Re: Topband: Monopole Radiation Patterns, takeoff angles etc
The program W6ELProp gives the take-off-angle needed for any path. Looking at 80 meter paths (it does 801-0 meters) the angles for DX paths are in the range of 3-15 degrees. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
What I am saying is that ground loss must increase the higher we go in frequency, attenuating the surface wave more and more the higher and higher we go. But Rich is also talking about the radiation at zero degrees bouncing off the ionosphere and returning to the earth at some distant point. Groundwave propagation losses increase directly with frequency and inversely with earth conductivity. However my statements in this thread, and the graphics I have linked to do not support the conclusion that the radiation at zero degrees elevation is the source of the low-angle fields launched by a monopole. A review of the comparison linked next below (again) shows in the NEC plots that it is the space wave radiation from the monopole at elevation angles above about 1 degree that are responsible for the skywave fields existing 100 meters above the ground plane -- not the groundwave field radiated at zero degrees. Nothing prevents those fields at 100 m AGL from traveling on to the ionosphere. http://i62.photobucket.com/albums/h85/rfry-100/Measured_vs_NEC2D_Fields2.jpg The far field pattern will accurately capture what is going to reach the ionosphere. A surface wave table will accurately capture your groundwave range. If you were to try to do a plot as far as the distance to the ionosphere at a low angle, the above plot would be misleading because the earth has dropped away significantly, taking the strongest part of the earth-hugging surface wave with it The NEC surface wave includes low-angle fields well above zero degrees elevation that do not appear in a NEC far-field plot, and they are in fact space waves (see link below). Those fields can propagate to the ionosphere and back if the paths are unobstructed. The surface wave field in this plot is that for a 50 kW broadcast station on 760 kHz, over a 145.3 km groundwave path with a conductivity of 8 mS/m. http://i62.photobucket.com/albums/h85/rfry-100/WJRElevationField.gif ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Thats not exactly what I meant, I was simply stating that ground wave on both bands is excellent. When I was a lot younger those bands were very popular with commuters on AM. Radiation at zero degrees wont bounce off anything, it will eventually be all absorbed by ground losses. Its also doubtful that radiation at 5* will do much better unless its all over salt water. Carl KM1H - Original Message - From: Mike Waters To: topband Cc: ZR Sent: Monday, May 07, 2012 10:22 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc I've never operated mobile, but it sounds like you're saying the daytime local range on 160 and 10 is comparable. But Rich is also talking about the radiation at zero degrees bouncing off the ionosphere and returning to the earth at some distant point. That's what I'm wondering about. Local is one thing, but DX is another. 73, Mike On Mon, May 7, 2012 at 9:04 PM, ZR z...@jeremy.mv.com wrote: Try operating 160 and 10M mobile, you would be surprised at the daytime range even with low power into a 8' antenna on 160. I'm pretty sure this surface wave at ~0 degrees elevation is useful on (and below) the AM broadcast band (especially the lower portion) and 160 meters. But what about at 3.5, 5, 7, 10, 14, 18, 21, 24, and 28 MHz? That's what I've been trying to figure out: exactly how useful is this radiation at zero degrees on the different ham bands? Based on my experiences --and what I've studied-- since 1976, I'm not sure that it is. 73, Mike -- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2425/4985 - Release Date: 05/08/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
ELF sub communication was to get a signal to a submerged sub and it still took megawatts and an extremely slow bit rate. All it did was to tell the sub to come up enough to deploy its satellite antenna and get high speed burst data. Carl KM1H - Original Message - From: Hardy Landskov n...@cox.net To: Mike Waters mikew...@gmail.com; topband topband@contesting.com Cc: ZR z...@jeremy.mv.com; Richard Fry r...@adams.net Sent: Monday, May 07, 2012 11:02 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc - Original Message - From: Mike Waters mikew...@gmail.com To: topband topband@contesting.com Cc: ZR z...@jeremy.mv.com; Richard Fry r...@adams.net Sent: Monday, May 07, 2012 7:35 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc Let me expand on what I said previously. I always thought that ground wave propagation decreased with frequency. For example, don't AM broadcast stations in the lower end of the AM broadcast band have greater coverage than at the high end, all things being equal? Yes most definately. Ground wave is substantial over sea water. Why do you think the international distress frequency for ships was at 500 KHz? I have always thought that, and I also think that this phenomenon increases as we move through 160 meters, then through 80, 40, etc. etc. and we become more and more dependent on higher angles there for at but local communications. Of course, this is somewhat dependent on the time of day, whether we are talking about daytime or nighttime propagation. What you say is about lowering frequency is true. This is why submarines can communicate throughout the World because at low enough frequencies, the whole planet Earth looks like an insulator. 73 Hardy N7RT - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2425/4985 - Release Date: 05/08/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
