CommoFreq
Member
Understanding how radio waves travel is a must. If you don't know this information, you will be one of those who have a perfect radio and a perfect antenna, and not understand why you're having trouble communicating. By the way, this accounts for roughly 90% of everyone who has a radio of some sort.
There are different "worlds" to how radio waves travel, because well, there are different radio waves. So, we'll just take this one step at a time, start simple, and then go complex.
Two things to know before going into this:
1) Water, ice and metal reflect radio waves.
2) Sand, soil, and wood absorb them.
You probably already noticed this with "sound". You get an echo in the mountains, and in the desert, you don't. Sound is also just "waves".
VHF/UHF (FM)
This includes radios that operate on 30.0MHz or higher - that is to say, FRS walkee-talkees, for example. I'm sure you've already figured out that these walkee-talkees are for local communications only. You won't be receiving any signals from China, that's for sure. With that in mind, think of a swimming pool. A swimming pool? Yes, a swimming pool!
If you threw a rock in the middle of a large swimming pool, and then looked at the ripples, you'll notice that the waves closest to where the rock landed are strong, and the further out they spread, the weaker they get. Radio works the same way. I bet you already knew this. See what happens to them when they hit the sides? They bounce off at a perfect symmetrical angle, and are even weaker. Okay, boring stuff.
In the VHF/UHF world, your main worry is going to be these "walls". Sometimes they will reflect the signal, and sometimes they will actually *absorb* the signal. It just depends on the material. With an FRS walkee-talkee, most of the signal will be absorbed, while only some will be reflected.
This is why on every "high place" you see around you, there are antennas. The next time you go for a drive, look at the hill tops (if there are any) water towers, or tall buildings. Most of them have antennas on them. The idea here, is to actually "shoot over" all of these potential obstacles, like trees, houses, pretty much everything (those absorb radio signals). Sometimes the hills themselves are obstacles. You probably call them "dead zones" when you lose your cell phone signal.
You might have known this too, but not really understood why it's important to "get high". You want, if possible, to somehow physically "see" who you're talking to, in an ideal world.
HF (AM)
This includes radios that operate under 30.0MHz - that is to say, CB radio. Now, all of what I mentioned above applies here as well. But, there's more to the story. The reason for that is because these waves are very bouncy, and all of the things that normally absorb the higher FRS walkee-talkee frequencies, will otherwise reflect these types of lower frequency waves on CB. The rule of thumb here, is that 50% of your signal will bounce, while the other 50% will be absorbed. And no, that is not an exact science.
And this is why CB radio has a "longer range" than FRS walkee-talkees. Two boats out at sea, for example, one with a CB and one with an FRS radio. . . will have the same range (because water is reflective, and there are no obstacles out at sea). On land, the FRS walkee-talkee signals are absorbed by virtually everything, while the CB signals bounce around a lot more. On paper, they have the same range, but in application, well, that's a different story. Like communism!
The other, perhaps more interesting feature about 30.0MHz and below, is that they are so bouncy, they actually bounce off of the atmosphere, and back down to the ground. You can observe this yourself, if you want. Here's how:
1. Wait for night time (I'll explain why in a 201 lesson at a later date).
2. Go to your car, and turn on your stereo.
3. Put it on the AM band, for AM radio stations
4. Turn off the auto-search function
5. Manually browse through the AM band.
The weaker signals are still readable, and you'll notice that they are coming in from all over the country! Notice how much quieter it is at night - during the day, you hear mostly loud static.
Why is this happening? Well, it's not as if they love you, and are purposely aiming their antennas toward the sky just so that they can bounce the signal to you, and you can get their signal and listen to their station. Radio waves travel in a straight line, and planet Earth is more of a "curved" kind of thing. If you had a powerful laser, and pointed it toward the horizon, eventually it would start to leave the surface of the Earth, and go out into space.
Well, radio waves travel the same way, but the atmosphere (for the most part) won't allow these waves to pass through it. And so, like the swimming pool, they bounce, and come back down again. If you wanted to, though, you *could* point an antenna at an angle, and change the angle that it bounces off of the atmosphere. That also works. Just sayin'. . . with a little bit of math, you could intentionally target places to talk to.
Anyway, these types of long-distance waves are known as "skip" in the CB world, because they "skip" over long distances. Other people call this "short wave", although I have no idea why - they are the longest waves on the radio spectrum.
If you are sitting directly underneath the place where the radio waves hit the atmosphere, you won't be receiving them. They are essentially "skipping" over your head. You're only going to receive the ones that have been bounced down toward YOU. Make sense? Applicably, you won't be doing much of this in the CB world, because there are already so many people using these radios, that it's practically chaos. Night time is the best time to hear these types of signals. And ham radio is the best to use for these long-distance communications.
So effectively, if you are having trouble communicating, and you know that it's not because of your equipment, then there are only 3 possibilities:
1) You are too far away.
2) Their waves are skipping over your head, or vise versa.
