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End-feeding dipoles
Several authors recommend against
end-fed dipoles because of alleged difficulties in matching to a 50-ohm line. Unfortunately, the "slur" is dropped without a hint of explanation. Other authors see it as simple and reliable, and recommend it with enthusiasm. A parallel tuned circuit with tapped inductor is usually the recommended impedance transformer. In my own experience, matching has always been extremely easy and trouble-free. So does anyone know why this might be thought so frought with problems that its general use would be discouraged? Chuck, NT3G ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
On Mon, 18 Jun 2007 10:42:08 -0400, Chuck
wrote: In my own experience, matching has always been extremely easy and trouble-free. So does anyone know why this might be thought so frought with problems that its general use would be discouraged? Hi Chuck, The slur may attend the illusion that just the antenna is being matched and the operator cries foul about transmission line common mode currents. However, if those currents go unnoticed; then end fed antennas are marvelous and have this undeserved bad reputation. On the other hand, if those currents are noticed and fixed, the antenna probably doesn't work any better; but after all that effort "it damned well should and no one is going to convince me otherwise." 73's Richard Clark, KB7QHC |
End-feeding dipoles
On Jun 18, 8:42 am, Chuck wrote:
Several authors recommend against end-fed dipoles because of alleged difficulties in matching to a 50-ohm line. Unfortunately, the "slur" is dropped without a hint of explanation. Other authors see it as simple and reliable, and recommend it with enthusiasm. A parallel tuned circuit with tapped inductor is usually the recommended impedance transformer. In my own experience, matching has always been extremely easy and trouble-free. So does anyone know why this might be thought so frought with problems that its general use would be discouraged? Chuck, NT3G The matching doesn't have anything to do with it. It's the excess common mode currents that I don't like. Sure, they work, but I would never use one if I can center feed the antenna. And I've never really had a case where I couldn't center feed. MK |
End-feeding dipoles
One other thing, I see, is that End Fed Dipoles
have a extremely high impedence, and hence a very HIGH VOLTAGE (altho at little current), unlike center-fed dipoles. Might make insulation problematic to prevent arcing . Can generate hundreds (if not Thousands) of volts, at the feed point! Jim NN7K Richard Clark wrote: On Mon, 18 Jun 2007 10:42:08 -0400, Chuck wrote: In my own experience, matching has always been extremely easy and trouble-free. So does anyone know why this might be thought so frought with problems that its general use would be discouraged? Hi Chuck, The slur may attend the illusion that just the antenna is being matched and the operator cries foul about transmission line common mode currents. However, if those currents go unnoticed; then end fed antennas are marvelous and have this undeserved bad reputation. On the other hand, if those currents are noticed and fixed, the antenna probably doesn't work any better; but after all that effort "it damned well should and no one is going to convince me otherwise." 73's Richard Clark, KB7QHC |
End-feeding dipoles
On Jun 18, 4:09 pm, Jim - NN7K wrote:
One other thing, I see, is that End Fed Dipoles have a extremely high impedence, and hence a very HIGH VOLTAGE (altho at little current), unlike center-fed dipoles. Might make insulation problematic to prevent arcing . Can generate hundreds (if not Thousands) of volts, at the feed point! Jim NN7K Then you have to have a pretty good tuner.. Along with whatever losses it provides.. I avoid tuners if at possible. None of my everyday antennas use one. I have a 989c, but I mainly use the wattmeter, and switch.. The tuner itself sees little use. Probably has spiders inside.. :/ MK |
End-feeding dipoles
Correct me if I am wrong, but if you end feed a wire, it isn't a
dipole, its a monopole. On Mon, 18 Jun 2007 10:42:08 -0400, Chuck wrote: Several authors recommend against end-fed dipoles because of alleged difficulties in matching to a 50-ohm line. Unfortunately, the "slur" is dropped without a hint of explanation. Other authors see it as simple and reliable, and recommend it with enthusiasm. A parallel tuned circuit with tapped inductor is usually the recommended impedance transformer. In my own experience, matching has always been extremely easy and trouble-free. So does anyone know why this might be thought so frought with problems that its general use would be discouraged? Chuck, NT3G ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- -- 73 for now Buck, N4PGW www.lumpuckeroo.com "Small - broadband - efficient: pick any two." |
End-feeding dipoles
"Chuck" wrote in message ... Several authors recommend against end-fed dipoles because of alleged difficulties in matching to a 50-ohm line. Unfortunately, the "slur" is dropped without a hint of explanation. Other authors see it as simple and reliable, and recommend it with enthusiasm. A parallel tuned circuit with tapped inductor is usually the recommended impedance transformer. In my own experience, matching has always been extremely easy and trouble-free. So does anyone know why this might be thought so frought with problems that its general use would be discouraged? Chuck, NT3G Take a google at "J-Poles" - an end-fed half-wave. (I'm reluctant to call it a dipole.) The 2-meter version of the j-pole is used by bunches of folks. The matching section at the bottom allows hooking it up to 50-ohm cable. I have not tried it on lower frequencies. But hey - making antennas is fun, so get hold of an antenna analyzer, and play eee ha |
End-feeding dipoles
Thanks for interesting comments by all.
My question was prompted by reports of alleged matching difficulties, rather than by questions of general utility, feasibility, or ancillary problems. For example, Lee's Vertical Antenna Handbook discusses various conventional matching circuits for vertical antennas. For the half-wave vertical, he comments tersely that "It is difficult to match well and should be avoided if possible". (page 25, 2d edition; context makes clear he is referring to end- or base-feeding) He shows the usual parallel tuned circuit with tapped inductor as the appropriate matching device. Although Lee doesn't logically link his assertion of matching difficulty with his admonition of avoidance, he conjoined them in the same sentence with abandon or intent. My interest is limited to the allegation of matching difficulty. BTW, I was assuming a half-wave, horizontal antenna, one end of which is brought directly into the shack with no intervening transmission line. Definitely not a dipole, but not a monopole either, I suspect. There are some reports out there of RF in the shack with this arrangement, but who has experienced matching problems? So if there were no common mode issues, the directly end-fed, half-wave wire would be an equal opportunity candidate along with the traditional dipole for the same radiator geometry? Or is that like saying if it weren't for gravity I could fly? 73, Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
On Tue, 19 Jun 2007 09:16:30 -0400, Chuck
wrote: BTW, I was assuming a half-wave, horizontal antenna, one end of which is brought directly into the shack with no intervening transmission line. Definitely not a dipole, but not a monopole either, I suspect. Hi Chuck, It is merely an off-center dipole that hasn't come out of the closet. The wiring in your shack supplies that other half, and supports the common mode current/voltage. There are some reports out there of RF in the shack with this arrangement, but who has experienced matching problems? The complaints made here are far from sparse. On the other hand, those who don't notice, don't complain. I will bet you have one outlet in your home with inverted neutral/hot and a floating ground. Does it bother how your lamp works? Plug in a toaster and reach for the faucet and the morgue attendant will tie a nice card to your toe. Some folks have common mode complaints, others don't. So if there were no common mode issues, the directly end-fed, half-wave wire would be an equal opportunity candidate along with the traditional dipole for the same radiator geometry? Or is that like saying if it weren't for gravity I could fly? For wires less than 5/8ths (end-to-end), you have to work (or screw up) damned hard to gain or lose half a dB from the typical lobe geometry. I will be generous and call it a whole dB, but that is barely the width of your S-meter's needle. There are other things to worry about in life, like that outlet with a floating ground. In that vein, you stand to come out ahead if you seriously examine your shack's quality of ground for all applications. 73's Richard Clark, KB7QHC |
End-feeding dipoles
Hello Richard,
