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One of the features of high-frequency electromagnetic waves used by UHF and TV transmitters is that they diffract on natural obstacles. As Slovenia is mostly mountainous, transmitters must be placed at the highest possible points. This is the difference from medium-wave transmitters, which until the introduction of UHF transmitters were installed exclusively on flat surfaces, in valleys and by the sea. Five basic transmitter centres were set up in Slovenia, specifically at Krvavec, Kum, Pohorje, Plešivec and Nanos. All these centres were built in the early 1960s and, with the help of a converter network, almost 100% of the populated areas were covered with their signal.
First UHF audibility measurements in the area where the Nanos transmission centre stands today were made in 1953-1954. Since a large part of the Primorska and Notranjska regions can be covered from Nanos, Slovenian radio UHF programmes started to be broadcast in 1955, and Italian television programmes in 1957. Initially, these broadcasts supplemented the broadcasts of the Yugoslav Radio and Television.
At first, a small house was built for equipment, while the technical staff lived in the Vojko Lodge. As the measurement results were favourable, UHF radio programme started to be broadcast in 1955 from an altitude of 1,248 metres with a 250 W Rohde & Schwarz transmitter.
The Italian TV programme started to be broadcast in 1957 with a 100 W RCA transmitter. The programme was received from the Italian transmitter Belvedere above Trieste. The Yugoslav Radio Television programme started to be broadcast regularly in 1958. The transmitter tower was approximately 20 m high. It was at that time that employees of RTV Ljubljana launched an initiative for a "modern facility" to be built on Nanos. The proposal from RTV Ljubljana was accepted in Belgrade on 19 July 1960 and it was decided that radio and TV transmitters, a 60 kW power generator, a transformer station, a workshop, a garage and a housing facility for technical staff will be built on Nanos. A 50 m high antenna tower was also installed, and a 10 kV electric cable was laid down in the length of 1,300 metres from Razdrto. A new, wider road leading to the facility was also built, and the opening ceremony was held on 15 December 1962. Two radio UHF programmes and one television programme on channel six were broadcast at the time. Microwave transmission towards Italy (Belvedere above Trieste) and from Nanos towards Krvavec included Yugoslavia into the Eurovision network. In the event of a power outage, a 60kVA diesel generator was also available.
On the night of 4 February 1969, a hurricane-force bora wind brought down the antenna tower. It was established with subsequent measurements and comparisons that the wind reached a speed of 240 km/h that night. Work on the new antenna tower was concluded on 28 November 1969. Until then, programmes were broadcast with antennas placed on metal structures around the facility. A new 3 kW Rohde & Schwarz UHF transmitter was acquired in 1970, and a 20 kW Philips UHF transmitter with two klystrons was acquired towards the end of the same year. At that time, it was one of the most state-of-the-art transmitters in Europe, and was intended for the programmes for the Italian ethnic community in Slovenia.
1970 was an important year, as the colour TV test for Television Slovenia was broadcast for the first time, on 11 November. After the Philips transmitter was installed, the colour test and test programme from the TV Koper studio started to be broadcast on a regular basis. Colour programme has been regularly broadcast from Nanos since 28 June 1971.
The FM programme network was expanded in the 1970s and 1980s, with three programmes of Radio Slovenia and two programmes of Radio Koper – Capodistria being broadcast. The transmitters started to regularly broadcast the signal in stereo technology for the first time. A new power facility with three generators and more powerful transformers was also built during this time.
New microwave links towards Slavnik, Beli Križ, Tinjan, Koper, Skalnica, Kanin and Krim were established by 1991. A part of the new road to the transmitter, which previously passed through a very dangerous section below Grmada, was constructed in 1984.
During the Ten-Day War for Slovenia’s independence in 1991, the broadcasting centres of RTV Slovenia were attacked from air. The transmission centre on Nanos was attacked twice. The UHF antenna system and a large part of microwave waveguides were destroyed. A new antenna tower for radio transmitters was erected in autumn of the same year.
Construction work on a new extension to the existing building was completed in 1992. A year later, all UHF transmitters were replaced with state-of-the-art, fully solid-state power stages, and TV transmitters were also later replaced.
In December 2010, RTV Slovenia started broadcasting TV programmes in DVB T digital technology, and analogue TV transmitters ceased to be used altogether. The Nanos transmission centre was the only centre where the majority of analogue transmitters were preserved. In other centres, analogue transmitters were mostly scrapped. For this purpose, a museum collection of analogue transmission technology was opened on Nanos on 6 July 2014, where analogue transmitters are on display to visitors under the expert guidance of the professional staff.
MUSEUM COLLECTION OF ANALOGUE TRANSMISSION TECHNOLOGY
On Sunday, 6 July 2014, a museum collection of analogue transmission technology opened for the first time in the Nanos transmission centre.