3) Your signal (or their signal) is being blocked by something.
The solution? Get high. If that doesn't work, then the answer is #1.
There are different "worlds" to how radio waves travel, because well, there are different radio waves. So, we'll just take this one step at a time, start simple, and then go complex.
Two things to know before going into this:
1) Water, ice and metal reflect radio waves.
2) Sand, soil, and wood absorb them.
You probably already noticed this with "sound". You get an echo in the mountains, and in the desert, you don't. Sound is also just "waves".
VHF/UHF (FM)
This includes radios that operate on 30.0MHz or higher - that is to say, FRS walkee-talkees, for example. I'm sure you've already figured out that these walkee-talkees are for local communications only. You won't be receiving any signals from China, that's for sure. With that in mind, think of a swimming pool. A swimming pool? Yes, a swimming pool!
If you threw a rock in the middle of a large swimming pool, and then looked at the ripples, you'll notice that the waves closest to where the rock landed are strong, and the further out they spread, the weaker they get. Radio works the same way. I bet you already knew this. See what happens to them when they hit the sides? They bounce off at a perfect symmetrical angle, and are even weaker. Okay, boring stuff.
In the VHF/UHF world, your main worry is going to be these "walls". Sometimes they will reflect the signal, and sometimes they will actually *absorb* the signal. It just depends on the material. With an FRS walkee-talkee, most of the signal will be absorbed, while only some will be reflected.
This is why on every "high place" you see around you, there are antennas. The next time you go for a drive, look at the hill tops (if there are any) water towers, or tall buildings. Most of them have antennas on them. The idea here, is to actually "shoot over" all of these potential obstacles, like trees, houses, pretty much everything (those absorb radio signals). Sometimes the hills themselves are obstacles. You probably call them "dead zones" when you lose your cell phone signal.
You might have known this too, but not really understood why it's important to "get high". You want, if possible, to somehow physically "see" who you're talking to, in an ideal world.
HF (AM)
This includes radios that operate under 30.0MHz - that is to say, CB radio. Now, all of what I mentioned above applies here as well. But, there's more to the story. The reason for that is because these waves are very bouncy, and all of the things that normally absorb the higher FRS walkee-talkee frequencies, will otherwise reflect these types of lower frequency waves on CB. The rule of thumb here, is that 50% of your signal will bounce, while the other 50% will be absorbed. And no, that is not an exact science.
And this is why CB radio has a "longer range" than FRS walkee-talkees. Two boats out at sea, for example, one with a CB and one with an FRS radio. . . will have the same range (because water is reflective, and there are no obstacles out at sea). On land, the FRS walkee-talkee signals are absorbed by virtually everything, while the CB signals bounce around a lot more. On paper, they have the same range, but in application, well, that's a different story. Like communism!
The other, perhaps more interesting feature about 30.0MHz and below, is that they are so bouncy, they actually bounce off of the atmosphere, and back down to the ground. You can observe this yourself, if you want. Here's how:
1. Wait for night time (I'll explain why in a 201 lesson at a later date).
2. Go to your car, and turn on your stereo.
3. Put it on the AM band, for AM radio stations
4. Turn off the auto-search function
5. Manually browse through the AM band.
The weaker signals are still readable, and you'll notice that they are coming in from all over the country! Notice how much quieter it is at night - during the day, you hear mostly loud static.
Why is this happening? Well, it's not as if they love you, and are purposely aiming their antennas toward the sky just so that they can bounce the signal to you, and you can get their signal and listen to their station. Radio waves travel in a straight line, and planet Earth is more of a "curved" kind of thing. If you had a powerful laser, and pointed it toward the horizon, eventually it would start to leave the surface of the Earth, and go out into space.
Well, radio waves travel the same way, but the atmosphere (for the most part) won't allow these waves to pass through it. And so, like the swimming pool, they bounce, and come back down again. If you wanted to, though, you *could* point an antenna at an angle, and change the angle that it bounces off of the atmosphere. That also works. Just sayin'. . . with a little bit of math, you could intentionally target places to talk to.
Anyway, these types of long-distance waves are known as "skip" in the CB world, because they "skip" over long distances. Other people call this "short wave", although I have no idea why - they are the longest waves on the radio spectrum.
If you are sitting directly underneath the place where the radio waves hit the atmosphere, you won't be receiving them. They are essentially "skipping" over your head. You're only going to receive the ones that have been bounced down toward YOU. Make sense? Applicably, you won't be doing much of this in the CB world, because there are already so many people using these radios, that it's practically chaos. Night time is the best time to hear these types of signals. And ham radio is the best to use for these long-distance communications.
So effectively, if you are having trouble communicating, and you know that it's not because of your equipment, then there are only 3 possibilities:
1) You are too far away.
2) Their waves are skipping over your head, or vise versa.
3) Your signal (or their signal) is being blocked by something.
The solution? Get high. If that doesn't work, then the answer is #1.