Richard Clark wrote: It is merely an off-center dipole that hasn't come out of the closet. The wiring in your shack supplies that other half, and supports the common mode current/voltage. Interesting concept. Not technically a dipole, though. But similarly true of less-than-perfect, center-fed dipoles, no? The complaints made here are far from sparse. I've seen no complaints here at all about matching difficulties. Even posters who had used the antenna omitted matching difficulties from their reported experiences. On the other hand, those who don't notice, don't complain. I will bet you have one outlet in your home with inverted neutral/hot and a floating ground. Does it bother how your lamp works? I understand. But I really hoped to talk about matching difficulties and find myself awash in discussions of potential common mode currents, about which I have no truck. ;-) Some folks have common mode complaints, others don't. Sure. And I'd extend that to real, center-fed dipoles with less than perfect transmission line/antenna symmetry. All a matter of degree? For wires less than 5/8ths (end-to-end), you have to work (or screw up) damned hard to gain or lose half a dB from the typical lobe geometry. I will be generous and call it a whole dB, but that is barely the width of your S-meter's needle. There are other things to worry about in life, Agreed. like that outlet with a floating ground. In that vein, you stand to come out ahead if you seriously examine your shack's quality of ground for all applications. I'd do it immediately if it would help explain the alleged matching difficulties. ;-) 73, Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
On Tue, 19 Jun 2007 16:45:15 -0400, Chuck
wrote: Hello Richard, The complaints made here are far from sparse. I've seen no complaints here at all about matching difficulties. Even posters who had used the antenna omitted matching difficulties from their reported experiences. As I said, those that don't notice, don't complain. This is the human condition. If they didn't notice, it must have matched (or they didn't measure it, which is the same thing as not noticing). We've seen plenty of complaints. Certainly they didn't lead with their chin, the symptoms bore out the problem and they were complaining of something they thought was remote from tuning; but not far remote - meaning they "thought" it was tuned, but their rig was going whacko. On the other hand, those who don't notice, don't complain. I will bet you have one outlet in your home with inverted neutral/hot and a floating ground. Does it bother how your lamp works? I understand. But I really hoped to talk about matching difficulties and find myself awash in discussions of potential common mode currents, about which I have no truck. ;-) You simply have to recognized the symptoms. If there are no symptoms, there are no complaints. However, that doesn't mean their systems are free of common modalities. It simply means the currents/voltages are below the threshhold of notice. Common Mode currents/voltages exist in EVERY system. It is merely the degree and tolerance that become the issue. Some folks have common mode complaints, others don't. Sure. And I'd extend that to real, center-fed dipoles with less than perfect transmission line/antenna symmetry. All a matter of degree? Yup, as I anticipated in my earlier comment. In that vein, you stand to come out ahead if you seriously examine your shack's quality of ground for all applications. I'd do it immediately if it would help explain the alleged matching difficulties. ;-) One solution for common mode problems is a ground tuner. This is also called a virtual ground if the wire terminates in an open instead of going to ground. What this does is references your rig/bench/room to RF neutral. In that condition you don't notice that slight tingle from the chassis as you brush the back of your fingers over it; or the sizzle from the mike when your lips touch it. If your shack is relatively close to the service ground, and the wire from your rig/bench/ground runs only several feet; then everything should be hunky dory. That is: up to a point where that length becomes a significant fraction of the wavelength with a sizeable energy content. At that point, you want to reduce the reactance of that wire by making it one big Honker! Or, for a bench, you use a conductive sheet and tack your equipment to the sheet. Usually a star (branching) system of grounds is the best, but our equipment rarely exists in isolation and there are cross connects. This can lead to ground loops (common mode really rears its ugly head in this circumstance). So in that instance, you cross connect like mad (and hence build your own mesh of that sheet you should have laid down in the first place). Most folks we hear from who don't complain about tuning (it loaded fine, works fine, and lasts a long time) wail a tale of grief about RF getting into their speaker, bathroom fault isolation, hall dimmer, VCR - you name it, but it isn't called a tuning problem fer sure. We ask them to jumper in an extra few feet of transmission line and check their SWR. They usually are astonished that their antenna needs tuning again. This is a slam dunk indication of common mode problems. Like I said, these complaints are not uncommon. On the flip side, some folks think more tingle on the lips is simply their excitment of working DX (whose going to complain about that?). 73's Richard Clark, KB7QHC |
End-feeding dipoles
Thanks for the elaboration, Richard.
73, Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
Richard Clark writes:
On Tue, 19 Jun 2007 16:45:15 -0400, Chuck I'm not trying to argue against your main points, but I have a problem with this: We ask them to jumper in an extra few feet of transmission line and check their SWR. They usually are astonished that their antenna needs tuning again. This is a slam dunk indication of common mode problems. Unless the SWR on the line is 1:1, changing the length of transmission line *will* change the impedance seen. Whether there is common mode current or not. 73 LA4RT Jon |
End-feeding dipoles
"Jon Kåre Hellan" wrote in message ... Richard Clark writes: On Tue, 19 Jun 2007 16:45:15 -0400, Chuck I'm not trying to argue against your main points, but I have a problem with this: We ask them to jumper in an extra few feet of transmission line and check their SWR. They usually are astonished that their antenna needs tuning again. This is a slam dunk indication of common mode problems. Unless the SWR on the line is 1:1, changing the length of transmission line *will* change the impedance seen. Whether there is common mode current or not. 73 LA4RT Jon True it will change the impedance seen but not the SWR so unless you are checking your line with an impedance bridge you should see no change except that due to cable loss and normally a few feet of feedline does not add any significant loss. If you do see a change it will be due to currents on thec coax. Jimmie |
End-feeding dipoles
"Jimmie D" writes:
"Jon KÃ¥re Hellan" wrote in message ... Richard Clark writes: On Tue, 19 Jun 2007 16:45:15 -0400, Chuck I'm not trying to argue against your main points, but I have a problem with this: We ask them to jumper in an extra few feet of transmission line and check their SWR. They usually are astonished that their antenna needs tuning again. This is a slam dunk indication of common mode problems. Unless the SWR on the line is 1:1, changing the length of transmission line *will* change the impedance seen. Whether there is common mode current or not. 73 LA4RT Jon True it will change the impedance seen but not the SWR so unless you are checking your line with an impedance bridge you should see no change except that due to cable loss and normally a few feet of feedline does not add any significant loss. If you do see a change it will be due to currents on thec coax. Jimmie If you only measure SWR, you will see no change. But the text I commented said "their antenna needs tuning again". You *will* have to adjust your antenna tuner. Antenna tuner settings don't only care about the magnitude of SWR, but also about the specific resistive and reactive impedances. 73 LA4RT Jon |
End-feeding dipoles
Chuck,
I just recently finished a round of antenna tuner thrashing that included some vertical, half wave wire, bottom fed antennas... This was through a tuner(s) of my own design and construction including hand built variable caps, with the feed points being head high and the 1/2 wave antenna worked against a half wave elevated counterpoise, with the coax dropping straight to the ground and running on the ground hundreds of feet to the shack...... The ground was wet with half melted snow and rain during most of the test... I had to stand in a flowing stream to make tuner adjustments - snow melt water will get your attention when it runs over the top of your boots! While I got the tuner design to work - which was the whole reason for the exercise as opposed to being primarily an antenna test - I was not impressed with the half wave, end fed, vertical antenna overall - 80, 40, and 20 meter antennas were tested... They were distinctly more noisy than ground mounted quarter wave antennas for the same bands... Often, deafeningly more noisy... The recovered signal strengths we 1. often less than for the quarter waves - 2. sometimes comparable - 3. the strong signal exceptions being the times that the very low arrival angles were exactly what the half wave vertical wanted to see... (you can never have too many antennas) On 20 meters the separation between the two antennas was 500 feet, and expanding to some 900 feet for 80 meters test antenna being the half wave end fed, and the reference antenna being 1/4 wave ground mounted... I feel that the distances were sufficient that mutual coupling was minimized enough as to not skew the results - it certainly was not eliminated, however... The circulating tank current on a tuner used transform 50 ohms to an end fed half wave is impressive - often melting the dielectrics used for the variable caps... denny |
