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In message , J. Mc Laughlin
writes There is more to the Franklin rods used in England: George III is said to have required the ends to be converted to round from pointed when the Revolution started - a pointed slam at Dr. Franklin. Nevertheless, the houses (once there were two) of parliament were protected by Dr. Franklin's rods. It would have been so easy for the English to have co-opted Dr. Franklin and quite changed the course of history. Instead, he conned the French out of the critical support needed to win our freedom. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: Very interesting! However the American Benjamin Franklin's pointed lightning rods (it was not a British design) was never scientifically challenged until a couple of years ago. Scientists have now shown that blunt-tipped air terminals are attached by lightning with significantly higher frequency than sharp tipped rods are. Pretty amazing that it took over 230 years to "discover" this! So scrap the concept that a sharp edge attracts charges, at least it does not attract lighting, the ultimate charge. http://www.usatoday.com/weather/reso...ghtn-rod-tests .htm http://www.esdjournal.com/articles/f...n/franklin.htm http://www.mikeholt.com/news/archive...tningblunt.htm etc, etc Jack Painter Virginia Beach VA In message , J. Mc Laughlin writes There is more to the Franklin rods used in England: George III is said to have required the ends to be converted to round from pointed when the Revolution started - a pointed slam at Dr. Franklin. Nevertheless, the houses (once there were two) of parliament were protected by Dr. Franklin's rods. It would have been so easy for the English to have co-opted Dr. Franklin and quite changed the course of history. Instead, he conned the French out of the critical support needed to win our freedom. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: 'Protected' is the word. What is not always appreciated is that the primary purpose of lightning rods (usually called 'lightning conductors' in the UK) is to PREVENT a strike by allowing the electrical charge to leak away before sufficient voltage builds up to cause an actual strike. Ian. -- |
Richard Harrison wrote:
Ian White, G3SEK wrote: "---but not a cage." A cage according to my American dictionary is: "A boxlike receptacle or enclosure for confining birds or other animals, made with openwork of wires, bars, etc." Ian sent me to my dictionary of electronics which reads: "Faraday cage-See Faraday Shield" Usage varies from place to place. I don`t know if I`m vindicated or stand corrected. Me neither! The main lesson is that we have to be careful to define what we mean, because there's a strong risk that other people might understand something different. Faraday cages are used at CERN and other large particle accelerators, to keep the sensitive particle detectors isolated from the pulsed megawatts of RF energy that are kicking the particles around the ring. CERN is an international facility, so each country has its own experiments using separate Faraday cages. Several years ago, I needed to call a friend who was working at CERN. Someone picked up the phone, and a voice said "British Cage". "Well," I thought, "that certainly puts us in our place..." -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
"Julia Child" wrote in message ... What's with all the recipe bull**** posts? Who's posting these? Ed Price wrote: SNIP No, I didn't write that. However, "Julia", rest assured that, by posting your question, your address will soon be harvested for use by the Hipcrime bot in the DOS attack. Don't reply, don't post about it, don't help the bot. Ed wb6wsn |
"Gary Schafer" wrote Jack, All three references are of the same article. Note the rebuttals at the end of one of them. I would also find it hard to believe that ANY rods on a 12000 foot mountain were not hit in 7 years! That study would suggest that pointed rods were excellent lightning repellers and would protect things from being struck. Exactly what Franklin first thought. If not excellent repellers then it would be highly suspect of the placement of the pointed rods on the mountain. 73 Gary K4FMX Hi Gary, the study is of course much more detailed than the articles describe, I'll see if I can find you a link or post the abstract here anyway. But no, there is absolutely no such conclusion in that study (or any other accepted work) that any device can prevent lightning from striking a particular point by "draining off" charges. 73, Jack |
"Ian Jackson" wrote 'Protected' is the word. What is not always appreciated is that the primary purpose of lightning rods (usually called 'lightning conductors' in the UK) is to PREVENT a strike by allowing the electrical charge to leak away before sufficient voltage builds up to cause an actual strike. Ian. Hi Ian, while Franklin originally thought this was the case, he and others soon realized that safe handling of a lightning attachment was the function of his Franklin Rods, NOT avoidance of attachment. There has never been any proof that any device can prevent a strike from attaching to a particular point. The controversy surrounding the CTS (Charge Transfer System) and ESE (Early Streamer Emitters) exposes some of the dumbest junk science ever to hit the lightning-rod snake-oil trail. It has been thoroughly discredited as having absolutely zero effectiveness as a preventer and limited usefulness as a standard Franklin Rod when installed as its snake-oil purveyors proscribe. So please never assume that any rod, termination device, voodoo-doll on the roof or anything else can have any affect whatsoever of preventing a strike from attaching at any particular point. Jack Painter Virginia Beach, Virginia |
In message QkAAd.35660$7p.12710@lakeread02, Jack Painter
