This Tansmission Line Transformer (sometimes called “HexBeam BALUN”) is in fact a special variant of the well known ON7FU 1/1 UNUN Line Isolator.
On the coaxial cable side an SO 239 connector is provided, while on the antenna side a 30 cm long “pigtail” with PL259 is installed that connects directly to the HexBeam connector.
Because the transformer is based on a torroidal ferrite core, the common-mode choke impedance obtained is several times higher than what’s achievable with the standard “string of beads” solution often offered with a HexBeam antenna.
The general mechanical and electrical specifications of this variant are similar to those of a standard Line Isolator.
Optimized frequency range: 7 – 55 MHz