Simple Jumper Feed Line Choke
The simplest, most cost effective feed line choke is a ferrite ring installed as shown in the picture (at the antenna feed point) to stop feed line radiation or at the radio end of the coax to suppress common mode coax noise current on the coax braid.
Improves antenna pattern by preventing your dipole from becoming a tripole
Suppresses pesky coax braid radiation and RFI
Reduces coax braid common mode current up to -30 dB ( 6 "S" units) on receive
Use one choke for each antenna feed line
Add a double female barrel connector to act as an "extension" of the existing coax.
Magnetic Loop Users: use 1 JC-1-1500 at the antenna feed point to keep all of transmit power on antenna and another at radio end to remove common mode noise received on the coax braid.
Need the ring only and not the jumper, select F240-31-1 as the part #.
The impedance transformers are classified in ratios of 2:1 (100:50 ohm) to 16:1 (800:50 ohm). The outputs can be configured as balanced (Balun) or as unbalanced (unun) with respect to the inputs which are considered all unbalanced coax at 50 ohms. All impedance transformers are designed for 1.8-31 MHz unless otherwise specified.