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E/M radiation from a short vertical aerial
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E/M radiation from a short vertical aerial
"Spike" wrote in message
... Not in the UK... We have a progressive licensing system here, in which most people never progress at all. The level they qualify at is more concerned with how to fit mains plugs - something that isn't required here as moulded plugs have been compulsory for 20 years. WHS And the tragedy is that even those who pass at the highest level can show no technical acumen whatsoever, to the extent that on Usenet they join in sneering but without ever understanding any of the technical content. We have one such person over in uk.radio.amateur who is currently being shunned for his infantile outbursts of ignorance. |
E/M radiation from a short vertical aerial
"Spike" wrote in message
... What I'm after is the relative amounts of power that finish up at the ionosphere, travelling through the atmosphere, and travelling along the surface, for a typical mobile set-up. Which is, after all, quite a reasonable line of enquiry for any self-respecting _REAL_ radio amateur, but perhaps the thread has developed in an unfortunate direction because of the characterisitics of questions posed off-the-cuff and not as a reasoned thesis? (I know that I have fallen iinto that trap on a number of occasions) |
E/M radiation from a short vertical aerial
Spike wrote:
On 08/03/15 18:08, Jeff wrote: Spike, you seem to think that there are different components coming from the antenna that make up the sky-wave component and the ground wave. That is not correct the antenna only radiates one kind of wave (EM). Whether it finds its way to the receiver by sky-wave or ground wave is purely due to what angle the wave hits the atmosphere/ground, and the state of the atmosphere. As an Example take a transmission on top band; during the day normally there will be virtually no sky-wave propagation; use exactly the same set up during the night and there will be considerable sky-wave. I think I knew that, Jeff... If your question is what do you have to do to maximize the ground wave the it is obviously to keep the maxima in the polar diagram as low as possible and don't waste power shooting it at high angles. No, I know how to do that. What I'm after is the relative amounts of power that finish up at the ionosphere, travelling through the atmosphere, and travelling along the surface, for a typical mobile set-up. Of course that is easier said than done, particularly with a mobile where the ground is likely to be poorer than a fixed station with a good ground mat. My initial conditions were a ground of average conductivity. Using something like NEC to model antennas will show the effects of various antenna configurations and ground configurations on the low angles of radiation. But it's only a model, and results depend on how it was constructed. I would rephrase your original question as follows. The approximate signal strength of the space wave at a certain distance, assuming a fairly low angle of the main lobe of the aerial with a moderate amount of gain over isotropic, can be calculated from simple physics. At about the same distance (and where of course you are not likely to see the space wave unless you have a very tall pole, but it has a defined signal strength well above you), what is the likely signal strength of the ground wave? Is it very much lower due to poor coupling, losses etc.? Is it about the same? Or is it much higher due to some phenomenon which I can't explain at the moment? That is really the same question as the one you asked (I think!), but couched in practical and testable terms. (It is rather trying to see the ignorant mocking a perfectly reasonable question from a position of total incomprehension. A bit juvenile, methinks.) -- Roger Hayter |
E/M radiation from a short vertical aerial
Stephen Thomas Cole wrote:
rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. There is no "fundamental misunderstanding" unless it be yours. At worst, loose phraseology. -- Roger Hayter |
E/M radiation from a short vertical aerial
On 09/03/2015 06:26, Stephen Thomas Cole wrote:
rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. Nor do you spend your time putting done newcomers and claiming only the route you claim to have followed into the hobby was the right one. |
E/M radiation from a short vertical aerial
"Spike" wrote in message
... Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. (etc) __________ Below is a link to a NEC study showing the 1.9 MHz fields radiated by a 3-meter vertical monopole driven against 4 x 2-meter horizontal radials, where the entire assembly is elevated 9" above earth of average conductivity. This might approximate a mobile installation of a whip antenna mounted on a vehicle, except for the pattern distortions produced by the body of the vehicle. Radiation from this system at elevation angles other than near zero degrees could act as direct waves, space waves or skywaves, depending on propagation paths, propagation conditions, and the physical locations of receive antennas. http://s20.postimg.org/ipzwlc9kd/Fie...t_Vertical.jpg R. Fry |
E/M radiation from a short vertical aerial
On 3/9/2015 3:29 AM, Jeff wrote:
I've been lurking in this thread and it reminded me of a time many years ago when I was working on a receiver setup. A colleague gave me a book with an equation for signal strength of a signal in the cell phone frequency range in various terrestrial environments. I had a little trouble accepting an arbitrary equation that wasn't at least close to the typical 1/r^2 formula in free space. I seem to recall there was no 1/r^2 term at all rather it was more like a linear or maybe had a rlog(r) term. In any event, no one could explain where the equation came from. I suppose it was an empirical equation rather than something derived from theory. Ignoring waves bounced off the upper atmosphere, I assume the earth acts to help focus the signal and strengthen it close to the ground? You are correct, most of those formulas are empirical, base on actual observations. Look up papers by Egli and by Hatta, they will five you some idea on how theses formulas were derived. Jeff As are basically all formulas. Even Ohm's Law was derived from actual observations. Although Einstein's equations such as E=mc^2 wasn't derived from actual observation, it did come by projection of existing knowledge by an exceptional mind. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