writes "Ian Jackson" wrote 'Protected' is the word. What is not always appreciated is that the primary purpose of lightning rods (usually called 'lightning conductors' in the UK) is to PREVENT a strike by allowing the electrical charge to leak away before sufficient voltage builds up to cause an actual strike. Ian. Hi Ian, while Franklin originally thought this was the case, he and others soon realized that safe handling of a lightning attachment was the function of his Franklin Rods, NOT avoidance of attachment. There has never been any proof that any device can prevent a strike from attaching to a particular point. The controversy surrounding the CTS (Charge Transfer System) and ESE (Early Streamer Emitters) exposes some of the dumbest junk science ever to hit the lightning-rod snake-oil trail. It has been thoroughly discredited as having absolutely zero effectiveness as a preventer and limited usefulness as a standard Franklin Rod when installed as its snake-oil purveyors proscribe. So please never assume that any rod, termination device, voodoo-doll on the roof or anything else can have any affect whatsoever of preventing a strike from attaching at any particular point. Jack Painter Virginia Beach, Virginia As I said, I WAS scraping the very bottoms of the memory banks (and licking them clean as well)..... Ian. -- |
Wasn't Franklin that lunatic who used to walk around flying kites in the
middle of thunderstorms? And he now gets praised for it! |
"Richard Clark" wrote in message
... On Sat, 11 Dec 2004 14:11:44 -0800, "Ed Price" wrote: You are asking him to allow a potentially dangerous device to be operated just for your convenience and entertainment. Switch roles for just a minute. Why is an AM/FM radio receiver potentially more dangerous than laptop PCs, gameboys, DVD players, and other electronic devices that are used quite routinely on airplanes? |
"Robert Baer" wrote in message
... "Faraday shield" to some degree is a myth. I'd say it's more a case of people tending to think that various metal structures such as cars, airplnes, metal boxes, etc. are close to ideal 'Faraday shields' when, in actuality, they might only be a poor approximation. (It's this line of reasoning that usually flummuxes people when they try to shield a monitor that has a wavvy display from some extneral field with a steel box and find it's not very effective.) I have seen radars inside quonset huts track a *bird* flying a few miles away (thru the metal wall)! Hmm... any idea if the folks inside weren't being exposed to far more radiation that what we'd typically consider safe? :-) ---Joel Kolstad |
"Reg Edwards" wrote Wasn't Franklin that lunatic who used to walk around flying kites in the middle of thunderstorms? And he now gets praised for it! That was an experiment thousands of schoolteachers must dread, or rather that it actually made the schoolbooks and includes artist renderings, in case enterprising young minds wish to recreate this "experiment". Frightening thought how many may have actually tried it, eh? ;-) 73, Jack Va Bch |
My favourite technological American Hero is a name which I cannot remember at present and I seldom have much success with Google. It was in the age of early chemical engineering and the manufacture of sulphuric acid. Sulphuric acid was, in the Victorian age, and still is, the foundation of chemical engineering. From the age of steam the progress of an industrial country could not advance without great quantities of sulphuric acid which was usable in the production of a vast range of other chemicals from fertilisers, explosives, medicines, battery acids, dyes and eventually micro-processor chips. The person concerned was the usual ragged-trousers European who arrived penniless at the shores of America before they took fingerprints. He had some rudimentary chemical engineering experience obtained probably in France or Germany where sulphuric acid was already being manufactured in small quantities. Manufacture was in small vats made with very pure thick lead. Lead is a metal relatively impervious to attack from sulphuric acid. But pure lead was a very expensive metal in those days. It probably still is. To reduce the exorbitant manufacturing costs of sulphuric acid the person had the brilliant idea of using ridiculously cheap timber vats painted with ridiculously cheap coal tar. The whole USA chemical industry immediately boomed, eventually overtaking Germany, and expanded into all fields making the USA what it is at present - far and away the World's greatest and richest industrial nation. All based on dirt-cheap timber and coal tar. What a pity USA presidents still have their brains lined with heavy lead, unable to walk and chew gum at the same time. Praps someone will remind me of the person's name. ---- Reg. |
Why is an AM/FM radio receiver potentially more dangerous than laptop PCs,
gameboys, DVD players, and other electronic devices that are used quite routinely on airplanes? The other devices may have circuits that incidentally radiate a little noise in the aircraft VHF band. A broadcast FM receiver almost certainly has an oscillator running by design, in the band. Where it lands in the aircraft band, is determined by where it's tuned to. |
"Reg Edwards" wrote My favourite technological American Hero is a name which I cannot remember at present and I seldom have much success with Google. It was in the age of early chemical engineering and the manufacture of sulphuric acid. Sulphuric acid was, in the Victorian age, and still is, the foundation of chemical engineering. From the age of steam the progress of an industrial country could not advance without great quantities of sulphuric acid which was usable in the production of a vast range of other chemicals from fertilisers, explosives, medicines, battery acids, dyes and eventually micro-processor chips. The person concerned was the usual ragged-trousers European who arrived penniless at the shores of America before they took fingerprints. He had some rudimentary chemical engineering experience obtained probably in France or Germany where sulphuric acid was already being manufactured in small quantities. Manufacture was in small vats made with very pure thick lead. Lead is a metal relatively impervious to attack from sulphuric acid. But pure lead was a very expensive metal in those days. It probably still is. To reduce the exorbitant manufacturing costs of sulphuric acid the person had the brilliant idea of using ridiculously cheap timber vats painted with ridiculously cheap coal tar. The whole USA chemical industry immediately boomed, eventually overtaking Germany, and expanded into all fields making the USA what it is at present - far and away the World's greatest and richest industrial nation. All based on dirt-cheap timber and coal tar. What a pity USA presidents still have their brains lined with heavy lead, unable to walk and chew gum at the same time. Praps someone will remind me of the person's name. ---- Reg. You might enjoy this site, Reg: http://www.oldandsold.com/articles10...trade-22.shtml Cheers, Jack Va Bch |
Reg, G4FGQ wrote:
"Wasn`t Franklin that lunatic who used to walk around hlying kites in thunderstorms?" Story is that Ben Franklin (see $100 bill for portrait) was looking around his house searching for a metal key to use as an attraction for lightning. (My neighbor says his kids have lost so many tools that his back yard is struck repeatedly in thunderstorms.) Ben thought he had mislaid a new key somewhere. When Ben asked his wife for it she told him to "go fly a kite". So Franklin showed that charge in a cloud was the same in nature as chsrge in a jar (an early capacitor). Best regards, Richard Harrison, KB5WZI |
"Jack Painter" wrote You might enjoy this site, Reg: http://www.oldandsold.com/articles10...trade-22.shtml ================================ Jack, I enjoyed the whole site. Thanks for your introduction. So the production of sulphuric acid began in the USA around the time of the French Revolution and the guillotine. The very first enterprising production engineer, John Harrison, who must have been aware of the most serious, Earth-shaking, consequences of events in Paris, clearly had other more useful, less destructive yet beneficial, things to think about. I just love linking unrelated facts together. But Harrison is not the name of the person on my mind who transformed the USA chemical industry to one based on sulphuric acid, timber planks and coal tar. I am under the impression he was of a later generation. Out of the canal and barge-horse age and into the age of Watt's condensing steam engine. But what's in a name anyway? I sometimes think that the relatively few engineers between 1790 and 1890 performed greater engineering feats than the many who followed them into the present age of electronic and genetic engineering. They devoted the whole of their lives to their work. As for us poor souls, the best we can manage is haggling about imaginary SWR and conjugate matches which were all sorted out 120 years back. But it's all good fun. Cheers, Reg. |
On Thu, 30 Dec 2004 18:41:40 +0000 (UTC), "Reg Edwards"
wrote: based on sulphuric acid, timber planks and coal tar Hi Reggie, I can see why you would have such trouble with Google in this regard. The words tar and sulphuric acid would lead to a jillion pages about creosote production and the words wood and sulphuric acid would lead to a mega-jillion pages about paper production. I spent a lot of time spilling H2SO4 on me while measuring the K and Kappa of paper. Anyway, it seems that lead kiln towers (upwards to 5 stories tall) were used in acid production well into the mid century: http://www.ul.ie/~childsp/CinA/Issue...mClassics.html Some odd facts: In 1746, John Roebuck established the lead chamber process, In 1831, the modern Contact Process was patented by Peregrine Phillips, a British vinegar merchant 73's Richard Clark, KB7QHC |
Reg, G4FGQ wrote:
"My favorite technological American Hero is a name which I cannot remember at present and I seldom have much success with Google." The very successful American producer of sulphuric acid shares a name made famous by an English carpenter who won the prize offered for the first chronometer or orher means accurate enough to determine one`s position at sea. John Harrison was that carpenter. His inspired and determined work is honored at the British National Maritime Museum at Greenwich. The scientific community would not believe that the carpenter clod had succeeded, Besides, the instrument didn`t look like a chronometer. Ir looked more like a pocket watch. So, Harrison was only able to collect his entire prize after an audience with the king who agreed he had won. The hing declared: "By God, you shall have your prize!" Best regards, Richard Harrison, KB5WZI |
Jack Painter wrote:
"Scientists have now shown that blunt-tipped air terminals are attached by lightning significantly higher frequency than sharp rods are." I would have expected that sharp-pointed rods would be struck more often. My CRC "Handbook of Chemistry and Physics" starts its coverage of "Electricity and Magneyism with a page on Spark Gap Voltages. In every case for a given breakdown voltage, the gap must be substantially wider when the electrodes are needle-points than when they are spheres. For example: With a voltage across the electrodes of 5 KV, the gap space between needle-points needed to prevent a spark is 0.42 cm. The gap between 5-cm sphheres is 0.15 cm under the same conditions. Much closer before sparking points obviously means sharp points engourage breakdown of the air between the points, while spherical (blunt) spark-gap electrodes discourage the spark. It`s been said that if the chsrges dont pile op at the pointed end of a conductor, it would not have an equipotential surface as is required by the conductivity ("College Physics" by Franklin Miller, Jr. Best regards, Richard Harrison, KB5WZI |
"Richard Harrison" wrote Jack Painter wrote: "Scientists have now shown that blunt-tipped air terminals are attached by lightning significantly higher frequency than sharp rods are." I would have expected that sharp-pointed rods would be struck more often. Hi Richard, yes, you and Ben Franklin agreed on that. Modeling examples you cited below appear to be incorrect for lightning, similar to how modeling for ocean waves cannot be done in a bathtub, and even a swimming pool does not closely replicate the action of waves in a large body of water. The experiments and the conclusions offered by the blunt-tip lightning rod tests were peer reviewed, are repeatable, and are being further studied. Their conclusions describe behavior that was not expected or explainable by current modeling. However it is easy to rocket-trigger lightning and this is being done on a daily basis, so a few thousand repeatable findings should soon arrive at a more permanent conclusion. Whether or not that is explainable in terms that classroom scientists can model remains to be seen. An awful lot of engineers have accepted the findings already, and specify blunt-tip rods on new construction. The same cannot be said about other questionable and unrepeatable theory such as charge transfer systems and lightning charge dissipators. Their popularity relies soley on the ability of snake-oil salesman conning a confused public. 73, Jack Painter Virginia Beach, Virginia My CRC "Handbook of Chemistry and Physics" starts its coverage of "Electricity and Magneyism with a page on Spark Gap Voltages. In every case for a given breakdown voltage, the gap must be substantially wider when the electrodes are needle-points than when they are spheres. For example: With a voltage across the electrodes of 5 KV, the gap space between needle-points needed to prevent a spark is 0.42 cm. The gap between 5-cm sphheres is 0.15 cm under the same conditions. Much closer before sparking points obviously means sharp points engourage breakdown of the air between the points, while spherical (blunt) spark-gap electrodes discourage the spark. It`s been said that if the chsrges dont pile op at the pointed end of a conductor, it would not have an equipotential surface as is required by the conductivity ("College Physics" by Franklin Miller, Jr. Best regards, Richard Harrison, KB5WZI |
