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Why does the size and shape of a transmitting dish aerial dictate the use of microwaves instead of long-wave radio signals?
The purpose of the shape and dimensions of any antenna is to prevent power
from being radiated in directions that aren't useful to the communications, and
concentrate the power in the direction toward the intended receiver.
In order to accomplish that, all kinds of antennas are built out of an incredible
array of pieces of wire or metal. which are all in the general ballpark of the size
of a half wavelength of the power to be radiated. Nothing much shorter than that
has much effect on how the power is focused, and on where it goes.
Commercial AM radio broadcast operates with wavelengths between roughly 175 to
550 meters (575 to 1,800 feet). When you look at an AM broadcast tower, you don't
see any antenna mounted on it. It just looks like a bare, naked tower, and you wonder
where the antenna is. The answer: The tower itself is the AM antenna, because the
wavelength is hundreds of feet, and the antenna must have similar physical dimensions.
When you go higher in frequency (shorter in wavelength), practical antennas can be
much smaller ... like the skinny rods or tubes on a TV antenna.
"Dishes" are wonderful antennas. They can focus all of the transmitted power into
a beam that's only a few degrees wide! The larger the dish is, the smaller the
beam. But what's a 'large' dish and what's a small one ? In order to be effective,
the dish must be large compared to the wavelength. If the dish is less than maybe
10 wavelengths across, then forget it. It's no help.
Dishes are great for intercity microwave in, say, the 6 GHz band, where the wavelength
is maybe 5 centimeters ... around 2 inches ... and you use a dish with a diameter of
6-ft, 8-ft, or 10-ft. That gives us plenty of bang for the buck, and that's how we build
bullet-proof communication over 20 miles with 1/2 watt of microwave power !
There's no theoretical reason that you couldn't use a dish to transmit music and news
at, say, 850 on your AM dial. The wavelength there is about 1,158 feet, so a minimal
dish of 10 wavelengths' diameter would be 2.2 miles across. Expensive, perhaps, but
you could do it if you really felt like it, I suppose.
Next time you're Surfing the web, search "Arecibo", and have a look at the photos of
the National Astronomy and Ionosphere Center, the observatory for radio astronomy
located near that town in Puerto Rico. The dish for the radio telescope there is the
largest dish antenna in the world. It's built into a natural valley, and it's 305 meters
(1,000 feet, 0.1895 mile) in diameter.
What else can I help you with?
Did the Australians play the theme to Hawaii 5 0 instead of the American National Anthem during the moon landing?
No. This was just a tongue-in-cheek inclusion in that great movie "The Dish", which told the story of how the radio telescope at Parkes played a vital role in transmitting the moon landing of 1969. There is no truth to it. Australians like to poke fun at themselves in movies.
What can you use instead of LimeWire?
Ares
Does beyonce have another sister instead of solange?
No
Why are car radio antenna's vertical?
Car radio antennas are typically vertical because they are designed to receive radio waves that are vertically polarized. Vertical antennas are more efficient at picking up vertically polarized signals, which are the most common type of radio wave used for broadcasting. Additionally, vertical antennas are less susceptible to interference from nearby objects compared to horizontal antennas. Overall, a vertical orientation maximizes the antenna's ability to receive radio signals effectively.
When dressing up like Sandy from Grease can you wear pink shoes instead of red?
Yes. Pink shoes instead of red would be fine.
Why are there microwaves instead of radio waves in a mobile device?
your mum :D
What stops microwaves from penetrating certain materials?
Certain materials, like metals and thick metals, can block microwaves because they reflect the waves instead of letting them pass through. This is due to the properties of the material that prevent the microwaves from penetrating.
Why can't metal objects be inside a microwave oven when this is working?
They reflect the microwaves instead of absorbing them.
What did they used to use in the 1800's instead of microwaves?
NO! there wasnt much of elecrticity yet.
Why are microwaves efficient?
They create heat inside the object being cooked, instead of wasting it outside.
What people used instead of microwaves in 1800?
Wood stoves. (They burned wood or coal to get hot).
Do airplanes have microwaves on board for heating up food?
No, airplanes do not have microwaves on board for heating up food. Instead, they use ovens or hot plates to heat up meals for passengers.
What materials absorb microwaves completely?
Materials that are good absorbers of microwaves include water, certain plastics, ceramics, and some types of food. These materials are able to absorb and convert microwave energy into heat due to their molecular structure and composition. Metals, in contrast, are poor absorbers of microwaves and reflect them instead.
Which phenomenon occurs when a wave encounters a non-transmitting barrier?
When a wave encounters a non-transmitting barrier, reflection occurs. This means the wave bounces off the barrier instead of passing through it. The angle of incidence is equal to the angle of reflection.
Why are microwave doors lined with a metal net?
The metal net reflects microwaves that hit the door back to the food instead of through the glass and into you.
Why does the glass panel on a microwave contain a metal mesh?
The metal mesh on the glass panel of a microwave is a safety feature that prevents the microwaves from escaping while allowing you to see inside. The mesh acts as a barrier that reflects the microwaves back into the oven, ensuring that they do not leak out and potentially harm you.
What can you rub over a persons body where a tic is in the skin to make them get out?
If you remove the tick that way, you increase the risk of the tick transmitting disease. Use tweezers instead.
