Also referred to as line isolators, these choke off RF currents on the shield!
These In-Line Baluns have an SO-239 UHF type connector on both the input and output side.
In-Line baluns provide similar performance to their respective wire balun counterparts. Applications for In-line baluns include line isolation anywhere along the coax transmission system and use on Quad and Yagi antennas.The W2DU's RF choke design can be used anywhere along your coaxial transmission path to help eliminate RF feedback and TVI.
While the RF currents flowing along the coax shield are "choked" out by the balun/isolator, the internal 50 ohm signal is completely unaffected. Some users have noted a reduction in interference with the use of line isolator between their transmitters (transceivers) and linear amplifiers. Another use is placing one at the vertical, beam, or quad antenna to augment the antenna's matching system to coax.