End-feeding dipoles
Jon Kåre Hellan wrote:
If you only measure SWR, you will see no change. But the text I commented said "their antenna needs tuning again". You *will* have to adjust your antenna tuner. Antenna tuner settings don't only care about the magnitude of SWR, but also about the specific resistive and reactive impedances. There are some, like Cebik, http://www.cebik.com/trans/cmp.html A Common-Mode Current Picture Show who believe common mode RF getting into some electronic metering circuits produces erroneous SWR readings. Could that be the reason small changes in transmission line length sometimes result in apparent changes in SWR? Of course, if there are common mode currents on a coax transmission line, the impedance of the line seen by the SWR meter (50 ohms in parallel with the impedance between the shield's outer surface and ground) is no longer 50 ohms and the meter calibration is no longer correct regardless of whether RF is getting into the electronics of the meter. Changing the length of the coax gives you a new, out-of-calibration measurement. ;-) 73, Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
Denny wrote:
The circulating tank current on a tuner used transform 50 ohms to an end fed half wave is impressive - often melting the dielectrics used for the variable caps... Thanks for the report, Denny. Some of the T- and L- network tuners also pass some hefty currents at high power. It is difficult to find much enthusiasm for the performance of half-wave verticals from folks who have actually tried them. Your experience sure supports that. 73, Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
On Wed, 20 Jun 2007 06:49:46 -0400, "Jimmie D"
wrote: Unless the SWR on the line is 1:1, changing the length of transmission line *will* change the impedance seen. Whether there is common mode current or not. True it will change the impedance seen but not the SWR You are both wrong. 73's Richard Clark, KB7QHC |
End-feeding dipoles
On Wed, 20 Jun 2007 09:14:04 -0400, Chuck
wrote: who believe common mode RF getting into some electronic metering circuits produces erroneous SWR readings. This would be an exceedingly strange meter. Of course, there are any number of ways to do something wrong. If this were the case (the "infected" meter) then the antenna's being tuned is also suspicious. Could that be the reason small changes in transmission line length sometimes result in apparent changes in SWR? No. Of course, if there are common mode currents on a coax transmission line, the impedance of the line seen by the SWR meter (50 ohms in parallel with the impedance between the shield's outer surface and ground) is no longer 50 ohms and the meter calibration is no longer correct regardless of whether RF is getting into the electronics of the meter. What you have done is tuned the entire antenna/feedline system to 50 Ohms (this includes the common mode effects). Changing the length of the line (which should not change the SWR in a CM free system) also changes the reactance of the this length that was formerly tuned out. Changing the length of the coax gives you a new, out-of-calibration measurement. ;-) By giving you an out-of-50-Ohm load (antenna plus unchoked line). Fellows, this is all classic stuff and has been fodder for discussion for years. The solutions have met the test of time. 73's Richard Clark, KB7QHC |
End-feeding dipoles
Richard Clark wrote:
What you have done is tuned the entire antenna/feedline system to 50 Ohms (this includes the common mode effects). Changing the length of the line (which should not change the SWR in a CM free system) also changes the reactance of the this length that was formerly tuned out. Thank you for that clarification/correction, Richard. What I should have said was that with CM effects, the SWR meter will not show the actual SWR "in" the coax, which could be wildly different from the 1:1 measured for the entire antenna/feedline system. 73, Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
End-feeding dipoles
On Wed, 20 Jun 2007 09:20:15 -0400, Chuck