We have to spend so much time during our own time
in education learning the achievements of past heroes, that perhaps when our own time comes, we are intellectually exhausted? Also, "Necessity being the mother of invention" does not feature when you can buy large quantities of hi-tech sophistication at bargain-basement prices. The spirit of enquiry dies. We can do our bit in the world of Ham Radio by encouraging our fellows to dabble in the innards of radios (rather than by visiting the local emporium in order to buy a rice box and then returning to the emporium when the "snap crackle and pop" has gone out of it) "Reg Edwards" wrote in message ... I sometimes think that the relatively few engineers between 1790 and 1890 performed greater engineering feats than the many who followed them into the present age of electronic and genetic engineering. They devoted the whole of their lives to their work. |
"Reg Edwards" wrote in message ... SNIP I sometimes think that the relatively few engineers between 1790 and 1890 performed greater engineering feats than the many who followed them into the present age of electronic and genetic engineering. They devoted the whole of their lives to their work. As for us poor souls, the best we can manage is haggling about imaginary SWR and conjugate matches which were all sorted out 120 years back. But it's all good fun. Cheers, Reg. That was back in the days when fantastic claims were settled with a working model. If you wanted to argue about the efficiency of a venturi, or the strength of a gear tooth profile, you built it and then actually used it. If your drill bit stayed sharp longer, or you pumped more water with less coal, you won your argument. We spend a lot of time now arguing about how well the computer model replicates reality, and whether the math has enough variables accounted for. Working models seem so old fashioned. Ed wb6wsn |
Jack Painter wrote:
"Modeling examples listed below appear to be incorrect for lightning, similar to how modeling for ocean waves cannot be done in a bathtub and even a swimming pool does not closely replicate the action of waves in a large body of water." OK. Here are full-scale examples. My company had radio towers over much of the earth. Standard practice was protection of the beacon atop the tower with a Copperweld ground rod alongside the beacon with its sharp tip pointed at the sky. No protected beacon was ever damaged by lightning. Our company headquarters skyscraper was protected by short air terminals ringing the perophery of the builsing at short regular intervals. No lightning damage yet in half a century. You may say it is squivalent to the fellow who walks into a bar with a strange contrivance suspended around his neck. Asked what the gadgst does, the new arrival says: "it`s an elephant whistle". Reply is: "There`s no elephants around here." New arrival says: "See. It works, doesn`t it?" I can assure that there have been plenty of lightning strikes safely bypassed to ground around the protected people and equipment, just as Ben Franklin and others have predicted. Best regards, Richard Harrison, KB5WZI |
"Richard Harrison" wrote Jack Painter wrote: "Modeling examples listed below appear to be incorrect for lightning, similar to how modeling for ocean waves cannot be done in a bathtub and even a swimming pool does not closely replicate the action of waves in a large body of water." OK. Here are full-scale examples. My company had radio towers over much of the earth. Standard practice was protection of the beacon atop the tower with a Copperweld ground rod alongside the beacon with its sharp tip pointed at the sky. No protected beacon was ever damaged by lightning. Our company headquarters skyscraper was protected by short air terminals ringing the perophery of the builsing at short regular intervals. No lightning damage yet in half a century. You may say it is squivalent to the fellow who walks into a bar with a strange contrivance suspended around his neck. Asked what the gadgst does, the new arrival says: "it`s an elephant whistle". Reply is: "There`s no elephants around here." New arrival says: "See. It works, doesn`t it?" I can assure that there have been plenty of lightning strikes safely bypassed to ground around the protected people and equipment, just as Ben Franklin and others have predicted. Best regards, Richard Harrison, KB5WZI Hi Richard, because it is completely unlike you to so widely miss the point, I question whether I understood your responses correctly. The standard Franklin rods (with pointed tips) have been completely validated in their application of safely terminating lightning strikes. Nothing in the new study repudiates that in any way. It simply finds that a lightning rod of similar length, thickness and composition but with a rounded or blunt-tip, has attached lightning that was coming to it's twenty-odd foot area everytime and missed the nearby Franklin rods everytime. The study clearly restates what engineers all over the world already know, that Franklin rods work just fine. But it ADDS that the blunt-tip rods work better, end of study. Because lightning is impossible to predict, and often it strikes areas of a grounding system and building below the lightning rods (evidence is the Empire State Bldg, which has video showing dozens of strikes bypassing the Franklin rods), then if an improved rod-tip design is validated, then it is validated, simple as that. Your experience describing a pointed tip protecting a radio tower sounds rather simplistic as examples, don't you agree? Nothing could be easier than attaching lightning to the top of a tower for Pete's sake. Where lightning rod placement and design becomes critical, is in areas such as multi-level/shaped building corners, appurtenances, high explosive and flammable liquid storage, etc. Here, the best available science is used to describe how many feet apart, at what elevations, etc the air terminal system must be in order to achieve the desired level of confidence that no lightning attachment will cause damage to structures, materials or personnel. Happy New Year and best wishes, Jack Painter Virginia Beach, Virginia |
