RadioReference Wiki:Ka3jjz

Verticals

These antennas have a nasty characteristic. Tbey are (generally) very prone to receinving 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. You do have to deal with proper grounding of these antennas (including installing radials, if you are using it for transmitting) but if you put it in the right place, they can be hard to spot.

There is one that is evidently popular in Europe that is sold by Universal Radio - the Apex Radio 303WA-2. While I haven't found any specific reviews, anecodotal evidence on the RadioReference forums and Facebook suggest that this is a pretty quiet antenna. It's only 6 foot high, which is a plus. Sadly it is currently marked as not available, but who knows- you might find it elsewhere.

Active Antennas

These antennas are attractive because their receiving element is relatively small and have a good amount of gain. But it's that gain that can get you into trouble, particularly if you have a lot of MW, FM or TV stations about, and you are using a SDR (Software Defined Radio) or a portable. Too much gain, and you will hear all sorts of stations appearing as distorted spurs all over the place. Too, 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 as far away from your home as possible is essential, as is proper grounding. This is the same antenna that is used at the popular University of Twente online SDR.

One such antenna that has seen good reviews is the LF Engineering H-900. There is a review of this antenna here (note that it is a PDF)

Wire Antennas

If you have the space, it's really hard to argue against what could be considered the king of small wire antennas - the Vibroplex Par EF-SWL. It sports a wire length of 45 foot, along with a connection box with connectors on top. It will take some tinkering to find out which connection works best for you. Grounding or not grounded is will be a matter of your own local environment.

Now at 45 foot you may think that's a bit big for a city lot. But you can bend the antenna around without compromising the performance much; just don't bend it back on itself; under certain circumstances you might cancel some of the energy you are trying to hear. You can even install this antenna as a sloper.

Purists will claim that such an antenna needs a counterpoise, and if we are talking about an antenna that is resonant, this is strictly speaking true. However, we are not dealing with a resonant antenna here, nor are we transmitting. You can certainly try putting a counterpoise on the connection box and see if it helps. You can bury it if it helps to hide the installation. A counterpoise of about the same length as the antenna will do for a start, but usually more than one is needed. You will not damage anything if it doesn't work for you. I've tried them on various random wire antennas when I lived in NJ, and they didn't seem to do very much, but that may not be your experience.

There are a couple of other options

• 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, and the plus to this antenna is that it 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

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. 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 1kw 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.

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.

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.

Passive Loops

These loops are probably the ones you would identify most easily. Those loops on those old classic radios from the 1900s were passive in nature. They didn't have, nor need, an amplifier as the radio did more of the work to amplify the signal.

Today, passive loops should be used on radios that are very sensitive, such as a SDR. There are a great many plans for passive loops on the net - recently a very inexpensive one known as the YouLoop came on the market. You can certainly buy one, but you can build one if you have a good junkbox handy. Here are some ideas and plans from the SWLing.com blog;

• How to Build a Noise Cancelling Passive Loop (NCPL) Antenna
• Hack a Broken VGA Cable to Make a Binocular Ferrite Core for your NCPL Antenna
• More About Hacking VGA Cables to Make Binocular Ferrite Cores

We have plans for many more such passive loops in the Loops article. 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...

Active Loops

These are loops with amplifiers to boost the signal. For many years, Wellbrook loops have held their place as the king of loops. Indeed they have gathered more than a few awards, notably from the World Radio TV Handbook. However they are made in the UK, and getting them here can get pricey due to Customs and shipping charges

In recent years several challengers have appeared. The RF Engineering Pixel loop is one; however that one is almost as pricey as a good Wellbrook. Enter the W6LVP series - they cost about 1/2 the cost of a Pixel, and the customer service has been nothing short of outstanding. W6LVP has been known to add filters to help counter the effects of nearby FM and TV stations - something no other loop distributor does. In addition there is the MFJ-1886, which has also garnered some good reviews. The links for these and others can be found in the Loops article.

Hidden

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?

The Loop on the Ground (LoG)

There was an extensive discussion on RadioReference regarding the LoG. 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 in the Loops article.

Indoors

Let's set this straight - using an antenna indoors is nowehre near as effective as getting something outside and away from the house. It's a compromise at best. They will inevitably interact with wiring or metallic objects in their vicinity or hear any noise sources in the home

Do you have an attic?

If you do, the larger the better. It's not far enough away from the home to avoid noise issues, but it's away from prying eyes of the condo nazis and HOAs. Aluminum siding can have a real detrimental effect on Evenanything you put up there; the roof's construction is also important. Is there any romex up there? Take a look around - if this is your only option, it can be made to work

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 a loop if there's enough vertical clearance. You can even build this antenna. 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.

Carpet loop

This antenna is one I built after reading the article. I had tried a few others such as the Broomstick and even The McGyver(tm) special but they never really filled the bill. At the time, I was using 3 receivers - a Drake R7A, a Radio West modified Yaesu FRG7 and a TenTec RX320D. I had a few transmatches available - one from MFJ, one from Grove and a homebuilt L/Series tuner.

I really didn't have a loop per se - I simply covered about 20 foot in a square (which is way too big for a true loop) in my attic (which was huge and had the advantage of being on the 4th floor). Even with these limitations, it worked a lot better than the helicals, and certainly better than just throwing a hank of wire around the room. I had some noise issues below 3 Mhz or so that could have easily been a common mode issue, but I was quite satisfied with the results. If you have the parts in a junkbox, you should be able to assemble it easily in an afternoon. I would substitute for the diodes, though, and replace it with a choke as discussed in this thread on RadioReference.