Antennas are normally directive, receiving more signal, or transmitting more signal in one direction than another.
To ensure that the best performance is obtained, it is necessary to align or point the antenna in the right direction. This antenna alignment or orientation is an key part of any antenna installation. Incorrectly aligned and pointing in the wrong direction, the antenna will perform poorly.
Whether a professional installer, caravaner, or DIY enthusiast installing a television antenna, it is necessary to be able to accurately align or point the TV antenna to provide the best reception.
Typical television antenna
Antenna directivity
Antennas, particularly those used for television reception have a directional pattern and when they are installed they need to be orientated or pointed towards the television transmitter if the best reception is to be obtained.
Antennas have a directional pattern or polar diagram. For most television antennas they have a marked increase in performance in one direction, and reduced performance in others.
The gain in the main direction enables a much better television signal to be received, but in others it is much reduced. This enables any interference to be reduced in level at the input to the television.
However, this directional pattern means that the antenna must be correctly aligned or orientated, otherwise the main direction of sensitivity will not be aimed at the transmitter and the performance will be reduced.
Typical TV antenna polar diagram
Accurate alignment of the TV antenna is essential if the best performance is to be obtained. Typically the longer the antenna, the higher the gain and also the narrower the directional pattern. This makes accurate alignment crucial.
Methods of aligning an antenna
It may sound as if TV antenna alignment would be an easy job. As the television receiver is normally located well away from the antenna it is not easy to move the antenna, and then check the performance. Small adjustments can take a long time if only one person is present, moving between the antenna and the receiver. Small adjustments can therefore be difficult to make. Even when two people are available, it is still surprisingly difficult.
There are several techniques that can be used to align the antenna:
Visual alignment: This is probably one of the simplest methods of aligning the antenna. When up with the TV antenna, simply point it in the direction of the television transmitter mast. Obviously, this required the TV transmitter mast to be visible, but if not, it is often possible to align the antenna in the same direction as other local antennas. This may be satisfactory in some instances, but signal strengths can vary from one house to the next and with reflections often present, the direction required in one location may be different to that needed in another.
Use smartphone app: There are several smartphone apps which help orientate the antenna towards the television transmitter. There is a good selection, both for Android and also for Apple iOS. Typically they have a list of the television transmitting antennas with their locations and then they use position location and the orientation capabilities of the smartphone to be able to provide the direction or orientation for the various transmitters. Typically a list of close stations is provided, as the nearest one may not always be the best.
This method may not always work as well as expected if the television transmitter mast is not directly visible because the if the transmitter cannot be directly seen the signal used may be a reflection. It could bounce off buildings, hills and the like. In this way it is best to ensure that all options are taken to get the best signal and picture quality.
Signal strength meter: There are several low cost TV antenna signal strength meters or alignment meters that can be used. These antenna alignment signal strength meters are straightforward and can enable the easy alignment of the antenna actually at the point of the antenna if it is possible to access the cable to connect to the meter.
These TV antenna alignment meters are generally very basic and measure the strength of signal across the whole TV band - they are just a simple analogue RF signal strength meter and typically they give a basic strength indication on a set of LEDs. This enables the antenna to be orientated to obtain the strongest signal.
The TV antenna alignment meters provide a basic indication of the strongest signal, but as they are wide band they could pick up other signals and provide a false reading. However with a bit of intuition they can work reasonably well, although the sensitivity is limited.
When thinking of investing in a TV antenna alignment signal strength meter, remember to check whether it is for satellite television antenna alignment, or terrestrial television antenna alignment. As signals from these two different types of transmission are on vastly different frequencies, different alignment meters are needed. Some TV antenna alignment meters are able to accommodate both terrestrial and satellite and are advertised as such.
It is obviously important to know which way any antenna will have its direction of maximum gain. Most terrestrial antennas are based on the Yagi array.
This has a reflector at the back and a series of directors at the front. The element to which the feeder is connected is often what is termed a folded dipole and somewhat larger than the others. The reflector is right at the back, followed by the driven element and the a series of directors progressively getting slightly smaller.
Yagi Uda antenna showing direction of maximum radiation
With a little intuition it is possible to determine the direction in which the antenna should point. This can then be aligned with the direction of the television transmitter.
Using a signal strength meter to align a TV antenna
The best method of aligning the TV antenna is to use a TV signal strength meter. There are professional meters that are available and these work very well, but they are quite costly and tend to be used by professional TV antenna installers.
Alternatively, for the amateur or DIY enthusiast trying to align their television antenna, there are some low cost TV signal strength meters available. These are not sophisticated, but with a little experimentation they will give the required result.
If selecting a TV antenna alignment meter, first check that the one to be used operates on the right frequencies. For example satellite TV operates at frequencies over 10 GHz (10.7 - 12.75 GHz for Europe). Even though the Low Noise Box on the TV antenna converts this down to much lower frequencies a different satellite of antenna meter is required.
For terrestrial TV antenna alignment and installation, simple TV signal strength meters are widely available.
Typically these have a meter unit with connections to the antenna and a battery power source.
First orientate the antenna in the general direction of the required transmitter - make sure it is aligned along with neighbours TV antennas, or with a map reading. This gives a good starting point. Also make sure it has the required polarisation - horizontal (which is more common) or vertical.
