| Page 2 of 2 | 1 | 2 |
|
|
Honus wrote:
Let's stay on topic, shall we? Back to cuhulin: The pervert's puny pecker porked a pretty pudgy Pekingese. With his habits, that's NOT alliteration. It's alimenterycanalation. I'm starting to think 'hulin means something disgusting in Celtic. Mcmike II |
The Tips can be Elevated above ground or
the Tips can be at/near ground level and a Ground Rod placed at both ends (Tips) with a Lightning Aresster (GDT) mounted on each. .................................................. ....... The higher the ends above ground, the better. You have less earth loss. There is no need to use lightning arresters at the tips of the dipoles to ground. If the wire were actually close enough to ground to arc to ground, it will do it, arrester, or not. Being as you are not protecting any devices at the ends, there is no real point in using arresters. The arrester should be in the feedline leading to the radio. If the inv vee is supported by a tree or mast, the lightning is more likely to take that path to ground, than the path of perpendicular antenna wires to ground. Lightning doesn't like to take sharp turns. So you should always ground the supporting mast well, if it's metal. It's gonna take the brunt of the strike to ground... Horizontal wire antennas are not near as prone to be a lightning target, as say a vertical, or other tall mast. IE: a dipole, or inv vee hung in a tree will add little to the overall likelyhood of that tree being struck. It would probably be struck anyway, antenna or not, if lightning was that close, to choose that target. I bet in most cases, the antenna would basically be untouched, unless the strike found the feedline running down the tree, and decided to use it....You can always snub the feedline to ground at the base of th tree in a case like that. I know I have had two direct strikes to my mast supported my various dipoles, and have never had any indication of wire, or coax damage. That tells me most of the strike is carried to ground by the mast, which does stick up about a foot above my antenna apex. "I currently have 160/80/40 dipoles on one feedline...Appx 440 ft of wire in the air...The apex about 42 ft high supported by a metal mast. So far, in 35 years of hamming, SWLing, I've never had a horizontal wire dipole be a lightning target. But mine are never higher, than surrounding objects, trees, etc unless supported by a mast, or tree, which then becomes a more preferred target than the dipole itself... Not saying it can't happen. It surely can. But not near as often as vertical targets. Even at 42 ft, I've still got trees taller than that in the yard... That helps...The last strike hit the tree in the front yard.... If the vertical target is well above the house, other objects, you can bet on it taking a zap sooner or later. Most people don't have wire antennas higher than the surrounding trees, etc, unless they have a vertical support to support it...When they get above the surroundings, is when their chance of a strike goes up sharply. Even horizontal metal can be a problem if it's really high...IE: beams, etc..MK |
Dr, Artaud,
|
From: "RHF" Organization: http://groups.google.com Newsgroups: rec.radio.shortwave Date: 22 Apr 2005 07:18:06 -0700 Subject: Antenna Suggestions and Lightning Protection Dr, Artaud, . You are interested in installing a 'shallow' Inverted "V" Antenna that would be center over your House; and you want to improve your Lightning Protection at the same time. (Snip) RHF - I don't recall Dr. Artaud's particular circumstance, but here is mine: My radio table faces an inside wall. The widow is across the room. Under the window is a long concrete patio. So I can't have an earth ground nearby. I can put up an antenna as you describe. My question: Is it safe to disconnect the antenna input (center of coax) from the radio and switch it to the household AC ground for lightning protection? Greg |
I told y'all before Greg doesn't know ****.There are such things as
drill bits made for drilling through concrete.(I own several different sizes of them) Drill a hole through the concrete patio and then hammer a six foot long ground rod down into the ground. cuhulin |
Lightning doesn't start at the top and travel down.Lightning starts at
the bottom and travels up. cuhulin |
