Pirate Nation Radio
Coaxial Sleeve Antenna

This coaxial sleeve antenna is basically a center-fed 1/2-wave vertical dipole. The advantage of this design is that the active elements fit inside of a single pvc pipe for an antenna thats compact, weatherproof, easy to mount and easy to tune. The half wave dipole cutting formula is: Length in feet = 468 divided by the Frequency in Mhz. Our example is for 90 MHz, values are 468/90 = 5.2 feet or 62.5 inches total side to side. The upper element is made from 1" wide tape measure steel, from a $1.99 bargain 12 foot tape, and the lower element is 1.25" copper pipe. Each side of the dipole approx 32" long with a 1/2" gap at the center feed point. Solder a 1.25" (with a 3/8" hole in the center) copper disc or endcap to top of the pipe. Use a 1.25" X 1.25" piece of copper pcb material for the connection of the top element and the center of the coax. Cut a notch in the bottem for the coax to feed through the endcap's hole and file a line accross the center so that the top is insulated from the bottem, then solder it over the endcap's hole. Then solder the coax center conductor to the top element and the shield to the bottem with the cable running downward inside the pipe. Make a coaxial choke under the antenna by winding 5 turns of the coax into a 2" approx loop and securing the cable with tie wraps or black tape. Use a wire brush to completely remove all the paint from the steel tape end and pre tin before you solder it to the top. Make a 3" coil of 5 turns of the coax about 6" below the pipe bottem, tape or tie wrap it tight. This assembly then slides into a chunk of pvc pipe, standard 1.25" schedule 40 "sprinkler pipe" thats 8' long. Use black tape on the copper pipe to make spacers that keep the antenna's lower element from flopping around inside the pvc pipe. Slide the antenna into the pvc pipe, if it is snug, use a broom stick or pole to assist. With the antenna properly placed at the top of the pvc pipe, drill two small hole through the pvc and into the copper pipe, then secure with 2 small self tapping screws, be careful of the coax inside the pipe. Install the top pvc end cap. Depending on how you mount this antenna, drill a 3/8" hole near the bottom of the pvc pipe or in the lower end cap (if installed) and run the coax out to your station. Do not glue it together until the it is tuned and tested for the chosen frequency - DJ Pirate Joe