For several decades, amateur radio has been the most powerful means of communication, with its ability to send messages from one point to another. Many antennas were invented out of simple necessity. At the time of the Titanic disaster, for example, spark gap transmitters were used. Already at the time that system was called wireless, and even today the wire antennas send signals by air. Amateur radio has come a long way from spark gap transmitters of that time. To power them, high-voltage coils were used that sent "dots" and "lines" of Morse code, and the recipients wrote down the symbols to decipher the message. Despite being an outdated means of communication, it still retains its charm.
Steps
Step 1. Emphasis on the antenna
The heart of amateur radio lies in the antenna. Many uninformed people claim that power is the deciding factor at stake. It is not so! For every radio, be it amateur, commercial, business, city band, etc., the heart of the broadcast is the antenna! Without good reception, you won't be able to pick up much. And of course, without good antennas you won't be able to transmit much, even if you use a radio frequency amplifier or high wattage.
Step 2. Designing an antenna construction requires you to think about many things, so keep every feature in mind
Height, length, transmission line, balun or antenna symmetrizer (which we will discuss later), insulators, which cables and types of metal to use, what you want to do with this antenna, how many bands you want it to cover … Also ask yourself if you know how to use the right materials, if you have space to put one and - first of all - if you live in an area subject to land use plans, which require a permit before installing an antenna on your land.
Step 3. Use materials that match easily
Antennas can be made of many different materials. Remember to use metals of a similar nature, as metals that are different from each other tend to corrode, or lose their conductive properties. Copper, aluminum, tin, and steel are all good conductors, but when we talk about radio frequency (or high frequency RF electrical signals), we are talking about "silky" electricity. It is not advisable to use an aluminum cable for the antenna, because it risks to break easily, it stretches and deforms, and cannot be welded using a common welding machine. Aluminum cable is not expensive, but in this case it is the least appropriate. The price of copper cables has soared in recent years; finding old ones is the best option. A 12 gauge cable is approximately 2mm in diameter. It is not difficult to work with, and is probably the best metal for the antenna. Tin cables, such as those used for electric fences, are perfect to use, and are not expensive. The only inconvenience is that there are rolls of hundreds of meters for sale. If you think you need to build several antennas then this shouldn't be a problem.
Step 4. What works with which current?
Direct or alternating current (DC and AC) and voltage run through the center of the cable, while electrical RF signals move along the outer parts of the wire. Imagine you have a cable with the severed tip towards you. If we could see the current inside it, it would be easy to describe it. AC and DC currents move from the center outwards. The RF, on the other hand, along the outer portions of the cable, as if it were the coating. The type of metal used will have a certain conductivity scale. Certainly no one would use a precious metal to make an antenna, however rare metals such as gold, silver and platinum are the best conductors; but since they cost a lot, you have to fall back on copper, or on steel coated with brass or copper, or on tin with or without copper cover, or finally on an aluminum cable (but only if you have nothing else to use). Any good conductor of electricity will do for RF. The least advisable is the mechanical cable, which has high strength and corrodes and rusts quickly, causing unwanted resistance and antenna failure. When there is bad weather, the mechanical cable tends to rust very easily, breaking down irreversibly or having even more difficulty in carrying out the conduction. It already does not normally spread RF energy well, and does not receive broadcasts from other users. One of the best, and probably the cheapest, is the cable used for electrical enclosures that are clad in brass or copper. Since we have to take into account the "silk effect", only the outer casing will conduct the RF current. The steel cable should also be avoided. It rusts quickly, even if coated with brass or copper. The tin wire used for the fences can be used even if it doesn't have the lining, but be sure to examine the connections from time to time to fix any corroded spots, and re-solder if necessary. Insulated copper wires for home use are the best choice for an antenna. At least 70% of amateur radio antennas are made this way. They are the ones we will talk about in this article.
Step 5. Start by choosing the space in which you are going to erect your antenna
ALWAYS keep your distance from a power line where current is flowing. Many people have been seriously injured or even electrocuted by contact with highly charged power lines. Just a little contact is enough for whoever is putting up an antenna to be killed. Check that there are no low-altitude electrical cables. The closer you are to the room you're broadcasting from, the better off it will be. Antennas in the courtyard, right next to the room, make it easier to organize and manage the broadcast. Avoid placing any antenna point near where electricity connects to the house. Use a nice straight yarn, without any particular folds or curves. If you are using a tin wire with a brass or copper jacket, be careful not to let the wire wrap around itself. This is a problem that can actually affect different types of cables, regardless of the materials used. Some cables also have a tendency to have sharp ends when cut (steel is the worst in this case). Even sharp pliers or wire cutters can leave small sharp protrusions when cutting certain metals. The thinner the cable, the more difficult it will be to use. Using cables with a diameter of about 1 mm or less can cause several problems, primarily resistance. Wind could destroy the antenna in no time if too small a gauge is used. I recommend, do not stay below the millimeter for most antennas. There are places, which will be discussed later, which do not allow the construction of antennas. A dipole antenna in your attic is a good idea if you have enough space to put one, and especially if you don't have a metal roof.
