Most Powerful MW/AM Stations

/ Broadcasting, Station information, Technical

The Most Powerful MW/AM Stations

by Steve Whitt

What is the most powerful AM station in America?

The most powerful AM broadcast transmitter is 450kW operated by TransWorld Radio from the island of Bonaire. This religious station operates on 800kHz as “Shine 800” and targets audiences across the Caribbean and South America. But its powerful signal is widely heard in the USA.

In addition it uses three different directional antenna patterns to boost the strength of its signal into its target listening areas. Shine 800 broadcasts in Spanish, English, Portuguese  Walapi and Macuxi languages.

Three selectable coverage patterns used by Shine 800 in Bonaire

The 440 kW Nautel NX400 transmitter feeds into a four tower Kintronic antenna system which was completed in January 2019.

Four mast array at TWR Bonaire by night

Bonaire is an island municipality of the Netherlands, which lies off Venezuela’s coast in the southern Caribbean. Bonaire was part of the Netherlands Antilles until the country’s dissolution in 2010 when the island became a special municipality (officially, a “Caribbean public body”) within the country of the Netherlands.

What is the most powerful MW station in Europe?

Kossuth Radio in Hungary transmits with 2000kW of output power from the Solt transmission station on 540kHz. The transmitter site traces its origins back to 1975 and started using 2MW from soviet constructed equipment. But five modern high efficiency NX400 transmitters by Nautel were installed in 2017 as part of a major renovation project.

Solt is located in the centre of Hungary to provide country wide coverage from its single 304m tall mast. It is located on the central Hungarian plain and the good ground conductivity and low frequency ensure a large daytime coverage area.

The single mast and coax feedline at the Solt transmission station. The cage-line will be running at ~10000V and carrying ~200Amps to the mast. (Deneb at German Wikipedia)
Daytime coverage from Solt (www.frekvencia.hu)
Night time coverage from Solt

Interesting fact

The Solt transmitting station replaced the Lakihegy transmission tower which dated back to 1933 and which is the tallest structure in Hungary. It is famously one of the Blau-Knox antenna designs. However there was a public outcry when it was to be demolished. It was subsequently declared a public monument and renovated in 2006 and now remains as a standby facility for Solt.

What was the strongest MW radio station ever?

That’s a tricky question. There have been dozens of MW and LW transmitters over 1MW over the years. And at different times different stations could claim the crown of “most powerful”.

But it all started with WLW Cincinnati on 700kHz in the USA which increased its power to 500kW in 1932.

During the 1970s there was race for higher power, in part driven by the Cold War in Europe and a rise in pan-Arabic politics. Many 2000kW transmitters were installed but few remain in use in the 21st Century due changing political climate and the outrageous cost of running and maintaining stations based on a 60% efficiency of AM transmitters of the time.

Some of these super power transmitters used a single mast antenna for omni-directional coverage of a country or a region but others boosted their power in certain directions to reach a target audience.

A few 2MW examples (mostly now silent or on reduced power)

  • Radio-TV Belgrade, Yugoslavia 683kHz Continental Electronics D323A – 2,000 kW (1974)
  • MOI, Dammam, Saudi Arabia 1440kHz Continental Electronics D323C – 2,000 kW (1979)
  • Radio Luxembourg Beidweiler, Luxembourg 234kHz 2x THOMSON-CSF TRE 2175 units with a capacity of 1000 kW each, used 1994-2011
  • Medi – 1 Nador, Morocco 171kHz Thomson-CSF 2000kW pre-2009 plus 3 masts in line antenna system with a gain of 5.6dB. The 380m tall masts were at one time the tallest structures in Africa.
  • MOI, Duba, Saudi Arabia 1521kHz Continental Electronics – 2000kW (also 2000kW on 594kHz)
  • Egypt, Batra Continental Electronics 2000kW then used as two 1000kW on 621 and 819kHz
  • RTA Bechar 153kHz and Ouargla 198kHz, Algeria 2000kW units by ABB plus a 3 (357m tall at Bechar) masts in line antenna system giving 6.4dBi gain
  • Ajloun, Jordan 801kHz Continental Electronics 2000kW
  • Polskie Radio, Poland 227kHz 2x1000kW Brown Boveri from a 646m tall mast (tallest structure in the world until collapse in 1991)

What is strongest MW station today?

Of the above list, Saudi Arabia still operates several 2MW transmitters. Two are located on the Red Sea coast at Duba and have six mast antenna systems apparently beaming directly towards Cairo. 594kHz is used during the day and 1521kHz at night. The antennas could be generating 9-10dB gain to the NW. That is true superpower! (Listeners have noted the signal isn’t as strong as it used to be, so perhaps the power has been reduced?)

Aerial view of the super-power transmitter at Duba, Saudi Arabia. The upper line of 6 numbered masts are larger because they operate at the lower frequency.

Conclusion

Sadly the era of super-power MW/AM radio stations is mostly over. It’s heyday was the 1960s-1980s. It does mean that many radio listeners will no longer hear foreign voices and different points of view bursting out of their radios. For many listeners hearing exotic signals often 1000km or more away emanating from an exotic or mysterious location was the catalyst to a life-long interest in radio and its possibilities.

However the absence of numerous high power signals does mean that listeners stand a better chance of hearing weaker or more distant signals. That’s the foundation of DXing and our activities here at the Medium Wave Circle.