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lightning
I would like to know how much am and fm radio waves are made by
lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers Kurt Stocklmeir -- --- Posted from http://lu7abf.org.ar/news --- news://freenews.netfront.net/ - complaints: --- |
lightning
Kurt Stocklmeir wrote:
I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers Kurt Stocklmeir -- --- Posted from http://lu7abf.org.ar/news --- news://freenews.netfront.net/ - complaints: --- Very little FM, but as the EMF generated by lightning ranges from near DC to gamma rays, you likely need to be a bit more specific. There are these for free: https://helda.helsinki.fi/bitstream/...7/electrom.pdf http://www.dtic.mil/dtic/tr/fulltext/u2/a234306.pdf http://www.lightning.ece.ufl.edu/PDF/01396360.pdf There are also papers that cost to get if you are interested. -- Jim Pennino |
lightning
In article ,
Kurt Stocklmeir wrote: I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers I think you'll find that your question doesn't "map well" onto how lightning works. Saying "AM radio waves" or "FM radio waves" implies that there is a carrier wave, which is being either amplitude-modulated or frequency-modulated. Neither of these is the case for lightning strikes. Lightning consists of strong, irregular pulses of current with rapid rise times. Each pulse generates a broadband burst of electromagnetic energy, with energy content distributed widely across a whole range of frequencies. The figure I'm seeing is that a single lightning strike typically releases about 5 billion joules of energy (5 billion watt-seconds). Most of this is released in a very short period of time (under a millisecond). According to http://www.lightningsafety.com/nlsi_info/thunder2.html about 90% of the lighting's energy is released as heat, less than 1% is released as sound, and the rest (call it 10%) is released as light (and, I presume, other frequencies of electromagnetic energy). There's a very strong electromagnetic pulse near the lighting stroke and the earth impact point, due to the high current flow. In the "radio" frequencies per se (e.g. from a few hundred kHz to a few hundred MHz) it's probably a fraction of a percent of the total lightning strike energy... mostly in sharp bursts at the beginning (and perhaps end) of each individual sub-stroke. |
lightning
wrote:
Kurt Stocklmeir wrote: I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers Kurt Stocklmeir -- --- Posted from http://lu7abf.org.ar/news --- news://freenews.netfront.net/ - complaints: --- Very little FM, but as the EMF generated by lightning ranges from near DC to gamma rays, you likely need to be a bit more specific. There are these for free: https://helda.helsinki.fi/bitstream/...7/electrom.pdf http://www.dtic.mil/dtic/tr/fulltext/u2/a234306.pdf http://www.lightning.ece.ufl.edu/PDF/01396360.pdf There are also papers that cost to get if you are interested. I expect that when the OP says AM and FM he means medium wave and VHF broadcast frequencies. The loud impulse noises one hears on a radio during storms tend to confirm that quite a lot of EM energy is put out at all frequencies, as you say. Even FM radios usually fail to reject it completely, but then they may be receiving it in their audio circuits. -- Roger Hayter |
lightning
On 2/20/2015 5:26 PM, Dave Platt wrote:
In article , Kurt Stocklmeir wrote: I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers I think you'll find that your question doesn't "map well" onto how lightning works. Saying "AM radio waves" or "FM radio waves" implies that there is a carrier wave, which is being either amplitude-modulated or frequency-modulated. Neither of these is the case for lightning strikes. Lightning consists of strong, irregular pulses of current with rapid rise times. Each pulse generates a broadband burst of electromagnetic energy, with energy content distributed widely across a whole range of frequencies. The figure I'm seeing is that a single lightning strike typically releases about 5 billion joules of energy (5 billion watt-seconds). Most of this is released in a very short period of time (under a millisecond). According to http://www.lightningsafety.com/nlsi_info/thunder2.html about 90% of the lighting's energy is released as heat, less than 1% is released as sound, and the rest (call it 10%) is released as light (and, I presume, other frequencies of electromagnetic energy). There's a very strong electromagnetic pulse near the lighting stroke and the earth impact point, due to the high current flow. In the "radio" frequencies per se (e.g. from a few hundred kHz to a few hundred MHz) it's probably a fraction