WLW: 700 kHz, 500 kW, 100% modulation, no limiter (2000) | Hacker News Reader

WLW: 700 kHz, 500 kW, 100% modulation, no limiter (2000)

ominous-valve.com

105 pointsnkurz25 comments

I've worked in radio, got to work with the KMOX ('the mighty 'MOX' as many in the Midwest, USA called it) transmitter, and even at a 'measly' 50 kW[1], it was quite a power to behold.

The room where the power fed into the antenna regularly had charred remains of field mice, squirrels, snakes, etc. that ventured too close to the high powered connections.

It's a lot of power, and I can't imagine half a megawatt!

1. http://www.stlmediahistory.com/index.php/Radio/RadioArticles...

UK: Radio 4 still puts out at least 400KW am on 198KHz for the time being, but will be phased out in the next decade or so. There is something slightly magic about pumping that much power into an impedance that is basically the air...

https://en.wikipedia.org/wiki/Droitwich_Transmitting_Station

http://www.bbceng.info/Operations/transmitter_ops/Reminiscen...

Edit: typically I can't find a definitive figure for the power output...

Deutschlandfunk also used to operate two 500kW (250kW at night) transmission sites until the end of 2014. They were shutdown as a cost-saving measure (one of the two sites was even upgraded to more modern transmitters just ~5 years before the end).

https://en.wikipedia.org/wiki/Sender_Donebach https://en.wikipedia.org/wiki/Aholming_transmitter

The links at the bottom of the article are also excellent.

At the 2013 Dayton Hamvention, there was a tour of the facility shown here: https://www.youtube.com/watch?v=CbHjcwIoTiY. Apparently, the engineer who first designed the transmitter was barely 21.

I drove under the WLW antenna for the first time recently. It's a megastructure for where it sits. https://en.wikipedia.org/wiki/WLW#.22The_Nation.27s_Station....

I picked up (what may have been) a 1 MW Algerian Longwave station yesterday on 150 KHz. My QTH is Kansas. LW propagation was very good yesterday.

This?

https://en.wikipedia.org/wiki/Kenadsa_longwave_transmitter

Yes, probably. Female voice in English and French. It was at 150 kHz though, not 153. Gone today. Propagation and noise were very good yesterday. I was also seeing aviation NDB beacons on top of one another.

What rx are you using?

Flex 6500 and active loop: https://www.qrz.com/db/KD4HSO/?mlab=

The article briefly mentions VOA Bethany Station. That site was impressive to say the least. The tops of the antennas would peek over the hills as you traveled north on I75 from the Cincinnati suburbs, coming into full view as you passed Tylersville Rd. It was sad to see such a historic site disappear, and of course now it's a complex of chain stores and restaurants like every other recently developed chunk of land in the Midwest.

Why did the FCC allow for a 500kW transmitter? What did powell have to do to get it?

Reading the Wikipedia article, it sure sounds like it was worth trying out once as an experiment. At the very least, it established that 50kW was a good maximum.

Globally 500 kW transmitters aren't actually that special, Europe has a lot of transmitters even more powerful, some transmitting at up to 2000 kW: https://en.wikipedia.org/wiki/List_of_European_medium_wave_t...

I'm honestly wondering why 50 kW is considered a good maximum in one part of the world while others have way more powerful stations...

My guess would be public vs private. A lot, if not all, of the stations on that list seem to be government owned but in the USA they are corporate owned. 2000kW is fine if you own all the airwaves and don't have a company in the next city over complaining that you are crowding out their airwaves (of course they might have had other countries complaining...)

I suspect you're right, and WLW did have to modify its antenna setup due to issues with Canada.

That's a story from the early history of radio. There were various proposals for how radio would grow. RCA wanted to have three high power stations to blanket the whole US. But a monopoly on radio didn't go over politically. Hence the 50KW power limit.

The power increase from 50 kW to 500 kW is only 10 dB, which isn't really a lot considering you get the same increase going from 5 kW to 50 kW, or from 500 watts to 5 kW. You can see that there's a dramatic point of diminishing returns for any given class of radio service.

International SW stations are just that -- international -- so they're more likely to be able to justify the additional power.

Sad to see these stations going off the air. Yes, you can stream all this now over IP, but there is still something fascinating about tuning across the spectrum at night time and receiving transmissions from distant lands.

For those who are curious, this is what the current WLW radio tower looks like in Mason, OH (http://www.johninarizona.com/wlw/wlw-700-cincinnati-oh-tower...). It's hard to get a sense of how big it is in the picture but this thing is MASSIVE

That is a fun read. I love AM radio for this kind of history attached, and because I was a HAM as a kid. Spent many fun late nights in front of various glowing tubes, listening and transmitting on a variety of antennas, all made from what one could find around the rural setting I lived in.

Love this: "for when it blew up, which everyone knew it would..."

This article is great. But I realised it gets so much better if you read it in the voice of 60s tech advertisement.

Similar to Hugh Stegman (operator of Ominous Valve) is Tom Jennings: http://sensitiveresearch.com/

tesla model S has over 500kW peak power

Sure, but the Model S isn't radiating most of that power into the air around you :)

It's pretty amazing to think that there are electromagnetic fields with hundreds of kilowatts of power shooting out around those antennas.

You wouldn't want to stand too close

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