Connecting and Tapping WireFigure 1 shows the definite patterns that exist with rod, toroidal and coax winding. The schematics, in these cases are for Ruthroff 1:4 unun transformers. Figure 2 shows the patterns that exist for quintufilar transformers. The trifilar and quadrifilar transformers can be easily visualized form Figure 2. Putting numbered tags on the ends of each wire will also help in keeping track of them. The photographs supplied with each kit will show how the connections can be made.
Generally, the trifilar transformer with a 2.25:1 impedance transformation ration or the quadrifilar transformer with a 1.78:1 ration can satisfy most 2:1 ratio requirements. They are much easier to construct. But in some cases, like 2:1 transformers and multimatch transformers, tapping is necessary in order to meet the objectives.
The author has found that a small, fine file has been found to be very helpful in obtaining successful taps. First the coating of the wire is removed (about 1/8 inch wide) at the right distance on the straight wire by the edge of the file. A narrow copper strip or flattened wire is soldered to the bare part of the wire. The connection is then rendered smooth y the edge of the file. Finally, two thicknesses of Scotch #92 are placed on the connection in order to provide adequate insulation between the wire (which is straight at this point) when the tap is required to be near the center of the winding (like 4 out of 8 turns). In this case, the winding of the transformer is started at the center of the wire where the tap should be.
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