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#2
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Jerry Stuckle wrote:
snip I've also run dipoles - I got WAS on 75 meters from Iowa with an inverted VEE running from 50' to near ground. And I had a strong signal on the Iowa 75M SSB net. Perhaps you can get all the antenna manufacturers to specify their antennas in terms of signal reports and QSL cards instead of those useless numbers like gain and pattern. -- Jim Pennino |
#3
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On 11/22/2014 7:39 PM, wrote:
Jerry Stuckle wrote: snip I've also run dipoles - I got WAS on 75 meters from Iowa with an inverted VEE running from 50' to near ground. And I had a strong signal on the Iowa 75M SSB net. Perhaps you can get all the antenna manufacturers to specify their antennas in terms of signal reports and QSL cards instead of those useless numbers like gain and pattern. And you refuse to answer the question, instead trying to divert the conversation (again). It shows you're full of crap - just like all trolls. I rest my case. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#4
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On 11/21/2014 6:41 PM, Jerry Stuckle wrote:
On 11/21/2014 5:47 PM, Ian Jackson wrote: In message , Wayne writes wrote in message ... For those that do not have a firm understanding of what the chart of dipole height over ground shows, I offer the following explanation. The charts show, for a dipole antenna at various heights in wavelengths over perfect, very good, average, and extremely poor ground, the gain and elevation angle of the antenna main lobe. The main lobe is where the majority of the energy is radiated. To understand what the charts mean in the real world, first you have to understand a little bit about propagation of RF. For a dipole antenna, there are two modes of propagation that are relevant, and those are NVIS (Near Vertical Incidence Skywave) and skywave which is sometimes called skip. Both modes depend on the RF being reflected or refracted back toward Earth by the ionosphere. For NVIS mode, the RF is directed straight up, that is an elevation angle close to 90 degrees is desired. The range of NVIS communications is on the order of 50 - 650 km, depending on the state of the ionosphere. The amateur bands where this is effective is limited primarily to the 160M to 40M band, again depending on the state of the ionosphere. It is not impossible to have NVIS communications on the higher bands, just much less probable to happen. For skywave mode, a low elevation mode is desired. Most of the literature recommends angles of 30 degees or less. In this mode the RF "bounces" at more obtuse angles, and with good conditions in the ionosphere, more than once, providing communication over global distances. Skywave depends heavily on the condition of the ionosphere and during sunspot peaks often occurs well past 10M. Now since a dipole with a main lobe at 90 degrees still has some gain at low angles, though it can be 20 to 60 dB down from the main lobe, when conditions are very good some stations can still be heard by skywave mode, though it is a rarity and can not be depended on. Conversely a dipole with a low elevation angle of the main lobe has some gain at very high angles and can occasionly hear stations by NVIS mode, but again it is a rarity. The bottom line of all this is that if you desire NVIS communications, you should mount your dipole at a height where the elevation angle is close to 90 degrees while if you desire long distance communications you should mount your dipole at a height where the elevation angle is less than 30 degrees, or higher if possible. If the required height is impractical at your location, then the alternative is a ground mounted vertical or a close to ground mounted ground plane antenna, which will have an elevation angle in the 20 degree range. Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. Despite the obvious theory, and over 50 years in amateur radio, I still find it hard to believe that, in real life, an 80m dipole at (say) 20' ever really outperforms (at any distance) one at (say) 100'. Given the choice, I know which one I would choose! I never said a dipole at 20' outperforms one at 100'. But I DID say a dipole at 20' does NOT necessarily "suck". It can be a good antenna, depending on a lot of other factors. I've also run dipoles - I got WAS on 75 meters from Iowa with an inverted VEE running from 50' to near ground. And I had a strong signal on the Iowa 75M SSB net. Doesn't sound like it "sucked" to me. If you two really have balls, you will get on Skype, look at each other, and hash out your differences there. Or, maybe become friends. It can happen! |
#5
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On 11/23/2014 12:20 PM, John S wrote:
On 11/21/2014 6:41 PM, Jerry Stuckle wrote: On 11/21/2014 5:47 PM, Ian Jackson wrote: In message , Wayne writes wrote in message ... For those that do not have a firm understanding of what the chart of dipole height over ground shows, I offer the following explanation. The charts show, for a dipole antenna at various heights in wavelengths over perfect, very good, average, and extremely poor ground, the gain and elevation angle of the antenna main lobe. The main lobe is where the majority of the energy is radiated. To understand what the charts mean in the real world, first you have to understand a little bit about propagation of RF. For a dipole antenna, there are two modes of propagation that are relevant, and those are NVIS (Near Vertical Incidence Skywave) and skywave which is sometimes called skip. Both modes depend on the RF being reflected or refracted back toward Earth by the ionosphere. For NVIS mode, the RF is directed straight up, that is an elevation angle close to 90 degrees is desired. The range of NVIS communications is on the order of 50 - 650 km, depending on the state of the ionosphere. The amateur bands where this is effective is limited primarily to the 160M to 40M band, again depending on the state of the ionosphere. It is not impossible to have NVIS communications on the higher bands, just much less probable to happen. For skywave mode, a low elevation mode is desired. Most of the literature recommends angles of 30 degees or less. In this mode the RF "bounces" at more obtuse angles, and with good conditions in the ionosphere, more than once, providing communication over global distances. Skywave depends heavily on the condition of the ionosphere and during sunspot peaks often occurs well past 10M. Now since a dipole with a main lobe at 90 degrees still has some gain at low angles, though it can be 20 to 60 dB down from the main lobe, when conditions are very good some stations can still be heard by skywave mode, though it is a rarity and can not be depended on. Conversely a dipole with a low elevation angle of the main lobe has some gain at very high angles and can occasionly hear stations by NVIS mode, but again it is a rarity. The bottom line of all this is that if you desire NVIS communications, you should mount your dipole at a height where the elevation angle is close to 90 degrees while if you desire long distance communications you should mount your dipole at a height where the elevation angle is less than 30 degrees, or higher if possible. If the required height is impractical at your location, then the alternative is a ground mounted vertical or a close to ground mounted ground plane antenna, which will have an elevation angle in the 20 degree range. Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. Despite the obvious theory, and over 50 years in amateur radio, I still find it hard to believe that, in real life, an 80m dipole at (say) 20' ever really outperforms (at any distance) one at (say) 100'. Given the choice, I know which one I would choose! I never said a dipole at 20' outperforms one at 100'. But I DID say a dipole at 20' does NOT necessarily "suck". It can be a good antenna, depending on a lot of other factors. I've also run dipoles - I got WAS on 75 meters from Iowa with an inverted VEE running from 50' to near ground. And I had a strong signal on the Iowa 75M SSB net. Doesn't sound like it "sucked" to me. If you two really have balls, you will get on Skype, look at each other, and hash out your differences there. Or, maybe become friends. It can happen! I don't make friends with trolls. And I'm not going to waste any time on Skype with him. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#6
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On 11/23/2014 12:20 PM, John S wrote:
On 11/21/2014 6:41 PM, Jerry Stuckle wrote: On 11/21/2014 5:47 PM, Ian Jackson wrote: In message , Wayne writes wrote in message ... For those that do not have a firm understanding of what the chart of dipole height over ground shows, I offer the following explanation. The charts show, for a dipole antenna at various heights in wavelengths over perfect, very good, average, and extremely poor ground, the gain and elevation angle of the antenna main lobe. The main lobe is where the majority of the energy is radiated. To understand what the charts mean in the real world, first you have to understand a little bit about propagation of RF. For a dipole antenna, there are two modes of propagation that are relevant, and those are NVIS (Near Vertical Incidence Skywave) and skywave which is sometimes called skip. Both modes depend on the RF being reflected or refracted back toward Earth by the ionosphere. For NVIS mode, the RF is directed straight up, that is an elevation angle close to 90 degrees is desired. The range of NVIS communications is on the order of 50 - 650 km, depending on the state of the ionosphere. The amateur bands where this is effective is limited primarily to the 160M to 40M band, again depending on the state of the ionosphere. It is not impossible to have NVIS communications on the higher bands, just much