Shortwave Antennas

Understanding Shortwave Radio Listening
and Antenna Design and Construction

Copyright © 1999-2012 by Harold Melton KV5R. All Rights Reserved.

Understanding Shortwave Antennas: Page 1

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Who needs this article? Anyone who is a new shortwave radio listener. Shortwave listening is a bit more complicated than AM or FM radio listening, and satisfactory results depend upon designing and installing a good antenna.

Why? Shortwave radio signals travel great distances. They bend around the earth by reflecting off the ionosphere.

What’s that? The ionosphere is a finicky mirror! In the daytime, it reflects higher frequencies, and absorbs lower ones. At night, it reflects lower frequencies and passes higher ones. Around sunrise and sunset, the middle frequencies seem to travel best.

Sooooo... Is that daytime at my house, or at the far-away radio station? Good question! Answer: Somewhere in between. It means that higher frequency, daytime bands will bounce into the US from the west in the evening, because it’s still sunny over the Pacific. Likewise, stations from the east will bounce into the US in the early morning hours, increasing in strength through midday, then fading out as the sun goes down over the Atlantic.

This is too complicated! Not at all. You will soon learn to locate your favorite shortwave stations on the right frequency, depending on what time it is. Shortwave broadcasters may use several frequencies, rotating through them every day. When it’s time to change, they make an announcement.

What if I’m not listening when they make the announcement? Part of being an avid shortwave listener is collecting radio schedules. These are found on the Internet. You can also just spin the dial and listen, and keep notes of what is where, when, and make your own custom listening schedule.

Ok, so what else do I need to know to get started? Your little portable shortwave radio has a useless antenna. Oh, it’s fine for FM — but shortwave antennas need to be at least fifty feet long to be useful!

Oh no! I can’t put up some big, ugly antenna! All it takes is a very fine wire. It can run out the window to a tree, or stapled along under the eaves, or even in the attic. Another part of being a shortwave listener is designing and deploying the most clever antenna possible, balancing visibility, reliability, and performance.

Ok! I think I can do that! Sure! Anybody can do it. Millions of people all over the world use shortwave as their primary or only source of information.

So, just what is an antenna? Technically speaking, an antenna is an impedance matching transformer. It matches the low impedance of a transmitter or receiver to the extremely high impedance of the surrounding space. It converts power alternating in a wire into power alternating in free space (or air), and vice-versa.

Do I need to know about impedance matching? No, but if you want the best possible performance from your antenna, you should design it correctly. You need to know how to get enough signal to your radio to increase your listening options, and reduce annoying signal fading. A poor antenna converts very little signal, but a good antenna converts a lot more. Antennas also pick up noise — man-made and natural — and you want your antenna to receive more signal than noise. Also, you will want an antenna that is physically strong, so it will stay up through many years of storms. In most areas, it must also be well hidden.

Why does the antenna need to be so long? Because shortwaves are long (they are called “short” waves because longwaves are thousands of feet long!) If you only want to listen in the daytime, 50 feet of wire is fine. However, if you also want to listen to the lower, night-time frequencies, you’ll need 100 feet or more.

Why? The length of the antenna needs to agree with the length of the longest radio waves that you want to receive. Shortwave broadcasters use frequencies that are from about 50 to about 400 feet long, and an effective antenna needs to be at least one-fourth of that length — and one-half is much better.

I live in a Property Owners’ Association… Many people in the US now live in restricted neighborhoods. These usually have rules (which you agreed to by signing the contract) that prohibit outdoor antennas. They don’t want you messing up the neighborhood by exercising your constitutional rights, so they require you to enter into a contract that restricts your rights. I call it, “Communism by Contract,” for that is exactly what it is. It is also discrimination, because shortwave radio is just another information source, like TV and the Internet.

What to do? I’ll show you how to put up simple, effective shortwave antennas that are almost invisible. If your local communists can’t see it, they can’t object to it, since the rationale for their anti-antenna ruling is one of visual appearance. If they do object, you still have options. You can fight the ruling and get an exemption. You can fight on the grounds of a federal FCC ruling called PRB-1, which covers small satellite dishes, but may, in the spirit of the law, add weight to your argument. Or, you can simply hide your antenna better, such as running it under the eaves or in the attic.

Is this going to be complicated? Not at all. There are standard formulae for various antenna designs, and standard (common-sense) mechanical practices.

Why are there different designs? Again, it depends. You may want your antenna to transmit or receive equally well in all directions, or in one direction only. You may want it permanent, temporary, or hidden.

Oh! You mean, like a CB ground plane versus a TV antenna! Correct; and there are serveral other designs and parameters which we will consider herein.