E/M radiation from a short vertical aerial
Roger Hayter wrote:
Stephen Thomas Cole wrote: rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. There is no "fundamental misunderstanding" unless it be yours. At worst, loose phraseology. I suggest you re-read Spike's multiple, confused posts about all the different types of waves that pour forth from an antenna. -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
rickman wrote:
On 3/9/2015 2:26 AM, Stephen Thomas Cole wrote: rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. The problem has nothing to do with radio theory. No, you're right. It's to do with Spike's stupidity. -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
"gareth" wrote:
"Spike" wrote in message ... Not in the UK... We have a progressive licensing system here, in which most people never progress at all. The level they qualify at is more concerned with how to fit mains plugs - something that isn't required here as moulded plugs have been compulsory for 20 years. WHS And the tragedy is that even those who pass at the highest level can show no technical acumen whatsoever, to the extent that on Usenet they join in sneering but without ever understanding any of the technical content. We have one such person over in uk.radio.amateur who is currently being shunned for his infantile outbursts of ignorance. SHUN FAIL -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
On 3/9/2015 10:11 AM, Jeff wrote:
As are basically all formulas. Even Ohm's Law was derived from actual observations. That is certainly not correct in a lot of cases. The inverse square law for free space path loss, for example, is derived intuitively and simply from the transmitted power being equally distributed in all directions, not from observations. S= P*(1/(4piD^2)) Jeff Jeff, Actually, not. It was observed first back in the 1700's-1800's when the link between electricity and magnetism was being investigated. And hundreds of years before that, it was a know property of magnets. The equations didn't come until later. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
E/M radiation from a short vertical aerial
Stephen Thomas Cole wrote:
Roger Hayter wrote: Stephen Thomas Cole wrote: rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. There is no "fundamental misunderstanding" unless it be yours. At worst, loose phraseology. I suggest you re-read Spike's multiple, confused posts about all the different types of waves that pour forth from an antenna. I have. Your comprehension of common expressions is lacking. Some of the Americans pedantically criticised his description, but I think we have all come round to knowing what he meant now, and that disagreement has been resolved. You seem to want to repeat it just to be abusive rather than to contribute to the discussion. -- Roger Hayter |
E/M radiation from a short vertical aerial
On 3/9/2015 5:11 AM, Spike wrote:
On 09/03/15 00:14, rickman wrote: On 3/8/2015 6:56 AM, Spike wrote: I'm beginning to think that this topic is either so simple or so complex that most Amateurs have either forgotten it or have never heard of it. I think everyone understands the question just fine. But it is a question without an answer. But that *is* an answer! What you are saying is that the research remains to be done. There is no research than can answer the question any better than what you have been given. The wave transmission modes you ask about are very little dependent on the antenna and much more dependent on the state of the environment. So there is no way possible to give an answer that relates the antenna design to something that depends on other variables. What you are asking is when you feed a bird, how much of that feed produces crap that lands on your car based on the composition of the feed? If the feed has more fat and less protein does that put more crap on the car or the driveway? I'd say, based on that, that nutrition science is better understood than the e/m fields emitted by an antenna. Do you understand the responses you have been given? Why do you feel the antenna has anything to do with the modes of propagation? If there were an answer to your question, why do you think it would not have been answered 50, 80 or 100 years ago? -- Rick |
E/M radiation from a short vertical aerial
On 09/03/15 15:48, Roger Hayter wrote:
Stephen Thomas Cole wrote: Roger Hayter wrote: Stephen Thomas Cole wrote: rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. There is no "fundamental misunderstanding" unless it be yours. At worst, loose phraseology. I suggest you re-read Spike's multiple, confused posts about all the different types of waves that pour forth from an antenna. I have. Your comprehension of common expressions is lacking. Some of the Americans pedantically criticised his description, but I think we have all come round to knowing what he meant now, and that disagreement has been resolved. You seem to want to repeat it just to be abusive rather than to contribute to the discussion. While Steve has used words I do not condone, his point is valid. Spike's post was nonsense- so much so that I thought it was some joke. Had a newcomer made a similar post he, and probably you in your Percy phase, along with your cronies, would have ridiculed him and made adverse comments about newcomers, the new licensing scheme, etc. etc. Your reaction now merely shows your hypocrisy. |
E/M radiation from a short vertical aerial
On 09/03/15 15:43, Jerry Stuckle wrote:
