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half-wave dipole in the forest
i live in a neighborhood where the sight of a half-wave dipole would
cause a riot. however, a portion of my property is heavily wooded. i could easily hide even a 160m half-wave among the branches and leaves, leaving it invisible. is this practical? risky? caveat: i'm still studying for my technician's license so go easy on me :-). /mark |
I live in the forest, and use a couple of resonant dipoles hiding in the
trees. I have no problems at all. Once, during our ice storm, one of them came down when a tree broke off and fell. SWR is fine, and get good signal reports. Go for it. -- Mike-K5VSE Formerly WB6VSE, Senior Tech, Amateur Division, SBE/Linear Systems Watsonville, CA All out going Email, scanned with Norton Anti-Virus 2004 "Radios That Glow in the Dark" "3922 khz". |
K5VSE wrote:
I live in the forest, and use a couple of resonant dipoles hiding in the trees. I have no problems at all. Once, during our ice storm, one of them came down when a tree broke off and fell. SWR is fine, and get good signal reports. Go for it. Only caviet-- You need at least a general for 30 MHz, or below, but the absorbsion of rf at those freqs is minimal, tho the HEIGHT, at lower freqs for a good pattern (for long distance) might be a problem. But , say on 80-40 even at around 20 foot elevation, can work reliably several hundred miles! 20 and up meters shouldn't present much of a problem, and at 6 and 2 meters yagi be best bet, but relatively small size. Have fun- Jim NN7K |
"Mark T. Kennedy" wrote in message ... i live in a neighborhood where the sight of a half-wave dipole would cause a riot. however, a portion of my property is heavily wooded. i could easily hide even a 160m half-wave among the branches and leaves, leaving it invisible. is this practical? risky? caveat: i'm still studying for my technician's license so go easy on me :-). /mark I have several wire antennas strung between trees, and found that even #14 or #16 wire with black or blue insulation at 50 feet is invisible against the trees, and almost invisible when viewed against the sky. What sticks out is the feedline, if it is hanging in the clear. You want that coming down next to a tree. You really don't want contact between the wire and branches. However, my 75m antenna goes through branches at one point, and it seems to be OK. Stay away from white, yellow, or red insulation. Tam/WB2TT |
K5VSE wrote:
I live in the forest, and use a couple of resonant dipoles hiding in the trees. I have no problems at all. Once, during our ice storm, one of them came down when a tree broke off and fell. Please allow me to apologize in advance, but I can't resist asking: "If a dipole falls in a forest and there's no one there to hear it, does it make a sound?" 73, John NU3E :-) |
Bill Turner wrote:
The voltage at the ends of a half wave dipole can reach thousands of volts even with relatively low power. Trees have been set on fire with as low as 100 watts. Be careful! A rule-of-thumb that I use is: For a resonant half-wave dipole, the voltage at the ends is *about* 20 times the feedpoint voltage, nothing to be sneezed at. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
That depends upon whether it is a pole (tree) that is dying.
"John DeGood" wrote in message ... K5VSE wrote: I live in the forest, and use a couple of resonant dipoles hiding in the trees. I have no problems at all. Once, during our ice storm, one of them came down when a tree broke off and fell. Please allow me to apologize in advance, but I can't resist asking: "If a dipole falls in a forest and there's no one there to hear it, does it make a sound?" 73, John NU3E :-) |
I have 160m Inverted Vee in the trees, works fine. Just make sure that the ends
(last third) are in the clear. They have high voltage and prone to ignite fires when situation favorable. Use insulated wire. Yuri, K3BU.us |
"If a dipole falls in a forest and there's no one there to hear it,
does it make a sound?" =============================== Yes. All falling trees make a sound. But if there's nobody to hear it who cares? But this business about 100 watt transmitters causing forest fires is exaggerated. Even if there's a conjugal impedance match between a dead leaf and the transmitter there's little to worry about even when its not raining. And the density of foliage is hardly likely to allow flames, should they occur, to leap from one leaf to another. The climate and type of tree involved is, of course, of some consequence. Deciduous trees and those found in South American and Indianesian jungles can be disregarded from this discussion, If you should live in Australia, the home of Eucaliptus trees, during the dry season, and it's always dry, there is a one in 100 million chance of a tree catching fire by radio. Always supposing by some remote chance it hasn't first been struck by lightning. Eucaliptus trees positively enjoy fire. They depend on it to propagate efficiently. This may be an unfortunate trait insofar as kangaroos and wallabies are concerned but alligators are quite happy with the way things have been arranged. The Aussies themselves take care not to build their houses too near to eucaliptus plantations. The Abbo's, with their 50,000 years of experience, radio or not, are quite happy and sensible enough to leave things as they are. The USA has wide variations in climate and tree population. Thoughtful citizens ought to concentrate their minds on hurricanes, twisters, atmospheric pollution and gun laws. 100-watt transmitters and G5RV's can look after themselves. ;o) --- Reg. |
"Reg Edwards" wrote The USA has wide variations in climate and tree population. Thoughtful citizens ought to concentrate their minds on hurricanes, twisters, atmospheric pollution and gun laws. 100-watt transmitters and G5RV's can look after themselves. ;o) --- Reg. I assure you we are concentrating very carfefully, Reg! Last week we had about 20,000 gun laws on the books, counting all federal and state laws. This weekend we have one less federal gun law, and soon there may be less. When free people use their minds instead of letting foolish emotions be their guide, the concept of restricting firearms from law abiding citizens is one of the first things to go. Btw, so far my dipole hasn't set the pine trees on fire, or been torn down by a hurricane, despite three attempts by them so far this year ;-) 73, Jack |
On Sun, 19 Sep 2004 15:01:15 -0400, "Jack Painter"
wrote: When free people use their minds instead of letting foolish emotions be their guide, the concept of restricting firearms from law abiding citizens is one of the first things to go. Hi Jack, The D.C. sniper (a known non-law abider) got his firearm from non-law abiding citizens out the back door of a local gun-shop here. Foolish emotions had nothing to do with their inability to account for several hundred missing guns they just shrugged off as bookkeeping discrepancies. Clearly they had more guns than necessary to stay profitable. Imagine how long your supermarket would stay in business at that kind of employee pilfering rate. Now, if we bring the foolish emotion issue into it, then Mr. John Allen Muhammad, clearly an emotional person, could now simply walk up to the counter and get more bang for his buck. And if denied, I suppose he would have had to pay more at the back door. James D. Martin, James Buchanan, Kumar Walekar, Sarah Ramos, Lori Ann Lewis-Rivera, Pascal Charlot, Woman shot, wounded, 13-year-old boy wounded, Dean Harold Myers, Kenneth H. Bridges, Linda Franklin, 37-year-old man shot, Conrad Johnson, killed or wounded between October 2 and October 22. Another foolish, emotional personality that appeared before committees to argue that we retain the prohibition against assault rifles was Reagan's Press Officer James Brady. One may say he is emotional simply because he survived being shot (the alternative is being un-emotionally dead). Well, let's just mark it up to the dispassionate tenor of the Republican Guard who have over the years jettisoned