This article expands on the detail behind A low Insertion VSWR high Zcm Guanella 1:1 balun for HF with focus on InsertionVSWR and possible compensation schemes.
A low Insertion VSWR high Zcm Guanella 1:1 balun for HF – more detail #2 discussed the imperfection caused by the quite short pigtails, and although small, it is measurable.
Chris, NX0E, related experience with Dr E M T Jones at TCI where they made, among other things, TCI’s HF baluns. These baluns were compensated using capacitors, and we see that very occasionally in ham grade baluns.
The pigtails can be seen as a short transmission line of higher Zo, and although not uniform, it provides a model for understanding their effect.
Above is a Simsmith model that treats the pigtails as short sections of 300Ω line, the lengths adjusted to calibrate the model to the observed impedance at 30MHz.
Continue reading A low Insertion VSWR high Zcm Guanella 1:1 balun for HF – more detail #3