The first reports about transmission of wireless telegraph radio signals in this country go back to 1903 when the Sofia military garrison made such broadcasts. The first official Bulgarian radio transmitter was operational in the early 1911 on board the Nadezhda cruiser off the Varna coast. A radio telegraph station opened in 1914 in Sofia too, and later three other stations with smaller capacities were launched in the capital's vicinity.
All transmitters used the Morse code for transmission and reception and were of the so-called spark-gap type. At the time they operated it was impossible to listen to any foreign radio stations with speech and music in their vicinity resulting from the powerful jamming created by the spark-gap transmitter. In 1926 the authorities decided to buy new radio telegraph transmitters for dislocation in Sofia. A tender was held that was won by the British company Marconi Wireless. It delivered the devices and in 1929 they were already functioning.
One of them was for telegraph and telephone communications on long waves at a frequency of 105 kHz, and the other two – on shortwave on 7460 and 14970 kHz, for radiotelegraphy. In 1929 Bulgaria had more than 2000 radio subscribers. They listened to speech and music from foreign countries as there was no Bulgarian transmitter available. Under international agreements a Bulgarian transmitter should have the frequency of 1390 kHz, but following the conference in Prague, Czechoslovakia in 1929, that frequency changed to 940 kHz.
While the authorities failed to act for the purchase of a transmitter for speech and music, some enthusiasts from the army's radio-technological service decided to carry out the job. In 1929 a group of military technicians led by Georgi Vulkov assembled a radio transmitter for broadcasts of speech and music. Georgi Vulkov was a Bulgarian born in 1902 in Tulchea in present-day Romania. He had graduated from a polytechnic in Germany in 1917 and worked as a radio technician in the army. In 1935 he assembled his own telegraph radio transmitter and came in radio contact with telegraphers from all continents. And so we come to the date of 24 November 1929 when at 9 am Bulgarian time on 210 m or 1429 kHz the words, "Radio Sofia calling" were heard on the air.
This has been recognized as the first radio broadcast in the history of Bulgaria. In the days that followed broadcasts were carried on 350 m or 857 kHz. For the transmission of the programs a receiver antenna 50 m long and 14 m high, was used positioned on the roof of the barracks. The power for the radio transmitter came from a petrol motor with a generator. The transmitter itself was equipped with two Marconi radio bulbs with a capacity of 80 watts each. This was how radio broadcasting in Bulgaria started. It continued using the transmitter of the civil association Rodno Radio (Native Radio). In 1935 the radio became the monopoly of the state.