Step 6. Select the cable you want to use
Make sure it can handle the weather, both summer and winter, and that it works well for the job you want to do. In other words, don't use a cable that gets you in trouble over time. I always remember that insulated copper wires are excellent. DO NOT remove the insulation! It is a fact that the life of an antenna lasts much longer if the cable jacket is left behind. Also, it avoids that there can be a short circuit due to contact with trees, leaves, even grass. If it's a bare wire, make sure it stays off the ground (we'll see this again later), so no one can come into contact with it if it's electrified by RF signals. RF burns can really hurt, and burn the skin deeply. It is a kind of invisible energy.
Step 7. Many current circuits can actually burn several layers of skin with one contact
Sometimes, in addition to burning, they fry the skin until it becomes a kind of white powder. This is what is known as a "bite of the RF", as it looks like you have been bitten by a bad insect, or stung by a bee … no poison but a lot of pain. The RF amplifier hurts even more, due to the additional power applied to the antenna. If you use a tube amplifier, depending on the watts it is set to, be careful not to hurt yourself: its "bite" can be dangerous.
Step 8. Create the antenna following correct and verified methods
Dipole antennas are often the simplest to build, and are the inverted V-shaped ones, obtained by lifting the center of the antennas. The antenna must be as high as half its wavelength (¼ is the minimum height from the ground for it to start working). If you want to use the VHF band, build simple J-shaped Zeppelin antennas that can also be used in an emergency. These inventions use the ever popular 300 ohm cable antenna. You can use them at any frequency, including the HF bands, but you will need a very tall stand, or a tree, to make them soar into the sky. As this type of cable is quite rare, a roll of 300 or 450 ohm only some time ago was around 50 euros, now in some cases it has even increased by double.
Step 9. Here are other power cords you might use
Choose the one that seems to you best suited to your needs. The RG8 mini withstands up to 2 kilowatts. The RG8U is larger, features foam or plastic insulation, and can be used up to 3 kilowatts. Heavy duty cables like the 9913 series are best for VHF or UHF transmissions. Two-wire 300 ohm cables are fine if the antenna is at least about 50m away. Open bifilar lines can be used IF NOT antenna. Avoid using long transmission lines, so as not to interfere with your neighbors. For example, car alarms that are not shielded can often sound if certain frequencies are used. But remember, if you are using the radio in an amateur way, and it works properly, it is NOT your fault that the neighbors have problems. It's the fault of precarious designs and shielding, and the sensitivity of the equipment. Sometimes the problem can be fixed, other times there is no other solution but to have the neighbors install a filter or suppressor on what has the problem to avoid malfunctions. The Federal Communications Commition (FCC) states that the equipment must not cause unwanted interference. To defend yourself, take note of the frequency you were using at the time the incident occurred, and if you have not yet had your material analyzed, have it checked with a spectrum analyzer or harmonic meter to PROVE that your equipment is NOT is causing unwanted interference. If you have everything in order, then it's up to others to take action to protect their belongings.
Step 10. Shield the VHF and MHF bands
Some children blame the radio operators, while they themselves make mistakes. There are frequencies that, if used, can cause malfunctions to their precious games such as radio-controlled cars, airplanes and robots. Problems of this type are due to design flaws, lack of shielding or the games behaving like receivers, and because of that they blame you. There was a case like this not long ago, and we'll talk about it shortly, but first let's talk about how to build the antenna.
Step 11. Maximum output power
What is the maximum output power? The term Peak Envelope Power indicates the maximum power authorized by law. Due to recent changes in some laws, local governments regulate the power to be used. Legally, radio amateurs can go up to 1500 watts! That's a lot, but bear in mind that the antenna must be able to handle the power, otherwise it won't do any good. Whether you live in the countryside or in the city, the antenna is essential for good transmission and reception.
Step 12. Do your calculations, then fine-tune them
The way to find out the length of the dipole antenna, which is the most used one, is to divide 468 by FMhz, where 468 is a fixed number, FMhz instead is the frequency in MEGAHERTZ: thus you will get the total length (in feet) of the dipole antenna. Divide by two and put, halfway between the two parts of the antenna, an insulator (which can be a PVC, ceramic or bone tube); you will have your own dipole antenna. Connect it with a power line to your radio transmitter or, if you use resonant antennas, to the reflectometer, and check the value of the high frequencies. Usually, 1: 5 to 1 (or less) is acceptable, but 1: 1 is the best situation. Using resonant antennas can be quite a rewarding experience, however space and materials could compromise their use.
Step 13. Raising or lowering the antenna changes the reflectometer value, however always keep in mind that a good idea is to raise the antenna at least a quarter of the wavelength from the ground
Inverted V antennas can connect as high as possible, but fixing them around a meter is already enough. Put a warning sign on the connection point if the antenna is in a handy place, signaling the presence of high voltage and a warning never to touch the cables.
