Total posts : 45366
There is no radiation advantage to a folded dipole vs. just a plain dipole. The difference between the two configurations is the feed point impedance. A folded dipole is 300 ohms and a dipole is 75 ohms. Both antennas are 1/2 wavelength total length which can be calculated from Neil’s post.
Assuming you want to feed the antenna with 75 ohm coax, you should construct a dipole, not a folded dipole.
Orienting the dipole vertically will produce an omnidirectional pattern, which is better suited to broadcasting.
A vertical dipole should be constructed using tubing or pipe for the lower element to allow you to pass the coax up inside the bottom element to the center point. Either tubing or rod stock can be used for the top element. At the center, the coax shield should be bonded to the bottom element and the center conductor bonded to the top element. See http://www.alpharubicon.com/elect/vertdipoleniet.htm for an example.
When mounting a vertical dipole on a supporting pipe (mast pipe), the bottom dipole element should be insulated from the mast pipe. Ideally, the bottom element should be mouted at the top of the mast pipe with some sort of insulated coupling between the element and the mast pipe. A less desirable, but usable alternative is to clamp or screw the bottom element to the top of the mast pipe with maybe a foot of overlap for stability. If you dp this, there is no electrical contact between the bottom element and the mast pipe.
