Pipe-cap Filter Construction

摘要

There are two ways to couple energy into and out of a band pass pipe-cap filter. Well known to the this microwave community is to place E field probes close to the open air end of a quarter wave long tuning screw where the E fields are the greatest. These E field coupled band pass pipe-cap filters can be found in Down East Microwave transverters. Another way is to couple into the magnetic field at the other end of the tuning screw. The construction detail in this design have the H field coupling loops close to where the H field is the greatest. The H field at the end of the tuning screw close to where the screw connects to the pipe cap, where the RF current is the greatest, is where the H field is the greatest.