Reagan's mandates as easily as they shrugged off the prohibition against assault weapons. The Republican Guard has even offered laws to reduce the liability of the local gun shop and emotional others like them that whine they are too hard pressed by rational laws to balance their books or lock their back doors. The example of the Russian school debacle where the collapse of rational law has seen plenty of assault weapons were available makes the Columbine massacre seem like a Saturday afternoon picnic. "In countries like the Untied States, it's perfectly legal for members of the public to own certain types of firearms. If you live in such a country obtain an assault rifle legally, preferably an AK-47 or variations" -- Al Qaeda training manual the Ossama seal of approval to our nation's administration 73's Richard Clark, KB7QHC |
Richard Clark wrote:
The D.C. sniper (a known non-law abider) got his firearm from non-law abiding citizens out the back door of a local gun-shop here. Exactly! If one advocates disarming *law-abiding citizens*, one is siding with the *non-law abiders*. Advocating disarming non-law abiders by creating laws that are only obeyed by law- abiding citizens is ridiculous. We might as well create a law making it illegal for hurricanes to hit Florida. Hitler, Mao, and Stalin all supported strict gun control laws. If one likes gun control laws, some of the most severe will be found in Castro's Cuba at the present time. So Richard, if you don't like the second amendment and want to feel really safe, simply move to Cuba. :-) -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Sun, 19 Sep 2004 16:05:07 -0500, Cecil Moore
wrote: Hitler, Mao, and Stalin all supported strict gun control laws. Bush, Arrafat, the Columbian Drug Lords and Ossama do not. |
"Richard Clark" wrote "Jack Painter" wrote: When free people use their minds instead of letting foolish emotions be their guide, the concept of restricting firearms from law abiding citizens is one of the first things to go. Hi Jack, The D.C. sniper (a known non-law abider) got his firearm from non-law abiding citizens out the back door of a local gun-shop here. Foolish emotions had nothing to do with their inability to account for several hundred missing guns they just shrugged off as bookkeeping discrepancies. Clearly they had more guns than necessary to stay profitable. Imagine how long your supermarket would stay in business at that kind of employee pilfering rate. Hi Richard, what's your point here, that more gun laws would deter crime against gun stores? Not! Stolen guns don't react to laws making them illegal in the first place, and neither do criminals who can smuggle tens of millions of pounds of contraband and aliens int the country every year have any problem, now or ever, obtaining firearms. Same of course goes for the Ur-a-Peon's who have successfully disarmed their sniveling subjects as the rate of violent crimes against them skyrockets. More police-state control, such as you called "rational law" must be required for them, since disarming the law abiders did not stop the crime waves. Now, if we bring the foolish emotion issue into it, then Mr. John Allen Muhammad, clearly an emotional person, could now simply walk up to the counter and get more bang for his buck. And if denied, I suppose he would have had to pay more at the back door. You don't know anyone or any store that makes such illegal sales in your city, and neither does the BATF, who harass gun store owners about their bookeeping more than the NRC watches hopsitals to keep track of their dangerous radioactive materials. /snip Another foolish, emotional personality that appeared before committees to argue that we retain the prohibition against assault rifles was Reagan's Press Officer James Brady. One may say he is emotional simply because he survived being shot (the alternative is being un-emotionally dead). There is more emotion than you will hopefully ever know, than if the life of a loved one was taken because they were too timid, (too emotionally irrational) or too restricted in the ability to protect themselves from a common or uncommon criminal, who uses firearms as a tool of their trade, irrespective of any gun law ever enacted now or in the future. Don't confuse free speech of Jim Brady with our right to prevent getting shot in the head ourselves. All the cops and secret service carrying automatic weapons and trained to spot and actually prevent such attack from succeeding failed. How in God's name do you think anyone could be protected? Maybe your Ted Kennedy who's armed bodyguards surround the scotch-reeking murderer 24-7 as he lobbys for the disarmament of all law abiding citizens? Well, let's just mark it up to the dispassionate tenor of the Republican Guard who