"Greg" wrote From: "RHF" Organization: http://groups.google.com Newsgroups: rec.radio.shortwave Date: 22 Apr 2005 07:18:06 -0700 Subject: Antenna Suggestions and Lightning Protection Dr, Artaud, . You are interested in installing a 'shallow' Inverted "V" Antenna that would be center over your House; and you want to improve your Lightning Protection at the same time. (Snip) RHF - I don't recall Dr. Artaud's particular circumstance, but here is mine: My radio table faces an inside wall. The widow is across the room. Under the window is a long concrete patio. So I can't have an earth ground nearby. I can put up an antenna as you describe. My question: Is it safe to disconnect the antenna input (center of coax) from the radio and switch it to the household AC ground for lightning protection? Greg Greg, before you entertain such suicidal thoughts again, please browse my website explanation of why your home's electrical wiring and ground system are not meant to handle lightning surges. While Cuhulin entertains us with his every post, his comment is nonetheless correct that a patio ground is possible. So is drilling a hole and sinking a ground rod through your radio room floor. But if renting a Hilti hammer-drill and concrete drill bits isn't your cup of tea, then consider coming through a different wall of the radio room that does have a short path to deep earth ground. The very best plan, no matter what room in your home you want to connect and listen from, would be to route all antenna feedlines to the AC service entrance ground FIRST, (shield grounding the coax at the base of the antennas and at the service entrance, install lightning arrestors on the coax at the same ground rod, then snake them into your radio room any way/direction you have to. It would be safer if your radio room was also right next to the AC service entrance ground, but you will see options on the website to deal with that problem if it's not close. http://members.cox.net/pc-usa/station/ground0.htm Best regards, Jack Painter Virginia Beach, Virginia |
Alternately,if a woman is the manager of the complex you live in,make
love to her every night and she just might let you run a ground wire wherever you want to. cuhulin |
wrote Alternately,if a woman is the manager of the complex you live in,make love to her every night and she just might let you run a ground wire wherever you want to. cuhulin We used to call that "thinking out of the box" ;-) Jack |
Greg,
=2E If you build the Shortwave Listener (SWL) Antenna as described in my post. 1=2E The Shortwave Listener (SWL) Antenna which is a basic [Horizontal] Random Wire Antenna will be 'remote' from your house. 2=2E The Primary Ground for your Shortwave Listener (SWL) Antenna will be 'remote' from your house. 3=2E The Matching Transformer will provide some 'isolation' between the Shortwave Listener (SWL) Antenna and the Coax Cable Feed-in-Line. 4=2E Burying the Coax Cable near the 'remote' Shortwave Listener (SWL) Antenna and Ground Point will 'improve' the Lightning Protection of the system. 5=2E Using a Coax Cable Feed-in-Line with the Outer-Shield Grounded and Buried at the Far-End near the 'remote' Shortwave Listener (SWL) Antenna; will 'improve' the Lightning Protection of the system. 6=2E Using a Commercial Heavy Duty Antenna Switch that 'facilitates' the Connection of the Shortwave Listener (SWL) Antenna to your Radio Equipment when "In-Use" and Disconnecting the Shortwave Listener (SWL) Antenna and Grounding-the Antenna-Out when Not-In-Use. =2E -IF- You do not have a Ground for your Shack's Radio Equipment that is "Bonded" to your House's Electrical System : Then the above 'remote' Shortwave Listener (SWL) Antenna and Grounding Point will provide you some level of Lightning Protection that is "Better-Than" NO Ground at All when you use Using a Commercial Heavy Duty Antenna Switch. =2E WARNING "DO NOT" 'connect' the Center-Wire of the Coax Cable to the House's Electrical System via one of the little Round Holes or one of the little Screws of a common Three-Prong Electrical Box. Caution - This is NOT Good or Smart Lightning Protection for your Radio Equipment; your House; and you and your Family and Loved Ones. =2E HOUSEHOLD GROUNDING "A PROJECT" {In and of Itself} : Building a 'reasonable' Household Safety GROUND for your Shack's Radio Equipment that is "Bonded" to your House's Electrical System is a Project in and of itself. Somewhere between Nothing (No Ground) and a "Certified" Grounding System is a 'reasonable' Household Safety GROUND that meets and satisfies your expectations for your personal level of Electrical Safety comfort and Local Lightning Conditions. =2E =2E iane ~ RHF =2E =2E All are WELCOME and "Invited to Join" the Shortwave Listener (SWL) Antenna eGroup on YAHOO ! http://groups.yahoo.com/group/=ADShortwave-SWL-Antenna/ =2E Some Say: On A Clear Day You Can See Forever. http://groups.yahoo.com/group/=ADSho...message/=AD502 =2E I BELIEVE: On A Clear Night . . . You Can Hear Forever and Beyond, The BEYOND ! With a Shortwave Listener SWL Antenna of your own making. "If You Build It {SWL Antenna} You Will Hear Them !" =2E . . . . |