"Reg Edwards" wrote in message ... Wasn't Franklin that lunatic who used to walk around flying kites in the middle of thunderstorms? I've done that, repeated his results and am still hear. Not recommended though. |
Ed said -
That was back in the days when fantastic claims were settled with a working model. If you wanted to argue about the efficiency of a venturi, or the strength of a gear tooth profile, you built it and then actually used it. If your drill bit stayed sharp longer, or you pumped more water with less coal, you won your argument. We spend a lot of time now arguing about how well the computer model replicates reality, and whether the math has enough variables accounted for. Working models seem so old fashioned. ======================================= It is a fatal mistake to treat a modelling program, even if you think it has no bugs (errors), as a bible which always tells the gospel truth. ALL programs have limitations. Limitations result from the computer itself, those deliberately introduced by the programmer, those accidentally introduced by the programmer because he didn't understand how the thing being modelled really works, those introduced by the user because he doesn't understand how the program is supposed to work or what the programmer was thinking about when he wrote it. The result is UNRELIABILITY. Ideally, the originator of the thing being modelled and the programmer should be one and the same person. Committies produce drumadaries with 3 or more humps. Or elephants with trunks at both ends. The definition of Reliability is Quality versus Time, and therefore confidence (or lack of it) can be gained only with both use and time. Given time, and use, with large programs, such statistics as mean-time-between-failures can be produced. But when the next error might arise and its magnitude is anybody's guess. One is always caught unawares. More insidiously, one may not be aware that an error HAS occurred. Or most insidiously, one may imagine an error has occurred when it hasn't. Problems will surely persist - if a failure is suspected, is it the program which has failed, is it the computer, is it the modelling, or is it the actual thing being modelled (it may not exist) which is defective? The proof of the pudding lies in the eating. Get off your ass, wrench yourself away from the keyboard, do what you should have done in the first place, erect the thing and use an instrument which purports to measure SWR, hope for the best, don't swear by it, and take care to record the instrument manufacturer's name and its serial number. ;o) To summarise, the reliabilty of a modelling program is always worse than the quality of the blamed programmer. Initially, don't believe anything it produces. And whatever you do, don't become depressed. Even if the program doesn't work the radio will. Most happy-band radio amateurs don't realise how fortunate they are - almost anything works thank goodness. At present I'm on Spanish Red, Berberna, Reserva 2000. I know it's Spanish because, unusually, the entire blurb on the bottle is in that language. But I feel somewhat guilty because at the back of my mind there's the continuing unbelievable horror of the enormous disaster in the countries surrounding the Eastern Indian Ocean. The worst effects may still be to come. ---- Reg, G4FGQ |
Jack Painter wrote:
"Modelimg examples cited below appear to be incorrect for lightning, similar to how modeling for ocean weaves cannot be done in a bathtub,---." As far as I know there is one set of rules which rules electrical phenomena, not rules for weak snd onother set of rules for strong electricity. Lightning is so stromg that it sometimes seems to play by its own rules, but it really does not. Jack`s waves in a bathtub metaphor was particularly ironnic. Franklin`s experiments proved the electricity he was studying was the same stuff on whatever scale. He charged Leyden jars from the clouds then used the stored charge to conduct other experiments with the stored charge as his contempories were doing. Franklin found that hemp twine was a conductor of sorts while silk was an insulator. Irony springs from Jacj`s bathtub metaphor. According to the December 2001 issue of "Modern Maturity": "Alexander Graham Bell - yes, of telephone fame - also invented the hydrofoil, a boat that rides on a duchion of air. He tested models of this invention in his tub." Best regards, Richard Harrison, KB5WZI |
"Dave VanHorn" wrote in message
... The other devices may have circuits that incidentally radiate a little noise in the aircraft VHF band. A broadcast FM receiver almost certainly has an oscillator running by design, in the band. Where it lands in the aircraft band, is determined by where it's tuned to. Ah... you're thinking... FM broadcast range is 88-108MHz... with a 10.7MHz IF... a high side LO is at ~98-118MHz, easily landing within the aircraft band (which is... 108-??? MHz, right?). |
"Airy R. Bean" wrote in message
... We have to spend so much time during our own time in education learning the achievements of past heroes, that perhaps when our own time comes, we are intellectually exhausted? Nah, we're all just becoming specialists. Colleges today have their various 'electrical engineering tracks' where you choose between, e.g., power, communications, digital logic, etc. -- I think that change come about some 20? years ago now. We can do our bit in the world of Ham Radio by encouraging our fellows to dabble in the innards of radios (rather than by visiting the local emporium in order to buy a rice box and then returning to the emporium when the "snap crackle and pop" has gone out of it) Unfortuately it can be difficult to motivate people to study the innards of radio when you have to explain to them that a modern cell phone has perhaps some 100 man years of engineering work in it -- and that any attempt to apply some of this same technology to amateur radio is going to be met by protest as well! ---Joel Kolstad |
"Ed Price" wrote in message