have over the years jettisoned Reagan's mandates as easily as they shrugged off the prohibition against assault weapons. The Republican Guard has even offered laws to reduce the liability of the local gun shop and emotional others like them that whine they are too hard pressed by rational laws to balance their books or lock their back doors. The example of the Russian school debacle where the collapse of rational law has seen plenty of assault weapons were available makes the Columbine massacre seem like a Saturday afternoon picnic. The collapse of rational law? My friend, you mistake the iron fist of martial law and governmental murder by edict that ruled the Soviet Union for rational law? The world is at war (or will come to that relaization as they die in sufficient mass numbers) against the nation of islam, who is sworn to a new level of their timeless hatred for all things rational and peaceful. What happened in Russia is an act of that war, and does not reduce to technical descriptions of the tools used to carry out the attack. In two recent school shootings in America, it was a teacher in one case and a student in another that ran to their cars, and retrieved legally owned firearms that enabed them to stop the killings and subdue the attacker! No police force, not even the iron fist of the former iron curtain could *ever* respond to a crazy person trying to commit mass murder faster than an armed citizenry can. Count your blessings that you have always lived in such an armed and peaceful citizenry, with citizens who will step up to the plate to defend your miserable and pathetic existance that relies on the bravery and good citizenry that you lack, and would save you from the attack you spend your life trying to prevent them from being able to do for you or their loved ones. Just don't call yourself a citizen, not in my Country. "In countries like the Untied States, it's perfectly legal for members of the public to own certain types of firearms. If you live in such a country obtain an assault rifle legally, preferably an AK-47 or variations" -- Al Qaeda training manual the Ossama seal of approval to our nation's administration That's really sad, and I liked you a lot more when I thought you could keep such drivel from a good argument. Surely you don't believe that Al Queda pretended to be planning anything now or later, that would rely on compliance with laws to accomplish. I am offended by your comment that our government approves of Bin Laden in any way, or does anything to make it easier for him to murder Americans. It offends the sensibilities of all humans in fact. 73's Richard Clark, KB7QHC Try to pay attention to who the enemy is Richard. It is not lawful American firearm owners who would gladly add you to the list of terrorist organizations if you persist in subverting the rights both enumerated and not enumerated by the Constitution. That you may continue to live as a free man while actively subverting our Constitution is a priviledge that I wish you did not have, but hopefully you are educable before your old age renders that possibility moot. Jack Painter |
On Sun, 19 Sep 2004 17:53:24 -0400, "Jack Painter"
wrote: You don't know anyone or any store that makes such illegal sales in your city, and neither does the BATF Hi Jack, It is already been LONG documented: " Bushmaster Firearms Inc. of Maine will pay $550,000, all of which is covered by its insurance policy. And Bull's Eye Shooter Supply, in Tacoma, will pay $2 million, the largest settlement of its kind by a gun dealer, the Brady Center said." I would pause to add that the "Brady" of the Brady Center has already been dissed by the Republican Right Whiners. Clearly they would prefer that Bull's Eye paid nothing and perhaps give Bushmaster a rebate. And if Brady hadn't taken a bullet for Reagan, what kind of spin would they have to offer? A marksmanship medal for Hinkley? "Federal agents traced the weapon used in a number of the shootings, a .223-caliber XM 14 Bushmaster rifle, back to Bull's Eye." The linkage was proven through target practice shells obtained at the sniper's former address - HERE locally. "The shop had problems for several years. Records show that Bull's Eye could not account for the sales of 238 weapons" "Its security was so abysmal that it appears that a 17-year-old, Malvo, was able to stroll into the store and stroll out holding a 3-foot-long assault rifle," Lowy said. "And Bull's Eye didn't even know the gun was missing until the police called several weeks later to tell them it was found in the trunk of the snipers' car." Copyright © 2004 The Seattle Times Company Let's see, you cannot catch a kid walking out with a 3 foot assault rifle every day of the week for a year (we will skip holidays and weekends when they are more diligent). Yeah, right, that's how it happened! Shoplifters every day for a year and no one notices it at the till, or in the records, or in the stock room. Clearly a society of profitable retards if we are to believe that. If Safeway did business like that, they would fold in a week. 73's Richard Clark, KB7QHC |