On 3/9/2015 10:11 AM, Jeff wrote: As are basically all formulas. Even Ohm's Law was derived from actual observations. That is certainly not correct in a lot of cases. The inverse square law for free space path loss, for example, is derived intuitively and simply from the transmitted power being equally distributed in all directions, not from observations. S= P*(1/(4piD^2)) Jeff Jeff, Actually, not. It was observed first back in the 1700's-1800's when the link between electricity and magnetism was being investigated. And hundreds of years before that, it was a know property of magnets. The equations didn't come until later. You are confusing a magnetic field with an EM field. You can have a magnetic field with no E field- eg from a bar magnet. It will have a magnet field which exhibits the inverse square law but no E field. |
E/M radiation from a short vertical aerial
On Sun, 08 Mar 2015 20:03:20 -0400, rickman wrote:
I can see you are right in the running yourself... This always seem to happen - an interesting and informative thread gets hijacked and abused by ignorant trolls. Charlie. M0WYM. -- Hello Wisconsin! |
E/M radiation from a short vertical aerial
On Mon, 09 Mar 2015 13:10:00 +0000, Brian Reay wrote:
Nor do you spend your time putting done newcomer Here we go - sigh, another group you have to be plonked from.. Please give it rest. TIA. -- Hello Wisconsin! |
E/M radiation from a short vertical aerial
"Charlie" wrote in message
... On Sun, 08 Mar 2015 20:03:20 -0400, rickman wrote: I can see you are right in the running yourself... This always seem to happen - an interesting and informative thread gets hijacked and abused by ignorant trolls. 'Ello? have reay and cole been spouting forth abuse yet again? (If so, do not elaborate, best to leave them in the KF with the dunce's caps on their heads) |
E/M radiation from a short vertical aerial
On 3/9/2015 12:54 PM, Brian Reay wrote:
On 09/03/15 15:43, Jerry Stuckle wrote: On 3/9/2015 10:11 AM, Jeff wrote: As are basically all formulas. Even Ohm's Law was derived from actual observations. That is certainly not correct in a lot of cases. The inverse square law for free space path loss, for example, is derived intuitively and simply from the transmitted power being equally distributed in all directions, not from observations. S= P*(1/(4piD^2)) Jeff Jeff, Actually, not. It was observed first back in the 1700's-1800's when the link between electricity and magnetism was being investigated. And hundreds of years before that, it was a know property of magnets. The equations didn't come until later. You are confusing a magnetic field with an EM field. You can have a magnetic field with no E field- eg from a bar magnet. It will have a magnet field which exhibits the inverse square law but no E field. Brian, No, I'm not confusing the two. But my point is that one led to the other. The equations didn't appear out of mid air - measurements preceded them. The observations I was talking about in the 1700's-1800's were for EM fields. And my point was their loss with distance is the same as with M fields - which had been known for a much longer time. And E fields were also measured back in the days of Leyden jars and the like. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
E/M radiation from a short vertical aerial
Roger Hayter wrote:
Stephen Thomas Cole wrote: Roger Hayter wrote: Stephen Thomas Cole wrote: rickman wrote: On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote: Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans G4SDW a run for his money here. I can see you are right in the running yourself... Hey, I'm not the one with the fundamental misunderstanding of radio theory after 50+ years in the hobby. There is no "fundamental misunderstanding" unless it be yours. At worst, loose phraseology. I suggest you re-read Spike's multiple, confused posts about all the different types of waves that pour forth from an antenna. I have. Your comprehension of common expressions is lacking. Some of the Americans pedantically criticised his description, but I think we have all come round to knowing what he meant now, and that disagreement has been resolved. You seem to want to repeat it just to be abusive rather than to contribute to the discussion. Tosh. Spike posted gibberish, several times, and was quite rightly corrected for it. His subsequent petulance about being put right is the icing on the cake. He's done a Gareth. -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
On 3/9/2015 12:54 PM, Brian Reay wrote:
On 09/03/15 15:43, Jerry Stuckle wrote: On 3/9/2015 10:11 AM, Jeff wrote: As are basically all formulas. Even Ohm's Law was derived from actual observations. That is certainly not correct in a lot of cases. The inverse square law for free space path loss, for example, is derived intuitively and simply from the transmitted power being equally distributed in all directions, not from observations. S= P*(1/(4piD^2)) Jeff Jeff, Actually, not. It was observed first back in the 1700's-1800's when the link between electricity and magnetism was being investigated. And hundreds of years before that, it was a know property of magnets. The equations didn't come until later. You are confusing a magnetic field with an EM field. You can have a magnetic field with no E field- eg from a bar magnet. It will have a magnet field which exhibits the inverse square law but no E field. The problem would seem to be that there is confusion with an equation being preceded by measurements (pretty much *every* equation known) with equations that were crafted in the absence of derivation solely to fit data. Even Einstein's equations had measurements that preceded them and were essential to their formulation. Michelson and Morley made the measurements that set the stage for E=Mc^2. I would hardly call that an empirical equation. Not much point in trying to discuss this. It will be impossible to find any common ground I am sure. -- Rick |
E/M radiation from a short vertical aerial
On 3/9/2015 1:08 PM, Charlie wrote:
On Sun, 08 Mar 2015 20:03:20 -0400, rickman wrote: I can see you are right in the running yourself... This always seem to happen - an interesting and informative thread gets hijacked and abused by ignorant trolls. I apologize. Sometimes I think I am trying to do some good, but there is no point in trying to teach pigs to sing. I'll stop feeding the trolls. -- Rick |
