The simplest, most cost effective feed line choke is a ferrite ring installed as shown in the picture (at the antenna feed point).
Improves antenna pattern by preventing your dipole from becoming a tripole
Prevents pesky coax braid radiation and RFI
for best results use multiple turns through center
Use one choke for each antenna feed line - take a 3 foot piece of G-8X (part# RG8X-3) and wrap 10-12 turns thru center for a good feed line choke.