© WB5CXC 2011
HF J-Poles
I  have seen several sites on the Internet making HF J-Poles.  They are made similar to other J-Pole but most use 450 ohm ladder line.  I had some ladder line so I made several.  The 10M and 15M turned out real good and seem to work good also.  I made a 20M one but haven’t used it yet as it is    ~ 49 feet long, and haven’t found a good support for it.  These make pretty good stealth antennas as the ladder line is black and I used #14 black THHN wire. Start with the bottom of the ladder line.  Strip off 3/4” of the insulation on both conductors.  Remove any insulation from the center.  Bend the conductor toward the middle, and solder the conductors together (shorted stub). Measure from the shorted stub ‘L2’ distance and cut the ladder line.  Measure from the shorted stub ‘L3’ distance and strip the insulation on the conductors on each side. Prepare 4’ - 6’ of RG-8X or RG-58 coax cable.  Prepare the coax by separating the center conductor and shield.  Solder the coax center on one conductor  and the shield at the ‘L3’ location.  Measure a stranded wire (I used #14 THHN) the length of ‘L1’ plus 1/2”.  Strip the insulation off one end (1/2”) and attach it to the ladder line conductor (on the coax center conductor side).  (Solder the conductor - make sure it is a good mechanical as well as electrical connection.) Put an insulator on the end of the long wire.  Install the J-Pole and check the SWR.  You can move the feed point ‘L3’ up or down to obtain the best match.  The bandwidth should cover the entire band.  To dress up the J-Pole you can use 3/4” shrinkable tubing to cover the connections, etc. 
HF - J-Pole Measurements