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.
We specify impedance ratios as an output to input ratio where the output (or load) is given first and the input is given second (e.g. 100:50 (2:1) would mean a 100 ohm output and a 50 ohm input; a 25:50 (1:2) would mean a 25 ohm load and a 50 ohm input). Most all products use a 50 ohm input unless otherwise specified.
We have products that are available as kits for the do-it-yourself (DIY) person or fully assembled and tested units for the “Plug & Play” crowd.
Our impedance transformers are available using two different topologies: Binocular cores or toroid cores with multiple turns for increased effectiveness and wide band frequency transformations. We utilize single and multiple core transformers using high order windings when needed to extend product performance.
We rate the power ratings as watts PEP (Peak Envelop Power) with standard duty cycles for various modes. To determine the PEP rating required for your needs, see: Choke & Transformer Power Ratings
This website page serves as a link page to the frequency ranges of our impedance transformers configured as either baluns or ununs. You can click on a picture to go to the specific page about the products described in the picture.