On Sun, 19 Sep 2004 15:01:15 -0400, "Jack Painter"
wrote: "Reg Edwards" wrote The USA has wide variations in climate and tree population. Thoughtful citizens ought to concentrate their minds on hurricanes, twisters, atmospheric pollution and gun laws. 100-watt transmitters and G5RV's can look after themselves. ;o) --- Reg. I assure you we are concentrating very carfefully, Reg! Last week we had about 20,000 gun laws on the books, counting all federal and state laws. This weekend we have one less federal gun law, and soon there may be less. When free people use their minds instead of letting foolish emotions be their guide, the concept of restricting firearms from law abiding citizens is one of the first things to go. Jack, please explain why we need battlefield weapons in a civilian society. How many times do you need to shoot that beautiful deer before you drag it to the sausage maker? bob k5qwg Btw, so far my dipole hasn't set the pine trees on fire, or been torn down by a hurricane, despite three attempts by them so far this year ;-) 73, Jack |
"Richard Clark" wrote "Jack Painter" wrote: You don't know anyone or any store that makes such illegal sales in your city, and neither does the BATF Hi Jack, It is already been LONG documented: " Bushmaster Firearms Inc. of Maine will pay $550,000, all of which is covered by its insurance policy. And Bull's Eye Shooter Supply, in Tacoma, will pay $2 million, the largest settlement of its kind by a gun dealer, the Brady Center said." Hi Richard, this is exactly why there must be a stop brought to the assanine litigious fervor that ambulance chasing loafs like John Edwards bring against this country's honest businesses every day. Bushmaster's insurance paid that token of "shut-up idiot and go away" ransom, not Bushmaster. If left to Bushmaster, it would have gone to a very expensive trial and in the end, like every other case in history (except one communist judge in NY) it would have been dismissed. Does the Brady center tell you that? Look it up before you listen to any more of that dribble that an intelligent and worldy man such as your self has no business falling for. Which is again, why we must make the law read that *losers* in assanine cases like that pay *all* the legal bills. Either that or else ban lawsuits against gunmakers. You pursue these unconstitutional bans against guns and gun owners, well then we'll ban your lawsuits. Have it you way, you're going to make enemies of yourselves either way and the rest of us will go on with our lives. Even defending yours. /dribble snipped/ "The shop had problems for several years. Records show that Bull's Eye could not account for the sales of 238 weapons" "Its security was so abysmal that it appears that a 17-year-old, Malvo, was able to stroll into the store and stroll out holding a 3-foot-long assault rifle," Lowy said. "And Bull's Eye didn't even know the gun was missing until the police called several weeks later to tell them it was found in the trunk of the snipers' car." Copyright © 2004 The Seattle Times Company Gee what kind of idiots do you grow in Seattle? It's liberal-land for crying out loud, don't any of you folks obey the law? We take gun shop owners to jail for less than that in the East, and ruin their lives for trying to make an honest living most of the time. 73's Richard Clark, KB7QHC 73, Jack |
"Bob Miller" wrote "Jack Painter" wrote: "Reg Edwards" wrote The USA has wide variations in climate and tree population. Thoughtful citizens ought to concentrate their minds on hurricanes, twisters, atmospheric pollution and gun laws. 100-watt transmitters and G5RV's can look after themselves. ;o) --- Reg. I assure you we are concentrating very carfefully, Reg! Last week we had about 20,000 gun laws on the books, counting all federal and state laws. This weekend we have one less federal gun law, and soon there may be less. When free people use their minds instead of letting foolish emotions be their guide, the concept of restricting firearms from law abiding citizens is one of the first things to go. Jack, please explain why we need battlefield weapons in a civilian society. How many times do you need to shoot that beautiful deer before you drag it to the sausage maker? bob k5qwg Hello Bob, whether I used a bow and arrow, a single shot musket, or an autoloader Remmington .308 rifle to take a deer is not the point. Self defense and American's right to keep and bear arms is not about