FROM IDEA TO MUSEUM COLLECTION
In 1992, construction work started on a new facility, which was added to the existing building from 1962. It was a result of shortage of space and demand for new programmes, which increased greatly since Slovenia became an independent state. New transmitters started to be installed in these premises immediately after the construction work was completed at the end of 1993. The first to arrive were state-of-the-art Harris UHF transmitters, and TV transmitters were also gradually added in the following years. The transmitters that served as the main transmitters in the old building became a back-up for the new transmitters.
It was at this time that employees first came up with the idea to keep the old transmitters on Nanos. While the shortage of space was resolved, every trace of the transmitters and other written-off equipment would be lost had they been removed from Nanos. It was therefore decided to continue to maintain the transmitters and provide them with a new value. This is why practically all transmitters that are now part of the museum collection operated almost until they were disconnected from the antennas.
A few years ago, members of the Podnanos Tourism Association and RTV Slovenia employees came up with the idea to preserve analogue transmitters at the RTV broadcasting centre on Nanos and put them on public display as a museum collection. The idea was supported by the Municipality of Vipava, which in partnership with the Podnanos Tourism Association and RTV Slovenia successfully applied as the project leader for a call for applications of the Upper Vipava Valley and Komen Karst Local Action Group (LAG) and obtained a EUR 61,000 grant for the collection from the European Agricultural Fund for Rural Development (LEADER axis).
Transmitters for analogue TV broadcasting at RTV broadcasting centres were switched off in 2010 and television signals started to be broadcast exclusively in digital technology. A lot of analogue devices ended up in scrapyards.
The museum collection on Nanos is thus the only such collection of technical heritage in Slovenia on display for the general public. Some equipment has already been brought from other transmission centres, such as a BHG transmitter from 1960. It was brought to Nanos from the Krvavec transmission centre. The legendary Marconi microwave link from that transmitter was also brought to Nanos. Items will be added to the collection for many years to come, as they are still looking for exhibits that are interesting for display and that make it easier to understand the development of television and radio from the beginnings to the present day.
The opening of the exhibition was addressed by the Deputy Mayor of the Municipality of Vipava Bogdan Godnič, President of the Upper Vipava Valley and Komen Karst LAG Janez Furlan and acting Director General of RTV Slovenia Marko Filli. All speakers noted that the museum collection of analogue broadcasting technology on Nanos is proof that good ideas that benefit a broad circle of people can be realised with joint effort and partnership cooperation.
This museum collection is also a great acquisition for the Municipality of Vipava, with a new tourism product being added on Nanos.
Many hikers on Nanos stop by the fence of the transmission centre, wanting to see the interior of the facility. They did not have this opportunity before Sunday, 6 July 2014, and now that the museum collection of analogue technology has opened, the curious eyes of mountaineers can have a peek inside the facility. Currently, the collection can be seen by prior arrangement with the Podnanos Tourist Association (email@example.com).
STORIES FROM EMPLOYEES
"You had to get educated"
Stane Perpar and Janez Štravs worked on Nanos more than 45 years ago. At the time, transmission system technology was new to everyone, so they spent a lot of time learning. All literature was in foreign languages. The work was complex and the responsibility to the listeners and viewers was great. They did most of the repairs and measurements themselves. They have many fond memories of the time they spent on Nanos, and all employees were like one large family. Nanos meant a second home for many. Perpar admitted that sometimes a prolonged downtime of the programme meant that the damage was greater than his house was worth. One needs to know that, at the time, there were no cable systems, internet and satellites and transmitters were the only source of programmes.
"Did we lose an antenna on the tower?"
Between 1995 and 2009, the Nanos transmission centre was headed by Srečo Rovšek. He got a job on Nanos as early as 1969, the same year when the tower collapsed. He still vividly remembers all events at the time when he started his first job. "In January 1969, I came to work on Nanos for the first time. Until then, all I knew about Nanos was that it was a mighty hill not far from Postojna, along the road to the sea, and that there was an antenna tower at the top. The first week on the job was foggy and there was uneasiness among technicians because there was a major malfunction in the antenna system. I felt lost, I wanted to help, but I didn't know how, because everything was new, from people to the equipment.
The tower collapsed when I got to work for the next shift. An exceptionally strong bora wind had been blowing for several days. According to data and subsequent calculations, wind gusts reached a speed of 240 kilometres per hour. Rattling could be heard on the roof all day as pieces of rime ice were falling on it from the tower. Around midnight, there was a loud rattle again, and alarm sounded off after a few seconds. A colleague sent me out to check if any piece of the antenna might have fallen off. On all fours, I crawled to the corner to see a part of the antenna tower on the ground, leaning against the roof and facing Razdrto. The colleague did not believe me at first and then we both headed out again. The drama was not over yet, as we had to inform the head of our service in Ljubljana. This was not as simple then as it is now, as we did not have direct telephone connections back then. Our message was forwarded by the transmitter on Krvavec. I remember well what the boss told us: "Save what can be saved!"
We did not have many options in that strong bora wind and snow, so we tied the tower to the foundations with a rope that we had in the garage. Had the tower started sliding further down into the valley, this rope would certainly not have held it back…”