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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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