E/M radiation from a short vertical aerial
rickman wrote:
On 3/9/2015 12:54 PM, Brian Reay wrote: On 09/03/15 15:43, Jerry Stuckle wrote: On 3/9/2015 10:11 AM, Jeff wrote: As are basically all formulas. Even Ohm's Law was derived from actual observations. That is certainly not correct in a lot of cases. The inverse square law for free space path loss, for example, is derived intuitively and simply from the transmitted power being equally distributed in all directions, not from observations. S= P*(1/(4piD^2)) Jeff Jeff, Actually, not. It was observed first back in the 1700's-1800's when the link between electricity and magnetism was being investigated. And hundreds of years before that, it was a know property of magnets. The equations didn't come until later. You are confusing a magnetic field with an EM field. You can have a magnetic field with no E field- eg from a bar magnet. It will have a magnet field which exhibits the inverse square law but no E field. The problem would seem to be that there is confusion with an equation being preceded by measurements (pretty much *every* equation known) with equations that were crafted in the absence of derivation solely to fit data. Even Einstein's equations had measurements that preceded them and were essential to their formulation. Michelson and Morley made the measurements that set the stage for E=Mc^2. I would hardly call that an empirical equation. Not much point in trying to discuss this. It will be impossible to find any common ground I am sure. OK, lets not treat it as aerial question. Though this is an aerial group, I would have thought propagation was on topic. Can I ask if there is any information around which would give us some guidance on what power one would need in a dampish country about 200 by 800 miles across to intercommunicate by ground wave at 1.8MHZ? I think this is actually the gist of Spike's question, assuming everyone uses decent vertical aerials (a big assumption, of course). -- Roger Hayter |
E/M radiation from a short vertical aerial
Roger Hayter wrote:
snip OK, lets not treat it as aerial question. Though this is an aerial group, I would have thought propagation was on topic. Can I ask if there is any information around which would give us some guidance on what power one would need in a dampish country about 200 by 800 miles across to intercommunicate by ground wave at 1.8MHZ? I think this is actually the gist of Spike's question, assuming everyone uses decent vertical aerials (a big assumption, of course). http://www.itu.int/rec/R-REC-P.368/en Follow the link to the latest version, language, and format desired. Covers the frequency range of 10 kHz to 30 MHz. -- Jim Pennino |
E/M radiation from a short vertical aerial
On 09/03/15 17:10, Charlie wrote:
On Mon, 09 Mar 2015 13:10:00 +0000, Brian Reay wrote: Nor do you spend your time putting done newcomer Here we go - sigh, another group you have to be plonked from.. Please give it rest. TIA. Well, if that were true, it would cut down your abuse. Sadly, we all know it isn't true and you will continue your silly interjections. Now run along and play in your fantasy village, you can probably play your silly games there and make believe someone cares. |
E/M radiation from a short vertical aerial
On Monday, March 9, 2015 at 4:12:45 AM UTC-5, Spike wrote:
That's space wave on 10m. Not in the UK! Even the flatlands of Norfolk and Lincolnshire have enough surface topography to make space-wave unlikely. It's very unlikely to be surface wave at that frequency. If they are able to communicate over that land on 10m, they almost surely are using the space wave. If not purely direct within the normal radio horizon, by refraction or reflection or both. And you are not stating how high the antennas are mounted, which would be a large factor also. I hope you are not trying to tell me that no one in that area can receive any VHF or UHF TV or radio transmissions.. :/ Well, not everyone does. I know many on 160m who favor verticals. Not only for ground wave, but better DX. Not in the UK... We have a progressive licensing system here, in which most people never progress at all. The level they qualify at is more concerned with how to fit mains plugs - something that isn't required here as moulded plugs have been compulsory for 20 years. These people tend to buy the one aerial they've heard of, the G5RV. I'm fairly sure not everyone in the UK depends solely on the GR5V as a 160m antenna. :/ The ground wave is pretty good on 160m if using a vertical. Nearly as good as on the MW AM broadcast band, being the two bands are right next door to each other, so to speak. I'm a big fan of 160m ground wave/surface wave. It can be handy. I like listening to AM broadcast in the daytime which at any real distance is surface wave. One thing that is handy about it, is you can often totally null it out to receive stations on the same frequency, but in different directions if using a small loop, etc.. I've made a few recordings which I posted here in the past demonstrating that. I could make most AM-BC stations via surface wave flat out vanish if I felt so compelled. :) And then another one would be listenable in it's place. With a wire or vertical, it would just be a jumble of two or more stations all being received at once. |
E/M radiation from a short vertical aerial
On 06/03/15 23:02, Spike wrote:
Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. Many thanks to all who took the trouble to reply, with input ranging from from the uncouth through the unhelpful to the deeply technical. The modelling results and the graphs of the surface-wave propagation that were provided will likely prove very useful for another propagation project currently under study here. One fact that has become apparent is that ground conductivity maps that assign a value to region-wide areas are not to be trusted - there are sometimes quite severe changes in local conductivity, and these could encompass the ground that affects the radiation pattern from one's antenna. However, models have now become sophisticated enough to incorporate these into their predictions; the difficulty lies in obtaining reliable conductivity figures for one's location, especially those of poor conductivity where earth currents can run deep in the soil. Although this isn't strictly an 'antenna' issue, it is nevertheless fundamental to LF/MF/HF operation and highly pertinent as to how the antenna contributes to the station performance. -- Spike "Hard cases, it has frequently been observed, are apt to introduce bad law". Judge Rolfe |