From: "RHF"
Organization: http://groups.google.com Newsgroups: rec.radio.shortwave Date: 23 Apr 2005 05:18:00 -0700 Subject: Antenna Suggestions and Lightning Protection Greg, . If you build the Shortwave Listener (SWL) Antenna as described in my post. Okay, thanks RHF. You answered my question about grounding to the household elec ground. At first I thought you meant it was okay to ground through the third hole in the outlet. But it's not. So I still have to run a heavy ground wire from the inside wall to the nearest elec ground, which would be 20 to 25 feet, up through the wall and across part of the attic. Greg |
Jack the Painter wrote:
Greg, before you entertain such suicidal thoughts again, please browse my website explanation of why your home's electrical wiring and ground system are not meant to handle lightning surges. (Snip) Well, by "entertaining such ...thoughts" I guess you are referring to my questioning whether it was safe to ground the antenna to electrical ground when not in use. As you, and RHF pointed out, it isn't. Drilling the patio won't help, as I still would have to run the ground wore across the room. Drilling through the floor? Nope. So here's the deal - I can put up the antenna, ground the coax (shield) & "balun" at the far end, run the coax to the AC service ground (& ground shield to it there), install lightning arrestor, then run the coax through the attic, down the wall, and out to my NRD-525. so far, piece of cake. Now, when when thunder storms come, I disconnect the coax from the xcvr and do what with it? Prob. just let it hang, since the coax pretty well grounded already? Thanks Jack, I will check your web site. Greg W. Central Fla. Lightning Capital of the U.S. |
"Greg" wrote Jack the Painter wrote: Greg, before you entertain such suicidal thoughts again, please browse my website explanation of why your home's electrical wiring and ground system are not meant to handle lightning surges. (Snip) Well, by "entertaining such ...thoughts" I guess you are referring to my questioning whether it was safe to ground the antenna to electrical ground when not in use. As you, and RHF pointed out, it isn't. Drilling the patio won't help, as I still would have to run the ground wore across the room. Drilling through the floor? Nope. So here's the deal - I can put up the antenna, ground the coax (shield) & "balun" at the far end, run the coax to the AC service ground (& ground shield to it there), install lightning arrestor, then run the coax through the attic, down the wall, and out to my NRD-525. so far, piece of cake. Now, when when thunder storms come, I disconnect the coax from the xcvr and do what with it? Prob. just let it hang, since the coax pretty well grounded already? Thanks Jack, I will check your web site. Greg W. Central Fla. Lightning Capital of the U.S. Greg, you've got it. And yet you still have that dilemma that faces thousands of hobbyists; what to do with that disconnected coax? Good news! Since yours will now be shield grounded at the antenna base and the AC service entrance ground rod, and a lightning arrestor providing center conductor protection at the AC service ground rod, very little potential exists at the end of that coax, and it should be left connected to your radio at all times. Congratulations. HOWEVER - you should disconnect the radio's AC power supply (from the back of the radio) before a thunderstorm. This is because there is still a high probability that damage from a nearby strike would be imposed on your electrical system. Only installing fairly expensive AC surge protection equipment can protect against this danger, and they are not available at WalMart or Circuit City, etc. I'm not saying you can't use cheap line-protector power strips to power your radios. But do not rely on them to do anything except cause damage if your powerlines take a hit, or a strike comes very close to your home, and imposes major energy on your house wiring itself. My cost to protect from AC surge damage was over $2,000 in labor and materials, and it cannot be done by the homeowner. So unplugging all AC power to sensitive equipment remains an important part of lightning protection, EVEN