The NEC surface wave includes low-angle fields well above zero degrees elevation that do not appear in a NEC far-field plot, and they are in fact space waves (see link below). And that's the piece that probably not been underscored in this discussion. Some have probably concluded that the surface wave plot in NEC only includes ground wave conduction. An interesting exercise I went through a couple days ago (using NEC/4.2): distance was varied between 1km and 10km from a 160m 1/4-wave vertical radiator over a 60-radial field. I then modified the ground conductivity between poor and very good while observing the surface wave plot with changing distance. Even over average ground, and unlike the far-field analysis, the surface wave and the space wave are reasonably close out to about 4-5 km. That's roughly 25-30 wavelengths on 160m. Over poor earth, you start seeing the effects low-angle field strength attenuation much earlier as is expected. So, just how much distance is required to effectively launch a 160m field into the ionosphere to the point where the ground surface and conductivity is no longer relevant? By 25 wavelengths, can we safely say that it's launched absent some other factor like a mountain range? How about 5-10 wavelengths -- is that enough? Clearly, the traditional far-field plots are at odds with the NEC surface wave plots (that also include the space wave as Richard mentions) in that unless the ground is extremely poor, the far field plots are not accurate as far as NEC is concerned. Yes, the far field plot does show the lobe from a ground-mounted vertical radiator coming down closer and closer to the earth as ground conduction improves but only gets there with super-conductive ground like salt water, leaving us to conclude that with normal earth conductivity there's no field at all below the far-field curve. A surface wave plot over salt water does show extremely close field strength over very long distances between the far field and surface wave as one might expect. So, if the NEC surface wave tool is accurate, we've not been looking at the entire picture when considering only far-field analysis. Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Some USN subs used to be retrofitted here in the VI and I was called to pick up some of the transmitters which required a fork lift to put the transformers on the back of a truck. The RF deck used a pair of 4CX5000's and they appear to drive some sort of transducer for underwater communication. One of the techs called them fish phones for underwater to surface communications. I am not sure what the modulation scheme was nor what technology it was replaced with but both methods were a form of two way underwater communications. I had heard that the mile long trailing wire method was abandoned in favor of a brute force method to drive data via salt water to the surface. Herb Schoenbohm, KV4FZ On 5/8/2012 9:38 AM, ZR wrote: ELF sub communication was to get a signal to a submerged sub and it still took megawatts and an extremely slow bit rate. All it did was to tell the sub to come up enough to deploy its satellite antenna and get high speed burst data. Carl KM1H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Dave WX7G wrote: The program W6ELProp gives the take-off-angle needed for any path. Looking at 80 meter paths (it does 801-0 meters) the angles for DX paths are in the range of 3-15 degrees. Assuming those angles are true for DX paths, note that if the NEC far-field elevation pattern for a 1/4-wave monopole was the only radiation leaving the antenna, the field at 3 degrees elevation would be about 8.9 dB below the field at the center of the so called take-off angle (see link below - note Photobucket stripped the decimal from the 3.9MHz link). The surface wave really needs to be recognized in such evaluations. http://i62.photobucket.com/albums/h85/rfry-100/39MHz_Elepat_6_mS.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
If the radiation at 3 degrees is -8.9 dB relative to the maximum amplitude we can still work DX. Dave WX7G On May 8, 2012 9:18 AM, Richard Fry r...@adams.net wrote: Dave WX7G wrote: The program W6ELProp gives the take-off-angle needed for any path. Looking at 80 meter paths (it does 801-0 meters) the angles for DX paths are in the range of 3-15 degrees. Assuming those angles are true for DX paths, note that if the NEC far-field elevation pattern for a 1/4-wave monopole was the only radiation leaving the antenna, the field at 3 degrees elevation would be about 8.9 dB below the field at the center of the so called take-off angle (see link below - note Photobucket stripped the decimal from the 3.9MHz link). The surface wave really needs to be recognized in such evaluations. http://i62.photobucket.com/albums/h85/rfry-100/39MHz_Elepat_6_mS.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
One really needs to evaluate the usefulness of 5 degrees and under in a case-by-case basis. Most people in populated areas have 5 degrees completely obliterated by conductive and semi-conductive clutter...houses, trees, overhead powerlines, buildings, yada yada. And probably 10 and 15 degrees are obliterated as well. And unless you are someplace where they talk about big sky or on a mountain top, you are most likely NOT in a completely flat place, so plus 5 degrees (85 degrees below zenith) is beneath the horizon on at least half your compass. Not only that, if I'm reading it right, the math of ground wave DEPENDS ON, REQUIRES monolithic uniform dirt, both over distance and to depth, to support to the level of those good numbers. Those who have their gold standard radial fields out in open meadows with vistas low to the horizon surely WILL reap the rewards of their gold standard labors, no argument, and you WILL be able to find that small bump up at the low low angles that the far field plot does not show. BUT you are talking about gnats on the windshield of Queen Elizabeth's Rolls Royce. Great, wonderful, if you got that kind of stuff. But Average Joe Ham in the usual clutter of urbia and suburbia, with dirt over land fill rubble in his building plot, full of rocks, sand and whatever else, and with an average conductivity of 0.5 milli-Siemens, if even that, will never see such a bump up from ground wave. He will be quite fortunate to have vertical angles of 10 or 15 degrees in play, forget 5, and maybe not even the ten. For him the ground wave discussion is angels on the head of a pin. BLE gave their study conductivity limits as between 20 and 100 milli-Siemens !!! And the photographs in the IEEE synopsis show black dirt, and absolutely flat out to well beyond a mile. Just simply do not bother to extrapolate those circumstances downward to Joe Average Ham in Levittown. OF COURSE BLE had a ground wave. They better have. And again, SO WHAT? God forbid I wind up a widower and can go anywhere I want, I may go find 500 acres of absolutely flat black dirt with 40 milli-Siemens conductivity. Then I'll call up Rich Fry and ask him, remind me about all that ground wave stuff. I got me this new farm, and I'm only going to grow crops on the black dirt to keep down the trees. And I'll prove that everything Rich said was correct. And for the first time in my life I WON'T have to add the And so what? The thing that will get Joe Average Ham going is how to design a counterpoise that is NOT LOSSY in just plain awful dirt. Everything else is so what. How many of you guys out there have uniform outward and to depth 30 milli-Siemens dirt and can see the low horizon from your back yard? Forget it. Get rid of loss in your counterpoise. Do that first, do that before you even THINK about doing anything else. Will someone please tell me what is noble about starting out your 160 meter career having been recommended and installed a design with a counterpoise that even NEC duns at -18 dB. Tell me how worrying about ground wave fixes that. Why is ground wave even being brought up? Let's worry about the No-Wave. 73, Guy. On Tue, May 8, 2012 at 11:58 AM, DAVID CUTHBERT telegraph...@gmail.comwrote: If the radiation at 3 degrees is -8.9 dB relative to the maximum amplitude we can still work DX. Dave WX7G On May 8, 2012 9:18 AM, Richard Fry r...@adams.net wrote: Dave WX7G wrote: The program W6ELProp gives the take-off-angle needed for any path. Looking at 80 meter paths (it does 801-0 meters) the angles for DX paths are in the range of 3-15 degrees. Assuming those angles are true for DX paths, note that if the NEC far-field elevation pattern for a 1/4-wave monopole was the only radiation leaving the antenna, the field at 3 degrees elevation would be about 8.9 dB below the field at the center of the so called take-off angle (see link below - note Photobucket stripped the decimal from the 3.9MHz link). The surface wave really needs to be recognized in such evaluations. http://i62.photobucket.com/albums/h85/rfry-100/39MHz_Elepat_6_mS.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Guy Olinger wrote: BLE gave their study conductivity limits as between 20 and 100 milli-Siemens !!! Those who believe so might want to review the conversion from the e.m.u. units used for earth conductivity in the BLE publication to the mS/m units more commonly used today. -- The conductivity values used by BLE as quoted above are overstated by a factor of ten. -- Other details that may have been overlooked or forgotten: - The BLE tests were conducted in the sandy soil of New Jersey, where according the FCC M3 chart of earth conductivities, that state ranges from 2 mS/m to 4 mS/m. - Field intensities were measured by BLE at a distance of 3/10 of mile from the radiator, and mathematically converted to an equivalent IDF at 1 mile. - The test frequency was 3 MHz. - Even with such rather low earth conductivity at/near the BLE test site, the fields they measured for monopoles of ~45 degrees and more, using 113 x 0.412-wave buried radials were within several percent of the maximum fields possible for the applied power when using perfect monopoles of those heights driven against a perfect (zero loss) ground plane. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
A common use for correctly defined NEC models shows the electrical characteristics of the radiator system itself. But NEC also will show the field intensities that system will produce at a given distance for a given applied power, frequency, and earth characteristics -- and do so quite accurately. The link below leads to a comparison of the groundwave field measured from a real-world AM broadcast system by a broadcast consulting engineering firm vs. the NEC-2D output using those same system parameters. Included in the NEC analysis is the value of the space wave field at an elevation of 100 meters above the (level) ground plane, for this installation -- which should help better understand the points of the opening post in this thread. Note that the value of the space wave at 100m elevation and 100m downrange is lower than the groundwave 100m downrange, and increases as the range increases. This is as expected, because the relative field (E/Emax) of the elevation pattern launched by this 1/4-wave monopole reduces as the elevation angle increases. Hope this graphic and explanation are useful. http://i62.photobucket.com/albums/h85/rfry-100/Measured_vs_NEC2D_Fields2.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
