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Basic HF Antennas

From The RadioReference Wiki

After you get your radio, you're next question is likely to be 'what else do I need to hear something on shortwave'. The answer is greatly dependent on many factors. If you are using a portable, the whip antenna will get you started, but generally speaking, that's about it. On HF, these small whips are very inefficient, and would likely capture the stronger signals, but not anything much weaker. Using a desktop, you will need some sort of antenna to hear anything at all.

A Couple of Basic Rules

Before you erect anything, survey your property carefully. If the antenna should get knocked down in a storm, will it fall over a power or telephone line? If it would, then find another spot. Remember, safety first.

Every home has appliances in it that generates noise; noise is the bane of the HFer. Ideally, you would want to mount your antenna far enough away from the house to avoid this problem.

Proper grounding is often an essential concept that is very often overlooked. There are numerous sources of information on this, and it's beyond the scope of this article to cover them all. If you live in the US, the NEC code should be followed as closely as possible. There's no easy way to make an existing structure lightning proof- the best you can do is to try to mitigate its effects.

Portables and Multi Band Handhelds

click to enlarge

These radios are designed to work with the relatively small input that a whip antenna would supply; in many cases, putting a substantial antenna on them would cause more grief in the form of overloading than it's worth. Sometimes an extendable whip will help, but you may find you will need to fiddle a bit with the length to get it right.

In most cases, a small hunk of wire - 20 or 30 foot or so - attached to an appropriate plug into the antenna jack on the side of the radio (if it has one) will do. Try to avoid clipping anything directly to the whip (although that will do in a pinch). Any static charges that might build up would likely damage the radio if discharged into the whip. To avoid that same issue with the antenna jack, you can build a small box with some inexpensive diodes which would blow in the case a static charge were encountered. The diagram shown on the right includes a small variable resistor (potentiometer) that would serve as a crude RF gain control so you can reduce the level of the signal if needed.

If you live in an urban area with lots of MW, TV or FM stations nearby, you may find that this circuit actually causes hash, overloading and other issues. The problem is the diodes - under certain conditions, they may rectify a large RF signal and cause issues. You may substitute something else in their place, such as a small gas discharge tube, or even an old flashlight bulb will work. See the Static Drain for Outside Long Wire Thread for additional ideas.

Portatops, Desktops, SDRs and Amateur Radio Transceivers

People using a desktop radio (Drake, JRC, etc.), a portatop (like the Tecsun H501X) or a modern ham transceiver (which often has a general coverage radio built in) tend to perform better with larger antennas because their front ends tend to be more robust. But make no mistake, they can be overloaded, too.

If there’s only one range that is giving you issues, then a filter will very likely solve the problem. If you have multiple ranges that are affecting you (MW and FM, for example) , adding some passive preselection to help protect your front end is almost a must. Our Improving HF Reception article has several links for these. If you have added filtering and still have issues, it’s very likely the offending RF is either being picked up and re-radiated by something (long leads from power cubes are a good possibility) or is forcing its way through the casing of the radio (many cheaper radios use plastic which is invisible to RF). Choking and grounding may help in these instances, but overload issues like this tend to be a very tough nut to crack.

With that out of the way, let’s start with...

The Most Popular Antennas (if you have the room)

The most basic form of the antenna is the inverted L or random length (many folks would call this a 'long wire' - that term should be avoided, as that describes a very different type of antenna). See the article from MT here for a description. This antenna is very broad banded, and easy to construct. Some folks have used coaxial cable as the lead in to help shield against noise pickup.

A very popular antenna for folks just getting started is the Vibroplex Par EF-SWL end fed. This antenna comes pre assembled - all you need to do is to supply the coax (and waterproofing for the feedline connection), and you're good to go. The wire can be mounted in numerous different configurations, and the included transformer will help with noise reduction. The transformer has several connections - you must experiment with them to see which one works the best for your environment. The reviews on this antenna are all superb - just don't try transmitting with one! This antenna is available from numerous suppliers.

If you are interested in certain bands, the basic dipole will work well. Be sure to mount it at a height at least 1/4 wavelength from the ground for best results. To find this height, use the standard formula 234/f(mhz) where f(mhz) is the desired frequency in megahertz. Dipoles will also work well on their odd harmonics - so a 3 mhz dipole would work very well on 9 mhz, a 4 mhz dipole would work well on 12, and so on. It is described here.

There are many other antennas that can be used, if you have the space. These include the G5RV (and its many variants) and the T2FD. Antennas such as these are probably best used on a very good desktop (Drake, JRC, etc.) or on a ham transceiver. Other types of receivers such as SDRs and many portables would likely need some filtering or preselection to tame the higher levels of RF these antennas can deliver. There are numerous books by the American Radio Relay League and the Radio Society of Great Britain on this subject.

