Retrotechtacular: A Tour Of WLW, A 500,000 Watt Radio Transmitter


This is an overview of a 500,000 Watt radio transmitter site. It’s one of the slides shared in a guided video tour of the transmitter’s hardware. The radio station — whose call sign was WLW — called itself the Nation’s Station because of its ability to reach so much of the country.

It operated at the 500 kW level starting back in the 1930’s. The technology at the time meant that there were a lot of challenges involved with transmitting at this level of power. It took 750 kW input to achieve the 500 kW output. To reach that the station had a set of AC motors in the basement generating the 4500 Amps at 33 Volts DC needed to power the transmitter to heat each filament. Obviously there was a lot of heat generated at the same time. The system was water-cooled. An elaborate network of Pyrex pipes carried distilled water to and from the tubes to handle the heat dissipation.

The video tour lasts about thirty minutes. It’s just packed with interesting tidbits from the experts leading the tour so add it to your watch list for some geeky entertainment over the weekend.

[Thanks Jesse]

61 thoughts on “Retrotechtacular: A Tour Of WLW, A 500,000 Watt Radio Transmitter

      1. I BET it isn’t. I bet it’s link spam. I’m not gonna go follow it tho, but long-distance carriers, that smells like a can o’ spam to me. Those crafty spammers and their psy-ops training!

    1. Assuming it’s actually 500kW, not 500MW, that still means they need 1000 Horsepower worth of motor/generator output, which is not to shabby. Most of the big radio stations I’ve heard have been 50kW AM stations, which is enough to hear them from at least the Appalachians to the Rockies, so you can drive halfway across the country without having to retune your radio away from that station in Wheeling or Fort Wayne. (It’s not my favorite kind of programming, but country music with occasional news breaks seems to be just about right for all-day long-distance driving.)

      1. OMG I just wanted to post a comment about how strange it is that the unit Watt is used in the US. I mean it is a metric unit and was wondering why it is used in the US there must be a non metric Unit around.
        You just made my day with your Watt Horesepower conversion.

        1. The Watt isn’t originally a SI unit. It wasn’t offically adopted into the SI until 1960.

          Before that, you would have to speak in units like coulomb-volts per second to remain strictly within the SI, although most people just said “fuck it”.

        2. 1 horsepower = 750W thereabouts, I thought everyone knew that. They measure the same thing. There is the story that James Watt deliberately found the crappiest and most worn-out horse he could to calibrate against, so his engines would sound more impressive. Not sure it’s true.

          1. Just for the record, Kermill, the “retards” are the folks who can’t be arsed to do simple math to put answers in their preferred units. –Tain’t that hard, Dood, a kg weighs 2.2 pounds, a pint of water weighs a pound, two pints in a quart, a liter is a tick over a quart, a liter of water weighs…? (And there’s all your weight and volume conversions, ready to be unpacked.) 4″ is 10 cm, 1″ is 2.54 cm and a meter is a yard and a tenth. None of that is totally right but it’s all close enough. Get over it.

      2. Yes, but WLW had a million watts for a short time (test). At 500KW, the signal could penetrate mountain ranges. Remember that the later Mexican stations (e.g. XERB) boasted a million watts or MORE. But this was in the 1950s and 60s. Still the same problems remained. High power is high power!
        Read about WLWs problems building a main radiating tower that could handle a million watts. This will blow your mind.

    2. But not an uncommon error. You write 500.000, think something like “that’s a lot of kilowatts” and write kW. Unfortunately I made a similar mistake at one of the first tests at the university. Proofreading did NOT help as I made the mistake already when writing down the statements from the paper with the questions to the paper where I did the calculations. The result seemed way too high (by 1000, tons of storage batteries), but I thought OK, for 1000s of kWh this makes sense. :-(

    3. Indeed. I love that they had to use DC heater power, as even modest AC ripple was enough to modulate the valve, plus with feedback, it could have spiraled out of control! My only regret in life is that I could not have been an X-mitter engineer at WLW back in the mid 1930s. GLORIOUS!
      Does anyone know about the aerial tuning coils that 600 KW Radio Aspidistra x-mitter employed? What material could possibly have been used as a form to hold the main copper coils in place? It does not look like ceramic or even Bakelite. Moreover, there are odd little barrels placed throughout the tuning coils -roller inductors for fine tuning? I sure would not want to have to tune that signal while the current was flowing through the transmission line!
      What FINE engineers and brilliant pioneers.

    1. One of the few remaining Blau-Knox diamond cantilever towers left in the world. It’s still there. We have one in Nashville as well. WSM’s tower is celebrating its 80th anniversary this year, I believe…one of my favorite Nashvegas icons.

  1. generating the 4500 Amps at 33 Volts DC needed to power the transmitter.
    Please correct, it hurts:
    1. It would give you around 150kW and thats way too less, as stated in the article (750kW)
    2. These 150kW are needed for filament..
    But very interesting video!

      1. You think you’d be able to see power like that flowing through the tube? Even a few spare air molecules in there must light up like xmas trees under that much electron bombardment. Haven’t seen the vid yet so I’ll guess they were enclosed in metal and thus unseeable.

  2. While you’re at it trace the history of RF up to the first radio stations, pretty interesting stuff like most science subjects and history.

    The physics stuff is pretty boring, but the influence it had on electrical engineering and manufacturing are interesting, also on culture and social science.

  3. Hi
    WLW is still on the air and transmiitting there. They just don’t run at 500Kw. The antenna is a huge trusswork driven element sitting on a massive ceramic insulator. Crosley designed and built the transmitters and sold them also the federal government. They built the Voice of America radio stations 1/4 mile away. VOA ran the old Crosley transmitters until the 90’s at powers up to 250Kw if I remember correctly. They had water cooled tubular copper transmission lines. A fluorescent tube put within a few feet of the transmission lines would light right up and then it would stay lit as you handed it around the room. No wires needed.

    1. Actually there were two 500 KW transmitters the second was to go to WJZ in MD but never got authority. It was sold to the Brits and used at 650 KW as a ‘dis-information’ station against the Axis during WW!!. the transmitters were build by Westinghouse and GE under a management contract by RCA (they were RCA badged). As a point of fact it was an amplifier; a Western Electric 7C 50KW was used as the driver (one hell of an IPA). The VOA transmitters, just down the road, were build by Collins Radio. The VOA site is open occasionally for tour, The WLW site is operational at 50 KW with a Harris transmitter and has been opened for an invitation only tour around the time of the Dayton Hamvention in May. WLW= Whole Lota Watts; amen to that! Ted WA8ULG

  4. Proof positive that there’s no one on this site that’s over 50. There were a number of “Nation Stations”. I have a radio that tunes to them like a push-button car radio.

  5. There is a radio station in my home city – Gliwice (formerly Gleiwitz), built in 1934-35 is entirely made of larch wood and brass connections, 118 m (387 ft) high (including the 8 m (26 ft) long spire on its top.It is known as “Silesian Eiffel Tower”
    This radio station is the place where World War II started ( The Gleiwitz incident – on 31 August 1939, the German SS staged a ‘Polish’ attack on Gleiwitz radio station, which was later used as justification for the Invasion of Poland)


    1. The Aspidistra referred to above is the sister transmitter mentioned in my earlier post, If you are a ham the chief engineer on that UK project was Ray Varney as in G5RV, The WLW 500 has been OFF since 1940..Ted WA8ULG

  6. I just picked up a old Hallicrafters S-76 which came with a 3rd edition print of a 1974 book, “The Complete Shortwave Listener’s Handbook.” Just two days ago, I read a blurb which stuck in my mind because I’ve driven past this station and was just speechless at the size of that tower and was just blown away by what they once cranked through it.

    The excerpt from the book follows.

    “\My greatest DX achievement on the old set occurred a number of years ago when WLW, Cincinnati, Ohio, operated with the super power of 500,000 watts on a test basis after midnight with the experimental callsign of W8X0, on 700 kHz.” -[Hank Bennett]

    Thanks for this article.

  7. Most folks smoked tobacco, the coal fired generators made the electricity and America was in the absolute forefront of the world. The vacuum tube and AM ruled, and rock and roll was about to be born. Oldsmobile the top brand after Chevrolet. We were so grand. I remember it all so well.

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