posted by charlie on .
A radio station with a power of 20 kW sends out an omnidirectional wave at 1.25 MHz.
a. If the electromagnetic wave has an electric field of 0.22 V/m, what is the magnetic field amplitude?
b. What is the intensity of the wave at 5 km?
c. What is the wavelength of the electromagnetic wave?
after 50 years in radio, I have no idea what an omni-directional antenna is. Does it radiate upwards? Downward? in a Donut shape? It is easier to just say the gain in db in a particular direction, and stop the nonsense about omnidirectional antennas. This is a real world.
solve for wavelength.
This is what is normally called omni-directional antenna patterns by radio users, it is not OMNI in the sense physicists mean, a spherical pattern. http://www.inl.gov/featurestories/i/antenna_02.jpg
In this pattern, one has to know the flatness in azimuth, which is complicated. It is just much easier to specify gain in db over a the mythical spherical omni, which does not exist.
That idea of "omni directional" kind of confused me also... I would guess that it can be assumed as just a regular wave?