Enter the commercially available Elecraft BL-2. A switchable 1:1 or 4:1 balun that is very well designed and quite capable of handling 250 Watts as well as small enough to be used in portable operations.
The BL2 is shown compared to my early Mini-Balun prototype. Both utilize the same electrical connections.
The goal here is to transform the load down to an acceptable match before it hits the balun, this will eliminate the mismatch loss. After reviewing several balanced line tuners I decided to go with the air coil approach for maximum efficiency. I had a piece do coil stock that didn't really fit any of the commercially available B&W or MFJ offerings. The pitch or L values didn't seem to line up with what was available. This coil was #14, 1-1/5" diameter and had approximately 20μH of inductance. I cut this coil in half only to use 9 or so microheneries.
I affixed a 110pF APC style air variable capacitor and clip leads to its terminals that allowed me to tap any point along the coil I desired. This gives maximum flexibility in choosing tuning solutions.
The coil is center tapped and the balanced port of the BL2 is attached 4 turns up from the center rap.
The antenna can be attached by clips, clip lead or whatever is necessary to make the connections.
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