or turns ratios were
employed to accomplish what the isolation of the line provided
naturally. It is confined to a narrow range of frequency, but
conceptually replacing the isolation of line length with the
application of choking extends its coverage by orders of magnitude.

This subject is not nearly so complicated as
some in this group makes it out to be and the topic certainly does not
rate articles in amateur publications any more than basic application
of ohm's law does.

Choking, shielding, and isolation - all of a piece - is a very
complicated topic and generally dismissed inappropriately. The
complexity lies in the breadth of application demands. Analysis
proceeds by simple concepts, certainly, but this does not abstract to
simple solutions.

I will again repeat the admonition that choking a transmission line
does NOT choke each lead individually (which appears to be your sole
experience dominated by RFI suppression in 60Hz applications). If
this singular statement is cryptic, then you should invest your energy
in the study of how the core isolates the input from the output of any
"Guanella BalUn." A perfectly good tutorial has already been
recommended to you by Roy.

73's
Richard Clark, KB7QHC