hunting. Nowhere in the Constitution do any of the founding fathers who adamantly supported our permanent right to keep and bear arms, mention "hunting" or "sport". Radio is regulated because the airwaves belong to the pubic. Use of a radio for survival (of life or property I will add) is not regulated in any way. Firearms are regulated because it is reasonable to restrict felons (ie: not peaceable citizenry) access to them, the same as we restrict the mentally or physically incapable or repeat offender drunks from driving an automobile on our public roads. But use of a firearm for self-defense is not regulated by any Constitutional-supported law, although some states make saving your own life a near crime. In Britain it *is* a crime to defend your life *or* property with a firearm, and there are recent cases to prove that is the intent of the crown to make it so. Please don't pretend there is a legislature who upholds anything in Britain. If it were not for a very few brave men left there, the whole place would just fold to muslims and dutch pedophiles the way the rest of europe already has. To our brave friends in Britain, come to America, we await you with open "arms". So Bob, whether an american owns a pistol, muskey, sport rifle, hunting rifle, assault rifle or sausage maker, it's none of your damn business anymore than your choice of radio manufacture or your ability to fix it or improve it is mine. 73, Jack Btw, so far my dipole hasn't set the pine trees on fire, or been torn down by a hurricane, despite three attempts by them so far this year ;-) 73, Jack |
Richard Clark wrote:
Cecil Moore wrote: Hitler, Mao, and Stalin all supported strict gun control laws. Bush, Arrafat, the Columbian Drug Lords and Ossama do not. Richard, if your wife/mother/sister/daughter were being raped and you could stop it with a gun, what would you do? Lay down the gun and initiate touchy-feely negotiations with the rapist? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Radio is regulated because the airwaves belong to the pubic. And because they are a very finite resource. Use of a radio for survival (of life or property I will add) is not regulated in any way. Specifically and unconditionally permitted by the FCC. |
Richard Clark wrote:
Let's see, you cannot catch a kid walking out with a 3 foot assault rifle every day of the week for a year (we will skip holidays and weekends when they are more diligent). Yeah, right, that's how it happened! Shoplifters every day for a year and no one notices it at the till, or in the records, or in the stock room. You are shooting your own argument in the foot. The people you are describing are *LAW-BREAKERS*, not law-abiders. There are already laws against what they are doing. They already broke the law and you want yet another law for them to break??? Why not advocate enforcing the existing laws which are not being properly enforced? How many laws do they have to break before you realize that law-breakers don't obey laws? As I said before, you might as well be advocating laws prohibiting hurricanes from hitting Florida. Gun control laws don't keep guns out of the hands of criminals. Gun control laws keep guns out of the hands of law-abiding people who need guns to defend themselves against criminals. You and the criminals would like to see all law-abiding citizens disarmed and helpless. In case you missed it: LAW-BREAKERS don't obey laws. They don't obey the present laws and they won't obey any new laws that you are advocating. To keep the thread on topic: IMO, you can't see the forest for the trees. -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Sun, 19 Sep 2004 19:01:16 -0400, "Jack Painter"
wrote: Gee what kind of idiots do you grow in Seattle? Hi Jack, This is the gun crowd you are speaking of. 73's Richard Clark, KB7QHC |
On Sun, 19 Sep 2004 18:27:10 -0500, Cecil Moore
wrote: what would you do? You still lamenting about Dukakis losing in '98? |
Bob Miller wrote:
Jack, please explain why we need battlefield weapons in a civilian society. That's simple. Because the criminals are armed with battlefield weapons. Don't know about you, but I think it's stupid to take my 66 year-old fists to a gunfight. How many times do you need to shoot that beautiful deer before you drag it to the sausage maker? Deer don't shoot back. Criminals, including terrorists do, and sometimes with fully automatic weapons. The criminals obviously want the ordinary citizens to be disarmed. But why should you want exactly the same thing as the criminals? Did you know that the crime rate is falling in the concealed-carry states? Did you know that a majority of states are concealed-carry states? If you were a criminal, would you really want to take on someone who might be packin' a concealed Colt .45? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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Richard Clark wrote:
Cecil Moore wrote: what would you do? You still lamenting about Dukakis losing in '98? Worse than that. I'm lamenting about every Libertarian presidential candidate losing every single year. How are your non-weapon negotiations coming with that 250 pound guy in the process of raping your daughter? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"Bill Turner" wrote The voltage at the ends of a half wave dipole can reach thousands of volts even with relatively low power. Trees have been set on fire with as low as 100 watts. Be careful! ============================== Hi Bill, A half-wave dipole is a resonant tuned circuit. A 40 meter dipole using 14-gauge wire has a Q of about 11. At 100 watts there is 85 volts at the feedpoint. The voltage between the ends of the antenna is 85 times Q which equals 956 volts. Therefore, the voltage between one end of the antenna and ground is only 478 volts. And this falls to a much lower value when the end of the wire is in contact with anything by virtue of the very high antenna impedance of around 1500 ohms. Furthermore, the antenna is immediately detuned when it comes into contact with anything and Tx power falls. From where do you get your "thousands of volts" - the old wive's monthly magazines? There are far more Californian forest fires caused by arsonists than 100 watt transmitters. Fortunately, it doesn't seem to have a bad effect on the quality of the wine. ---- Reg, G4FGQ |
"If a dipole falls in a forest and there's no one there to hear it, does it make a sound?" No, but makes a lot of QRM... ;-) |
I assure you we are concentrating very carfefully, Reg! Last week we had about 20,000 gun laws on the books, counting all federal and state laws. This weekend we have one less federal gun law, and soon there may be less. When free people use their minds instead of letting foolish emotions be their guide, the concept of restricting firearms from law abiding citizens is one of the first things to go. Gun control is using both hands. In any event, if the trees are at all flammable, best use some non conducting rope (that won't absorb moisture when it rains) to support the ends of the antenna away from the tree limbs. The antenna would work better without those lossy tree trunks right next to the ends anyway. |
Reg Edwards wrote:
From where do you get your "thousands of volts" - the old wive's monthly magazines? Try this, Reg. A dipole is a standing-wave antenna. Most people know that the voltage 1/4WL away from a current maximum is pretty high. Since the current is zero at the end of the dipole, all the energy is contained in the E-field. So what is the voltage when all the energy is in the E-field? A 1/2WL dipole is a lot like a lossy piece of 600 ohm transmission line. 600 ohms is in the ballpark of the natural Z0 of a dipole if there were no reflections on it, i.e. if it were terminated such that reflections were eliminated thus turning it into a traveling- wave antenna. If one assumes that at the dipole feedpoint, (VF+VR)/(IF+IR) = 50 ohms, and if the traveling-wave impedance of a dipole is 600 ohms, one can calculate the ratio of VR to VF. Turns out to be about 0.9. So VF is about ten times the feedpoint voltage. At the open-circuit at the end of a dipole, VF adds in phase with VR so the voltage at the open-circuit end of the dipole is about 20 times the feedpoint voltage. The feedpoint voltage at 100W is about 70.7V. Therefore, the voltage at the ends of the dipole is about 1414V RMS. Multiply by 2.8 to get peak to peak at about 4kv. When I worked for Schlumberger in the oil fields, we could easily draw a 4 inch arc if someone got their aluminum hard hat too close to the mobile radio whip during transmit. How much voltage does it take to draw a 4 inch arc? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Sun, 19 Sep 2004 19:08:28 -0500, Cecil Moore
wrote: Bob Miller wrote: Jack, please explain why we need battlefield weapons in a civilian society. That's simple. Because the criminals are armed with battlefield weapons. Don't know about you, but I think it's stupid to take my 66 year-old fists to a gunfight. How many times do you need to shoot that beautiful deer before you drag it to the sausage maker? Deer don't shoot back. Criminals, including terrorists do, and sometimes with fully automatic weapons. The criminals obviously want the ordinary citizens to be disarmed. But why should you want exactly the same thing as the criminals? Did you know that the crime rate is falling in the concealed-carry states? Did you know that a majority of states are concealed-carry states? I wonder if those same states might also have the highest number of crimes of passion committed with firearms? Don't know, just asking. If you were a criminal, would you really want to take on someone who might be packin' a concealed Colt .45? Personally, I wouldn't attack someone packing a cap pistol. But if your argument is carried to its conclusion, that law abiding citizens should have guns as big as what the worst criminals carry, then we'd all be walking around with machine guns. That's fine, until somebody loses his/her temper. One of the staples of San Antonio TV news is showing some family on the South Side mourning the death of yet another kid killed in a drive-by or whatever -- happens about two or three times a month. Bob k5qwg |
