<PSC> Antenna Tips

Everybody wants to make ultimate DX. From contacting that rare division, to contacting the other side of the world across the longpath. Or doing a few hundered km's a on a groundwave. Here are some useful tips in different categories:

What type of antenna:

Best antenna's for DX are antenna's that produce the maximum radiation in the angle 1° to 13° from the ground. There are different type of antenna's but we made a list of the most common verticals and beam antennas.

Groundplane:

If you have limited space, try using an omni-directional antenna like a 5/8 wave (lambda) groundplane. These antenna's are ideal if you do not have the space to put up a directional antenna. The radiation pattern of a 5/8 wave groundplane is better than a 1/2 or 1/4 wave groundplane, as there is more radiation in the particular lower angles needed for DX. If you also like to do a lot of local QSO, you could consider using a 5/8 wave groundplane next to a beam.

The gain that some manufacturers claim on these groundplane antennas are much higher than in theory possible, and in most cases very unreal. For example a 5/8 groundplane at 11m from an average type of ground produces 3.6dBi gain (to increase your signal with 1 S-point, you need 6dB gain), But some manufacturers even claim 9.9dBi gain, which is even more than a 3 element Yagi beam! That is simply impossible, unless you have the groundplane mounted an a 40m mast, and the Yagi on a 3m mast. More about that in the chapter "The Ideal Height".

Our favourite 5/8 GP: Sirio 2008/2012/2016.

5/8 wave groundplane with radials

Yagi:

If you have the space, a directional antenna (or a beam) like a Yagi will give you some advantages over a groundplane, as these antenna's direct the maximum radiation to a certain area like a flashlight. The more elements and the longer the boom of this antenna, the higher the gain. Because waves coming into the front of the antenna are amplified, waves coming in form the back and side seem reduced in strength (even up to 4 S-points), which can be very handy when you want to work a specific part of the world, and want to avoid QRM from other areas. These are called "front to back" and "front to side" ratios. The higher these ratios (in dB), the stronger the signals is that comes in at the front of the beam, in comparison with the signals that come in sideways or in the back of the antenna.

Our favorite Yagi: ZX-yagi

3 element Yagi

Cubical Quad:

A directional antenna that produces even more gain is an antenna named Cubical Quad. Instead of using element of 1/2 wave length like the Yagi, the Cubical Quad consist of elements that are a full wavelength. The actual elements are called loops and are wires that are spread into a square or diamond (see picture below) shape. In practice, a 2 element Cubical Quad does about the same as a 3 element Yagi, and is slightly stronger in the low radiation angles, which makes it more suitable for DX. It also has a more narrow beam, and is less influenced by static (from rain, etc.). My personal experience is that the Quad (and other loop antennas) produces less QSB in comparison to a groundplane or Yagi. It does require a stronger mast construction and some more space, and obviously a strong antenna rotor.

Our favourite Cubical Quad: PKW

2 element Cubical Quad

Delta Loop:

The ultimate DX antenna is also out of the family of loop antenna's. The Delta Loop, which has triangular loops, has almost the same characteristics as a Quad antenna. Users of Quads and Delta Loops report that the Delta Loop seems to have a more narrow beam in the vertical plane. However this does not show up in any computermodels.

The Delta Loop has become very popular last years, because it is very easy to construct one yourself. The construction is so simple that everyone can build it within a few days, for only a small investment.

3 element Delta Loop

Horizontal or vertical polarization?

If you operate a vertical antenna, you do not need to worry about polarization, because you can only choose vertical polarization. If you have a directional antenna you can choose vertical or horizontal polarization.

Now polarization changes in any kind of polarization when a radiowave is reflected in the ionosphere, so for DX it does not matter what you choose, in theory... There is also the influence of the ground. It has been proved that horizontal polarized waves are less absorbed when they are reflected ground, than vertical polarized waves. Horizontal waves also tend to do better as a groundwave, being less influenced by obstacles. That is very helpful on those days with bad conditions for DX, because with a quiet atmosphere and in a high pressure area, groundwaves can produce some interesting short distance DX over the ground (my personal record is 360km).

The ideal height:

The ideal height of course is as high as possible. All antennas should operate at a height, that the base of the antenna looks over the roofs and trees surrounding your QTH. For the antennas on this page, the radiation pattern depends on the height of the antenna. A simple rule is, the higher the antenna the lower angle it radiates at maximum. For example a 2 element Delta Loop with 1.3m (0.12 lambda) boom. We calculated the maximum radiation at different heights (we chose the surface conditions of an average suburban location):

 The height is even so critical that a 2 element Yagi at 25 meters outperforms a 3 element Yagi at 10 meters.

The ideal ground:

One thing you cannot change is the ground, unless you decide to move to a place where the ground conditions are better for DX. But what is the best type of ground to live on for DX?

The perfect ground would be the ground that conducts electrical currents with no loss of current. A situation you will never find on Earth, but there are situations where ground conditions can be very good for DX. The best place to be for DX is on a boat on the sea, while salt water is a very good conductor that reflects almost 100% of all radio waves, less good but still better than normal ground is fresh water (lakes, pools and rivers). Than followed by muddy and swamp like ground with lots of minerals (minerals add conductivity). Ground water level is also very important. High groundwater level means good conductivity (I am lucky living in a place where ground water levels are relatively high).

Bad places to be are industrial and urban areas, and areas that are filled with "concrete". But also mountainous areas with rocky soil, are not the best places. These type of surface absorb your signal significantly before it is being reflected...

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Good DX!

19DX072 Jean-Paul