if you do the very sensible and safe things regarding antenna grounding, shield grounding, lightning arrestors, etc. That part is not very expensive at all, and provides a LOT better sleep when you don't have worry about those feedlines entering your home. About bonding. You are "bonded" to your home's AC power ground system when your radio's three-prong power cord is connected. As long as your radios have no other ground connection, that's fine. But when people bring coax feedlines into their station, there exists the possibility that a nearby strike (to a tree next door for instance) will cause massive ground potential rise around your antenna and radio grounding systems. This can be drawn up into your shack, and exit out the radios through the AC power line (including it's third-prong ground connection). That is serious, and can be avoided only by disconnecting the power cords before a storm. But it can also be mitigated by running good bonding connectors from the OUTSIDE shack-ground rod, around the house to the AC service entrance ground. Then, ground potential rise from a nearby or direct strike will MOSTLY go the low impedance path to your AC ground rod, and the system remains "balanced" with no terrible potential existing between any two points. As long as there is no exit path out the back of the radios (the AC power cord), and your coax shield grounding is done, and arrestors guard the center-conductors of the coax, you will be fine. Best regards, Jack Painter Virginia Beach, Virginia |
If your house/home has any plastic pipeing at all,you can not expect any
grounding at all by grounding to the pipes.And,the water meter(s) are made of Brass,no grounding at all can be made at those water meters. cuhulin |
wrote in message ... www.lightningstorm.com There is another real good Lightning watch website too.I have it in one of my many,many thousands of webtv Save Folders thingys somewhere,or maybe I emailed it to meself.I have to watch Fighter Squadon movie on tb now. cuhulin TB? Is that short for TBN, Turner Broadcasting Network? As in Ted Turner, the guy that was married to Jane Fonda for six years? If so, then shame on you. |
From: "Jack Painter" Organization: Cox Communications Newsgroups: rec.radio.shortwave Date: Sat, 23 Apr 2005 13:13:33 -0400 Subject: Antenna Suggestions and Lightning Protection "Greg" wrote Jack the Painter wrote: Greg, before you entertain such suicidal thoughts again, please browse my website explanation of why your home's electrical wiring and ground system are not meant to handle lightning surges. (Snip) Well, by "entertaining such ...thoughts" I guess you are referring to my questioning whether it was safe to ground the antenna to electrical ground when not in use. As you, and RHF pointed out, it isn't. Drilling the patio won't help, as I still would have to run the ground wore across the room. Drilling through the floor? Nope. So here's the deal - I can put up the antenna, ground the coax (shield) & "balun" at the far end, run the coax to the AC service ground (& ground shield to it there), install lightning arrestor, then run the coax through the attic, down the wall, and out to my NRD-525. so far, piece of cake. Now, when when thunder storms come, I disconnect the coax from the xcvr and do what with it? Prob. just let it hang, since the coax pretty well grounded already? Thanks Jack, I will check your web site. Greg W. Central Fla. Lightning Capital of the U.S. Greg, you've got it. And yet you still have that dilemma that faces thousands of hobbyists; what to do with that disconnected coax? Good news! Since yours will now be shield grounded at the antenna base and the AC service entrance ground rod, and a lightning arrestor providing center conductor protection at the AC service ground rod, very little potential exists at the end of that coax, and it should be left connected to your radio at all times. Congratulations. HOWEVER - you should disconnect the radio's AC power supply (from the back of the radio) before a thunderstorm. This is because there is still a high probability that damage from a nearby strike would be imposed on your electrical system. Only installing fairly expensive AC surge protection equipment can protect against this danger, and they are not available at WalMart or Circuit City, etc. I'm not saying you can't use cheap line-protector power strips to power your radios. But do not rely on them to do anything except cause damage if your powerlines take a hit, or a strike comes very close to your home, and imposes