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Recently, there has been a change in the way digital terrestrial television is broadcast in Europe, with the replacement of the existing DVB-T system with the more efficient DVB-T2. In Poland, further DVB-T2 transmitters have been switched on. Although reception of the DVB-T/T2 signal in the vast majority of cases should not require replacement of the antenna set used so far, practice shows that in many situations, modernisation of the set is necessary. Also, every day many new locations are created, for which it is necessary to select an appropriate antenna set.
So we will try to answer the question posed: which antenna for DVB-T/T2?
Of course, this question cannot be answered unequivocally. A full success in each case should be guaranteed by a professional installer, who, using their own experience and suitable measuring instruments, will be able to choose the optimum solution for the location. People buying antennas on their own should at least look at the roofs of buildings in the vicinity and learn from the experiences of residents who already receive digital terrestrial television.
The parameters of the antenna necessary for proper reception of digital broadcasts depend on several key factors:
- distance from transmitter(s)
- transmitter emission power
- height of transmitter antenna systems
- directionality of transmitter
- terrain between transmitter and receiving site
- terrain at the reception site (open countryside, urban areas, etc.)
The first three factors can be checked using dedicated services on the Internet. Using the example of DIPOL headquarters in Krakow we will try to select an antenna that will ensure proper reception from the nearest TV transmitter.
Checking the distance from the transmitter and its transmission power
This operation can be done in several ways. The fastest and relatively simple method is offered by sat-charts.eu service with its locator (it supports only Polish DVB-T network).
By clicking on the appropriate location on the map, we select the area of interest:
General view of the map
Using the slider on the left we may reduce the scale of the map and set down the position of the receiving point:
Detailed view - location of the site
Once you have selected the location you are interested in, press the button:
A list of transmitters will then be displayed, in order from closest to furthest from the previously indicated location, together with a breakdown of the individual multiplexes. In addition, individual items on the list are marked with one of three colours:
- green - stable reception most likely
- orange - reception likely, interference possible
- red - reception impossible or almost impossible
The service also informs the user about the fact that the transmitter power and distance are not the only determinants of good reception (translation):
Stable reception depends on many factors, not only on the distance from the transmitter and its power. We must also take into account the terrain profile, the height the transmitting antenna is placed at, the gain of the receiving antenna, sensitivity of the tuner/receiver.
For the indicated location, i.e. the DIPOL headquarters in Krakow, Cieplownicza 40 Street, we get the following list of transmitters:
The list of transmitters for Krakow, Cieplownicza 40 Street
On the basis of the list above, it can be concluded that two multiplexes, i.e. MUX2 and MUX3, are available on channels 48 and 64 from the Chorągwica transmitter, located just over 10 km away. The transmitting power is 2 and 63 kW respectively.
We may also consider reception from Rabka, Katowice, Tarnow, Wisla, Zakopane, but only the Wisla-Skrzyczne transmitter provides MUX1 with a different set of programs.
The following tables are provided for optimal antenna selection based on the information obtained so far. The tables are for reference only. Due to the fact that reception of radio signals is the resultant of many factors, DIPOL does not give a 100% guarantee that the selection of an antenna on the basis of the tables below will result in trouble-free reception in each location.
On the basis of the above tables and the information obtained to date for the possibility of collection at DIPOL's premises, it can be concluded that:
- for Chorągwica transmitter (11 km, power 63 kW and 2 kW) the most optimal solution will be A1911 antenna
- possibly wanting to try to receive MUX1 from the Wisla-Skrzyczne transmitter (82 km, 10 kW), one of the antennas A2670, A3710 or A3380 will be a better solution. It is worth mentioning here the basic difference between A2670 and A3710 antennas. The gain of both antennas is similar, the ATX type antennas are more directional. If you are hoping to receive signals from several transmitters, the A2670 antenna with a wider beam will be a better solution.
Antenna with or without amplifier?
The vast majority of the aforementioned antennas can operate with LNA-type box amplifiers. Some of them can be purchased as a complete set: A1615, A2665, A2675 - equipped with the amplifier with the highest gain - LNA-177 B4009. If you wish to purchase a preamplifier for another antenna or a weaker preamplifier, you can choose one of three models - LNA-101 with 15 dB gain B4007, LNA-169 with 24 dB gain B4008 or LNA-177 with 30 dB gain B4009.
Generally accepted practice says that you should aim to avoid using preamplifiers when receiving DVB-T/T2 signals. However, again, as with antenna selection, it all depends on the power and distance of the transmitter. In the case of transmitters 40 km or more away, especially in the case of low-power emissions, the use of a preamplifier may be necessary. Often, too, the area in which the signal is to be received is not conducive to proper reception (dense buildings, trees, etc.). In such cases, e.g. when the signal is to be received from reflections, the use of a preamplifier increases the chances of reception.
What about broadband antennas with mesh reflectors?
Popular opinion says that broadband mesh antennas are not suitable for receiving digital signals. However, the practice shows that these antennas can be successfully used for that purpose and possible problems usually do not arise from their wide beam, but from low-quality preamplifiers which were used by some suppliers (no shielding, high noise figure).
Those with such antennas should verify that they are able to receive a digital signal on them before purchasing a directional antenna. In some cases, the wide radiation beam of a mesh antenna may cause the unwanted signals it collects to interfere with DVB-T/T2 reception.
On the other hand, these antennas may work well in dense urban areas, where the signal may be received from reflections and correct positioning of the directional antenna may be difficult.
On the other hand, these antennas may work well in dense urban areas, where the signal may be received from reflections and correct positioning of the directional antenna may be difficult.
Directivity of the transmitting antenna and coverage
High power and a relatively small distance from the transmitter do not guarantee correct reception of DVB-T signals. The decisive factor may be the directivity of the transmitting antenna. An example - one multiplex is broadcast with the use of directional antenna towards an urban area, whereas another one is broadcast with omnidirectional antenna to cover the entire area around the transmitter. This is the reason of frequently occurring problems with the reception of a multiplex by residents of a particular area.
The service that can help users in the final selection of suitable antennas is dvbtmap.eu providing means for:
- checking the location of most European DVB-T/T2 transmitters
- their signal coverage
- the profile of the terrain between the transmitter and the selected reception site
View of the homepage of the dvbtmap.eu service. The site has several language versions (Croatian, Czech, English, German, Hungarian, Polish). The "Coverage Map" option visualizes theoretical signal level for a selected transmitter from the list on the right side of the page.
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Example of a transmitter with omnidirectional (MUX2) and directional (MUX3) emissions. It should be noted that in the second case there are many locations in the immediate vicinity of the transmitter where direct reception of the signal will be impossible. In such a situation it is necessary to verify the possibility of reception from other transmitters or, in extreme cases, to try to receive the signal from reflections.
Distance and terrain profile
The last thing to check before deciding to buy an antenna for TV reception is the profile of the terrain between the transmitter and the reception site. You may find that if you want to receive multiplexes not broadcast from a local transmitter and are considering buying a more expensive, larger antenna, you are doing so pointlessly. Even if the transmitter transmits with high power, the terrain obstacles between it and the reception location may effectively prevent direct reception.
To check the terrain profile between a transmitter and the place of reception we may again use the dvbtmap.eu service and its map distance tool.
Choosing an appropriate transmitter from the list and selecting the reception location on the map, we get the distance and terrain profile between the points. The calculation takes into account the height of the placement of the transmitting antenna on the tower.
Example of terrain profile - no obstructions between transmitter and receiver.
Example of terrain profile - terrain obstacles between transmitter and receiver.
