J-Pole Antenna Plans

Jpole Antenna
The J-Pole antenna is fundamentally an end-fed 1/2-wavelength antenna that uses a 1/4-wavelength long transformer section to supply the very high feed voltage. It is an ideal end-mounted, single-mast antenna. For 3-meters (FM broadcast band) it is probably the antenna that is the best solution for many micro power radio stations. It is cheap and easy to build, very sturdy, simple to tune up, and performes quite well for 3-meter transmissions.

The Antenna shown is made from 1/2" copper tubing and it is soldered togeather with plumbing tees, elbows, and nipples. The spacer under "B" is 3/4" plastic pipe cut to hold and re-enforce the two copper pipes. The coax (RG-8 or Equivilant) is affixed to the pipe as shown with movable copper clamps. The fully constructed antenna is then clamped to a grounded metal pole.

Section A, the antenna radiator is 3/4-wavelength long, so its dimension is found from:

... and the quarter wavelength matching section length from: