First program of Bulgarian National Radio "Horizont" was off the air on its mediumwave frequency 576 kHz earlier today, most probably due to transmitter maintenance. Everything had returned to normal on my next check at 1700 UTC.
The power of the mediumwave transmitter of BNR on 576 kHz is rated at 400kW. It is supposed to cover the whole territory of Bulgaria with good quality signal round-the-clock. At night the signal reaches as far as Western Europe and Eastern North America.
Here is a video of reception of BNR in Newfoundland, Canada: