For impedance transformation/isolation applications when max power is < 10 Watts PEP, this transformer provides a simple interface between transmission lines with different connectors or impedances or simply common mode isolation. DC continuity for bias-T applications.
Feed Line Choke
Each end fed antenna needs a feed line
choke at the radio end of the coax to stop the antenna common mode
current (on the coax braid) from getting into the radio when
transmitting and also to stop RFI common mode noise when receiving. The
simplest, most cost effective choke is a ferrite ring (F240 size)
installed as shown in the picture (at the transceiver end of the coax)
Add the Feed line choke (part # EFFLC-240) for $10 to your end fed
today and stop the pesky RFI from getting into your radio and causing
audio distortion or unexpected operation!
NOTE: Coax shown in picture is NOT INCLUDED and is shown as an installation example only. If you want a pre-wound choke check part# JC-1-1500-3 or JC-1-1500-6.
For non-resonant end fed antennas placement of the choke from 16-95 feet away from the antenna feed point to use the coax braid as the counterpoise (since these antennas are really off center fed dipoles with the short side using the coax braid as the counterpoise. Wind 8-10 turns thru center for an effective 3-30 MHz choke. See Bullet Antenna configurations for exact choke placement depending upon wire length.
For End fed Half Wave antennas place 1-3 feet from antenna feed point to act as short counterpoise for these voltage fed antennas. Use 8-10 turns.