wrote: It is difficult to find much enthusiasm for the performance of half-wave verticals from folks who have actually tried them. Your experience sure supports that. Hi Chuck, I can report a bright side. During one field day, years ago, one fellow brought in a baloon and hoisted enough wire into the sky to work it as a halfwave 160M vertical. He used an optical rangefinder to measure the height. He had this Army surplus tuner that tuned it up to his rig. The 160M contacts he made told him he was the strongest signal on the band (working 100W). Perhaps it helped that we were in a school ball field on the top of a hill. To further add to the mix, I suggested he tie the tuner to the fence line and backstop. 73's Richard Clark, KB7QHC |
End-feeding dipoles
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End-feeding dipoles
To further add
to the mix, I suggested he tie the tuner to the fence line and backstop. 73's Richard Clark, KB7QHC That was canny advice, Richard... The top rail of the fence and backstop 'could' have been an NVIS antenna - which will get you smokin' reports out to a few hundred miles... I do this routinely for Field Day with a horizontal loop for 80 meters being strung about 20 feet high over a low, wet, fertilized field next to a river... The guys run QRP off a battery and are amazed how they can break pile ups... I have never bothered to point out to them that the vast majority of their contacts are within a 500 mile circle... They are happy and I believe in ignorance being bliss... denny / k8do |
End-feeding dipoles
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End-feeding dipoles
Richard Clark wrote:
Half wave antenna can be a monopole however the reverse is can only be true if its resonanance is at 1/2 wave. ... Richard Clark, KB7QHC Richard: I think he means a half-wave monopole is quite possible (I use 'em all the time!), and a half-wave dipole can exist with each leg being 1/4 wave ... both (having in common) being a half-wave antenna. Or, at least, that is the way I read it ... Regards, JS |
End-feeding dipoles
John Smith I wrote:
I think he means a half-wave monopole is quite possible (I use 'em all the time!), and a half-wave dipole can exist with each leg being 1/4 wave ... both (having in common) being a half-wave antenna. "Pole" can have two different meanings in this context. A physical fishin' "pole" is different from an electrical or magnetic "pole". Seems the word "pole" requires an adjective to define the context for antennas. -- 73, Cecil, w5dxp.com |
End-feeding dipoles
Cecil Moore wrote:
... "Pole" can have two different meanings in this context. ... 73, Cecil, w5dxp.com Cecil: You'd love to meet my mom; she is still alive, yanno? Anyway, her good advice was to always keep my "pole" in my pants, said something about children not needing to be raising children ... Anyway, the word "pole" has always been confusing to me ... grin Regards, JS |
End-feeding dipoles
Cecil, W5DXP wrote:
"Seems the word "pole" requires an adjective to define the context for antennas." It should not hurt. My dictionary says a dipole antenna is a straight conductor usually fed in the center. However, dipole characteristics are determined by current distribution, not the feeding if the reeder doesn`t radiate. Best regards, Richard Harrison, KB5WZI |
End-feeding dipoles
John Smith I wrote:
[stuff] Anyway, the context used here relates to north pole vs. south pole, up vs. down, right vs. left ... Regards, JS |
End-feeding dipoles
John Smith I wrote:
Anyway, the word "pole" has always been confusing to me ... grin Are you familiar with a plot of the poles and zeros on a unit circle, e.g. filter response? -- 73, Cecil http://www.w5dxp.com |
End-feeding dipoles
Richard Harrison wrote:
Cecil, W5DXP wrote: "Seems the word "pole" requires an adjective to define the context for antennas." It should not hurt. My dictionary says a dipole antenna is a straight conductor usually fed in the center. However, dipole characteristics are determined by current distribution, not the feeding if the feeder doesn`t radiate. Seems to me, technically speaking, the two poles in a "dipole" are electrical with opposite voltage polarities at each end of the 1/2WL dipole. An electric monopole has only one electrical pole, like a magnetic monopole has only one magnetic pole. A 1/2WL end-fed wire would then technically be a dipole and the passive elements on a resonant Yagi would be dipoles. -- 73, Cecil http://www.w5dxp.com |
End-feeding dipoles
On Thu, 21 Jun 2007 21:14:58 GMT,
wrote: In engineering there is good, fast and cheap. Pick any two. That summary fails at every turn. 73's Richard Clark, KB7QHC |
End-feeding dipoles
