Why does a dipole antenna need insulation in the center and the ends?
I wanted to build a dipole antenna, I understand the calculations but I don’t know why there needs to be an insulator at the ends and at the center? Does that affect the radiation pattern?
In the word dipole, “di” means 2. A dipole is a 2- element antenna, each 1/4 wavelength long. So they need separation at the centre, which is the feed point for a balanced transmission line.
The end insulators are necessary to allow electrical separation from metal or even timber or tree supports, as the ends of a dipole used for transmission are at a high voltage level.
It is hardly an expensive exercise to supply end insulators, even if the antenna is only used for receive functions. A very cheap type “egg” insulator can be found in retailers of electric fence components, or you could use ceramic ones scrounged or bought, but they are relatively expensive.
The centre insulator also provides a good anchor for a balun if used with coax cable feedline, and a firm attachment for it.
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