major energy on your house wiring itself. My cost to protect from AC surge damage was over $2,000 in labor and materials, and it cannot be done by the homeowner. So unplugging all AC power to sensitive equipment remains an important part of lightning protection, EVEN if you do the very sensible and safe things regarding antenna grounding, shield grounding, lightning arrestors, etc. That part is not very expensive at all, and provides a LOT better sleep when you don't have worry about those feedlines entering your home. About bonding. You are "bonded" to your home's AC power ground system when your radio's three-prong power cord is connected. As long as your radios have no other ground connection, that's fine. But when people bring coax feedlines into their station, there exists the possibility that a nearby strike (to a tree next door for instance) will cause massive ground potential rise around your antenna and radio grounding systems. This can be drawn up into your shack, and exit out the radios through the AC power line (including it's third-prong ground connection). That is serious, and can be avoided only by disconnecting the power cords before a storm. But it can also be mitigated by running good bonding connectors from the OUTSIDE shack-ground rod, around the house to the AC service entrance ground. Then, ground potential rise from a nearby or direct strike will MOSTLY go the low impedance path to your AC ground rod, and the system remains "balanced" with no terrible potential existing between any two points. As long as there is no exit path out the back of the radios (the AC power cord), and your coax shield grounding is done, and arrestors guard the center-conductors of the coax, you will be fine. Best regards, Jack Painter Virginia Beach, Virginia Okay, good information Jack. I do have surge protectors on all the electronics, but I know that's not the best protection. Our electric utility will install whole-house surge protection at a nominal charge per month. I'd better get that done ASAP. For now I'm using an active antenna in the attic. When I build one outside I will follow your guidelines for sure. Thanks, Greg |
From: "Honus" Organization: Death to Spammers Reply-To: "Honus" Newsgroups: rec.radio.shortwave Date: Sat, 23 Apr 2005 21:21:53 GMT Subject: Antenna Suggestions and Lightning Protection wrote in message ... www.lightningstorm.com There is another real good Lightning watch website too.I have it in one of my many,many thousands of webtv Save Folders thingys somewhere,or maybe I emailed it to meself.I have to watch Fighter Squadon movie on tb now. cuhulin TB? Is that short for TBN, Turner Broadcasting Network? As in Ted Turner, the guy that was married to Jane Fonda for six years? If so, then shame on you. TB - telebision. It's a Mississippi thang. Greg |
|
"Greg" wrote in message ... From: "Honus" Organization: Death to Spammers Reply-To: "Honus" Newsgroups: rec.radio.shortwave Date: Sat, 23 Apr 2005 21:21:53 GMT Subject: Antenna Suggestions and Lightning Protection wrote in message ... www.lightningstorm.com There is another real good Lightning watch website too.I have it in one of my many,many thousands of webtv Save Folders thingys somewhere,or maybe I emailed it to meself.I have to watch Fighter Squadon movie on tb now. cuhulin TB? Is that short for TBN, Turner Broadcasting Network? As in Ted Turner, the guy that was married to Jane Fonda for six years? If so, then shame on you. TB - telebision. It's a Mississippi thang. Seriously? The TB thing, I mean? |
|
"RHF" wrote in news:1113937736.278231.195640
@f14g2000cwb.googlegroups.com: Thnaks for your comments. Please see my response elsewhere in this thread concerning grounding needs. Dr. Artaud Dr Artaud & DX Ace, . The 'classic' Inverted "V" Antenna would usually have a combined Top Apex Angle of 90* to 120* or a Bottom Tip Angle of 30* to 45*. |
