In 2006 there was a conference in Geneva (RRC06) which had a task of making a new plan for TV channels using digital video broadcasting DVB-T . This is now called the GE06 plan. This plan was made on foundations of an old plan made in 1961 on a similar conference in Stockholm (the plan is called ST61). Of course, there were many pre-conference activities in order to assure that each country would come to the conference with some (at least partially) agreed channel plan. The task of making a channel plan was not easy. Taking into account technical properties of radio wave propagation, protection ratios to avoid interference, demands of neighboring countries, geographical properties of planned networks and many other facts, each country had to make a list of channels for each allotment (area for SFN network). Since a common approach was to plan for 7 layers in UHF, this task was close to mission impossible.
An additional challenge for Slovenia was to find a way for protecting the radio frequency spectrum at the Italian border. As you probably already know, Italian Republic is ignoring all international agreements regarding frequency usage. Therefore Italian radio and television stations cause severe interference to neighboring countries. Because of terrain configuration Slovenia is very affected in this regard.
Since other countries along the Adriatic coast (Croatia, Montenegro, Albania) also have similar problems those countries come to the conclusion that the only way to minimize theoretical possibility for Italy to operate on frequencies assigned to other countries, and thus causing interference, is to have a plan which will divide channels along the coast. The principle is based on the fact that there is a relevant area at the Italian peninsula that has some influence over the Adriatic Sea and vice versa (see picture below). This means that channels used in this area on Italian side and not be used in Slovenia, Croatia, Montenegro and Albania. On the other hands this also means that channels in this area used by Slovenia, Croatia, Montenegro and Albania can not be used in Italy. This idea was further developed into a so-called Adriatic Agreement. According to this agreement Italy got 25 UHF channels while other countries got 24. The channels are listed in the table below.
This Adriatic agreement was taken into account during the conference and all countries bound by the agreement have made their channel plan according to this agreement. Of course, such Agreement and plan made at the conference has no value if it is not respected. However, regardless of the aspect of complying with the rules, such an agreement is a very big step toward a sulution for avoiding interference. On Italian side the country is free to plan its 25 channels inside polygon almost without any limitations. On the other side Slovenia has to further agree with Croatia on using 24 channels, Croatia has to agree with Montenegro, etc. This Adriatic agreement has lead Slovenia into situation that in some areas near the Italian border all 24 UHF channels are availabe for digital television.
Some excerpts from the Adriatic Agreement
Considering technical difficulties in planning of the digital terrestrial broadcasting service in the coastal area of Adriatic sea, number of requirements submitted by the countries and principle of equitable access to the frequency spectrum, countries of Adriatic group have signed this agreement in order to facilitate planning of the terrestrial broadcasting service, establishment of Plan at the RRC06, implementation of DVB-T in the transition period and for all-digital future.
The planning is based on the principle of equitable access to the frequency spectrum.
The aim is to achieve a compatible pre-coordinated digital Plan between concerned countries within the defined area, which will be mutually agreed and submitted as requirements prior and during RRC06. Basic principles defined in this document and the requirements derived on these bases is going to be used in order to facilitate planning of the digital terrestrial broadcasting service and establishment of Plan at the RRC06, implementation of DVB-T in the transition period and for all-digital future.
Multilateral case of Albania, Montenegro, Croatia, Italy, Slovenia and San Marino
Inside Area of Incompatibility, administrations of Adriatic group can in the process of planning of the digital terrestrial broadcasting service prior and during RRC06, submit requirements (allotments/assignments) using only channels allotted to the Administration concerned as given in the table of Annex 2.
The administrations jointly agree that their input requirements to the RRC06 shall be in line with this agreement. Any modifications or extensions of Annexes given in this Agreement are subject of common negotiations and revision of the Agreement.
All disagreements between Contracting Administrations shall be settled according to the provisions of The United Nations Convention on the Law of Treaties, signed on Vienna, 23 of May 1969, entered into force 27 of January 1980, Vienna Convention on The Law of Treaties, 1969.