less probable to happen. For skywave mode, a low elevation mode is desired. Most of the literature recommends angles of 30 degees or less. In this mode the RF "bounces" at more obtuse angles, and with good conditions in the ionosphere, more than once, providing communication over global distances. Skywave depends heavily on the condition of the ionosphere and during sunspot peaks often occurs well past 10M. Now since a dipole with a main lobe at 90 degrees still has some gain at low angles, though it can be 20 to 60 dB down from the main lobe, when conditions are very good some stations can still be heard by skywave mode, though it is a rarity and can not be depended on. Conversely a dipole with a low elevation angle of the main lobe has some gain at very high angles and can occasionly hear stations by NVIS mode, but again it is a rarity. The bottom line of all this is that if you desire NVIS communications, you should mount your dipole at a height where the elevation angle is close to 90 degrees while if you desire long distance communications you should mount your dipole at a height where the elevation angle is less than 30 degrees, or higher if possible. If the required height is impractical at your location, then the alternative is a ground mounted vertical or a close to ground mounted ground plane antenna, which will have an elevation angle in the 20 degree range. Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. Despite the obvious theory, and over 50 years in amateur radio, I still find it hard to believe that, in real life, an 80m dipole at (say) 20' ever really outperforms (at any distance) one at (say) 100'. Given the choice, I know which one I would choose! I never said a dipole at 20' outperforms one at 100'. But I DID say a dipole at 20' does NOT necessarily "suck". It can be a good antenna, depending on a lot of other factors. I've also run dipoles - I got WAS on 75 meters from Iowa with an inverted VEE running from 50' to near ground. And I had a strong signal on the Iowa 75M SSB net. Doesn't sound like it "sucked" to me. If you two really have balls, you will get on Skype, look at each other, and hash out your differences there. Or, maybe become friends. It can happen! I should also add - I will not speak to him where something is not being recorded. At least here he can't claim I've said things I never did say - and when he does, I can call him on it. I can also prove he has said the things he claims he never said. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#7
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![]() "Ian Jackson" wrote in message ... In message , Wayne writes wrote in message ... For those that do not have a firm understanding of what the chart of dipole height over ground shows, I offer the following explanation. The charts show, for a dipole antenna at various heights in wavelengths over perfect, very good, average, and extremely poor ground, the gain and elevation angle of the antenna main lobe. The main lobe is where the majority of the energy is radiated. To understand what the charts mean in the real world, first you have to understand a little bit about propagation of RF. For a dipole antenna, there are two modes of propagation that are relevant, and those are NVIS (Near Vertical Incidence Skywave) and skywave which is sometimes called skip. Both modes depend on the RF being reflected or refracted back toward Earth by the ionosphere. For NVIS mode, the RF is directed straight up, that is an elevation angle close to 90 degrees is desired. The range of NVIS communications is on the order of 50 - 650 km, depending on the state of the ionosphere. The amateur bands where this is effective is limited primarily to the 160M to 40M band, again depending on the state of the ionosphere. It is not impossible to have NVIS communications on the higher bands, just much less probable to happen. For skywave mode, a low elevation mode is desired. Most of the literature recommends angles of 30 degees or less. In this mode the RF "bounces" at more obtuse angles, and with good conditions in the ionosphere, more than once, providing communication over global distances. Skywave depends heavily on the condition of the ionosphere and during sunspot peaks often occurs well past 10M. Now since a dipole with a main lobe at 90 degrees still has some gain at low angles, though it can be 20 to 60 dB down from the main lobe, when conditions are very good some stations can still be heard by skywave mode, though it is a rarity and can not be depended on. Conversely a dipole with a low elevation angle of the main lobe has some gain at very high angles and can occasionly hear stations by NVIS mode, but again it is a rarity. The bottom line of all this is that if you desire NVIS communications, you should mount your dipole at a height where the elevation angle is close to 90 degrees while if you desire long distance communications you should mount your dipole at a height where the elevation angle is less than 30 degrees, or higher if possible. If the required height is impractical at your location, then the alternative is a ground mounted vertical or a close to ground mounted ground plane antenna, which will have an elevation angle in the 20 degree range. Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. # Despite the obvious theory, and over 50 years in amateur radio, I still # find it hard to believe that, in real life, an 80m dipole at (say) 20' # ever really outperforms (at any distance) one at (say) 100'. Given the # choice, I know which one I would choose! A 20 foot high 75 meter dipole wouldn't be my first choice for an antenna. At the time, that was the highest supports I had available. I just dusted off EZNEC and out of curiosity ran the plot for a 75 meter dipole at 20 feet over "real" ground. The max lobe was 9.36 dbi straight up at 90 degrees and a 3 db down beamwidth of 99.4 degrees. The 3 db down points were at 40.3 degrees and 139.7 degrees. So at least according to EZNEC, and my own personal experience for short range HF communication on 75 meters, a low dipole is a pretty good choice. |
#8
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El 22-11-14 3:01, Wayne escribió:
"Ian Jackson" wrote in message ... In message , Wayne writes wrote in message ... For those that do not have a firm understanding of what the chart of dipole height over ground shows, I offer the following explanation. The charts show, for a dipole antenna at various heights in wavelengths over perfect, very good, average, and extremely poor ground, the gain and elevation angle of the antenna main lobe. The main lobe is where the majority of the energy is radiated. To understand what the charts mean in the real world, first you have to understand a little bit about propagation of RF. For a dipole antenna, there are two modes of propagation that are relevant, and those are NVIS (Near Vertical Incidence Skywave) and skywave which is sometimes called skip. Both modes depend on the RF being reflected or refracted back toward Earth by the ionosphere. For NVIS mode, the RF is directed straight up, that is an elevation angle close to 90 degrees is desired. The range of NVIS communications is on the order of 50 - 650 km, depending on the state of the ionosphere. The amateur bands where this is effective is limited primarily to the 160M to 40M band, again depending on the state of the ionosphere. It is not impossible to have NVIS communications on the higher bands, just much less probable to happen. For skywave mode, a low elevation mode is desired. Most of the literature recommends angles of 30 degees or less. In this mode the RF "bounces" at more obtuse angles, and with good conditions in the ionosphere, more than once, providing communication over global distances. Skywave depends heavily on the condition of the ionosphere and during sunspot peaks often occurs well past 10M. Now since a dipole with a main lobe at 90 degrees still has some gain at low angles, though it can be 20 to 60 dB down from the main lobe, when conditions are very good some stations can still be heard by skywave mode, though it is a rarity and can not be depended on. Conversely a dipole with a low elevation angle of the main lobe has some gain at very high angles and can occasionly hear stations by NVIS mode, but again it is a rarity. The bottom line of all this is that if you desire NVIS communications, you should mount your dipole at a height where the elevation angle is close to 90 degrees while if you desire long distance communications you should mount your dipole at a height where the elevation angle is less than 30 degrees, or higher if possible. If the required height is impractical at your location, then the alternative is a ground mounted vertical or a close to ground mounted ground plane antenna, which will have an elevation angle in the 20 degree range. Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. # Despite the obvious theory, and over 50 years in amateur radio, I still # find it hard to believe that, in real life, an 80m dipole at (say) 20' # ever really outperforms (at any distance) one at (say) 100'. Given the # choice, I know which one I would choose! A 20 foot high 75 meter dipole wouldn't be my first choice for an antenna. At the time, that was the highest supports I had available. I just dusted off EZNEC and out of curiosity ran the plot for a 75 meter dipole at 20 feet over "real" ground. The max lobe was 9.36 dbi straight up at 90 degrees and a 3 db down beamwidth of 99.4 degrees. The 3 db down points were at 40.3 degrees and 139.7 degrees. Maybe you confused directivity (D) with gain (G), or used a wrong simulation paramater. A 20' high half wave dipole for 75m over average soil has about D = 9 dBi. However because of the heat dissipation into the soil below the antenna, the actual gain will be around 3 dBi. In other words about 75% of the RF energy is dissipated into the ground. Is this problem? frequently