WLW's 500,000 Watt Transmitter - Big Iron back in the day - Page 1
Forum section: electronics / general

author: Vgkid
author_rank: Super Contributor
timestamp: July 31, 2013, 09:53:05 pm
content: Thanks for the video, it is amazing what could be acclomplished at that time.

author: xrunner
author_rank: Super Contributor
timestamp: August 01, 2013, 12:47:19 am
content: Quote from: Vgkid on July 31, 2013, 09:53:05 pmYea 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.

author: Corporate666
author_rank: Unknown
timestamp: August 01, 2013, 03:51:58 am
content: Awesome video and post - little piece of history there. Most impressive, especially for the period!

author: amyk
author_rank: Super Contributor
timestamp: August 01, 2013, 07:17:08 am
content: 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!

author: G7PSK
author_rank: Super Contributor
timestamp: August 01, 2013, 08:01:45 am
content: 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.Just think the whole output of Niagara falls put out as RF

author: Bloch
author_rank: Unknown
timestamp: August 01, 2013, 08:24:14 am
content: Thank you for showing this great video.

author: WV1800es
author_rank: Contributor
timestamp: August 01, 2013, 03:18:56 pm
content: O my HEAVENS!! THANK YOU!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.

author: N2IXK
author_rank: Frequent Contributor
timestamp: August 06, 2013, 03:41:22 pm
content: 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

author: ptricks
author_rank: Frequent Contributor
timestamp: August 09, 2013, 10:15:26 am
content: I love to see things like this.It is like walking inside a radio transmitter . Filter capacitors are in the basement, LOLFrom the wikipedia page:QuoteI wonder how many of these people thought they were crazy, hearing voices

author: WV1800es
author_rank: Contributor
timestamp: August 09, 2013, 01:28:17 pm
content: Farmers had to be careful too, electric fence wires would arc to the metal posts....

author: KJDS
author_rank: Super Contributor
timestamp: August 09, 2013, 01:54:33 pm
content: 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.

author: ptricks
author_rank: Frequent Contributor
timestamp: August 09, 2013, 08:21:22 pm
content: Quote from: xrunner on August 01, 2013, 12:47:19 amCrosley seems to have been obsessed with power, and the speed he accomplished the increases is impressive:March 22, 1922 50WSeptember 1922 500WMay 1924 1KWJanuary 1925 5KWOctober 4, 1928 50KWJanuary 1934 500KWBad efficiency though 1150KW in for 500KW out.

author: N2IXK
author_rank: Frequent Contributor
timestamp: August 12, 2013, 12:41:34 am
content: 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.