How to Wind an Aerial for Am Radio

The most common antenna used for AM is a 4" Ferrite antenna, which is nothing more than a type of iron core wrapped in wire, much like an electromagnet. These antennas are carefully engineered to be as compact as possible and any electronic parts store like a Radio Shack will sell them if you are seeking a quick and compact solution, but reduced size actually means reduced performance when it comes to antennas. Better options are available.


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    The ferrite rod antenna in an AM radio uses the property of core material permeability to reduce the length of wire and concentrates the signal. The #61 material rods are widely used for commercial AM (550 KHz to 1660 KHz )To get good reception the radio needs a few micro volts of received signal. Improving weak reception you may increase the mass of this core. Some designs use 5 each rods bundled together and wrapped with the right length of wire.
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    As an option you can add a variable air capacitor parallel to this ferrite
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    antenna, this will give you increased Q that and better frequency selection. Finally the antenna should be mounted securely inside a PVC pipe to protect it and facilitate aiming this directionally.
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    If you are determined to keep antenna length short (which still means reduced reception) and you have access to electronic-grade ferrite or iron rods, a better antenna than most portable radios can be constructed by going bigger. A good choice is to use a ferrite rod or high carbon steel rod, 516 inch (0.8 cm) in diameter and 7 inches (17.8 cm) long. Wind it with 90 turns of insulated 22g wire, which will cover the entire AM band without needing any special tuning, and will also give you additional reception well into the short-wave bands if you need it. A preamplifier is usually a good idea with setups like this.
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    Radio waves are far easier to capture with a copper wire antenna, which is nothing more than a piece of wire stretched between two points, with ceramic, glass, or plastic insulators at each end. A good AM band antenna can be strung between two trees or across the roof of a house along the ridgeline or over to a nearby tree. A modest twenty-foot length of insulated wire will give your receiver greatly improved reception with far less static than any ferrite antenna can hope for. In part, this is because signal pickup is occurring at a significant distance from the interference-generating appliances in your house. Use good quality ceramic insulators for holding the ends of the antenna wire and ALWAYS add a commercial lightning arrestor (Radio Shack again) where the antenna will attach to the house.
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    The wire may be tied directly to both insulators but as various things (like the tree) move over time, the wire will stretch. This means yearly or even sooner adjustments, so check the tips area for ways to avoid this. Place your arrestor directly above the point where your lines enter the house so that lightning can take the most direct route to ground. For your ground, run a very heavy gauge copper wire straight down from the arrestor to a water pipe, or drive a 6' copper pipe or ground bar directly into the earth there. Then attach the ground wire to your ground with a brass or copper grounding clamp. This same connection also makes an excellent ground for your receiver. A shielded cable lead-in wire (like coaxial cable) can give superior results if your residence has unusually noisy appliances or other EM noise.
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    If the long wire doesn't give you an acceptable AM signal, one additional option remains: you can add a loading inductor (a type of coil you can make yourself) before the antenna lead enters the radio. The vast majority of long wire antennas will be considerably less than a quarter of the wavelength at AM band frequencies and behave as though a small capacitor is connected in series to the wire. An inductor will resonate with this capacity and will increase the overall signal strength significantly. The required inductance range for AM is from about 200 microHenrys (mH) at the high end of the band to about 2 millihenrys at the bottom end of the band for a 20 foot (6.1 m) antenna.
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    A common ham radio trick is to make a loading coil with plastic pipe fittings or pipe and insulated 22 gauge wire. For AM radio, you can purchase a 4 inch (10.2 cm) PVC pipe outside coupling which you can pick up at any home improvement store (it will actually measure more like four and a half inches in outside dia), and some 22 gauge insulated wire. The coil is then wound with 100 turns, with taps brought out every ten or so turns by twisting a little loop in the wire. The end result will be the pipe fitting wrapped with a continuous turn of wire and a row of little twists sticking up above and along the coil in a row that you will then strip the insulation off of. The antenna attaches to one end of the coil, and the radio is attached to the other end or to any tap along the length as needed. The total inductance of such homemade inductors is usually around a millihenry, so short antennas may need twelve or more turns instead of the usual ten turns for the last two to four lower frequency taps to raise the overall inductance there. You can use a selector knob and attach the taps to the knob to make a clean little boxed device, or you can just move your radio attachment to the different taps directly to adjust your inductance and give your radio antenna that mad scientist look. Lots of books and resources exist for antenna layout and design if this has struck an interest, but trial and error is how the early radio experimenters did it and it still works today.


  • An insulator mounted to the trunk or high branch of a tree so that your long wire antenna has a large vertical rise as well as horizontal length gives excellent results.
  • Ceramic insulators are available with built-in wood screws and can then be screwed directly into a tree or the wood parts of the house by hand.
  • Two ways to avoid swaying trees breaking the antenna is to either: 1) attach a large but weak spring between the tree and your antenna insulator, or 2) Pass the antenna wire through the tree side insulator without attaching it directly and then fasten a large fishing weight to the antenna's end, so that the weight hangs 2–4 feet (0.6–1.2 m) below the insulator. As the tree sways in the breeze, the weight will take up the antenna slack, keeping the wire under tension. This method looks nifty but you will probably end up replacing the antenna sooner or later from wear to the insulation on the wire. A more reliable method involves attaching a lanyard (thin rope) to the tree end insulator, and running the lanyard over the wheel of a 2" to 3" pulley, allowing the fishing weight to do the same job described above, tension the wire. With a pulley, a second piece of lanyard or rope is securely fastened to the tree. This way the pulley and antenna are free to mechanically float, instead of being linked firmly to the tree.


  • ALWAYS use a lightning arrestor whenever you use external antennas. The same electromagnetic properties that make a good outside antenna will also make it a good lightning rod.
  • Use care when mounting antenna wires on roofs or in trees. Ladders need to be solidly on the ground and have assistance at ground level when you are running antenna wires.
  • ANY external antenna MUST be attached securely to both a ground and arrestor! If you aren't willing to wire the antenna correctly, don't run the antenna outside at all. The risk of serious damage in the event of a lightning strike is simply too great. It isn't necessary for lightning to strike the antenna directly for it to do serious harm, such as start a fire or greatly injure someone. A lightning strike will simply induce a very large current into conductors (like your antenna) nearby.

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