On Sun, 19 Sep 2004 19:17:09 -0500, Cecil Moore
wrote: Worse than that. I'm lamenting about every Libertarian presidential candidate losing every single year. You lament too much. |
On Sun, 19 Sep 2004 18:47:42 -0500, Cecil Moore
wrote: To keep the thread on topic: IMO, you can't see the forest for the trees. And how many trees do you have? Got any strange fruit? |
Bob Miller wrote:
Personally, I wouldn't attack someone packing a cap pistol. But if your argument is carried to its conclusion, that law abiding citizens should have guns as big as what the worst criminals carry, then we'd all be walking around with machine guns. That's fine, until somebody loses his/her temper. One of the staples of San Antonio TV news is showing some family on the South Side mourning the death of yet another kid killed in a drive-by or whatever -- happens about two or three times a month. Bob k5qwg Seems to me there is a big difference between people losing their tempers, and drive by shootings by gang members, such as the fact that normal citizens don't lose their tempers and shoot strangers. If you think they do, show me some evidence. tom K0TAR |
Bob Miller wrote:
One of the staples of San Antonio TV news is showing some family on the South Side mourning the death of yet another kid killed in a drive-by or whatever -- happens about two or three times a month. If laws can stop crime, why haven't the laws against drive-by shootings stopped the drive-by shootings? -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Mark wrote:
"Is this practical?" Trees near an antenna cause some loss. It`s hard to quantify in advance, but in ww-2, the signal corps estimated that hf loss is usually negligible if horizontal polarization is used (page 241 of 'electrical communications engineering'). I`ve found that horizontal HF dipoles, directly fed by coax in various Bolivian Chaco Jungle sites, below the the tree canopy, but not too close to the trees, communicated well with Cochabamba and La Paz, Bolivia. So, the dipoles didn`t suffer too much from the trees. The Signal Corps was right. Best regards, Richard Harrison, KB5WZI |
Dear Cec,
Like Brer Rabbit - I'm saying nuffin. --- Reg |
"Richard Harrison" wrote Mark wrote: "Is this practical?" Trees near an antenna cause some loss. It`s hard to quantify in advance, but in ww-2, the signal corps estimated that hf loss is usually negligible if horizontal polarization is used (page 241 of 'electrical communications engineering'). I`ve found that horizontal HF dipoles, directly fed by coax in various Bolivian Chaco Jungle sites, below the the tree canopy, but not too close to the trees, communicated well with Cochabamba and La Paz, Bolivia. So, the dipoles didn`t suffer too much from the trees. The Signal Corps was right. Best regards, Richard Harrison, KB5WZI Hi Richard, it's not easy to compare your rainforest canopy to loblolly pines, but at approximately 50' my dipole is well below the pine canopy, and well surrounded by them. If there is an impact from the pine trees it would be hard to quantify since the dipole exceeds everyone's expectations for short and long range performance. We have heard comments that pine-fron clusters when wet, affect a near field, but that has not been our experience. Neither does snow, ice or winds. Overall, there appears to be no effect on the antenna being in fairly close proximity to many tall trees, and suspended from them. Best regards, Jack |
Jack Painter wrote:
"Overall, there appears to be no effect on the antenna being in fairly close proximity to many tall trees, and suspended from them." That was the Signal Corps conclusion for horizontal polarization at HF. For vertical polarization, surrounding trees are better energy absorbers. At VHF and UHF, absorption gets worse and worse as frequency goes up. Too much foliage is impenetrable at VHF and UHF, regardless of polarization, humidity, ice, snow and wind. The Signal Corps advises trying horizontal HF antennas among the trees to avoid detection by the enemy. Best regards, Richard Harrison, KB5WZI |
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