A balun is often used in amateurs radio stations to couple
unbalanced equipment (such as transceivers) to balanced loads (such as a doublet antenna
fed with open wire transmission line.
At the shack end, the doublet has been tuned successfully on 10 - 80 m using the
classic 'Z Match' balanced antenna tuning unit (ATU) for all bands.
More recently, I have been experimenting with baluns and the use of ATUs installed
between the balun and the transmitter (and transmitters having built-in automatic
ATUs). This has resulted in very encouraging results on all bands between 6 m and 80