not, as the link budget on 75/80m has lots of margin under average conditions. Only onder worse conditions (large D-layer absorption and/or high local noise level at the target location) the one with the highest EIRP (=gain*power) will make the QSO. Several years during JOTA we had a better then average NVIS antenna for 80 m (with elevated reflection wires and a well fertilized production field). With 100W input we get complaints about why we were using a PA (we don't have one!). We decided to use a QRP TRX (10W) so the FT101ZD could be used for 40 m. We had no complaints about the signal. So on average there is nothing wrong when using an NVIS antenna with say 6 dB less performance (compared to an optimized one). Nowadays we use a "downgraded version". about 3..4 dB loss of gain, but it can be installed within 20% of the time required for the big one. So at least according to EZNEC, and my own personal experience for short range HF communication on 75 meters, a low dipole is a pretty good choice. -- Wim PA3DJS Please remove abc first in case of PM |
#9
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On 11/21/2014 5:22 PM, Wayne wrote:
wrote in message ... For those that do not have a firm understanding of what the chart of dipole height over ground shows, I offer the following explanation. The charts show, for a dipole antenna at various heights in wavelengths over perfect, very good, average, and extremely poor ground, the gain and elevation angle of the antenna main lobe. The main lobe is where the majority of the energy is radiated. To understand what the charts mean in the real world, first you have to understand a little bit about propagation of RF. For a dipole antenna, there are two modes of propagation that are relevant, and those are NVIS (Near Vertical Incidence Skywave) and skywave which is sometimes called skip. Both modes depend on the RF being reflected or refracted back toward Earth by the ionosphere. For NVIS mode, the RF is directed straight up, that is an elevation angle close to 90 degrees is desired. The range of NVIS communications is on the order of 50 - 650 km, depending on the state of the ionosphere. The amateur bands where this is effective is limited primarily to the 160M to 40M band, again depending on the state of the ionosphere. It is not impossible to have NVIS communications on the higher bands, just much less probable to happen. For skywave mode, a low elevation mode is desired. Most of the literature recommends angles of 30 degees or less. In this mode the RF "bounces" at more obtuse angles, and with good conditions in the ionosphere, more than once, providing communication over global distances. Skywave depends heavily on the condition of the ionosphere and during sunspot peaks often occurs well past 10M. Now since a dipole with a main lobe at 90 degrees still has some gain at low angles, though it can be 20 to 60 dB down from the main lobe, when conditions are very good some stations can still be heard by skywave mode, though it is a rarity and can not be depended on. Conversely a dipole with a low elevation angle of the main lobe has some gain at very high angles and can occasionly hear stations by NVIS mode, but again it is a rarity. The bottom line of all this is that if you desire NVIS communications, you should mount your dipole at a height where the elevation angle is close to 90 degrees while if you desire long distance communications you should mount your dipole at a height where the elevation angle is less than 30 degrees, or higher if possible. If the required height is impractical at your location, then the alternative is a ground mounted vertical or a close to ground mounted ground plane antenna, which will have an elevation angle in the 20 degree range. Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. Gee, according to jimp, your antenna should have "sucked". But then he isn't interested in facts that contradict his fantasies. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#10
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Jerry Stuckle wrote:
On 11/21/2014 5:22 PM, Wayne wrote: snip Along the lines of a "testimonial"... I once lived in the center of a state that had an active 75 meter net. At one point I was asked to be one of the net control stations because of my consistent strong signals within the net. The secret? A 75 meter dipole at 20 feet with 100 watts. On longer paths, of course, the "big boys" kicked my butt big time. Gee, according to jimp, your antenna should have "sucked". Which shows you are incapapble of understanding the difference between NVIS propagation and skywave propagation or anything else that I wrote. If you did understand it, you would know that what he said is TOTALLY consistant with what I wrote. But then he isn't interested in facts that contradict his fantasies. But then your aren't interested in facts that contradict your fantasies. -- Jim Pennino |
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