Several years of baluns investigation on a polygon of "Radial" company have shown that for some types of antennas, for example Windom (BR-800-4DR) or Delta (BR-800-4DR), there is also a currents cut-off from a cable braid needed except asymmetry. Appearance of spurious resonance due to the "antenna effect" of feeder forced to install a current choke.
This idea was proved by the analysis of the German company Fritzel products having a such choke in their constructions.
The problem has been solved after the choke installation and antenna’s resonances were clearly reflected at the SWR-meter screen without any spurious splashes.
The current choke is made of fluoroplastic cable wounded over the 12 ferrite rings. The current cut-off plot is shown on the DR chart.
However, this is not the only novelty. A BBRT (broadband range transformer) is used as a transformer. The principle of its operation is based on a transmission of a current over a communication line but not over magnetic field in a core, like in the conventional transformers. Such a scheme considerably increases the throughput power and reduces losses.
Each balun passes compulsory quality control. Typical SWR charts are shown on the figures.