"? Dr. Artaud ?" wrote Thanks for the response. We just last night had another thunderstorm, depositing plenty of noise and lightning nearby. Our house is physically lower than the houses on either side, and the end of our yard has a very tall Silver Maple tree, to which my random wire antenna runs from the house. The wire ends about 7 feet from the tree trunk, and is tied to the tree with the rubber strip that is used to hold screens in windows frames. I fear that a strike to the tree will impart more than static to the random wire antenna. Perhaps you, RHF, Jack Painter, or others can comment on how to protect the random wire from transferring a lightning strike to the tree from following the antenna wire. As I sleep by the radio, I don't with to be awakened writhing from a lightning strike. Regards, Dr. Artaud In my opinion, the best lightning arrestor products for up to 1.5 kw transmission systems are made by Industrial Communication Engineers (ICE). Solutions for either open-wire (no coax feed involved) or coaxial feedline arrestors are shown at Array Solutions, the distributor for I.C.E. http://www.arraysolutions.com/Products/ice/3.html ICE also makes very convenient grounding blocks for the custom connections of coax shield grounding. This allows a "manifold" connection of several coax shield grounds to a ground rod and works very well. But Andrews and Harger and others also make those, and Harger is probably the best for grounding materials in general. Local electrical distributors will carry (or order) Harger products. Jack Painter Virginia Beach, Virginia |
From: "Honus" Organization: Death to Spammers Reply-To: "Honus" Newsgroups: rec.radio.shortwave Date: Sun, 24 Apr 2005 03:26:26 GMT Subject: Antenna Suggestions and Lightning Protection "Greg" wrote in message ... From: "Honus" Organization: Death to Spammers Reply-To: "Honus" Newsgroups: rec.radio.shortwave Date: Sat, 23 Apr 2005 21:21:53 GMT Subject: Antenna Suggestions and Lightning Protection wrote in message ... www.lightningstorm.com There is another real good Lightning watch website too.I have it in one of my many,many thousands of webtv Save Folders thingys somewhere,or maybe I emailed it to meself.I have to watch Fighter Squadon movie on tb now. cuhulin TB? Is that short for TBN, Turner Broadcasting Network? As in Ted Turner, the guy that was married to Jane Fonda for six years? If so, then shame on you. TB - telebision. It's a Mississippi thang. Seriously? The TB thing, I mean? Actually, Dennis the Menace used to say "telebision" and I'll be that's where Cuhu picked it up. A friend of mine once worked for a Cuban gentleman whose last name was Vidal. Mr. Vidal spoke with a heavy Cuban accent. My friend overheard Mr. Vidal on the phone with a customer one day. The customer was asking his name and he said "Bidal". The customer must have asked him to spell it. "Bidal", he said, "'B' as in 'BICTOR'"! Greg |
"Greg" wrote in message ... From: "Honus" Seriously? The TB thing, I mean? Actually, Dennis the Menace used to say "telebision" and I'll be that's where Cuhu picked it up. Okay...I suspected it was a local station, or something like that. I should have gone with the most idiotic thing I could have thought of...and I'd have still been wrong, since I can't throttle my brain that far back. A friend of mine once worked for a Cuban gentleman whose last name was Vidal. Mr. Vidal spoke with a heavy Cuban accent. My friend overheard Mr. Vidal on the phone with a customer one day. The customer was asking his name and he said "Bidal". The customer must have asked him to spell it. "Bidal", he said, "'B' as in 'BICTOR'"! Ha! That's good! |
"Simon Mason" wrote in
: In a period of 1 and 1/2 hours, while doing other things on the internet as well, but being limited to a 56K Modem, I was not able to download the entire video. Thanks for the offer, it looked interesting, but you might want to reconsider posting it in another format that is more commensurate with slow modems, or else all the people with 56K modems will die off from lightning strikes, and only the Cable and DSL people would remain in the world. I can see why, here is Simon's other safety videos. "Every month I try and produce a safety related video for my work colleagues. For those with a fast connection and nothing better to do with their time, here is a selection." http://www.simonmason.karoo.net/page463.htm Regards, Dr. Artaud "§ Dr. Artaud §" wrote in message Lightning strikes very often happen on very pretty Summertime days/nights when you least expect lightning to happen.There are very good ways to protect your radio antennas and radios agains't lightning strikes.I don't know much of those ways,perhaps someone who does know will show up and elaborate about such things. cuhulin Or watch my safety video! http://www.swldxer.co.uk/safetyvideo23.mpg |
Dennis the Menance always liked to watch Cowboy Bob,Western movies on
Telebision.Isn't there some sort of a little "air valve" isolator device available somewhere that attatches to antennas and is suppose to be effective for isolating/preventing lightning strikes from frying radios and other kinds of electronic equipment.Seems to me I once saw an advertisement about something like that in a magazine or a catalog years ago. cuhulin |
