It looks like you're using an Ad Blocker.

Please white-list or disable AboveTopSecret.com in your ad-blocking tool.

Thank you.

 

Some features of ATS will be disabled while you continue to use an ad-blocker.

 

AM vs. FM

page: 1
0

log in

join
share:

posted on Jul, 25 2004 @ 01:36 PM
link   
i live here in chicago, and listen to WLS890 AM. what i was wondering one night coming home from work was this: How does an AM signal travel so far? when i went to alabama last year, i swear i was in kentucky or maybe tennesee, still listening to it, yet the clearer sounding FM stations only seem to broadcast for about 40-50 miles. also, this..why can an AM signal travel that far with no problem, yet every time i go under an over pass, i loose the signal. there are alot of trees between here and kentucky, why doesnt the signal break off?

can some post some info on this? (and in plain english, if possible..lol)




posted on Jul, 25 2004 @ 02:03 PM
link   
Two post about radio in one day... do a little research and you'll find all the answers are on the web.

AM travels far because it uses long wavelengths only, then the information is carried by amplitude modulation.

entertainment.howstuffworks.com...

There, read away. It will answer both your threads.



posted on Jul, 25 2004 @ 02:05 PM
link   
Well AM Radio operates at 540 - 1710KHz and FM radio operates on 88 - 108MHz.
The higher the frequency, the shorter the radio wave. Radio waves travel at the speed of light so a radio wave at 1Hz will be 186,000 miles long.

So take an AM radio wave, 1000KHz, or 1 megahertz: that is 1 million cycles per second. Because of the wavelength it will cycle 1 million times in that one second as opposed to an FM radio wave which would cycle 100 million times in a second (at 100MHz). Radio waves will bend around the surface of the Earth. The longer the wave is, the more it bends. The more it bends, the further it travels. This is why you can talk across the globe on AM radio. A cellular phone, operating in the range of 850Mhz, has a much shorter wavelength and is more easily obstrued by buildings, trees, and other objects, which is why it travels such a short distance (hence the need for towers every couple miles.) It also depends how much power the transmitting station is putting out.



posted on Jul, 25 2004 @ 02:25 PM
link   
AM radio waves are bounced off the Ionosphere and return back to earth. FM radio signals broadcast outward. That is why you lose the AM signal when you go under an overpass.

Am I right in saying that satellite radio has the lowest frequency?



posted on Jul, 25 2004 @ 04:03 PM
link   
The lower the frequency, the farther it goes and the better it penetrates things like buildings and mountains. This is the same reason why wireless networks that use 2.4 gig freq. go much farther and penetrates walls much better than the 5.2 gig freq.



posted on Jul, 25 2004 @ 04:07 PM
link   

Originally posted by sublime4372
i live here in chicago, and listen to WLS890 AM.


Hey Sublime...I'm a Roe fan! "Save Garry" LOL

I can tell you that I travelled to Toronto and was actually able to listen to WLS late one night.

Pretty cool, no matter what the science is!



posted on Jul, 26 2004 @ 06:42 PM
link   
I don't know about satellite radio, but satellites in general tend to be very high frequencies. The reason they travel so far even though they have high frequencies, is because there is nothing blocking the signal between you and the satellite. If a signal at the same frequency and power was sent from earth, it probably would not go more than a few hundred feet. Also, most satellite signals are sent and received using a satellite dish which focuses the radio waves from one direction and blocks the signals from any other direction. Thats why you can receive a satellite signal of only a few watts crystal clear even though the signal is coming from space.



posted on Jul, 26 2004 @ 07:24 PM
link   

Originally posted by perseus
I don't know about satellite radio, but satellites in general tend to be very high frequencies. The reason they travel so far even though they have high frequencies, is because there is nothing blocking the signal between you and the satellite. If a signal at the same frequency and power was sent from earth, it probably would not go more than a few hundred feet. Also, most satellite signals are sent and received using a satellite dish which focuses the radio waves from one direction and blocks the signals from any other direction. Thats why you can receive a satellite signal of only a few watts crystal clear even though the signal is coming from space.


If you get lower than a few hundred MHz (about 300) radio signals are absorbed by the ionosphere - so sattelite radio must use a higher frequency than that. The real benefit is a true line-of-site to everywhere on the surface of the earth and very little interference until you get to the earth's atmosphere.




top topics



 
0

log in

join