So, you have a radio (a CB, ham, or FRS walkee-talkee). That's a good start. Now you need an antenna. If you have a walkee-talkee, are you able to unscrew the antenna out? If so, you can make a different one and double your range! And no, it's not as simple as "Step 1" and "Step 2". It all ties into a few things that I will cover in this section. And yes, these are things that you need to know if you want to understand what's going on.
Antenna Length
The truth is, antennas are made to be used on only 1 frequency (or channel). When you use, for example, a 40-channel CB radio, and you change channels, well, the antenna is just not going to work as good. Let me explain:
A lot of people think that the signal comes out of the tip of the antenna, but that's not true. If you could actually see the waves coming out, you'd see them coming out of the entire side of the antenna. For learning purposes, when you send out a signal, the physical length of the radio wave must be exactly the physical length of the antenna. That's how you get it to come out nice and smoothly.
When you change channels, the length of the radio wave is a little bit shorter, or longer - depending on whether or not you're changing the channels up or down. Yet, the length of the antenna stays the same. Sure, it will still work, but not as well. That's why no matter what radio you have - the antenna that you have with it, has a length of whatever channel is in the middle. If you have a 14-Channel FRS walkee-talkee, that means your antenna will work best on channel 7. If you have a 40-channel CB radio, your antenna was cut for channel 20. The middle channel will give you the longest range. The lowest and highest channels will give you the shortest range.
Give it a try. Go to the middle channel, and get as much distance as it will go. Then both you and your assistant switch to either the lowest or highest channel. You will barely be able to hear each other, if at all. You see, in a perfect world, the length of the antenna would change each time you change the channel. But that's just not practical.
So, how do you know what length an antenna should be?
Making Antennas
Before I came into the world of communications, I looked at the ham operators making their own antennas and thought to myself, "nerds". Why make an antenna when you can just buy one? The thing is, most antennas that you buy were designed to make money. That's their primary purpose. If you can build an antenna yourself, you can double your radio's range (or more), and spend a lot less money. Depending on how well you work with your hands, you can make it look professional too. But remember, the antenna doesn't care what it looks like, and so, neither should you. Performance is what we're after. And making an antenna that outperforms antennas that you can buy is ridiculously easy to do.
So, let's use a very simple example for making a new antenna for an FRS walkee-talkee. First, we need to know how long it should be. And, we will use Channel 7, because that's what's in the middle.
1. Channel 7 is on a frequency of 462.7125 MHz. How did I know that? Google told me.
2. There is a formula to use for finding the wavelength (and thus, antenna length). It is 468/frequency = length in feet. (I assume because we're all speaking English, most of us are using inches and feet. Google will give the rest of you the formula for meters and centimeters.)
468/462.7125= 1.011 feet.
Simply cut a wire for that length, and you have a full-wave antenna. This is much better than the shorter one that came with the walkee-talkee, because that one is probably a quarter-wave antenna. . . meaning, the signal is choppy coming out, because it's being chopped as it comes out. (**There's a funny thing about full-wave antennas that may or may not apply to you. So, if you find that it actually doesn't work at all, then cut it precisely in half.)
Polarization
Scary word, very simple concept. Is your antenna sticking up in the air, or laying on its side? Yes, this matters. If you have an antenna sticking up in the air, and the person on the other end has their antenna laying on its side, well, they aren't going to hear you very well. And the reason why is also simple.
Stick out your index fingers on both hands. Your left index finger, we'll say, is sending out a signal. Your right index finger will be the antenna that receives the signal. Now, make a cross with them, as if you are trying to fight off a vampire. Notice the small amount of area of skin that is touching together. Now, place your index fingers side-by-side. Notice that the amount of skin that is touching is significantly greater.
You want your radio signals to "touch" as much of the other people's antennas as much as possible. And you want their signals to "touch" as much of your antenna as possible. Think about that while you're using your walkee-talkee. If everyone had their antennas at a perfect 90-degree angle, well, that will increase your range significantly.
Materials
Have you ever heard someone brag about their 102" steel whip CB antenna? If they knew that copper radiates 6x what steel can, they probably wouldn't be bragging anymore. In the radio communications world, copper is king. There is only one other metal that works better, and that is silver. Hey, if you're a millionaire and can afford a silver antenna, more power to you. The results will only be marginally better than copper.
It's a bit more complicated than that, though. You see, when a radio signal travels down a cable or an antenna, it actually rides along the outside edge. If you had a copper rod, for example, the inside of the rod would have almost no signal at all, while the outside (what you can see) is where the signal will be. We call this the "skin effect". It's why you can take apart a TV coax cable, and on the inside, you find a wire that is made of steel, but coated with copper. Aside from steel not being as good as copper, some steel (like a bicycle break cable) is coated with protectant to help to keep it from rusting. Remember the "skin effect".