E/M radiation from a short vertical aerial
Spike wrote:
On 06/03/15 23:02, Spike wrote: Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. Many thanks to all who took the trouble to reply, with input ranging from from the uncouth through the unhelpful to the deeply technical. The modelling results and the graphs of the surface-wave propagation that were provided will likely prove very useful for another propagation project currently under study here. One fact that has become apparent is that ground conductivity maps that assign a value to region-wide areas are not to be trusted - there are sometimes quite severe changes in local conductivity, and these could encompass the ground that affects the radiation pattern from one's antenna. However, models have now become sophisticated enough to incorporate these into their predictions; the difficulty lies in obtaining reliable conductivity figures for one's location, especially those of poor conductivity where earth currents can run deep in the soil. Although this isn't strictly an 'antenna' issue, it is nevertheless fundamental to LF/MF/HF operation and highly pertinent as to how the antenna contributes to the station performance. While your local earth conductivity may well vary from that for you region, in the scheme of things, especially if the path in question includes a transit of sea water, to suggest it will play a significant role is somewhat bold. To see this, look at the relative numbers I gave earlier for North America. Local conditions will, of course, impact antenna efficiency. I suggest you do some more thinking before you challenge the work of the eminent people who have studied this area and published papers etc. |
E/M radiation from a short vertical aerial
On 12/03/15 13:28, Brian Reay wrote:
Spike wrote: On 06/03/15 23:02, Spike wrote: Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. Many thanks to all who took the trouble to reply, with input ranging from from the uncouth through the unhelpful to the deeply technical. The modelling results and the graphs of the surface-wave propagation that were provided will likely prove very useful for another propagation project currently under study here. One fact that has become apparent is that ground conductivity maps that assign a value to region-wide areas are not to be trusted - there are sometimes quite severe changes in local conductivity, and these could encompass the ground that affects the radiation pattern from one's antenna. However, models have now become sophisticated enough to incorporate these into their predictions; the difficulty lies in obtaining reliable conductivity figures for one's location, especially those of poor conductivity where earth currents can run deep in the soil. Although this isn't strictly an 'antenna' issue, it is nevertheless fundamental to LF/MF/HF operation and highly pertinent as to how the antenna contributes to the station performance. While your local earth conductivity may well vary from that for you region, in the scheme of things, especially if the path in question includes a transit of sea water, to suggest it will play a significant role is somewhat bold. To see this, look at the relative numbers I gave earlier for North America. If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. Local conditions will, of course, impact antenna efficiency. The antenna efficiency is affected by its mechanical form. Earth losses are something else, which can be factored in to estimate antenna system efficiency, which, of course, isn't the same thing. I suggest you do some more thinking before you challenge the work of eminent people who have studied this area and published papers etc. I asked a simple and straightforward question, which has been answered only in part and not at all by you, in what appears to be your normal spirit of offering every assistance short of actual help. As you mention published papers, perhaps you'd let us know how many of yours have seen the light of day in peer-reviewed prestige journals? I find it difficult to accept input on this and similar matters from someone who not only avoided taking out an HF licence for 30 years but who also judges the finer points of HF receiver performance by noting which DXpeditions might be subsidised by which manufacturer. -- Spike "Hard cases, it has frequently been observed, are apt to introduce bad law". Judge Rolfe |
E/M radiation from a short vertical aerial
On 12/03/15 18:43, Spike wrote:
On 12/03/15 13:28, Brian Reay wrote: Spike wrote: On 06/03/15 23:02, Spike wrote: Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. Many thanks to all who took the trouble to reply, with input ranging from from the uncouth through the unhelpful to the deeply technical. The modelling results and the graphs of the surface-wave propagation that were provided will likely prove very useful for another propagation project currently under study here. One fact that has become apparent is that ground conductivity maps that assign a value to region-wide areas are not to be trusted - there are sometimes quite severe changes in local conductivity, and these could encompass the ground that affects the radiation pattern from one's antenna. However, models have now become sophisticated enough to incorporate these into their predictions; the difficulty lies in obtaining reliable conductivity figures for one's location, especially those of poor conductivity where earth currents can run deep in the soil. Although this isn't strictly an 'antenna' issue, it