I'm pretty sure this surface wave at ~0 degrees elevation is useful on (and below) the AM broadcast band (especially the lower portion) and 160 meters. But what about at 3.5, 5, 7, 10, 14, 18, 21, 24, and 28 MHz? That's what I've been trying to figure out: exactly how useful is this radiation at zero degrees on the different ham bands? Based on my experiences --and what I've studied-- since 1976, I'm not sure that it is. 73, Mike www.w0btu.com On Sun, May 6, 2012 at 10:10 AM, Richard Fry r...@adams.net wrote: Note in the link below that the value of the surface wave at 1 km at an elevation of 50 meters is about 110 uV/m ... http://i62.photobucket.com/albums/h85/rfry-100/Space_Surface_Wave_Compare.gif ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
And this seems like a good place and time to ask another question. I get the experience that the usefulness of NVIS radiation peaks around 80 meters. It's not useful on the AM broadcast band, and it's not useful on 20 meters. How accurate is my assumption? 73, Mike www.w0btu.com ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Try operating 160 and 10M mobile, you would be surprised at the daytime range even with low power into a 8' antenna on 160. Carl KM1H - Original Message - From: Mike Waters mikew...@gmail.com To: topband topband@contesting.com Sent: Monday, May 07, 2012 9:04 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc I'm pretty sure this surface wave at ~0 degrees elevation is useful on (and below) the AM broadcast band (especially the lower portion) and 160 meters. But what about at 3.5, 5, 7, 10, 14, 18, 21, 24, and 28 MHz? That's what I've been trying to figure out: exactly how useful is this radiation at zero degrees on the different ham bands? Based on my experiences --and what I've studied-- since 1976, I'm not sure that it is. 73, Mike www.w0btu.com On Sun, May 6, 2012 at 10:10 AM, Richard Fry r...@adams.net wrote: Note in the link below that the value of the surface wave at 1 km at an elevation of 50 meters is about 110 uV/m ... http://i62.photobucket.com/albums/h85/rfry-100/Space_Surface_Wave_Compare.gif ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2411/4983 - Release Date: 05/07/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
I've never operated mobile, but it sounds like you're saying the daytime local range on 160 and 10 is comparable. But Rich is also talking about the radiation at zero degrees bouncing off the ionosphere and returning to the earth at some distant point. That's what I'm wondering about. Local is one thing, but DX is another. 73, Mike On Mon, May 7, 2012 at 9:04 PM, ZR z...@jeremy.mv.com wrote: Try operating 160 and 10M mobile, you would be surprised at the daytime range even with low power into a 8' antenna on 160. I'm pretty sure this surface wave at ~0 degrees elevation is useful on (and below) the AM broadcast band (especially the lower portion) and 160 meters. But what about at 3.5, 5, 7, 10, 14, 18, 21, 24, and 28 MHz? That's what I've been trying to figure out: exactly how useful is this radiation at zero degrees on the different ham bands? Based on my experiences --and what I've studied-- since 1976, I'm not sure that it is. 73, Mike ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Let me expand on what I said previously. I always thought that ground wave propagation decreased with frequency. For example, don't AM broadcast stations in the lower end of the AM broadcast band have greater coverage than at the high end, all things being equal? I have always thought that, and I also think that this phenomenon increases as we move through 160 meters, then through 80, 40, etc. etc. and we become more and more dependent on higher angles there for at but local communications. Of course, this is somewhat dependent on the time of day, whether we are talking about daytime or nighttime propagation. Before my 1/4 wave 40 meter ground plane (elevated radials) came down last year, I repeatedly tried to make contact with KD0APS during the day, about 60 miles away with 100 watts. I also could barely hear him on any Beverage antenna on any band. Even feeding 800 watts into that antenna, he had difficulty copying me through his high ambient noise level. Only after I put up my dipole were we able to have a QSO, and signals were FAR stronger at each end, even with both of us using 100 watts. This was during the day, every time. This is by no means the only time I have experienced this. In the past, I have done many, many experiments --with different antennas-- on many different ham bands from 80 through 10 meters seeing which bands were better for the people I used to regularly talk to, most of which were in Ohio (where I lived) and surrounding states. Most (but not all) of this was done after dark. As we went up in frequency, the path loss got worse even thought the noise greatly decreased. I even had a 1/2 wave ground plane with elevated radials for 20 meters, and a 5/8 wave elevated ground plane for 10 meters, and so did some other stations I was communicating (or attempting to communicate) with. What I am saying is that ground loss must increase the higher we go in frequency, attenuating the surface wave more and more the higher and higher we go. Maybe there's another explanation for these observations? I am just trying to wrap my brain around what Richard Fry is trying to tell us here. I have a lot of respect for him, and I've learned a lot from him. But something is just not sinking in here. 73, Mike www.w0btu.com ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