If you want to make an antenna, use copper. Copper wire, copper pipe, copper anything. Not aluminum, not steel, not iron, not anything else.
And that's the basic stuff that you should know about antennas.
Antenna Length
The truth is, antennas are made to be used on only 1 frequency (or channel). When you use, for example, a 40-channel CB radio, and you change channels, well, the antenna is just not going to work as good. Let me explain:
A lot of people think that the signal comes out of the tip of the antenna, but that's not true. If you could actually see the waves coming out, you'd see them coming out of the entire side of the antenna. For learning purposes, when you send out a signal, the physical length of the radio wave must be exactly the physical length of the antenna. That's how you get it to come out nice and smoothly.
When you change channels, the length of the radio wave is a little bit shorter, or longer - depending on whether or not you're changing the channels up or down. Yet, the length of the antenna stays the same. Sure, it will still work, but not as well. That's why no matter what radio you have - the antenna that you have with it, has a length of whatever channel is in the middle. If you have a 14-Channel FRS walkee-talkee, that means your antenna will work best on channel 7. If you have a 40-channel CB radio, your antenna was cut for channel 20. The middle channel will give you the longest range. The lowest and highest channels will give you the shortest range.
Give it a try. Go to the middle channel, and get as much distance as it will go. Then both you and your assistant switch to either the lowest or highest channel. You will barely be able to hear each other, if at all. You see, in a perfect world, the length of the antenna would change each time you change the channel. But that's just not practical.
So, how do you know what length an antenna should be?
Making Antennas
Before I came into the world of communications, I looked at the ham operators making their own antennas and thought to myself, "nerds". Why make an antenna when you can just buy one? The thing is, most antennas that you buy were designed to make money. That's their primary purpose. If you can build an antenna yourself, you can double your radio's range (or more), and spend a lot less money. Depending on how well you work with your hands, you can make it look professional too. But remember, the antenna doesn't care what it looks like, and so, neither should you. Performance is what we're after. And making an antenna that outperforms antennas that you can buy is ridiculously easy to do.
So, let's use a very simple example for making a new antenna for an FRS walkee-talkee. First, we need to know how long it should be. And, we will use Channel 7, because that's what's in the middle.
1. Channel 7 is on a frequency of 462.7125 MHz. How did I know that? Google told me.
2. There is a formula to use for finding the wavelength (and thus, antenna length). It is 468/frequency = length in feet. (I assume because we're all speaking English, most of us are using inches and feet. Google will give the rest of you the formula for meters and centimeters.)
468/462.7125= 1.011 feet.
Simply cut a wire for that length, and you have a full-wave antenna. This is much better than the shorter one that came with the walkee-talkee, because that one is probably a quarter-wave antenna. . . meaning, the signal is choppy coming out, because it's being chopped as it comes out. (**There's a funny thing about full-wave antennas that may or may not apply to you. So, if you find that it actually doesn't work at all, then cut it precisely in half.)
Polarization
Scary word, very simple concept. Is your antenna sticking up in the air, or laying on its side? Yes, this matters. If you have an antenna sticking up in the air, and the person on the other end has their antenna laying on its side, well, they aren't going to hear you very well. And the reason why is also simple.
Stick out your index fingers on both hands. Your left index finger, we'll say, is sending out a signal. Your right index finger will be the antenna that receives the signal. Now, make a cross with them, as if you are trying to fight off a vampire. Notice the small amount of area of skin that is touching together. Now, place your index fingers side-by-side. Notice that the amount of skin that is touching is significantly greater.
You want your radio signals to "touch" as much of the other people's antennas as much as possible. And you want their signals to "touch" as much of your antenna as possible. Think about that while you're using your walkee-talkee. If everyone had their antennas at a perfect 90-degree angle, well, that will increase your range significantly.
Materials
Have you ever heard someone brag about their 102" steel whip CB antenna? If they knew that copper radiates 6x what steel can, they probably wouldn't be bragging anymore. In the radio communications world, copper is king. There is only one other metal that works better, and that is silver. Hey, if you're a millionaire and can afford a silver antenna, more power to you. The results will only be marginally better than copper.
It's a bit more complicated than that, though. You see, when a radio signal travels down a cable or an antenna, it actually rides along the outside edge. If you had a copper rod, for example, the inside of the rod would have almost no signal at all, while the outside (what you can see) is where the signal will be. We call this the "skin effect". It's why you can take apart a TV coax cable, and on the inside, you find a wire that is made of steel, but coated with copper. Aside from steel not being as good as copper, some steel (like a bicycle break cable) is coated with protectant to help to keep it from rusting. Remember the "skin effect".
If you want to make an antenna, use copper. Copper wire, copper pipe, copper anything. Not aluminum, not steel, not iron, not anything else.
And that's the basic stuff that you should know about antennas.
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