For a simple 1 / 4-wave whip, the radials are often sloped at a 45 degree angle to bring the feed point impedance closer to 50 ohms.
12.
Although it has a superficially similar appearance, the so-called halo antenna is not technically a loop since it possesses a break in the conductor opposite the feed point.
13.
Returning to the basic concept of current flows in a conductor, consider what happens if a half-wave dipole is not connected to a feed point, but instead shorted out.
14.
The polarization of such an antenna is not obvious by looking at the loop itself, but depends on the feed point ( where the transmission line is connected ).
15.
However, the output from each element has to be gathered up at a single feed point, and as the signals travel across the antenna to that point, their phase is changing.
16.
Since this will introduce RF energy on the shield of the unbalanced feed line which deforms the radiation pattern of the antenna, a choke is often placed near the feed point.
17.
In a two-element array this is not a problem because the feed point can be placed between them; any phase shift taking place in the transmission lines is equal for both elements.
18.
The fuel tank was as small as possible and, because its bottom feed point was located lower than the carburetor, had to be pressurised occasionally by a hand pump built into the tank.
19.
The Vienna-based International Atomic Energy Agency agreed to police the agreement and has placed seals on feed points at Iran's enrichment plant at Isfahan, meant to prevent new material from being introduced into the facilities.
20.
One way of thinking about the operation of such an antenna is to consider a parasitic element to be a normal dipole element fed at its centre, with a short circuit across its feed point.
