Antenna Explanation?

Question

How does a micro wave create a current that can be used for TVs?, can someone give me a detailed explanation of how the waves interact with the metal,do the waves interact with any metal? or is there something special about antennas?

Answer 1

Question A: A micro wave is an electro-magnetic wave. As you might know, when you change a magnetic wave near a metal (doesn't have to be near metal, but lets look at your antenna) it creates a current in your antenna. Whala!!!

Question B: The waves interact with any material actually, wood absorbs electro-magnetic waves very nicely, but just can't conduct the small current very well. It also depends on the frequency of the wave, some materials absorb some frequencies better than other. Do a little experiment, take some random stuff in put it in the microwave oven. If it heats up quick, then you know at least it absorbs the frequencies around 2.5GHz very well. This is the same frequency range as cellphones and wifi connections by the way. Also a good test to see what not to put between you and the neighbours wifi router.

Question C: Well there is a lot of ways to make an antenna better. For example, it should be at least 1/4 wavelength long, but preferably longer. The impedance should be more or less the same as the medium (air). This is high frequency impedance, the distance of the air does not matter, you look right there at the point the two meet. Then there are ways to make use of the resonant frequency for better gain. Then the shape also influences the radiation or absorption pattern.

But radio transmission and reception is really not simple to do well, and I'm not going to show any of the math here. In principle, just look at my answer A

Answer 2

Microwave antennae used in television either DBS or studio/transmitter

links commonly use a parabolic reflector to concentrate energy into a feed horn and coupled to a waveguide.because the wavelength of

signal is very small, waveguide is normally used as the 'transmission

line',and has similar wave propertys as transmision lines (twinlead,coaxial) for lower frequency radio waves.

DSS satellite systems often encorporate the feed,waveguide,and a low

noise amplifier/downconvertor into a single unit called a LNBF.

(low noise block converting feed)