of a percent of the total lightning strike energy... mostly in sharp bursts at the beginning (and perhaps end) of each individual sub-stroke. That website is a little bit misleading, probably in the interest of not confusing the non-technical readers. After all, heat is also electromagnetic energy :) But effectively, lightning is a very broad band pulse - running from a few kHz (or lower) well into the high electromagnetic range. Strong strokes are even known to generate gamma rays (and according to recent theories, antimatter). But you're correct - the total amount of energy in the RF range (say 3kHz to 30GHz) is pretty small. As a sidelight - I remember back in the 60's a lightning detector project. Basically it was a pair of hula hoops; slit each hoop and wrap them with several turns of small-gauge wire. These fed a pair of balanced amplifiers which then fed the X and Y axes of a oscilloscope. A vertical antenna fed an unbalanced amplifier which then fed the Z axis of the scope to brighten or darken the trace, depending on the phase (and therefore the direction) of the incoming signal. Properly calibrated, the result would be a line from the center of the scope in the direction of the lightning stroke with the length proportional to the strength (and roughly inversely proportional to the distance) of the bold. It pretty cheap to build (I was a high schools student, after all) but a lot of fun to play with. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
lightning
Dave Platt wrote:
In article , Kurt Stocklmeir wrote: I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers I think you'll find that your question doesn't "map well" onto how lightning works. Saying "AM radio waves" or "FM radio waves" implies that there is a carrier wave, which is being either amplitude-modulated or frequency-modulated. "AM radio waves" and "FM radio waves" are laymen's terms for "waves around 1 MHz" and "waves around 100 MHz" respectively. |
lightning
On 2/20/2015 4:36 PM, Kurt Stocklmeir wrote:
I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning The answer to the question "has anyone tried to find out" is yes, there have been a couple of genuine properly conducted studies (Several in fact) into how much power is present in a lightening bolt.. They did not, far as I know, break it down into AM or FM (RF power is RF power, how you modulate it is up to you) but they have measured it, Many times. now, the implied question: How much power in a lightening bolt? I once, long ago, knew the answer, Since I have read a couple of those studies, or read of them,,, and I have also, long ago, forgotten the answer. -- Home, is where I park it. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com |
lightning
On 2/24/2015 6:07 PM, rickman wrote:
On 2/20/2015 5:19 PM, wrote: Kurt Stocklmeir wrote: I would like to know how much am and fm radio waves are made by lightning has any person tried this - when lightning is around use their radio to find how many watts of am and fm radio waves are made by lighning thank you for any answers Kurt Stocklmeir -- --- Posted from http://lu7abf.org.ar/news --- news://freenews.netfront.net/ - complaints: --- Very little FM, but as the EMF generated by lightning ranges from near DC to gamma rays, you likely need to be a bit more specific. Gamma rays...? Really? I guess I should have read first. They speculate that electrons traveling at near light speeds encounter nuclei and release their energy as gamma ray photons. Very interesting. Seems this was discovered relatively recently (~20 years ago). Even so, the gamma rays are not a direct part of the radiation of the lightning bolt, but rather are a result of the large EM field and are relatively uncommon compared to lightning in general. -- Rick |
lightning
In article , rickman wrote:
Very little FM, but as the EMF generated by lightning ranges from near DC to gamma rays, you likely need to be a bit more specific. Gamma rays...? Really? Yup. First discovered over 20 years ago. http://en.wikipedia.org/wiki/Terrest...amma-ray_flash I've seen more recent reports that suggest that the gamma-ray (and, I think, X-ray) flux near a lighting stroke can be quite strong... possibly enough to pose a health hazard to those nearby. It was suggested that this could be another good reason for commercial airplanes to avoid flying near thunderstorm cells. Although a lightning stroke on an airplane does not generally present a shock hazard to the passengers and crew (the metal body makes a good Faraday cage) there might actually be enough gamma/X-radiation from the stroke to give people onboard a hazardous dose. |
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