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Old March 10th 05, 07:00 PM
Roy Lewallen
 
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clvrmnky wrote:
. . .


Hmmm. I understand that a balun is really a type of matching
transformer, and that the specific nomenclature used is really just to
distinguish the various use, application and materials of the transformer.


No, that's not correct. Balun is a contraction of "balanced-unbalanced".
A balun is sometimes combined with a transformer or made to transform
impedance, and sometimes it isn't. Its function is to balance the
currents on the two feedline conductors (either coax or parallel wire
line) to prevent radiation from the line when transmitting and pickup
from the line when receiving. The impedance transformation is a separate
function for a different purpose.

All the designs for homebrew longwire X:1 baluns I've seen are step-down
transformers using specific types of ferrite material. Of course,
typical use often has one side of the primary and secondary going to a
good RF ground (for balanced application, anyway), which I do not have.


A typical 1:1 "current" or "choke" balun, which does what I described
above, does not require any external "ground" or other connection. If
fact, such a connection provides a path for imbalance current and can
actually degrade balance. There are a number of ways of providing this
function, with and without ferrite cores.

My thinking is that since I'm going to be experimenting with different
wire antennas this summer, why not try a few different matching
techniques as well?


There's no reason not to experiment. Improving the match won't help your
signal-to-noise ratio. After your experiments show that this is so, you
can go back and learn why not.


The lack of good RF ground is going to be a challenge, and may preclude
any of this. I've got lots of wire, however, so I'm willing to give a
weekends up to try different things.


There's no need for an RF ground if you use a well-balanced antenna.

Roy Lewallen, W7EL
 
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