radio,radio wave theory

[fire_mat99]

Here is copy of how radios work ..I still have some questions

 

 

 

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Trees and buildings affect radio waves as well as the weather.

 

The sun can also affect radio waves; it can help the radio operator or cause problems.

 

If the sun was gone the radio wave would still work.

 

Why can a radio on the moon with a 5 inch antenna pick up NASA because NASA is transmitting at a very high power and using a very big antenna.

 

How can NASA pick up radio transmissions coming from a portable radio on the moon using 3 watts; because NASA is using a big antenna and also a very good antenna.

 

How can you transmit signals around the earth? Using HF signals bouncing off the ionosphere and keep bouncing so you can pick them up. Other signals are lying off site like VHF and UHF and are good for only short local transmissions but sometimes they can travel far. i.e 50 or 100 miles.

 

How can you trace a radio signal? By pointing the receiver different directions it will give you a signal strength. Then you walk in the direction of the strongest signals you get closer to the source the signal gets stronger. There are other devices you can use to trace radio signals. i.e. rotating device that stops in the direction the signal is coming from. It is sometimes mounted on vehicle.

 

When a radio reception is bad you can try different bands as some work better than others.

 

Check on internet: Doppler, fox hunting

 

The higher the frequency range, the less likely of skip especially 30 MHz and up.

 

The higher the frequency the harder it is to penetrate trees and buildings so repeaters are needed.

 

Repeaters are used mostly in VHF and UHF to get the signal to travel and to penetrate trees and buildings as a common problem with VHF and UHF. There is no skip in UHF and VHF only 30 MHz and down. The lower the frequency the better it is for signals to travel around the world.

 

Why are police and fire radio coverage short, only local?

Because they set up for their coverage area and use repeaters to extend the coverage they want. They don’t use HF if they did they would have skip. They use VHF and 800 MHz trunk and a line of sight transmissions.

 

Why were radios big in the Vietnam war?

Because radios back then were big. The technology keeps getting better and smaller. It wasn’t they wanted it big, it was the technology back then. Radios were big and heavy back then, now small and compact. In WWI they used Morse Code and telegraph and not radios.

 

How would you send signals to Mars? You transmit using a big antenna at high power using a very good antenna. NASA has very good antennas. You transmit to a satellite orbiting Mars then relays the communication to a portable radio on Mars.

 

Radio signals travel far in space and can pick up radio signals 30 light years away.All signals on earth eventually go in space and will travel far.

[fire_mat99]

my questions

 

 

 

What makes the radio signal weaken on earth but not in space?

 

 

 

Why can radio waves travel so far in space?

 

 

 

What other strange phenomena is there in space that can stop or weaken a signal?

[mmalluck]

Air is still matter. Sure it does a lousy job of blocking radiowaves, but given enough of it, it will attenuate the signal off to nothing. Also there's a lot of radio noise sources here on Earth that will 'hide' a signal as it becomes weaker.

 

Outerspace on the other hand is filled with mind-boggiling amounts of nothing. The waves will propigate unobstructed and there are very few noise sources in space.

 

I imagine clouds of dust, like nebulas, would interfer with radiowaves as would interference from the sun (random solar flares and the like).

[fire_mat99]

Outerspace on the other hand is filled with mind-boggiling amounts of nothing. The waves will propigate unobstructed and there are very few noise sources in space.

 

 

If you transmit 30MHz and up it will go in space and are called line of site

 

I imagine clouds of dust, like nebulas, would interfer with radiowaves as would interference from the sun (random solar flares and the like).

 

But does gravitation of planets and black holes interfer with radio waves

 

 

Also gases like this

 

[Klaynos]

But does gravitation of planets and black holes interfer with radio waves

 

Radio waves are a type of EM radiation, which I think I remember being effected by gravity (light bending around stars and things)... So yes.

[YT2095]

although certain bands at certain times of the day, it`s advantagious to be here on Earth, we use what`s called Skip, that`s when a signal bounces of the charged particles in the ionosphere and bounce back to earth again, Line of sight doesn`t mater then, it`s like skipping a flat stone over water, so you can literaly transmit to the other side of the globe on miliwatts of paower when the "sKip" propogation is right

[mmalluck]

But does gravitation of planets and black holes interfer with radio waves

 

No more than light or any other EM wave. Gravity-wells (planets, stars, blackholes) are known to bend space and therefore the travel of EM waves around them. As long as a blackhole isn't directly between your reciever and transmitter you'll probably be okay.

 

Gravity-wells can also help. In certain cirmustances, blackholes and the like are able to bend space into a magnifying lense of sorts. These are often refered to as gravity-lenses.

 

Here's a link that talks about light distortion due to gravity-wells and the lenseing effect it can cause:

http://www.suite101.com/article.cfm/astronomy_astrophysics/110308