An old buddy of mine was in the U.S.Navy.He once said there was a guy on
his Ship (USS Ticonderoga, www.dogpile.com USS Ticonderoga) who always pronounced Valve as Balve. cuhulin |
So,whatever became of Lightning Rods for homes and buildings? That is
old technology that still works very good.I think they are still available on the market.They are simple long metal rods that attatch to the roof and a cable or heavy wire that is grounded to a long rod driven into the ground,I think.I think I will look into that for my house. www.dogpile.com Lightning Rods cuhulin |
wrote in message ... So,whatever became of Lightning Rods for homes and buildings? That is old technology that still works very good.I think they are still available on the market.They are simple long metal rods that attatch to the roof and a cable or heavy wire that is grounded to a long rod driven into the ground,I think.I think I will look into that for my house. www.dogpile.com Lightning Rods cuhulin The lightning rod situation has reversed. The purpose of a pointy spike on the roof or tower was to break down and arc at lower voltages, causing a lower potential in the protected cone and encouraging lightning to go somewhere else. These days lightning ATTRACTERS are used. They look like large copper spheres on top of a building which do the opposite of a pointy spike, they breakdown at much much higher voltages (remember the Van Der Graf generators from school). Then when lightning strikes it is conducted directly to a really effective ground system via coaxial cable. Old lightning rods also create a lot of RF noise as the corona discharge increases. http://www.ferret.com.au/articles/ce/0c01fcce.asp Brad. |
"Jack Painter" wrote in
news:A4bbe.17243$Z73.17113@lakeread04: Read carefully before reacting. It gives both opinions concerning sharp and blunt pointed Air Terminals. Confusing, isn't it? Oddly enough, while watching a demonstration with a Van De Graph Static Generator at the local science center, the device was nullified in terms of generating static when a simple metal tack was placed point up on top of it. Also, coronal arching occurs with high voltage systems off any pointed surface, requiring the use of metallic mesh tape to smooth out the junctions. http://www.amasci.com/emotor/vdg.html http://www.infraspection.com/thermography/corona.html Dr. Artaud http://www.nab.org/membership/benefits/Nov00.asp "Presently, there is much debate among lightning protection experts regarding air terminal design. According to researchers, a sharp or pointed air terminal has built in defenses against lightning strikes. The strength of the electric field around the tip of a sharp air terminal is limited by a phenomenon called "point discharge." When the electric field around the air terminal reaches a certain strength, the current from a stepped leader is allowed to flow through the terminal from air to ground, before a lightning strike occurs. Overtime, the sharp point of a conventional air terminal or lightning rod erodes due to atmospheric conditions. This causes a rod to hold its charge and produce streamers, providing a path for a lightning strike. Therefore, a blunt lightning rod is more likely to intercept a lightning strike. While a sharp pointed lightning rod is more likely to prevent a strike. The effectiveness of sharply pointed versus blunt lightning rods is currently being studied." http://www.marinelightning.com/science.htm "In this respect, research reported by Dr. Charles Moore and associates in New Mexico only two years ago finally resolved that blunt lightning rods are actually more effective than the traditional sharp pointed rods." |
If it is stormy weather,my opinion is that it is always best to unplug
expensive electronic equipment anyway.For computers,it is best to have a good battery back up system.Better safe than sorry. cuhulin |
For One and All,
