Hi, Ladies and Gentlemen, I hope all is well. We're going to pick up the tempo a little bit now. Today we're going to cover antennas, feed lines, amateur radio signals and be safe.
As you are aware, I am in the No Nonsense Technician Class Study
Guide on page 19. We've talked about a lot of this already - about
horizontally and vertically polarized antennas. But there is something on this page that you definitely need to know and remember. It's wavelength in meters equals 300 divided by frequency in MHz. Here comes your 'T' formula again. Draw a 'T', put 300 on top, underneath the 300 put meters, and on the other side put frequency in megahertz, MHZ. Now this is not a precise formula, but it will get you in the general ballpark. The 300 is constant, it does not change. Here is an example. You have a 2 meter radio. Take 300 divided by 2 (meters) and you get 150 which is your frequency in MHZ. The VHF band for ham use is 144 to 148 MHZ. Let's take one more. You're operating on 10 meters. Take 300 divided by 10 equal 30. Now that's 30 MHZ, and the 10 meter HF band is 28 to 29 MHZ. Remember, this is not a precise formula, but you're going to use it and you're going to use it on the test. Remember we talked about: on a clean sheet of paper, after you start the test, to write down some formulas? This might be one you want to use. So, write down P = E x I and E = I x R. Remember to make them into a 'T' and the problems of the universe are solved. There will be one more 'T' formula I will share with you later. Don't forget horizontal and vertical.
Here we're going to talk about beam antennas. To understand the difference, a vertical antenna sticking up in the air is an omni directional antenna. Most horizontal wire antennas for the most part
are omni directional. But a beam is a directional antenna. We all know what a dish antenna is because of satellite TV. But the most popular directional antenna used by hams is the beam antenna. Okay, so what does one look like? Picture the older type TV antennas used to receive free air TV signals. This is called a Yagi. These antennas are directional and you will point them where you want to beam your signal. This is very similar to granny pointing her TV antenna toward the TV broadcasting tower. So, now you know what a Yagi is.
Now we are going to talk about SWR, standing wave ratio. Standing wave ratio can be looked at as loss. The more the SWR, the more the loss. What this means is when you're sending a signal from your radio through your coax out of your antenna, in a perfect world you would have a one to one
ratio. But, we don't live in a perfect world, so you're going to get a little bit of feedback. There are lots of reasons for feedback: poor antenna radio match up; your coax is too small or in poor condition; and there are many other reasons also. If your radio signal went out the antenna perfectly, again, it would be 1:1. But, let's say that your antenna is not matched with your radio, or you have water or moisture inside your coax, or your coax is too small to carry the power you're trying to put through it, or it's short distance coax that you're trying to run a long distance. All of these are factors, but what happens is part of your signal starts to bounce back. When the signal bounces back, your SWR, your standing wave ratio, increases, therefore, part of your power is lost or absorbed fighting waves coming back. If your SWR gets too high, you can overheat coax, or you can ultimately fry your radio. So, this is SWR.
You're getting to the point now where you need an Elmer. We've talked many times about the ARRL website. It is an excellent place to get human help. Now is the time.
Amateur radio signals. We've talked about this a bunch. We'll talk about it a little bit more. FM is frequency modulation. Yes, there is an FM radio in
your car, and it is FM. But in this case, it is referring to a band of numbers or frequencies. AM is amplitude modulation. And, yes, you have one of these in your car also. And it is also AM. But then again, this is talking about a group of numbers or frequencies. SSB is single side band. There is upper side band and lower side band. It's the same stuff as when I talked about CB radios, there is no miracle here, it's the same stuff.
Continue reading this section. There is stuff here you're just going to have to figure out on your own. Some free test advice here. You're going to start seeing questions where the answer is, "All of these choices are correct."
Okay, folks, the next part is be safe, page 24. You've heard this multiple times, "If you don't know what you are doing, DON'T DO IT!" You've also heard this before too, "You do not want to fry your little girl's brain." Read this page, then read it again and again. There is no substitute for safety. It is not advisable to bring a lead acid battery into your house. Notice at the top of page 25. What causes explosive gas is that the lead acid battery is charged or discharged too rapidly. So figure it out for yourself. A slow charge does not produce explosive gasses. But for safety purposes, do not bring one in your house.
There are many questions here about putting up a pole for your antenna. More than one good person has electrocuted themselves on a windy day trying to put up some type of antenna or pole near a power line. I can't repeat this enough. If you don't know what you are doing, DON'T DO IT. Read the information about antenna, RF burns and you will see numerous references to, "All these choices are correct."
As I mentioned earlier, we are going to pick up the tempo a little bit. Please read ahead. If you have questions, try to figure out the answers first. There are numerous publications online and there is your public library. Or even,
surprise, surprise, contact the ARRL. Some of these guys there have been doing ham radio since before I was born. They will be happy to help you. They don't want their little granddaughter's brain fried. I don't say that to be funny, because it can and does happen. Keep taking the free practice tests, or the paid ones, if you went that route. If you want a more thorough understanding the ARRL sells excellent manuals and most of them come with a CD version attached.
Now I have a favor to ask. I need feedback. Have any of you taken your test and passed it? And are any of you actively pursuing your license? This is information I need for my own personal satisfaction. Please leave a comment. Because, ladies and gentlemen, if you can't see what is happening around you, then I am just spitting in the wind. But if you can see, and you plan to include communications in your long term future, then now is the time to get it done. Every day, your options diminish. Get it done.
We'll talk more later. 73, Frank