Like what? Like whether the antenna design has a wide or narrow bandwidth.

Bandwidth?! You just read on!


6 thoughts on “Shortwave Antennas
  1. I have a Grundig SW radio with a telescopic whip and also a terminal for a external antenna. I live in the boondocks here in Florida and the internal whip antenna does not hack it. I am definitely not mechanically inclined and unable to make an antenna on my own. Do you make antennas for my purpose? If so, will pay for the antenna, shipping etc. if not, any suggestions or recommendations where I could purchase one suitable for my needs? My radio has AM, FM, air, SSB. Thanks. Russ Streiber

    • Hi Russ,
      I don’t sell antennas, and those that do get way too much for them, and 99% of the work is putting it up, which you’d still have to do even if you bought one. SW antennas are generally just a hunk of wire strung up to fit the available circumstances, so there’s really no one size fits all for sale anywhere.
      Many articles, including mine, make it look more complex than it really is–we writers like to provide the “optimized” version of everything–but really, you can run 50-100 feet of any ol’ wire from your eave to a tree, or even tack a wire under your eaves, bring it in thru a little hole, solder on a jack, plug it in, and it’ll work great.
      Even a wire run out the window and thrown over the roof will be 100x better than the telescopic whip.
      My current antenna is just 120 feet of #14 wire strung between two trees, about 20-25 feet high and it works well enough that I even decoded digital radio from New Zealand the other night…
      Just get a 100 foot roll of wire and a jack, then figure out the easiest way to string it up. A roll of #36 nylon trot-line string is handy for pulling up antennas thru tree crotches, just tie on a big wrench and give it heave. Then tie on the wire, pull it up, and tie the string off to a nail in the tree trunk.
      If no handy trees, just go from the peak of your roof gable (put a big eye-screw there) to a fence-post or utility pole. If wire doesn’t reach the available support, add nylon string. etc.

  2. Your article inspired me to build my first ever dipole for multiband sw listening only. I own a grundig s350dl as my only portable sw radio which has a 500ohm sw antena input for which I picked up exactly 87.5 ft of no 12 stranded and at HRO Burbank bought 3 insulators. My dipole is horizontally mounted on the eaves of a square building with the > making about a 30 degree (vee) pointing east perpendicular to pwr lines about 14 ft away. I’m not sure if my calc is right but I think this legth of 43 ft and 9 inches per pole works on 5.34mhz? about 60m?. the hro guys said the longer the better and that this would be multiband. Is that true?
    It is center fed with 450ohm hd ladder wire. Is this ok? What else can I do?
    Should I shorten it? I hear a very strong imposing tx on many of the fr that I pick up. I would love to learn more about multiband antennas and would love your help if you may correspond with me. Also, have no clue about another radio, (satellit 750?), for better listening esp to South America and France in particular.
    My phone number is 213 880-4053. Thanks for so much wonderful instruction.
    I’m looking to buy a radio and make a great antenna.


    • Hi,
      Exact antenna length is not critical unless you’re transmitting on it. Yes, your 87′ will give lots of signal down to 60 or even 80 meters, and up to 10 meters. But it would be better if you could straighten it out and not have a vee angle, if possible.
      Ladder line is very low-loss (compared to coax) but it’s 370-450 ohms and you may need a way to match it to your 50-ohm radio input, like an antenna tuner with a balun in it. But try without it first. You’ll need to mash the end of the ladder together and solder on a jack for your radio, else get an antenna tuner/balun and connect the ladder to the binding posts on it, then connect the tuner to radio with a short coax jumper. Look at MFJ antenna tuners and look for a low-power one, else look at a receiver preselector. Or just buy a balun (again, low-power rating).
      As for radios, I recently got a $25 RTL-SDR dongle and plug it into USB on the computer. Run SDR-Sharp free software; get the little adapter pigtail for connecting your antenna to the dongle. I’m getting 3.5 to 1800 MHz with the Nooelec Mini T2 dongle and the experimental HF driver. It turns your computer into a broadband radio. I added a discone scanner antenna (at 25 feet) for VHF/UHF. Loads of fun!

  3. I need help. I built a home made antenna shaped like a basket ball. Bent copper tubing and 14 awg wire 1200′. I need to calculate the impedance to match it to a 50 omb feed cable, it receives only

    • Try putting a variable trimmer capacitor at the feed-point, in series. Tune it for strongest signal on a weak station. You’d need the feed connection and capacitor in a weatherproof box, and you’d have to re-tune it when changing frequencies. Better to just stretch out a couple hundred feet of that wire in a straight line, connect it to the radio, and not use feedline. Antennas rolled up into a ball don’t actually work very well.

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