[ Just My Two Cents Worth ] 1=2E The "Classic" [Flat] Dipole Antenna : Starting with the Classic Center-Fed Half Wave Dipole Antenna. It is Rigged (Laid-Out) Flat (180*) with three support points of about equal Height. It is mounted at a Half Wave Length above ground level. It is designed for a specific frequency band and offers a generally bi-directional reception pattern for that frequency band. =2E 2=2E The Inverted "V" Antenna : { Semi-Vertical Dipole } Next we have a Center-Fed Half Wave Dipole Antenna that is NOT Rigged (Laid-Out) Flat (180*) with three support points of about equal Height. ? WHY ? - We do not have the ground space (length) for a Flat Dipole. - We do not have three "Equally" High support points. - - Both of the above. - We want some of the features of a Dipole (balanced and symmetric); but we want a broader frequency range and a more omni-directional reception pattern. Thus the Dipole takes on a Vertical Dimension and is called an Inverted "V" Antenna. Usually this designation applies when the Tips of the Inverted "V" are 15* or more below the Horizontal with the Apex Angle is 150* or less. The 'classic' Image of an Inverted "V" Antenna shows the Tips at 30* with an Apex Angle of 120*. The 'classic' Inverted "V" Antenna with an Apex Angle of 120* takes up 13% less ground space; has a relative 50% Vertical Dimension; and the Horizontal Dimension is reduced to 87%. If the Center Mounting Point is set at a Half Wave Length (1/2 WL) Above-Ground-Level (AGL) then the Tips would be 1/4 WL-AGL. =2E 3=2E The Horizontal "V" Antenna : { Bent "Corner" Horizontal Dipole } Next we have a Center-Fed Half Wave Dipole Antenna that IS Rigged (Laid-Out) Flat (180*) with three support points of about 'equal' Height. But we can not Rig it to run Straight-in-a-Line. ? WHY ? - We do not have the ground space (length) for a Straight-as-a-Line Dipole. - This is a Dipole using the available space. - This is a Dipole using the available structures. Thus the Dipole takes on a Bent Horizontal Dimension and is called a Horizontal "V" Antenna or more properly a "Corner" Dipole Antenna. Usually this designation applies when the Tips of the "V" are at 90* to each other and both are "Equally" High AGL. The Horizontal Apex Angle of this Bent Flat Dipole can be 150*, 120* or 90* and some times less. The 'classic' Image of an "Corner" Dipole Antenna shows the Tips are Perpendicular (90*) to each other; with an Apex Angle of 90*. Erected with one Horizontal Arm of the Dipole running along one property line and the other Horizontal Arm of the Dipole running along an adjacent property line from tree to tree to tree. The reception pattern of this Bent "Corner" Horizontal Dipole is 'focused' in the direction of The-Front of the Apex (Corner) and 'dispersed' Off-the-Back of the Apex. =2E 4=2E The Tilted Dipole Antenna : { One Tip Up and One Tip Down } Here is a Dipole that is Tilted at an Angle with One Tip Up and One Tip Down. It is still a Center-Fed Half Wave Dipole Antenna. It is Rigged (Laid-Out) Tilled {Not Flat] with One End support point Higher then the Center and the other End support point Lower then the Center. ?WHY ? - This is a Dipole using the available structures. - This is a Dipole using the available space. Usually this is because there is One Tall Support Point to Rig One End of the Dipole; and the other End is angled toward ground level. The Center Point of the Dipole can be set at a Half Wave Length AGL; or the Higher End Tip can be set at a Half Wave Length AGL; most often this is an available space/structure Antenna with the Higher End Tip Rigged to the Highest Structure Available an then simply 'angled' down toward the ground or some other lower structure. Tilted Dipoles by-design may have the Apex Angle (Slope) set at 60* or 45*; but most often the "Tilt" is 'whatever' the available space and structures allow. The 'classic' Image of an "Tilted" Dipole Antenna shows One Tip Up and One Tip Down with a Slope of 45* and the Bottom Tip near ground level. The usable frequency of this Tilted Dipole Antenna is claimed to be more broad banded then the classic Flat Dipole; as a result of the Tilted Dipole Antenna's variable distance (WL) from ground level. The reception pattern is claimed to be omni-directional; but the pattern may vary with frequency up and down the bands. NOTE - The this Tilted Dipole Antenna is usually 'morphed' into the more common Terminated Tilted Folded Dipole Antenna (T2FD) for the later's greater broad banded characteristics. =2E =2E iane ~ RHF =2E All are WELCOME and "Invited to Join" the Shortwave Listener (SWL) Antenna eGroup on YAHOO ! http://groups.yahoo.com/group/=ADShortwave-SWL-Antenna/ =2E Some Say: On A Clear Day You Can See Forever. http://groups.yahoo.com/group/=ADSho...message/=AD502 =2E I BELIEVE: On A Clear Night . . . You Can Hear Forever and Beyond, The BEYOND ! With a Shortwave Listener SWL Antenna of your own making. "If You Build It {SWL Antenna} You Will Hear Them !" =2E . . . . |
| All times are GMT +1. The time now is 10:55 PM. |
|
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
RadioBanter.com