Step 14. Extend the antenna arms as much as possible and make them extend as far into the sky as possible
The higher they are, the better the transmission will be. Secure the power supply with solid nylon or rayon rope. This way it will work best, but you will still need to check it a couple of times a year to make sure it hasn't worn out due to the weather. Replace it if necessary.
Step 15. Develop a new design
For many years, designing antennas has been a passion for many radio amateurs. The next model you could work on is the cage antenna. To make it you will need a sewer pipe, or water, 10-15 cm thick, which you will have to cut to form small "spacer collars" (1-1.5 cm). Use a miter saw to make your job easier. Use a 30 cm saw to cut the pipe. BE VERY CAREFUL, AS THE LAST PIECE OF THE PIPE COULD BUMP AGAINST THE SAW without breaking and bouncing off of you. Only cut where it is NOT dangerous, leaving at least 30-35 cm of pipe. Once you have made the cut, measure the outer circumference of the collar, divide by 6 if you use 6 cables, or by 8 if you plan to use 8. Use a drill to make holes in the spacer and trace the path of the cables (the size of the tip of the drill varies according to the gauge of the cables). Try to be as specific as possible.
Step 16. DO NOT USE THE SAME FORMULA AS THE DIPOLE ANTENNA
Your new antenna will be shorter than a normal dipole! You can use the above formula only as a starting point. Depending on the size of the collar you have to reduce the length by 4%, if not more! Remember that you will use 6 or 8 cables. Those used for electric fences are one of the best options for this type of antenna, as they are relatively inexpensive in spite of the large amount. However, copper is still the best choice, otherwise you can also consider tin.
Step 17. Measure accurately, although this is not critical in this step
Cut the 6 or 8 cables you will use. It is always better to stay wide rather than save cable. Get help from a couple of friends. Once you've taken your measurements, take the cables you cut in one direction.
Step 18. Assemble your antenna
Now comes the fun. Slip the cables into the holes inside 4 collars, leaving a fifth collar at one end of the cables. Then, space the collars at 45-50cm intervals. Put some glue into contact inside the holes so that the cables stay firmly in place. Build several of these bundles, using 4 or 5 collars at a time, always leaving one at a vertex. When you reach the last collar, join the cables and route them towards the center by tying them with another piece of wire. Place one arm of the dipole on either side.
Step 19. Take care of the details
If you use spaces of 45 or 50 cm between the collars, keep some consistency! If you leave a 45cm gap, stick to this measurement, and the same is true if you leave 50. 14- or 12-gauge cables add weight to the bundle, so it takes a long time to get these antennas to work. Do not rush! Take the time you need, work well once and you will see that you can count on a lasting yield. The diffusion area of a cage antenna consisting of 6 cables increases by 5 times! An 8 antenna goes as high as 7. Although difficult to build, this type of structure is best for radio amateurs.
Step 20. Fuck with the knobs, et voila
One of the most hidden secrets of amateur radio is the delta-loop antennas. Resonant antennas find the exact frequency, in the middle of the band, and can tune into different bands if the proper tools are used. The formula to use to calculate the height of such an antenna is 1005 / FMhz. The result will establish the height of the instrument based on the band you want to use. Placing the antenna horizontally in a triangle will form a delta. If you give it a square shape, here is the "box" antenna. This type of antenna is mainly used in the countryside, as it requires a large area of land to function. When you lift this little monster into the air, watch out for the ELECTRIC CABLES! You could use the height of the trees to erect the antenna and use them as a support pole with the help of a fishing rod and a 100g sinker, properly stretched on one of the highest branches. Once these tools are in place, connect the cable you will use as an antenna to the power supply, and gently roll it along the branch. Don't forget to always use ropes of the right length. As insulation in this case you could use a PVC pipe. From a tube about 4 cm thick, cut three or four pieces 15-18 cm long. Make holes 1 cm in diameter using a good drill, keeping yourself slightly away from the ends of the tube (at least 5 cm). For the feed point, use another piece of pvc pipe, making a hole in the middle to act as a strain relief. Focus on the tube, not the antenna or power line. Raise the antenna in the trees very carefully, making sure that the result comes close to the project you had in mind.
Advice
- Use cables of a similar nature. Avoid using materials that can easily corrode, break or lose conductivity.
- Place the antenna as close as possible to the transmission location to prevent RF energy leakage.
- Have fun building your plant. Antennas are the heart of any radio system.
- Using inappropriate tools to cut cables may leave sharp ends that can easily penetrate the skin. Check before you go to work to avoid harming yourself.
- Use pvc pipes to get inexpensive spacers and insulators.
- Stay away from electricity cables.
- Get help in carrying out the project. Friends may find it a fascinating experience.
- Measure twice, cut once. While it is not essential in the case of a cage antenna, it is important to know the exact length of the antenna in relation to the band you want to use.
