Making your JPole Antenna - Adapted design from Bob Hejl - W2IK and WD4JR


Take one length (based on chart) of 300 ohm twin lead (buy this from your local Radio Shack) This is the old type of TV twin lead we had on our TVs as kids. USE A NEW LENGTH, not an old run of wire ripped off from your house!!
On one end, strip off  about 1/2 inch of the insulation, exposing the parallel wires. Bend them towards each other so they TOUCH or overlap. Solder them together, making a nice, neat, tight connection. This is the bottom of your antenna.
Next, measure exactly (based on chart) from the end that you shorted together and cut a notch in ONE of the wires in the twin lead. The notch should be about 1/4 of an inch.
Next, measure exactly (based on chart)  from the same bottom of the shorted ends and strip the insulation exposing about 1/4 of an inch of the wires on BOTH sides of the twin leads.  At these two points, CAREFULLY solder in place a 25 foot length of RG58 cable, with the center conductor soldered to the long run (un-notched side of the twin lead) and the shield side soldered to the notched side. (Trust me on this. It should NOT be the other way around no matter whatever you've read or been told).

Make a nice tight seal where the coax is attached to the twin-lead with shrink tube or tape to extend to cover the entire lower section of the twin-lead as shown.

Left: Bottom of twin-lead shorted as per text.
Center: Notch on ONE conductor 16 1/2 inches from the bottom

Double check all your connections and then carefully use shrink tube or electrical tape to cover the bottom of the twin lead while holding the coax cable tightly against it so it makes a solid seal. Make sure that the coax connections to the twin lead aren't shorting together. Continue taping it until it seals all the connections you have made including the shorted bottom of the twinlead and beyond to just the coax cable for about 2 inches. This will seal all of the connections and add strength to your antenna/coax connection (right photo above).  Add a PL-259 connector to the end of the coax. Have an adapter handy so you can use this antenna with either your mobile radio or your HT.

At this point, due to variations in twinlead construction, you will need to "tune" the antenna by slipping it into a piece of 1/2 inch PVC tubing.  Cut the tubing several inches longer then the finished length of antenna.  Hang it vertically, keeping it away from metal objects. Use a fellow ham's antenna analyzer to make adjustments as explained next. It will probably be a bit long, so the resonant frequency measured will be low.

Slide the twinlead out from the pvc and trim the top of the twinlead, by removing 1/4 of an inch from the top of the twinlead AND on the side that has the notch: for each 1/4 inch you have cut from the top of the twinlead notch out an additional 1/32 of an inch enlarging the original notch from the bottom of the notched area... like you'd be increasing the original notch length (but not really, just trimming the "short" side of the parallel lead). Do this until it tunes lowest SWR on the version of antenna you selected when it is back in the pvc. (If you do not adjust it in this manner, you'll never get the lowest SWR or widest bandwith.

Cutting the PVC Pipe

Take a  piece (based on completed antenna length) of 1/2 inch PVC pipe (you can use the same pipe you used to tune that antenna) and on one end cut a 1 1/2 inch long slot about 1/4 inch wide. Snake the twin lead "J Pole" down into the pipe from this same end. When you see the twin lead appear at the other end, stop. By this time, the entire antenna has made it's way into the pvc along with several inches of the coax cable. Now fit the coax into that slot you've cut so the coax comes out from the side. Using the proper pvc "glue", cement a pvc end cap to the top of the antenna, where the twin lead was starting to come out. There is no need to secure the antenna into the pvc as it will not collapse down.

Next, take a 1/2 inch PVC coupler and cement it on to the end of the pvc tubing that has the coax coming out the side. Take an additional 9 inch piece of pvc pipe and cement it into the other end of the coupler.  Then put a small amount of coax seal where the coax has come out of the slot. This will prevent moisture from entering the pipe where the coax exits the pipe.  Leave the bottom of the antenna open.

When you are done, it should look like this at the coax end:

Next secure the cable to the coupler with 2 black UV resistant wire ties to prevent the coax along with the antenna, from being pulled down.

Attach the antenna to your mast or tower using stainless steel hose clamps.  Attach additional coax using a coupler to extend the length to the shack.