Author Topic: WLW's 500,000 Watt Transmitter - Big Iron back in the day  (Read 5073 times)

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Online xrunner

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WLW's 500,000 Watt Transmitter - Big Iron back in the day
« on: July 31, 2013, 07:39:49 pm »


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Online Vgkid

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #1 on: July 31, 2013, 09:53:05 pm »
Thanks for the video, it is amazing what could be acclomplished at that time.
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Online xrunner

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #2 on: August 01, 2013, 12:47:19 am »
... it is amazing what could be acclomplished at that time.

Yea really. With all the high power and outside cooling ponds it's almost like a nuclear power station. They wanted to transmit at 500,000 W, and by gawd, they found a way to do it.
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Offline Corporate666

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #3 on: August 01, 2013, 03:51:58 am »
Awesome video and post - little piece of history there.  Most impressive, especially for the period!
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Offline amyk

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #4 on: August 01, 2013, 07:17:08 am »
And no one was concerned about exposure to the RF... several orders magnitude higher than the output of a GSM tower which the ill-informed seem to be complaining about these days!
 

Offline G7PSK

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #5 on: August 01, 2013, 08:01:45 am »
Now that is real engineering on a heroic scale. It's a pity the government shut them down, it would have been nice to see the next step up in power and the one after that as well. :-DD
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Offline Bloch

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #6 on: August 01, 2013, 08:24:14 am »
Thank you for showing this great video.
 

Offline WV1800es

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #7 on: August 01, 2013, 03:18:56 pm »
O my HEAVENS!!  THANK YOU!  :clap: This is the kind of story that really makes one feel humble.  Too bad that a project like this - or the Saturn V / Apollo Project - couldn't be done for 100x the cash in ten years these days.   |O
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Offline N2IXK

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #8 on: August 06, 2013, 03:41:22 pm »
GREAT video!  Thanks for posting this.

Unlike the Apollo moonshot, though, this technology hasn't exactly been lost.  Broadcast transmitters in the 1/2 megawatt power class are available more or less "off the shelf", and nowadays, they can develop 500 kW using a SINGLE tube in the output stage:

http://www.contelec.com/sw419420drmfeatures.htm
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Offline ptricks

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #9 on: August 09, 2013, 10:15:26 am »
I love to see things like this.
It is like walking inside a radio transmitter . Filter capacitors are in the basement, LOL


From the wikipedia page:
Quote
Many reports have surfaced over the years of the power fluctuations from those who lived near the 500 kilowatt transmitter. Residents would see their lights flicker in time to the modulation peaks of the transmitter. It was widely reported that the signal was so overpowering some people picked up WLW radio on the metal coils of mattress and boxed bedsprings, similar to KDKA-AM in Pittsburgh, Pennsylvania. Arcing often occurred near the transmission site.

I wonder how many of these people thought they were crazy, hearing voices :scared:
« Last Edit: August 09, 2013, 10:25:23 am by ptricks »
 

Offline WV1800es

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #10 on: August 09, 2013, 01:28:17 pm »
Farmers had to be careful too, electric fence wires would arc to the metal posts....
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Offline KJDS

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #11 on: August 09, 2013, 01:54:33 pm »
I did a site RF safety survey a few years ago where there were four 100kW MW transmitters and a lot of others at many other frequencies too. Field strengths outside the exclusion zones which were around 100m from the antennas were well below ICNIRP danger levels. I suspect that they weren't quite so well controlled back then.

Offline ptricks

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #12 on: August 09, 2013, 08:21:22 pm »
... it is amazing what could be acclomplished at that time.

Yea really. With all the high power and outside cooling ponds it's almost like a nuclear power station. They wanted to transmit at 500,000 W, and by gawd, they found a way to do it.

Crosley seems to have been obsessed with power, and the speed he accomplished the increases is impressive:
March 22, 1922 50W
September 1922 500W
 May 1924 1KW
January 1925  5KW
October 4, 1928 50KW
January 1934 500KW

Bad efficiency though 1150KW in for 500KW out.
« Last Edit: August 09, 2013, 08:23:11 pm by ptricks »
 

Offline N2IXK

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Re: WLW's 500,000 Watt Transmitter - Big Iron back in the day
« Reply #13 on: August 12, 2013, 12:41:34 am »
A big contributor to the dismal efficiency were the 862 tubes themselves.  They used pure tungsten filaments, as opposed to later designs, which used thoriated tungsten for a large reduction in heating power requirement due to increased emission at lower temperatures. Each 862 tube needed 33V at 207A just to heat it up. With 20 of the tubes in the transmitter (12 RF amps and 8 modulators), that's nearly 140 kW just to keep the power tubes glowing! None of the filament heating power gets converted into RF output, so it is a total loss as far as overall efficiency.

The 862 filaments were operated from DC to reduce hum coupling into the output signal. Back then, that meant big motor-generator sets to produce the power, with all the inherent losses involved with all that rotating machinery.  The 862 was eventually replaced by the improved type 898, which had a 3 section "hum bucking" filament designed for operation from 3 phase AC, allowing the MG sets to be replaced with simple (and more efficient) transformers.
« Last Edit: August 12, 2013, 02:03:34 pm by N2IXK »
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