news:gAdBd.6143$yW5.2@fed1read02... We spend a lot of time now arguing about how well the computer model replicates reality, and whether the math has enough variables accounted for. Working models seem so old fashioned. That's because they're so expensive to build. You'd probably never finish designing something like a modern RF IC if all you could do was design it on paper, build it, probe around a little to figure out what it 'really' does, and repeat. Likewise, few companies can afford to design the autopilot for a jet without a great deal of simulation first. :-) |
"Joel Kolstad" wrote in message ... "Dave VanHorn" wrote in message ... The other devices may have circuits that incidentally radiate a little noise in the aircraft VHF band. A broadcast FM receiver almost certainly has an oscillator running by design, in the band. Where it lands in the aircraft band, is determined by where it's tuned to. Ah... you're thinking... FM broadcast range is 88-108MHz... with a 10.7MHz IF... a high side LO is at ~98-118MHz, easily landing within the aircraft band (which is... 108-??? MHz, right?). The original poster is long gone -- refused any info and advice we gave him including a list of airlines that prohibit AM/FM radios and other devices And the FAA stance on the matter Must have been 50+ responses So I guess we can put this to bed -- Caveat Lector |
On Wed, 5 Jan 2005 12:03:37 -0800, "Joel Kolstad"
wrote: "Ed Price" wrote in message news:gAdBd.6143$yW5.2@fed1read02... We spend a lot of time now arguing about how well the computer model replicates reality, and whether the math has enough variables accounted for. Working models seem so old fashioned. That's because they're so expensive to build. You'd probably never finish designing something like a modern RF IC if all you could do was design it on paper, build it, probe around a little to figure out what it 'really' does, and repeat. Likewise, few companies can afford to design the autopilot for a jet without a great deal of simulation first. :-) Hi Guys, Back when I designed the UFDR for the 757/767, they were the first airplanes designed entirely in software (conventional drafting went the way of the Dodo). Today's 7E7 was entirely modeled in software if I'm not mistaken. 73's Richard Clark, KB7QHC |
"Richard Clark" wrote in message ... On Wed, 5 Jan 2005 12:03:37 -0800, "Joel Kolstad" wrote: "Ed Price" wrote in message news:gAdBd.6143$yW5.2@fed1read02... We spend a lot of time now arguing about how well the computer model replicates reality, and whether the math has enough variables accounted for. Working models seem so old fashioned. That's because they're so expensive to build. You'd probably never finish designing something like a modern RF IC if all you could do was design it on paper, build it, probe around a little to figure out what it 'really' does, and repeat. Likewise, few companies can afford to design the autopilot for a jet without a great deal of simulation first. :-) Hi Guys, Back when I designed the UFDR for the 757/767, they were the first airplanes designed entirely in software (conventional drafting went the way of the Dodo). Today's 7E7 was entirely modeled in software if I'm not mistaken. 73's Richard Clark, KB7QHC There's nothing wrong with doing a lot of modeling. OTOH, Boeing didn't go from the computer model directly to production. Computer models don't do very well in predicting the unexpected; things like digital designers discovering the concept of parasitics ("There's nothing in my design that generates 832 MHz!") or mechanical designers exploring the wonders of RF stray coupling paths ("The RF gets from this compartment to that compartment through a BOLT?!" My initial point was that wondrous and amazing things can be proven through software being pushed to the outer edges of its parameters. Before you invest in several years of modeling, someone needs to take a whack at a brassboard model to calibrate the sanity of the software. Ed wb6wsn |
On Thu, 6 Jan 2005 04:21:19 -0800, "Ed Price" wrote:
OTOH, Boeing didn't go from the computer model directly to production. Hi Ed, That is arguably the goal if not the actual reality: "As computers have become faster and more powerful in recent years, we have been able to do a better job in modeling the entire airplane and predicting the three-dimensional effects of the airflow around it," Cogan said. "The codes we have developed allow us to look at more potential design options faster than ever before." Indeed, Cogan said the process for developing airplanes today begins with the computer model. The coding is so accurate that designers can evaluate miniscule changes in a design to determine impacts on aerodynamic efficiency, he added. In fact, the accuracy of the coding has also focused the application of another aerodynamics tool: wind tunnel testing. In the '80s, the Boeing 767 team took more than 50 wing designs into the wind tunnel to verify their designs, Cogan said. In the '90s, the Boeing 777 team took 18 designs into the tunnel. "We were really not verifying the designs as much as we were verifying that our computation tools were accurate and looking at performance at the extreme operating conditions, which the coding couldn't do," Cogan said. "With the 7E7, we will take fewer than 12 wings into the tunnel," Cogan said. "We are still proving our coding and testing the extremes. The tunnel is a great tool but it's not very cost-effective. So, being able to really focus on a few designs to get the data we need is helping us be more cost-effective." 73's from Jet City, Richard Clark, KB7QHC |
Jack Painter wrote:
"An awful lot of engineers have accepted the findings already, and specify blunt-tipped rods on new construction.: They should specify what works. Suppose a charged cloud arrives overhead and no lightning immediately flashes. If the charge is positive, it attracts electrons in the earth ond other conductors nearby. These electrons strain to reach the cloud, runnibg through conducting bodies to get closer to the positive charges overhead. The blanket of air insulates between the charges of opposite polarity. The field grows faster than these charges are neutralized. Sooner or later, the air at a high point starts to ionize (form a conductive plazma). Then, current flow starts with a flash and a bang. Thunder rolls as air rushes in to fill the void left by burnt atmosphere. Suppose that a lightning rod is at a high point beneath the positively charged cloud as it arrives. Electrons are pulled up to its sharp point (electrons repel each other, ao they tend to concentrate on the outside of the rod and find the least outside opposing forces at the tip of the rod. To avoid corona formation, some transmitting antennas are fitted with "corona balls" on their tips. This reduces the strain from a pointed tip. On a lucky day, the cloud is discharged without lightning. On an ublucky day, your lightning rod may get pitted. Best regards, Richard Harrison, KB5WZI |
