Antennas for 160

 

Antennas for 160

The best results work when you have an antenna with a large vertical component.  It is difficult to get a horizontal antenna (dipole) high enough to be an effective antenna on 160.  However, there are several easy things you can do with your present antenna to initially get on the best amateur radio band… 160. The following notes summarize the important items…and also list important reading material you must read if you are serious about developing a powerful signal on 160 meters.

An effective antenna system optimized for 160 meter operation can become large and extensive. However, we have found that even on normal city lot you can erect an effective antenna for 160 meters. Height, of course, is paramount in for any aerial: we have found that if you can get 50 feet of height you are will on your way for an effective antenna. This height can come from a tripod or structure on top of your house, a tree, or of course, a tower.

The type of antenna that you erect will be determined by the type of structures you can use to elevate your antenna. Every installation is different.  There are many books concerning wire antennas, some of which are referenced on this page. Study these to give you an idea of what others have found to be effective, based on your situation. Some types of antennas that many have found useful are: 40/80 meter dipole fed with feeders shorted, fed against ground; the inverted “L”; the sloper; 160 meter full size dipole (this requires a big lot!), and a vertical (full size or more likely shortened one such as the venerable AV-18HT  “High Tower”.  Several comments will follow concerning each of these antenna types.

40/80 meter dipole

The main advantage of this antenna is that in most cases it is already up! All you need to do is correctly feed the antenna for 160 meters, and you can get on 160 with a reasonable signal depending on how careful you are in setting things up.

Using a 40/80 meter dipole usually how hams get on 160 for the first time. They have an antenna for the higher bands which can be used with varying success on 160. This is done by tying the feeders (shorting the two conductors) together.  In the case of coax fed dipole  it means shorting the center conductor of the coax to the shield.  It might be convenient to make an adapter using a PL-259 plug and a socket, SO-239.   Here the center conductor and shield are shorted.   Now when you wish to try 160 meters, all have have to do is to add the adapter to the back of your transceiver and hook your antenna feed line to the adapter, thus shorting the line together.

If you are using twin lead or ladder line, the line can be shorted by using a set of clip leads to lies the two feed lines together.  Connect this to the “long wire” terminal of your tuner (we are assuming you have an external tuner). To make this configuration work, you must have a very good ground attached to your tuner. With your feed line connected as described above, you must install a robust ground wire from your tuner to your ground system outside.  As mentioned in other places, bear in mind that your antenna is only half of your antenna system, your ground provides the other part.  Your transceiver and antenna tuner are in the electrical middle between these two parts.  Be sure to review the notes about acceptable ground systems in this document. Click here to see the section on grounding. Remember, you do need a good ground system to use this technique, or you will have lots of RF in the shack or be unable to tune your system satisfactorily.

Ttop
By shorting your feeders (coax or twin lead) together and
hooking your tuner ground connection to a good ground will
result in an antenna that looks like the configuration shown at the left.
Some call this a “Marconi” antenna.

You might be able to get your rig’s internal tuner to match your antenna:  it will be an unusual situation where your limited range internal tuner can match your antenna. Give it a try! You never know, it might work. However, listen for sounds of distress in your rig’s tuner (arcing and snapping sounds) when you do this.  Most internal tuners are not robust enough for serious tuning on 160. Modern tuners simply give up trying to tune a badly matched antenna.

This antenna configuration shown above will work nicely if you have a wide range external tuner or a link tuner. See the details on building your own link tuner.

InvertedL-1The Inverted “L”

This is most likely the least expensive high performance antenna you can erect for 160. It is worth investigating since it needs only one high point in the relative clear to be effective (the horizontal far end can be at a lesser elevation, details later). It is constructed with available wire, a few insulators and some cord or line to hoist the wire into the air.

Most likely you will need to use an external antenna tuner.  A link tuner works very well, but a simple “L” tuner will also work nicely.  As shown here, only a capacitor (or inductor) in series with the feed line may be all that is necessary.  The choice of capacitor or inductor wired in series depends on the length of the antenna and thus, whether it shows as inductive or capacitive to the transmitter.

The main radiating component of the “L” is the vertical wire, that’s what makes it a very good groundwave and DX antenna. So it would be good if this can be kept in the clear, or several feet away from your tower, and of course, as high as you can make it.   The horizontal part may slope downward, or bent several times to accommodate any obstacles. Keep in mind, the more you bend the element back on itself, the more of the radiated signal is canceled out.

Sometimes it is not possible to have the vertical section longer than the horizontal section. This will result in more of the signal being radiated skyward to which NVIS (Near Vertical Incident Skywave) will occur.  NVIS is a propagation method that provides usable signals in the range between ground wave and skywave distances (usually 30 to 400 miles).

