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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

#41

Post by zurn »

estomagordo wrote: post #30
Nutmog wrote: post #27

Earlier quoted context omitted.

I think that usage is OK. It's like saying "40W of light". In this case, it tells us there's some RF energy and also that it's RF energy of the "50 kW" type.

I think "40 W of light" is a great example of why this imprecise, or quite frankly, incorrect usage is troublesome. 40 W of old timey lightbulb light is useful if you want to sit close and read a book in the evening, whereas 40 W of a modern LED bulb light is a great thing to have if you want to fend of a pack of marauding undead.

"40 W of light" in physics terms is quite unambiguous, it means 40 W in radiant flux.

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

#42

Post by zurn »

jacquesm wrote: post #32
estomagordo wrote: post #23

19 comments and not even one mentions that Watt, with a capital W, measures power, and not energy? I'm assuming 90% of posters know this, but it still bugs me. A modest proposal: "What 50 kilowatts of RF power sounds like through a jumper cable"

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

What's wrong with it?

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

#43

Post by arjie »

icpmacdo wrote: post #37
jakeogh wrote: post #26

Earlier quoted context omitted.

https://www.youtube.com/watch?v=hgll-XTqcS4 (youtube-dl with mpv fullscreen recommended)

Dumb question is it also creating the piano like sound in that video with the electricity? Very cool to watch.

There's a backing track.

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

#44

Post by Already__Taken »

connorlee wrote: post #7

Amplitude Modulation, or AM, works by modulating the sound on the "peaks and valleys" of the frequency. If you were to look at the waveform of the carrier frequency, you would see it as variance in the "power levels" of the signal, going higher and lower depending on what's being sent. Because of how AM works, you can actually hear what's being transmitted by causing an electrical arc. It's the same concept of hearin…

So could you tune into the singing tesla coils with an AM radio is that the same idea?

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

#45

Post by topspin »

therein wrote: post #14
voltagex_ wrote: post #11

Earlier quoted context omitted.

I don't think I'd want even minor RF burns - nasty nasty stuff.

What makes it worse than just a burn or a burn due to an electrical shock?

Disclaimer: I am not a doctor or burn expert of any sort. I am an extra class ham. An RF burn will penetrate more deeply than a "conventional" burn of similar degree, possibly burning nerve cells, circulatory and other structures that an external burn would not. RF burns typically heal very slowly.

I can't compare RF burns to burns caused by electrical current, except to say that electrical current will follow some path of least resistance while RF energy will heat flesh in a pattern corresponding to the field of the radiator and the impedance of the whatever matter absorbs it, so these types of burns will have different patterns.

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

#46

Post by dnet »

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…

Actually, Solt is not Middle East, but in Central Europe. (I live ~50 km from it.) But yes, it's 2 MW, and at night, it can be heard using conventional receivers as far as Belgium.

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

#47

Post by caf »

URSpider94 wrote: post #12
ronreiter wrote: post #4

Wow, can anyone explain this?

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…

It's definitely not an urban legend - I witnessed this first hand at a high school friend's house, where headphones attached through long extension cables across the room would pick up the nearby AM transmitter.

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

#49

Post by plorg »

URSpider94 wrote: post #12
ronreiter wrote: post #4

Wow, can anyone explain this?

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…

I have a friend who lives as close as one can legally live to a 100kW FM transmitter. He received a pair of very cheap speakers when he built a new computer but was unable to use them because if they were plugged in the radio signal would come right out of the speakers.

It seemed that the signal path into the speakers was through the input wire (rather than, say, the power cable or the wires between the amplifier and the cone). From what I understand from my undergraduate analog signals course I'm suspicious of the signal actually coming from the transmission tower itself, unless the speakers had just the right configuration to act as a simple diode-rectifier envelope receiver (terminology likely to be incorrect), which I would think of as unlikely for an FM signal.

It may be that the signal came from some other path related to the relaying of the signal from the studio (~1 mi away) to the tower, but I don't know enough about the specifics of the radio station's configuration to say more.

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