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What 50,000 watts of RF energy sounds like through a jumper cable

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Re: What 50,000 watts of RF energy sounds like through a jumper cable

#101

Post by StavrosK »

50CNT wrote: post #98
StavrosK wrote: post #92

Earlier quoted context omitted.

That doesn't sound very feasible. Microwaves work by standing waves, the magnetron doesn't just cook things when outside the oven.

I thought they worked by dielectric heating? Making polar molecules get all frantic and stuff. There is a safety mechanism to shut off the magnetron when the door is opened, and a screen to make the viewing window opaque to microwave radiation, but those can malfunction. [0][ https://en.wikipedia.org/wiki/Microwave#Effects_on_health ] [1][ https://en.wikipedia.org/wiki/Microwave_burn ]

As far as I know, that's the mechanism by which microwave radiation heats molecules, but the specific design of the oven is to produce standing waves so microwaves can become concentrated. I may be wrong, though.

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#102

Post by phantom784 »

hudibras wrote: post #52
madez wrote: post #48

I can’t watch this video without an account. A click on the video leads me to the login page. Is there a mirror?

I don't have an account and it played fine. No explanation of why tho.

I think it depends on what country you're in. In some countries, they have to block pages if you're not signed in for legal reasons (since they can't legally track you).

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#103

Post by StavrosK »

quarterwave wrote: post #94
laumars wrote: post #58

Earlier quoted context omitted.

Excuse my ignorance, but wouldn't the bird need to be grounded for the power to jump? Or does that only apply to electrical circuits?

This is in fact a profound question. The physics of electricity propagation in a powerline circuit is fundamentally the same as the propagation of FM radio waves, or even the beam from a flashlight. All of these examples involve electromagnetic energy propagating at the speed of light. So why do we need wires for powerlines, but not for propagating radio signals or light beams? The principle is that light (in a vacuu…

> Birds can no doubt sense this corona

So can humans, it's a crackling sound.

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#104

Post by dest »

Piskvorrr wrote: post #71
nielsole wrote: post #63

I was once in a completely empty swimming pool (~25*10 m size) The surface of the pool was completely undisturbed. When I put my head under water I could hear a radio voice. Since I could not rule out the possibility that it was simply audio from nearby speakers that I simply could not hear through the air, I was always wondering whether it would be possible to listen to radio waves in water.

Your first explanation is far more likely: water conducts sound waves far better than air.

IIRC, sound waves are hugely dispersed in water (group/phase velocity change with frequency) so it would be difficult to understand what the speakers say / to enjoy the music, etc...

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#106

Post by sathackr »

zurn wrote: post #42
jacquesm wrote: post #32

Earlier quoted context omitted.

> What 50 kilowatts of RF power sounds like through a jumper cable And you still got it wrong.

What's wrong with it?

I believe it's actually the arc producing the sound, otherwise the cable would make the noise regardless of the presence of the arc.

Whether that's what jacquesm is referring to or not, idk.

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#107

Post by redblacktree »

madez wrote: post #48

I can’t watch this video without an account. A click on the video leads me to the login page. Is there a mirror?

Another poster shared a direct link to the CDN, may help: https://video.xx.fbcdn.net/hvideo-xlt1/v/t42.1790-2/12709279...

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#108

Post by sathackr »

gcb0 wrote: post #59
eknkc wrote: post #53

Earlier quoted context omitted.

Why isn't there a bird / bug / etc cemetary at the base of the tower?

there is. it's very, very noticeable on micro wave towers. the drum like cover on microwave antennas is just a lame regulation to try to save birds. they still die just by passing by. the building were i lived had one that required constant "maintenance" (dead bird cleaning)

I have never seen this, and I work with microwave towers nearly every day.

The 'drum like cover' is called a radome, and it's primary purpose is to reduce the wind loading of the microwave dish. It also serves to protect the usually sensitive feedhorn inside the dish, keep out bird nests, ice, water, etc...

The common cause of bird deaths around radio towers is collision, not RF energy. In Florida it is very common to see osprey nests build on/in/around towers. Microwave dishes are a common location because they provide a large horizontal surface to support the nest. See Wikipedia article 'Towerkill'

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

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#109

Post by michael_h »

paulgerhardt wrote: post #39
URSpider94 wrote: post #12

Earlier quoted context omitted.

The voltage applied to the cable is directly proportional to the audio signal, overlaid on a ~1 MHz carrier. All you need is a mechanism that transforms those voltages into vibrations or pressure waves. Presumably, since it seems to happen only when he's striking an arc, it's related to the local heating of the air in the gap ... But I guess it could be electromagnetically induced vibrations of the cable or the tower…

That was one specific station - the infamous WLW / W8XO - the first and only US station authorized to operate at 500kW of power.[1] To give you an idea of how powerful that is, take a look at their coverage map: http://i.imgur.com/Aigz1Zh.jpg The back story is kind of interesting. It was run by Powel Crosley - a sort of 1930's version of Elon Musk. Advertising revenues from the station were so successful he applied t…

I grew up about 5 miles from that antenna. I can't say I ever heard the radio through the wiring in my house. The Voice of America antenna array down the street though? I could hear it clearly through my stereo speakers when everything was turned off.

It's been dismantled, but I can imagine the number of ghost stories that it spawned. Just sitting in your house, and then you faintly hear a man speaking German...

Re: What 50,000 watts of RF energy sounds like through a jumper cable

#110

Post by sathackr »

jacquesm wrote: post #33
vkou wrote: post #28

Earlier quoted context omitted.

The bird would be fine, due to the way parallel circuits work (Very little power travels through the more resistant one of two parallel circuits.)

The bird would be dead. RF power will happily fry tissue if you get close enough to the radiator.

Yes and no.

How do you think the human standing right next to the tower is not getting fried?

Humans climb live radio towers routinely.

The tissue absorption of RF energy at common AM station frequencies(below 2mhz) is negligible. Maximum absorption happens around the frequencies commonly used by FM stations (about 100mhz)

I have climbed near an live FM antenna. You can feel the heat(well, radiation, converted to heat by your body tissue) from the antenna, it feels like a heat lamp. Your eyes are the most sensitive parts as they have the least ability to dissipate excess heat. The old rule-of-thumb is, if your eyes are watering, you're too close to the antenna. But like most things 'the way they use to do it' -- by that point damage is already being done. Cataracts are one of the first signs of RF induced tissue damage.

It would take many thousands watts, transmitted at frequencies well above common AM frequencies to cause any sort of instant damage. I have never seen a field of dead birds near even major FM stations broadcasting with 50kw+ power.

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