Then set up the TV signal strength meter. Having read the instructions, make sure it is possible to connect the antenna via a lead to the meter and also make sure the connectors match those of the meter.
Connect the socket marker "Antenna" to the antenna cable, and also connect the power source to the other connector, or wherever it is required as they are normally battery powered. [Note any TV antenna amplifiers must be disconnected.] There may be some differences in the set up and method of operation according to the actual meter used.
With the meter connected, follow the instructions for using the meter, adjusting the sensitivity to obtain the best reading.
When making any readings, it is necessary to stand away from the antenna if at all possible so that the presence of any people does not affect the antenna and the readings, remembering this must be done within the realms of what is possible from a safety aspect. It is best to stand behind the reflector for the minimum affect on the antenna.
Adjust the antenna direction on both the horizontal and also slightly in the vertical plane to get the best signal. Normally the antenna will perform best when it is horizontal, but occasionally a small adjustment in the horizontal plane may give some benefit.
Reconnect the normal television down-lead and check the television performance. If the signal is good, then undertake a final tighten of the fixings and ensure that everything is suitable to be left.
Bonus tips for TV antenna alignment
Apart from the basic techniques for TV antenna alignment, a few additional tips may help make sure that the best performance is achieved.
Don’t rely on TV internal meter: Some televisions have internal antenna alignment meters to help measure signal strength and provide a tool for the TV antenna alignment. Although this can give an indication of the strength, the way it is done can be a little misleading in some instances. If difficulties are experienced, then it can be easier to rely on an external antenna alignment meter for more accurate antenna alignment, especially if it can be used at the antenna itself. This can mean that a direct indication can be seen at the antenna, and the results of any changes made at the antenna can be seen directly.
Use good quality TV antenna cable: TV antenna cables vary widely in quality. There will always be some loss in the antenna cable, but this should be minimised, especially in areas where the signal level is low because the transmitter is a distance away, or because of shielding by buildings, hills, etc. Cheaper coax will almost always give a higher loss, and it is likely to be more prone to picking up interference. Even small fly leads can introduce loss. Here, cheap fly-leads bought in supermarkets may not have the quality needed. Some have been noted to have noticeable levels of loss, even for very short lengths. Always by the best you can, and then the performance will be assured.
Placement as well as alignment is important: The placement of an antenna is often just as important, and sometimes more important than accurate alignment. Local terrain, trees, buildings, interference can make the antenna location very important. If the antenna is located externally, then there may not be too much choice in the location, but also the performance is likely to be better, but be aware of local obstructions - do trees, tall poles, buildings, etc mask a direct line to the transmitter, and would a small move improve the ‘radio visibility.’
Antennas located internally are more prone to local obstructions, etc, but also there is often more choice in the location. Make sure that the direct line to the TV transmitter is not obstructed by objects like water tanks, solar panels on the roof, etc. Also the direct line to the TV transmitter may not always be the best direct If in doubt use a signal meter to check for the best antenna alignment and performance.
Check polarisation: The polarisation of a television signal is important when aligning an antenna. Get the polarisation 90° out and there will be no signal. The polarisation of the antenna matches that of the signal it is receiving and is broadly that of the elements of the antenna. Vertically polarised TV antenna - note the elements are all vertical
Although most television signals are horizontally polarised and the elements of the antenna are the same, some are vertically polarised. Very occasionally some broadest stations may be what is termed slant or diagonally polarised, e.g. 45° to the vertical so that both horizontal antennas (often used for home reception) and vertical antennas (in cars and on portable radios) can be used. Check the polarisation - this can be done by referring to the local information, or just looking at what all the other local antennas have - and align the antenna polarisation accordingly.
Keep away from the antenna: When adjusting the antenna, try not to get too near to it when any adjustments are being made. The close proximity of people to the antenna can change its performance. Absorption, reflections, proximity capacitance effects that change its resonance, and a host of other things can affect the antenna. Definitely do not get in front of the antenna, probably behind it is best, but check that any movements you make do not change the signal meter reading unduly, and then finally tighten the fixings and then check the signal quality when you are well away from the antenna.
Adjust for best signal: Although there is a major move to digital transmission of television, there are still analogue transmitters on the air. Often interference from reflections or other sources can cause patterning on these analogue signals - sometimes called a herring-bone effect. The antenna can be aligned to minimise the interfering signal, whilst retaining an acceptable level of the wanted signal. Another effect seen on analogue signals is a ghost picture where the reflected signal is delayed by a small amount causing second ghost signal to appear. Aligning TV antenna for minimum interference
It can be seen that aligning the antenna for the highest wanted signal can also enable high levels of an unwanted interfering signal like a reflection. Offsetting the antenna slightly can considerably reduce the unwanted signal whilst only having a minor impact on the wanted one. Very occasionally it may also be useful to slant the polarisation of the antenna slightly to reduce the level of the interfering signal.
Aligning TV antennas can provide to be more difficult than it may appear at first sight. However with a bit of practice, reasonably good results should be obtained with all the above methods. It also means that when undertaking an antenna installation and alignment yourself, you can obtain the best results and ensure that you take the time to optimise the performance under all conditions.
Fact of the day: It was on this day in 1965 that Moore\'s Law was first published in an article about the future of semiconductor components. At the time, Gordon Moore who wrote about it was the head of research and development for Fairchild Semiconductor and later he went on to co-found Intel.
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