is nevertheless fundamental to LF/MF/HF operation and highly pertinent as to how the antenna contributes to the station performance. While your local earth conductivity may well vary from that for you region, in the scheme of things, especially if the path in question includes a transit of sea water, to suggest it will play a significant role is somewhat bold. To see this, look at the relative numbers I gave earlier for North America. If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. Local conditions will, of course, impact antenna efficiency. The antenna efficiency is affected by its mechanical form. Earth losses are something else, which can be factored in to estimate antenna system efficiency, which, of course, isn't the same thing. I suggest you do some more thinking before you challenge the work of eminent people who have studied this area and published papers etc. I asked a simple and straightforward question, which has been answered only in part and not at all by you, in what appears to be your normal spirit of offering every assistance short of actual help. As you mention published papers, perhaps you'd let us know how many of yours have seen the light of day in peer-reviewed prestige journals? I find it difficult to accept input on this and similar matters from someone who not only avoided taking out an HF licence for 30 years but who also judges the finer points of HF receiver performance by noting which DXpeditions might be subsidised by which manufacturer. As ever, by you inaccurate closing paragraphs you've shown yourself to be an foolish troll, like your friend Evans. I suggest that, to save yourself further embarrassment, you revert to your normal habit of avoiding the technical groups and revert to your role of telling fantasy stories about your past. |
E/M radiation from a short vertical aerial
On Thursday, March 12, 2015 at 1:43:04 PM UTC-5, Spike wrote:
I asked a simple and straightforward question. It's not that simple and straightforward though.. Best way to get some idea would be to model the antenna, and note the gain at the usual angles to be used for the various types of propagation. And being as skywave will depend on many different angles for the different bands at different times of day... :+ That makes it even more complicated. Space and surface wave will depend mostly on the lower angle performance. Modeling the antenna over ground of average conductivity, and then deciding what angles are likely to be used for each type of propagation, and then noting the modeled gain at those various angles is going to give you a better idea than anything we can tell you. :| |
E/M radiation from a short vertical aerial
On 13/03/15 07:30, Jeff wrote:
If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. I think it is your choice of words that is causing the confusion. It is not normally the practice to consider the ground conductivity over the entire transmission path when considering the radiation pattern of an antenna. It is usual to have a 'local' radiation pattern and then consider what happens on the path as a separate (path loss) issue. Mmm...my original question was concerned with how much power wound up where, I'm sure this sort of thing was asked after sky-wave propagation was discovered ~90 years ago. I believe that ground-wave/space-wave propagation was understood before then. Obviously with a sky wave path the intervening ground has no effect, but with a ground wave signal it can have a huge effect, particularly is there is water in the path. The ground causes the lower portion of the wave to be retarded so you can think of the wave-front as starting to slope, the degree of additional slope along the path depends on the ground properties (conductivity and permittivity) at any point. The wave will propagate like this until the 'slope**' becomes too great an angle for the wave to propagate. Yes, I'm familiar with the concept, I've mentioned it several times before now, usually in terms of an ultimate maximum surface-wave range. Interestingly, the ITU ground-wave curves that were referenced in this thread show no such phenomenon, even at 30 MHz, or suggest that this is a much gentler in action than might otherwise appear - perhaps this implies there is a limit to the veracity of the modelling? **apologies to Jeremy Clarkson .. I recall a cartoon about Spiro T. Agnew in the 1960s.....Unsurprisingly, I can't seem to find a reference to it. I think it was published in Time magazine, BICBW. Today, it's what's known as 'not politically correct', the current version of doublethink applying here. [1] Once upon a time, the group I worked in had brought in the UK's leading theoretical electromagneticist to act as an adviser. Afterwards, I buttonholed him and asked for his view on an e/m issue[2] I was responsible for. It was a straightforward question, but he had difficulty understanding it, nonetheless he said he'd look into it. He got back to me two weeks later. In apologising for the delay, he said that no-one had ever asked this question before, and he'd spent the intervening time researching the issue. I'm well used to asking awkward questions of experts, it's their replies that give them away as to whether they know their stuff or not. [2] related to what happens when an e/m wave meets a surface, so not entirely disconnected from this thread. It's a subject one would think would have been well covered, but apparently this was not the case, and asking a simple question revealed that. -- Spike "Hard cases, it has frequently been observed, are apt to introduce bad law". Judge Rolfe |
E/M radiation from a short vertical aerial
On 12/03/15 19:54, Brian Reay wrote:
On 12/03/15 18:43, Spike wrote: I find it difficult to accept input on this and similar matters from someone who not only avoided taking out an HF licence for 30 years but who also judges the finer points of HF receiver performance by noting which DXpeditions might be subsidised by which manufacturer. As ever, by you inaccurate closing paragraphs you've shown yourself to be an foolish troll, like your friend Evans. I suggest that, to save yourself further embarrassment, you revert to your normal habit of avoiding the technical groups and revert to your role of telling fantasy stories about your past. I note that when you have no technical input to a thread, you resort to insults and bluster. They didn't take long to find you out in the Ubuntu group, and I suspect this one is no different. No wonder you're in my Trolls filter over in UKRA. I've just posted a 'story about my past' in response to Jeff. Enjoy. -- Spike "Hard cases, it has frequently been observed, are apt to introduce bad law". Judge Rolfe |
E/M radiation from a short vertical aerial
"Spike" wrote in message
... On 12/03/15 19:54, Brian Reay wrote: On 12/03/15 18:43, Spike wrote: I find it difficult to accept input on this and similar matters from someone who not only avoided taking out an HF licence for 30 years but who also judges the finer points of HF receiver performance by noting which DXpeditions might be subsidised by which manufacturer. As ever, by you inaccurate closing paragraphs you've shown yourself to be an foolish troll, like your friend Evans. I suggest that, to save yourself further embarrassment, you revert to your normal habit of avoiding the technical groups and revert to your role of telling fantasy stories about your past. I note that when you have no technical input to a thread, you resort to insults and bluster. They didn't take long to find you out in the Ubuntu group, and I suspect this one is no different. No wonder you're in my Trolls filter over in UKRA. You have M3OSN down to a "T" |
E/M radiation from a short vertical aerial
Jeff wrote:
If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. Spike I think it is your choice of words that is causing the confusion. It is not normally the practice to consider the ground conductivity over the entire transmission path when considering the radiation pattern of an antenna. It is usual to have a 'local' radiation pattern and then consider what happens on the path as a separate (path loss) issue. Ground conductivity more that a few wavelengths from the antenna has an insignificant effect on the antenna pattern. Ground conductivity around the antenna has a small effect on the antenna pattern in the real world. If you doubt this, download the free demo version of EZNEC and compare the pattern of an antenna over average ground to an antenna over poor ground. -- Jim Pennino |
E/M radiation from a short vertical aerial
Spike wrote:
On 13/03/15 07:30, Jeff wrote: If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. I think it is your choice of words that is causing the confusion. It is not normally the practice to consider the ground conductivity over the entire transmission path when considering the radiation pattern of an antenna. It is usual to have a 'local' radiation pattern and then consider what happens on the path as a separate (path loss) issue. Mmm...my original question was concerned with how much power wound up where, I'm sure this sort of thing was asked after sky-wave propagation was discovered ~90 years ago. I believe that ground-wave/space-wave propagation was understood before then. Obviously with a sky wave path the intervening ground has no effect, but with a ground wave signal it can have a huge effect, particularly is there is water in the path. The ground causes the lower portion of the wave to be retarded so you can think of the wave-front as starting to slope, the degree of additional slope along the path depends on the ground properties (conductivity and permittivity) at any point. The wave will propagate like this until the 'slope**' becomes too great an angle for the wave to propagate. Yes, I'm familiar with the concept, I've mentioned it several times before now, usually in terms of an ultimate maximum surface-wave range. Interestingly, the ITU ground-wave curves that were referenced in this thread show no such phenomenon, even at 30 MHz, or suggest that this is a much gentler in action than might otherwise appear - perhaps this implies there is a limit to the veracity of the modelling? **apologies to Jeremy Clarkson . I recall a cartoon about Spiro T. Agnew in the 1960s.....Unsurprisingly, I can't seem to find a reference to it. I think it was published in Time magazine, BICBW. Today, it's what's known as 'not politically correct', the current version of doublethink applying here. [1] Once upon a time, the group I worked in had brought in the UK's leading theoretical electromagneticist to act as an adviser. Afterwards, I buttonholed him and asked for his view on an e/m issue[2] I was responsible for. It was a straightforward question, but he had difficulty understanding it, nonetheless he said he'd look into it. He got back to me two weeks later. In apologising for the delay, he said that no-one had ever asked this question before, and he'd spent the intervening time researching the issue. I'm well used to asking awkward questions of experts, it's their replies that give them away as to whether they know their stuff or not. [2] related to what happens when an e/m wave meets a surface, so not entirely disconnected from this thread. It's a subject one would think would have been well covered, but apparently this was not the case, and asking a simple question revealed that. LOL, you're taking this lampoon of Gareth a bit too far now, OM. Even he's not *this* deluded. -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
Jeff wrote:
If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. Spike I think it is your choice of words that is causing the confusion. It is not normally the practice to consider the ground conductivity over the entire transmission path when considering the radiation pattern of an antenna. It is usual to have a 'local' radiation pattern and then consider what happens on the path as a separate (path loss) issue. Obviously with a sky wave path the intervening ground has no effect, but with a ground wave signal it can have a huge effect, particularly is there is water in the path. The ground causes the lower portion of the wave to be retarded so you can think of the wave-front as starting to slope, the degree of additional slope along the path depends on the ground properties (conductivity and permittivity) at any point. The wave will propagate like this until the 'slope**' becomes too great an angle for the wave to propagate. **apologies to Jeremy Clarkson Jeff, Spike's too far down the hole he's dug to climb out now without losing face, so I fear your assistance will be rejected. -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
