On most of the J Pole designs out there, a choke should be used as close to the feedpoint of the antenna as possible to help prevent rf on the feedline and creating difficulty with SWR readings. For 2 meters, the coil is 4 turns of coax at 5 inches in diameter. You should get good results with the choke within 3 or 4 inches of the feedpoint on 2 meters.
Hints from builders:
"Iv'e built my j-poles out of 10ft sticks of 1/2" emt conduit. Drill a 1/4" hole at the place where the "J" goes. Make the "j"out of 1/4" soft copper, Solder it in place thru the hole and add the cable. Cost about $6 using new parts.
Convert a J Pole to a Slim Jim
J Pole Calculator and drawing used on this page are
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