You Dont Have a Lot of Room

  • You don't have enough space for the PAR? Then try this one. Coverage is good down to 3.5 Mhz, and doesn't take quite as much space
  • The EWE antenna is another possibility. The plus to this antenna is that it also works down on the tropical bands below 6 Mhz.
  • If you have a wood fence adjoining your property, would be to run a wire using the fence as a support. Don't let the wood touch the wire; in some cases when it gets wet, the antenna might crudely couple with the wood. Some small standoffs will work well here. A transmatch will be needed for this one.
  • Some have used gutters as antennas. One issue here is that the bonding between joints might not be very solid; some work will need to be done here to insure that there is a good mechanical and electrical bond. This is another antenna where a transmatch will be very helpful
  • How to Build a Simple Linear Loaded Dipole from SWLing.com
  • Palomar Engineers End Fed Antennas Go about 2/3 down this page for a 37 foot version
  • My Go2 Antenna
  • Slopers are well regarded antennas that don't take up as much space as you think, and have some directivity in the direction of the slope. You can mount antennas like the PAR in a sloper configuration. This is the classic sloper, made by Alpha Delta. You can find other designs on the web.

Transmatch, not Antenna Tuner

This is a term that is frequently misued, and is in part a ploy for marketing to make it easier for people to understand. First let's define an antenna tuner; this is a unit that when placed at the antenna feedpoint, attempts to tune the antenna to make sure the maximum amount of energy is delivered down the feedline. To do this, a small amount of RF is employed to trigger the tuner (SGC is one well known manufacturer). Obviously this isn't something a listener is going to be able to do. The term that should be used would be a transmatch. What we want to do is to create a resonant path for the antenna and feedline (notice I said both here) to deliver energy (RF) to the receiver. You certainly don't need a 1 kw version to do the job; there are many versions, some very complex, others quite simple. The classic Pi network is one that's easy to find plans for on the net - a variation of one is shown here. For some commercial units, see the Improving HF Reception article.

Verticals

Verticals have a nasty rap against them. They are (generally) very prone to receiving lots of noise. This is not to say that they don't have their place; If you can get them away from the home (and other people's homes) they are good DX performers. If you put it in the right place, they can be hard to spot. See this section from our HF Antennas wiki for some examples.


Solutions for HOAs

Sad to say, Home Owners Associations (HOAs) and their ilk are not radio friendly. It's not uncommon to find out that the condo rules prohibit outdoor antennas. That presents some challenges, but here are a few possibilities;

Active (E Field) Antennas

These antennas are attractive because the receiving element is relatively small (making it hard to spot) and use a broadbanded amplifier to supply the gain. But it's that gain that might get you into trouble. Too much gain, and you will hear all sorts of stations appearing as distorted spurs all over the place. The higher gain can also introduce issues with noise. Even reviewers of the well known PA0RDT Mini Whip will tell you that keeping the antenna up high, as far away from your home as possible and proper grounding are all key points. See this article at SWLing.com for a discussion of these topics.

You can find some examples of these of these antennas in the Active Antennas of the HF Antennas wiki. If you want an example of one in actual use, the famous University of Twente SDR (which is online) in Holland uses it.

But wait, there's a better kind of active antenna, and it doesn't (and shouldn't) be mounted high off the ground.

Loops

This kind of antenna has literally been around since the beginning of broadcasting. Did you ever notice that weird looking contraption on top of those old radios? Yep, that's a loop. While Loops are typically used on MW and lower, they work just fine on HF too. Up to about 2 Mhz or so, they can be directed to enhance or null out an offending station. And speaking of noise, loops are also resistant to it, which is very helpful in an urban situation.

A couple of other characteristics deserve a mention; while the word on wire antennas is that you have to get them up high, loops are better off no more than a few meters off the ground. Putting them up too high will make them overly sensitive to skywave propagation. There are many variations on a loop - a skyloop is usually quite large (depending on the frequency desired), but there are smaller options that will perform very well.

Active loops have rapidly gained favor with SWLs, hams and DXers for their small size, noise rejection and (below about 2-3 Mhz) the ability to discriminate one signal over another. It should be noted that like active antennas, you might get some headaches from overloading if you are in a heavy RF environment, particularly with cheaper portables and SDRs. In these cases, additional filtering will be required.

Many newcomers expect that a loop will produce a signal that rivals a good outdoor wire. This is incorrect; keep in mind that a loop rejects noise, and works very differently from a wire antenna. When you compare a loop to another antenna, compare the quality of the signal, rather than the signal strength.