Richard Harrison wrote:
SNIPPED Seems to me, technically speaking, the two poles in a "dipole" are electrical with opposite voltage polarities at each end of the 1/2WL dipole. An electric monopole has only one electrical pole, like a magnetic monopole has only one magnetic pole. A 1/2WL end-fed wire would then technically be a dipole and the passive elements on a resonant Yagi would be dipoles. DIPOLE: If there is a polarity DIFFERENCE between the ends of a wire it qualifies as a dipole [two poles ... two different charge levels ... two different voltages ... etc.] A RESONANT DIPOLE is a dipole with the voltages at the ends both equal in magnitude and opposite in polarity. Am I missing something? |
End-feeding dipoles
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End-feeding dipoles
Cecil Moore wrote:
... Seems to me, technically speaking, the two poles in ... In the following find, "# A monopole with a ground balance (mirror image). www.novastars.com/antenna/antenna-glossary.htm" However, this is far from what I expect to see when someone mentions "dipole." The use of dipole to indicate a monopole with the mirrored "pole" being created in the earth seems sparse in the material I have digested--however, technically, you seem to have a argument in the use you indicated ... however, I usually work with 1/2 wave monopoles exclusively ... a small counterpoise allows me to divorce the antenna from need of the ground (well, kinda ...) I usually figure monopoles to be non-symmetrical, most-usually vertical, unbalanced, and requiring a counterpoise ... Dipoles I figure to be symmetrical balanced antennas ... 1) Monopole (wikipedia): # A label used on some French wines to indicate sole ownership, or monopoly, of the wine's name, with no bearing on the wine's quality. www.valleyvineyards.com/wine_glossary_ijkl.htm # A single self-supporting vertical pole with no guy wire anchors, usually consisting of a galvanized or other unpainted metal or a wooden pole with below grade foundations. www.vapda.org/bylaw/gloss.htm # A single exposed radiator, usually requiring a ground plane to provide directivity (gain). www.novastars.com/antenna/antenna-glossary.htm # All known magnets have two poles, one south pole and one north pole. The existence of a single such pole, termed a monopole, has not yet been established but is believed by many physicists to exist on the basis of theoretical studies. Lunar samples have been carefully searched on Earth for the presence of monopoles. history.nasa.gov/EP-95/glossary.htm # The French term for a vineyard that is wholly owned by one estate. The German word is "Alleinbesitz." www.rieslingreport.com/glossary.html # Used to denote a vineyard owned exclusively by one proprietor, the word monopole appears on the label of a wine made from such a vineyard. www.weinbauer.com/glossary/index.cfm # A structure composed of a single spire used to support telecommunications equipment. http://www.co.jefferson.co.us/ext/dp...e-glossary.htm # In physics, magnetic monopole is a term describing a hypothetical particle that could be quickly clarified to a person familiar with magnets but not electromagnetic theory as "a magnet with only one pole". In more accurate terms, it would have net "magnetic charge". Interest in the concept stems from particle theories like Grand Unified Theories and superstring theories that predict either the existence or the possibility of magnetic monopoles. en.wikipedia.org/wiki/Monopole 2) Dipole (wikipedia): # Speakers with drivers on opposite faces that are wired electrically out of phase, creating an area of cancellation to the sides. Recommended by THX for use as surround speakers, with null directed at the listener to create a more ambient and non-localizable effect. www.hometheatermag.com/glossary/ # Chemical compounds with an unequally distributed electric charge, such as the water molecule: the oxygen atom is of negative charge and the two hydrogen atoms are of positive charge. Dipolar molecules mutually attract each other. This is how water molecules connect into clusters via hydrogen bridges. www.himalayasaltcrystal.com/glossary.htm # A type of antenna with two defined opposing radiating elements, both of the proper length for the frequency of operation, and each forming the counterpoise for the other. http://www.kareoke.com/glossary/micr...y_of_terms.htm # A monopole with a ground balance (mirror image). www.novastars.com/antenna/antenna-glossary.htm # a compact source of magnetic force, with two magnetic poles. A bar magnet, coil or current loop, if their size is small, create a dipole field. The Earth's field, as a crude approximation, also resembles that of a dipole. www-spof.gsfc.nasa.gov/Education/wgloss.html # (di·pole) (di¢p[omacr]l) 1. a molecule having charges of equal and opposite signs but in which the center of the positive charge does not coincide with that of the negative charge, a property which enables the molecule to be bound electrostatically by both positively and negatively charged groups. See polar compounds, under compound. 