FM J-Pole

[phrettbender]

I'm going to build an FM J-
pole antenna and see that the specs for the size of the elements varies. Some give 104" for the long element at 89.9 mHz and then using a J-Pole calculator it gives 94.3 for the same Freq? What's up? I'm going to use 3/4 inch copper rather than 1/2 inch, it should give me a bit better bandwidth, but I need to know the specs for the build and they are all a bit different by 10-12 inches. Should I just make it big and then tune down with SWR readings?
Thanx

[jackstraw]

J Poles work pretty effectively. Just build the main part of the antenna short, then use some smaller tubing to go into the ends of the larger main part. Cut an x in the main tube and use a hose clamp to secure the secondary element. It can be kinda hard to find copper to do that with so if I need it adjustable I use aluminum. You could also put "tuning" rods on the ends of it, just get some solid metal rods and affix them onto the ends of the main elements with hose clamps so the total length with them extended all the way is bigger then the biggest measurement you have there by a good bit and tune as needed..... Just my 2 cents, good luck!!!