Brian Reay wrote:
Spike wrote: On 06/03/15 23:02, Spike wrote: Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. Many thanks to all who took the trouble to reply, with input ranging from from the uncouth through the unhelpful to the deeply technical. The modelling results and the graphs of the surface-wave propagation that were provided will likely prove very useful for another propagation project currently under study here. One fact that has become apparent is that ground conductivity maps that assign a value to region-wide areas are not to be trusted - there are sometimes quite severe changes in local conductivity, and these could encompass the ground that affects the radiation pattern from one's antenna. However, models have now become sophisticated enough to incorporate these into their predictions; the difficulty lies in obtaining reliable conductivity figures for one's location, especially those of poor conductivity where earth currents can run deep in the soil. Although this isn't strictly an 'antenna' issue, it is nevertheless fundamental to LF/MF/HF operation and highly pertinent as to how the antenna contributes to the station performance. While your local earth conductivity may well vary from that for you region, in the scheme of things, especially if the path in question includes a transit of sea water, to suggest it will play a significant role is somewhat bold. To see this, look at the relative numbers I gave earlier for North America. Local conditions will, of course, impact antenna efficiency. I suggest you do some more thinking before you challenge the work of the eminent people who have studied this area and published papers etc. I'm really in two minds as to whether this is all just a massive send up of Gareth Alun Evans G4SDW or not. It's all there, the initial wrong-headed query, the subsequent aggressive/dismissive response to those helpful souls correcting the mistake, the rejection of long-established and well-researched principles. It's got to be a wind up, Spike isn't this much of a ****. -- STC // M0TEY // twitter.com/ukradioamateur |
E/M radiation from a short vertical aerial
Brian Reay wrote:
On 12/03/15 18:43, Spike wrote: On 12/03/15 13:28, Brian Reay wrote: Spike wrote: On 06/03/15 23:02, Spike wrote: Imagine a short rod vertical aerial not connected to ground, for the (say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed with RF energy and operating over ground of average conductivity. Many thanks to all who took the trouble to reply, with input ranging from from the uncouth through the unhelpful to the deeply technical. The modelling results and the graphs of the surface-wave propagation that were provided will likely prove very useful for another propagation project currently under study here. One fact that has become apparent is that ground conductivity maps that assign a value to region-wide areas are not to be trusted - there are sometimes quite severe changes in local conductivity, and these could encompass the ground that affects the radiation pattern from one's antenna. However, models have now become sophisticated enough to incorporate these into their predictions; the difficulty lies in obtaining reliable conductivity figures for one's location, especially those of poor conductivity where earth currents can run deep in the soil. Although this isn't strictly an 'antenna' issue, it is nevertheless fundamental to LF/MF/HF operation and highly pertinent as to how the antenna contributes to the station performance. While your local earth conductivity may well vary from that for you region, in the scheme of things, especially if the path in question includes a transit of sea water, to suggest it will play a significant role is somewhat bold. To see this, look at the relative numbers I gave earlier for North America. If you understand what I wrote above, you'll see my point was about local conductivity and how it affects the radiation pattern after being launched from an antenna, rather than the variability along a signal path, although I did mention for completeness that models can now take such variability into account. Local conditions will, of course, impact antenna efficiency. The antenna efficiency is affected by its mechanical form. Earth losses are something else, which can be factored in to estimate antenna system efficiency, which, of course, isn't the same thing. I suggest you do some more thinking before you challenge the work of eminent people who have studied this area and published papers etc. I asked a simple and straightforward question, which has been answered only in part and not at all by you, in what appears to be your normal spirit of offering every assistance short of actual help. As you mention published papers, perhaps you'd let us know how many of yours have seen the light of day in peer-reviewed prestige journals? I find it difficult to accept input on this and similar matters from someone who not only avoided taking out an HF licence for 30 years but who also judges the finer points of HF receiver performance by noting which DXpeditions might be subsidised by which manufacturer. As ever, by you inaccurate closing paragraphs you've shown yourself to be an foolish troll, like your friend Evans. I suggest that, to save yourself further embarrassment, you revert to your normal habit of avoiding the technical groups and revert to your role of telling fantasy stories about your past. This hasn't been a total waste of time, Brian, I haven't laughed this hard all week! -- STC // M0TEY // twitter.com/ukradioamateur |
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