Loops can be hidden in the most unlikely of places. Take this loop shown in a recent SWLing.com article - can you spot it? And how about this one? It resembles a volleyball net. Or this? Build an affordable (but stealthy) Magnet Wire Vertical Loop antenna to mitigate condo QRM

There's even a loop known as the Loop on the Ground (or LoG for short). There is an extensive Loop On the Ground Thread in our Forums area. There's even a Facebook group and a website for it. If you have a small plot and want to have something that's invisible, this might be a way to go. Ground losses may be something of an issue here; you may end up using an amp to overcome the loss, or even one of the experimenter's kits found in the Loops article.

But I cant put anything outdoors

Anything you put indoors on HF is a compromise. You will have trouble trying to keep from hearing noise sources in the home, you may be constrained as to how much antenna you can put up, home covenants prevent you from putting anything outside - these are just some of the issues.

Using the attic or crawlspace is a very good idea. It doesn't remove the antenna from the noise sources, but it is sometimes more convenient. You won't have to contend with moving furniture or carpeting. The larger the attic the better. It's not far enough away from the home to avoid noise issues, but it's away from prying eyes. Aluminum siding can have a real detrimental effect on anything you put up there; the roof's construction is also important. Is there any romex up there? It could cause noise issues.

What can you put up there? That depends on the size of your attic. A Vibroplex PAR could go into most larger attics; the same could be said of an active loop if there's enough vertical clearance. You can even build the Broadband Butterfly Terminated Dipole. Winding wire around the highest points of the attic and feeding it with a balun is also an attractive possibility. Try to keep whatever you put up there away from the romex and/or metallic objects if possible. You may need to consider some chokes if common mode noise (traveling on the braid of the coax) is an issue. Bending a receive antenna generally doesn't adversely effect it all that much; try to avoid bending the antenna back on itself, as that can sometimes cancel a signal out.

Ever hear of the Slinky Dipole? An example of one can be found here. It can be homebrewed out of a couple of steel Slinkies you can sometimes find at a toy store. To make a solid connection with a couple of large copper clips, you may need to file off some of the plating. It may need a transmatch to make it work over the entire HF spectrum..

If you have some skills with small tools and soldering, the Carpet Loop might be right up your alley, particularly if you can spread the wire element in the attic. There's less chance of people tripping on the wire element this way.

I have no attic

This is probably the worst case scenario for any radio hobbyist, regardless of specialty. There are still a few possibilities.

Passive Loops

Passive loops are probably the ones you would identify most easily, especially if you are into restoring vintage radios.. Those loops on those old classic radios from the 1900s were passive in nature. They don't have an amplifier as the radios of that day did more of the work to amplify the signal.

For MW DXers, Ferrite Sleeve Loop antennas are gaining ground with the ultralight crowd. See the Ferrite Sleeve Antennas section for several links.

Ferrite Rod antennas are another possibility. See these articles from SWLing.com


The YouLoop is an inexpensive antenna that works best with very sensitive receivers and many SDRs. You can buy them here. However, you can build one if you have a good junkbox handy. Here are some ideas and plans from the SWLing.com blog;


And there's this from eBay - you should write before sending any money, just to be safe...


We have plans for many more such passive loops in the Loops wiki. If you find your loop to be lacking a good signal, then perhaps an amplifier is in order. The wiki article above has plans (and kits) for that as well. Some kits provide the amp and power supply - you supply the loop. These experimenter's kits are great for the tinkerer as you can build various passive loops to try out. Again, as with other antennas, if one design doesn't work well, there's no damage to the radio - just maybe to your budget.

Can I Use An Active Loop Indoors?

Here, we're talking about antennas like the Wellbrooks, W6LVPs and many others. The answer is yes, but with a caveat - you may lose the directional properties due to reflections from conductive surfaces. Try to keep the loop as far away from these as possible.

In fact, W6LVP has an experimenter's kit which may appeal to those of you handy enough to build your own supports and use different loop materials. The kit may be found here.

Desktop Active Antennas

These are desktop units, usually with a whip as an antenna, and a tuned amplifier (active preselector) to supply the signal. We have some examples of these in our HF Antennas article. You will need to watch the amount of gain you apply. At some point, the signal simply stops getting stronger, but the noise increases. If this happens, back off the gain.

This is an expensive item, but the antennas from PK's Loop Antennas appears to be an appealing alternative if you don't have the room for a large active loop. They have models for VLF up to HF. Here are a few reviews; the first 2 are from SWLing.com

Is There Nothing More?

It's quite likely there is. This article has only scratched the surface of what is possible. Google Search has a bunch of sites that might have some ideas. Don't turn down using a ham antenna. As long as it has no traps that tune the antenna just for the HF ham bands, it's likely that such an antenna will work just fine for receiving. Examples would include the line of Chameleon Loops and even the Wonder Wand

You should also look at the various publications of the ARRL and the Radio Society of Great Britain. Both organizations have many well respected writers and books on the subject of antennas. If you want a readable book on the subject of loops, Joe Carr's Loops Antenna Handbook is highly recommended.


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