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Richard Clark, KB7QHC wrote:
"So much of this breathless science of rounded tips alludes to the legitimacy of publications equal in scope to those that announced the proofs of cold fusion." Well, I`ll give the rounded tips one advantage, less likely impalements and resulting lawsuits. But, I don`t know of any such cases on the sharp lightning rods. As for cold fusion, I`ll believe it when I see it. I really hope it happens. The price of fossil fuels and their cleanup is excessive. Best regards, Richard Harrison, KB5WZI |
"Richard Harrison" wrote Jack Painter wrote: "An awful lot of engineers have accepted the findings already, and specify blunt-tipped rods on new construction.: They should specify what works. Suppose a charged cloud arrives overhead and no lightning immediately flashes. If the charge is positive, it attracts electrons in the earth ond other conductors nearby. These electrons strain to reach the cloud, runnibg through conducting bodies to get closer to the positive charges overhead. The blanket of air insulates between the charges of opposite polarity. The field grows faster than these charges are neutralized. Sooner or later, the air at a high point starts to ionize (form a conductive plazma). Then, current flow starts with a flash and a bang. Thunder rolls as air rushes in to fill the void left by burnt atmosphere. Suppose that a lightning rod is at a high point beneath the positively charged cloud as it arrives. Electrons are pulled up to its sharp point (electrons repel each other, ao they tend to concentrate on the outside of the rod and find the least outside opposing forces at the tip of the rod. To avoid corona formation, some transmitting antennas are fitted with "corona balls" on their tips. This reduces the strain from a pointed tip. On a lucky day, the cloud is discharged without lightning. On an ublucky day, your lightning rod may get pitted. Best regards, Richard Harrison, KB5WZI Hi Richard, Your example of lightning was the opposite, and very rare, from the normal occurrence of lightning which is not positive-charged. You can read about the discovery of this rare form of positive-charged lightning at: http://www.ee.nmt.edu/~thomas/nyt/ny...lightning.html As a thunderstorm approaches, preceding its arrival there is a "wave" of positively charged ions that roll over the landscape like a wave. Buildups of these positive charged ions do gather on objects, and there is little favoritism that describes their formation on pointy or rounded objects, they attach to everything. Upward-flowing streamers are emitted from these objects as a negatively charged cloud adds its powerful attraction to these ions. This occurs from human heads, shoulders, lightning rods (of any shape) and your so-called corona balls that offer no protection from positive-ion streamer emission whatsoever. I would suggest that in this area, your recollections of early lightning theory require major updating, since it seems based in part on radio theory that never applied to lightning in the first place, however well intentioned many engineers in that field may have thought it so. Corona balls are examples of the antenna being in the bathtub and not influencing lightning in the least bit. Some things persist because people want them too, whether scientific support for them remains or not. Now, once lightning has broken down and been divided, lessened, etc, then it begins to take on a shape that fits in the bathtub. Be corona-ball happy then if you like. The junk-science of early-streamer-emission (and prevention of sufficient formation of same to attract a stepped-leader) relies on theories that you would find can work in the bathtub but have no relevance at all to lightning, for you see my friend, there are indeed great differences in the way electricity behaves when it has exponential power behind it. It would take thousands of Charge-Transfer-Systems (the ESE models) in a single location to effect a measurable favoritism of attracting or avoiding a single lightning charge. Yet in the bathtub (which is a very accurate example of how water does not behave the same as in the ocean) sized experiments, pointed-tip objects do attract charges. Too bad lightning doesn't actually behave that way, it would fit those classroom models so nicely! A good example of draining a pitifully weak thunderstorm cloud without experiencing an actual strike, is the St Elmo's fire (and lesser but physically noticeable yellow air-coloring and even wet skin hair standing up) that happen on sailboats in a storm. I have experienced the latter several times, and while lightning struck the water close around, did not strike the mast by great luck we could say. It was NOT a grounded sail boat (Morgan, Out Island-41) and the potential from chainplates to waterline would have been explosive had we been struck. There is no model that I am aware of in thirty years of reading about this, that explains why a 65' aluminum (but ungrounded) mast alone on the water in the middle of a thunderstorm is not struck. And the boat was never struck in countless exposure to such storms. I add this just to allude to the fact that while we have learned a lot more about lightning in the last twenty years than we knew in all of history up to that time, much remains a mystery. I still find myself out on the water in thunderstorms, and also operate a communications station without securing during storms, so it is certainly a field that I have a vested interest in learning more about. I probably learned more from your brilliant explanations of lightning protection experience than any fifty other people I have talked with. And although he lives in a area practically void of lightning, I include Richard Clark in this category also because he is so well versed in the annals of common mode, transmission theory, and a very well read liberal indeed. ;-) In case you're wondering, I have indeed added blunt-tipped lightning rods to the roofs of my residence. But I am also quite sure that the safety factor of impalement-avoidance is much more likely than the chances that my roof will ever be struck, with or without lightning rods. As there are now only four of the twelve pines which surround my home that have *not* been struck, somehow the odds seem to be approaching me! Four HF antenna systems are suspended or attached to three of those "virgin" trees ;-) 73, Jack Painter Virginia Beach Virginia |