Before we go any further, this antenna requires a robust ground system. The antenna is 1/2 your antenna system, and your ground is the other part of the antenna. If your ground is poor, the antenna efficiency will be poor, and you will be troubled with RF in the shack.

The radiation pattern is omni directional, with a possible minor lobe in the direction of the horizontal portion.

Build an Inverted “L” by John, N9LYE.

The Sloper

FullSloper
Full Sloper
sloper
Half Sloper

The sloper is considered the most unusual antenna system and can be difficult to get to work properly. The sloper may exhibit some gain in one direction, but usually has omni direction pattern. There are two types of sloper, the full sloper, really a dipole mounted with one end higher than the other. The half-sloper is fed at one end with a “ground system” or counter poise provided by either physical ground if fed at lower end of sloper. If the sloper is fed at the top, then other factors provide the “ground”. In most cases, a sloper mounted on a tower, then the tower and importantly, the beam mounted on top, act as the counterpoise.

One successful version of the sloper (most folks call any kind of sloper simply a “sloper” regardless of its type) is one that is fed with coax. The antenna is fed from the top and installed on a tower with a beam on top. The center conductor of the coax feeds the sloper wire and the shield is carefully bonded to the tower structure. In addition the beam, rotor, and mast are electrically bonded to the tower (here a heavy braided strap connecting the mast to the tower is recommended). The theory is that the sloper is fed at the top and the high current point is high just under the beam, leading away from the tower.

The sloper has been reported to be hard to get to work in some cases. When it works, its performance when used with a tower and a beam is very good. Considering the cost of materials (assuming the tower is in place already) the sloper should be considered. The sloper is best fed with a link tuner or a tuner with a balun for isolation.

A 160 meter dipole

The dipole for 160 meters is just like the dipoles that we build for 40 or 20 meters. The difference being that they are BIG! With out any loading coils to possibly shorten the antenna, it will be nearly 260 feet long! Of course, this is larger than a typical city home lot, so the dipole may have limited application. Further, for a dipole to be effective, it should be high above the ground for a given wavelength. Again, on 160 meters, this is very difficult to accomplish. At elevations below 40 or 50 feet the dipole’s radiation is nearly vertical (see NVIS antennas). Normally the dipole has poorer performance than a vertical or inverted “L” which would have the same or less real estate to install.

It has been shown in this Mobileers group that a simple vertical mobile antenna mounted in the clear can work as well as a dipole at, say 40 feet.  It is hard to get a 160 meter dipole high enough to compete with a vertical or inverted “L”.

One advantage of the dipole is that it is not as dependent on the ground system to be efficient as other antenna types. It is good to feed the dipole with ladder line and a tuner, so you can make large frequency excursions easily. The tuner allows you to compensate for any mis-match as you QSY.

Due to the physical limitations of the dipole at 1.9 Mhz, it is found by most hams that the vertical antenna is the best. This can be a 40 meter antenna that has the feed line shorted and fed against ground. If the dipole can be erected high and in the clear, it is certainly worth considering.

The Vertical

The vertical antenna consists of many variations of design as we will see. It can be simply a 40 meter dipole with feed lines shorted as mentioned above, to a single vertical radiator, such as a tower, pole, or a “High Tower” antenna. The consideration common to all of these antenna types is that they require a good ground system to work. Said another way, a good ground system is imperative, or don’t bother (on 160 meters, anyway)!

The vertical might be viewed as a half wave dipole mounted vertically and one end stuck in the ground.  The ground and radial system create a “mirror image” of the missing part of the dipole.   Thus the better the radial system is, the better the vertical (or inverted “L”) will work.

An advantage of the vertical, is that it does not require a lot of real estate to erect. Of course, it may require some room for supporting radials (for the antenna or the supporting tower) and also required is the ground field (radials) to work with the vertical. On 160 you may well not be able to erect an antenna that is 1/4 wavelength high (which would provide a resonant condition). The vertical responds nicely to loading coils to provide an adequate match.

The combination of a (1) vertical radiator, (2) matching network, and (3) a good ground system make up the typical 160 meter antenna system. Notice that we emphasize the word system. It takes all three to create an efficient and effective antenna installation.

The inverted “L” antenna mentioned above as well as the single vertical radiator are both considered to be vertical antennas.  They exhibit equal radiation in all directions, except as noted above.

When considering any antenna be sure to read the available literature.  A LOT has been written regarding antennas, so it is up to you to determine which antenna is best for your situation.

Link to a nice summary of various 160 meter antennas

Remember read, READ, read, READ, READ !!   Ask good questions and the Mobileers will surely be willing to loan you good books on the subject…but if you are serious about the subject, you should have your own library!

It is time to READ: here are some links and references.

 

 Posted by at 9:29 pm