RF Choke basics
RF Choke. To make a choke, all you need to do is wind a portion of the coaxial transmission line to form a coil. A choke balun made of coax is most effective when a single layer is close-wound on a form, such as 4in. plastic drain pipe or 6in /150.0mm. "schedule 40 (4.5 inches / 114.3 mm)" PVC pipe. The table below lists values for each HF amateur band. Form size and number of turns are optimized for each band.
I recommend one choke near the antenna feed point, and another one about a quarter wavelength down the line, before the coax enters your radio shack.
If you intend to use your dipole on its odd harmonics (more than one band) then use the following table to construct your RF chokes.