"Richard Clark" wrote So much of this breathless science of rounded tips alludes to the legitimacy of rare publications equal in scope and stature to those that announced the proofs of cold fusion. Did Pons and Fleishman turn their hands to designing Lightning protection systems to redeem their credentials? Interested in your comments *after* you have read the study. http://lightning-protection-institut...-terminals.pdf 73, Jack Painter Virginia Beach, Virginia |
On Fri, 7 Jan 2005 01:53:00 -0500, "Jack Painter"
wrote: Interested in your comments *after* you have read the study. http://lightning-protection-institut...-terminals.pdf Hi Jack, "It is quite obvious from these plots that the experimentally determined electric field strength is less than the "simple-minded" V/d value." Interesting brush-off so early in the paper begs for real editorial control. As very few would experience lighting sourced from a grid of wire 5M overhead this paper seems an example of the "laboratory factor" it set out to examine and yields a paper confined to laboratory arcana. All fine and well, but what is the point? "There is an urgent need for detailed theoretical modelling which can quantify the space charge effects around air terminals, particularly in relation to upleader development." Which seems at odds with your statement: On Fri, 7 Jan 2005 01:17:07 -0500, "Jack Painter" wrote: The junk-science of early-streamer-emission but I'm not terribly interested. I wasn't particularly intrigued by Pons and Fleishman either, beyond the hubris of their closet drama. It would seem some have a desperate need to topple Franklin from a pedestal of their own building. (Theirs is called the fallacy of "present mindedness.") I'm satisfied that contemporary Europeans held him in high esteem for many noble achievements. Reductionists are measured against their own few of baser metal. Hope you found that interesting, but I doubt it - rather banal stuff. 73's Richard Clark, KB7QHC |
Jack Painter wrote:
"Richard Clark" wrote So much of this breathless science of rounded tips alludes to the legitimacy of rare publications equal in scope and stature to those that announced the proofs of cold fusion. Did Pons and Fleishman turn their hands to designing Lightning protection systems to redeem their credentials? Interested in your comments *after* you have read the study. http://lightning-protection-institut...-terminals.pdf Yes, let's have more technical discussion and less name-calling, please. There seem to be three observations that need to be understood. 1. The electric field gradient near a sharp point is greater than the field gradient near a blunt point. This is basic physics and should be completely beyond dispute. But that is the field gradient IMMEDIATELY LOCAL to the point... and that's not what lightning protection is about. The whole point of lightning protection is to make a strike attach specifically to the installed "terminal' and lightning conductor, and not to any other part of the structure that the installation is aiming to protect. So what we want to know is: when a lightning probe leader (the column of ionized air coming down from the cloud) approaches the structure, how does the lightning protection terminal attract it from a distance of many feet away? How does it say "Hey, come over here"? 2. According to Moore et al (the source of the USA Today story that Jack quoted earlier) a very high field gradient immediately local to tip may actually be counter-productive, because it can produce corona discharge which *reduces* the field gradient at a greater distance; and this may make the probe leader attach somewhere else where there isn't a corona. At least, that's my reading of Moore's papers (following the trail of references from the USA Today page, back to the institute in NM where Moore and colleagues are based). They have a lightning observatory on top of a mountain, but there only seem to be three short guyed masts with a different type of terminal on each. Instruments in a small underground lab collect the data from lightning strikes. Going back through the paper trail, they have been operating this facility for more than 10 years, and occasionally produce a paper to one of the lightning-related journals accompanied by a press release (the latest of which was picked up by USA Today). However, lightning only strikes when it feels like it, so the statistical data only build up very slowly... and if they change the setup on the mountain-top, they'd effectively have to start again. Moore's conjecture that you can make the tip of the terminal *too* sharp is interesting, but his type of "live lightning" experiment doesn't provide any specific backup for what he's saying. It only produces the raw observations that he's trying to explain. Then there is: 3. The paper that Jack quotes above, which reports experiments in a large 'lightning lab'. The experimental setup is big enough to investigate effects over a range of several feet, so controlled lab experiments could bring us a lot closer to the basic physics. Unfortunately these particular experiments don't seem to help. Same as with Moore's work, the experiments are heavily biased towards commercially available lightning terminals which (rather like TV antennas) come in a variety of weird and wonderful shapes. The performance of commercial off-the-shelf terminals may be what the lightning protection industry wants to hear about, but these complex shapes (with their faint odor of snake oil) make it impossible to understand what's happening at a basic level. So it's still wide open for speculation and experiments. Moore's conjecture - that you *don't* want a corona discharge, so the optimum tip radius is the one that produces the highest possible field gradient but *without* inducing corona - looks attractive, but as yet it doesn't have much theoretical or laboratory backup. We have to be missing something here in this discussion. There has to be a whole range of scientific papers, in much more respectable physics journals that are far removed from the lightning industry, that we're not aware of. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
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