In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment.
An antenna is an array of conductors (elements), electrically connected to the receiver or transmitter. Antennas can be designed to transmit and receive radio waves in all horizontal directions equally (omnidirectional antennas), or preferentially in a particular direction (directional, or high-gain, or “beam” antennas). An antenna may include components not connected to the transmitter, parabolic reflectors, horns, or parasitic elements, which serve to direct the radio waves into a beam or other desired radiation pattern.
The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of waves predicted by the electromagnetic theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving. Starting in 1895, Guglielmo Marconi began development of antennas practical for long-distance, wireless telegraphy, for which he received a Nobel Prize.
I have a weird question I think... I'de like to know how low a frequency and how high a current can a wireless device transmit.
eg, radio frequency is over 1000s of Hz, can it be much lower than that?When you receive a radio signal to an antenna, a small current is generated which is...
Because of its direct link to self-fields such as described in the EM self-field theory, I want to talk about how antennas can be designed to emit zero nett radiation. Although antennas were shown by Hertz in 1888 to 'always' emit radiation he used only one antenna, a wire halfwave dipole with...
I have been looking for info on the physical basis for this antenna equation :
Gain = 4 * Pi * (Effective Area ) / Wavelength^2
I have found some tutorials that say it is based on reciprocity, and more specifically, on thermodynamic balance between a resistive load connected to an antenna...
I have a satellite antenna in my backyard (the big antenna, not the small one from Direct TV) and I don't know how to use it. I did some research and I think it's called the C-band antenna and I do have to pay around $30 for service/month just like we have to pay for cable TV. I have a receiver...
Hi,
I want to clarify some notiona in an antenna. The major components of an antenna are a generator, transmission line and an antenna (dipole). Let's say the whole system has a perfect matche, i.e. the dipole is about 70 ohms as the transmission line. If my generator ,the output voltage, is...
Hello all,
I have this weird idea for a cell phone booster antenna and I thought i would run it past you all here to see if it could work.
Where I live, we get really bad reception inside our house so I commonly have to step outside and use my cell phone in the driveway to get a decent...
I am aware of the apperent presence of electrons on the [flat, top] base of an antenna such as one on a radio. I took the time to obtain a magnet with moderate strength. I placed the magnet about a centimeter away from the [flat] base of the antenna and found it vibrated. As I decreased the...
Just wondering if anyone happens to have an electromagnetic diagram of how a four antenna array would look. Provided that all four antennas’ form a square and edges are one wavelength in distance?
Thanks
Philip
If light is just an EM phenomena like radio waves (with more energy) would it be possible to build a transmitter that transmits in the light range? If you were to do this, would you see light that just seems to propagating from the antenna?
Lets take a unidirectional antenna. The waves you acquire are transformed into light that you can see. You designate the freq. into specific colours and what would you see?
OK here is what I am trying to figure out
there is a large factory by my house which towers about 4 stories above the surrounding community. on the roof there is an array of 802.11b anttenas (im assuming its B and not A cause B has larger range) there are 10 large anttenas, 5 on one side of...