2. a pair of electric charges or magnetic poles separated by a short distance. http://www.mercksource.com/pp/us/cns...dmd_d_21zPzhtm # a basic antenna element to which most other antennas are compared for gain fwie.fw.vt.edu/tws-gis/glossary.htm # 1. Without qualification usually means electric dipole, a system composed of two charges of equal and opposite sign separated by a distance. A magnetic dipole is an electric current loop enclosing a finite area in a plane. See dipole moment. 2. Same as dipole antenna. amsglossary.allenpress.com/glossary/browse # A type of low-gain (2.2 dBi) antenna consisting of two (often internal) elements. www.wirelesstelcorp.com/glossary_of_terms.htm # A molecule which has a definite separation between its center of positive charge and center of negative charge. Such a molecule is said to be polar. A polar species will be more attracted to a charged species than will a non-polar one. eies.njit.edu/~kebbekus/definitions-aquatic-chem%20htm.htm # Magnetized object that possesses north and south magnetic poles. A bar magnet and Earth are two examples. http://www.physics.gmu.edu/~jevans/a...y/astrgl_d.htm # An object whose centers of positive and negative charge do not coincide. For example, a hydrogen chloride (HCl) molecule is an electric dipole because bonding electrons are on average closer to the chlorine atom than the hydrogen, producing a partial positive charge on the H end and a partial negative charge on the Cl end. http://www.madison.k12.wi.us/west/sc...vocabulary.htm # Gentian Violet. www.centurionndt.com/glossary.htm # This is an antenna that is fed from the center (such as rabbit ears). www.satellite-tv-hq.com/telecom-glossary-d.htm # A speaker which radiates sound primarily in opposite directions, 180 degrees out of phase, This creates a null, or area with no sound, to the sides of the speaker. Such designs are engineered by using drivers wired out of phase, or by using both sides of a flat driver. www.oregondv.com/Audio_FAQ_A-F.htm # a pair of equal and opposite electric charges or magnetic poles separated by a small distance # an aerial half a wavelength long consisting of two rods connected to a transmission line at the center wordnet.princeton.edu/perl/webwn Regards, JS |
End-feeding dipoles
Deek wrote:
A RESONANT DIPOLE is a dipole with the voltages at the ends both equal in magnitude and opposite in polarity. Am I missing something? Any center-fed dipole, fed differentially and shorter than 1/2WL, i.e. not resonant, has the voltages at the ends both equal in magnitude and opposite in polarity. -- 73, Cecil http://www.w5dxp.com |
End-feeding dipoles
Did you know that 6.02x10^23 angels dance on the head of a pin....
denny / k8do |
End-feeding dipoles
On Thu, 21 Jun 2007 04:34:14 -0700, Denny wrote:
To further add to the mix, I suggested he tie the tuner to the fence line and backstop. 73's Richard Clark, KB7QHC That was canny advice, Richard... The top rail of the fence and backstop 'could' have been an NVIS antenna - which will get you smokin' reports out to a few hundred miles... I do this routinely for Field Day with a horizontal loop for 80 meters being strung about 20 feet high over a low, wet, fertilized field next to a river... The guys run QRP off a battery and are amazed how they can break pile ups... I have never bothered to point out to them that the vast majority of their contacts are within a 500 mile circle... They are happy and I believe in ignorance being bliss... denny / k8do a local qrp contact is still a qrp contact. Many contacts is better than few, if that's what you are wanting to make. It might not win field day, but it has to be better than not being heard atall. -- 73 for now Buck, N4PGW www.lumpuckeroo.com "Small - broadband - efficient: pick any two." |
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