- Original Message - From: Mike Waters mikew...@gmail.com To: topband topband@contesting.com Cc: ZR z...@jeremy.mv.com; Richard Fry r...@adams.net Sent: Monday, May 07, 2012 7:35 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc Let me expand on what I said previously. I always thought that ground wave propagation decreased with frequency. For example, don't AM broadcast stations in the lower end of the AM broadcast band have greater coverage than at the high end, all things being equal? Yes most definately. Ground wave is substantial over sea water. Why do you think the international distress frequency for ships was at 500 KHz? I have always thought that, and I also think that this phenomenon increases as we move through 160 meters, then through 80, 40, etc. etc. and we become more and more dependent on higher angles there for at but local communications. Of course, this is somewhat dependent on the time of day, whether we are talking about daytime or nighttime propagation. What you say is about lowering frequency is true. This is why submarines can communicate throughout the World because at low enough frequencies, the whole planet Earth looks like an insulator. 73 Hardy N7RT ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Monopole Radiation Patterns, Takeoff Angles etc,
Hi all.. This thread has been very interesting and educational...I guess we all strive to make our installation as efficient as we possibly can...Much of the radial theory has to go out the window for those who don't have the room, (acres) to install a good radial field and have to compromise with whatever can be fitted into a given small space...That being the case probably for the larger majority of Topband operators, doesn't always mean that their station will be insignificant compared to those whom have the room and money to put in a large installation, 4sq and big radial fields.. I hear too many Topband operators complaining that they can't compete with the so called Big Guns and many probably don't give it a serious go for that reason... Well, I have news for you...I have been a consistent operator from VK for 35 years being a keen CW dxer...My observations over the years working thousands of dx stations world wide have showed a few definite observations...Given an average evening dxing and the band conducting shall we say signals are generally averaging S5 to S7...Many of these signals are those whom only have a wire antenna and whatever radials they can fit in their qth with no real to the book installations...In amongst these signals there will be a few of the better installations, most whom will be no better than the average 5-7 signal...Occasionally one or two signals will pop up 1-2 S units above the crowd..This may be a bigger antenna installation but more likely hit the propagation on a peak...You have to remember that the band is very dynamic and changing by the minute... We always hear about the so called big contest stationsLet me tell you that on an average their signals are not always any better than the average signals...I have heard of and seen written many tines about these so called super stations and can assure you that most don't rate any better in the long haul to VK than the average JoeI can name about five dxers from the US who have signals consistently above the average and most of these are fairly ordinary installations.. I think that much of it is the luck of the draw, location, and a bit of thought put into your antenna installation..Operating methods are also a big part of being successful...No point in having the biggest and best installation if your operating habits aren't up to scratch...The best Topband operators spend more time listening than banging away making lots of qrm... So I take my hat off to all those who have to really struggle to get a reasonable antenna system runningNever give up or feel intimidated by the Big Guns..I can assure you that if I hear you in the qrm and qrn I will always try to give you VK... 73 allBob..VK3ZL.. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Monopole Radiation Patterns, takeoff angles etc
All vertical monopoles of 5/8-wavelength __and less__ radiate (launch) their maximum relative field (E/Emax) in the horizontal plane. This is true no matter what the loss in the r-f ground connection they use. A lossy ground connection will reduce the gain of the antenna system, but it will not change the relative fields they radiate. IOW, their pattern shapes remain the same regardless of the loss in the ground connection, be that to salt water, or dry sand. The link below leads to a plot of the radiation patterns and directivities of several monopoles. These are the shapes of the radiation patterns leaving the monopole as they exist at the beginning of the far field of the radiator. These patterns were calculated for two ohms of loss in the r-f ground connection - which is about the loss that 120 x 1/4-wave buried radials provides even in poor soil. If fewer/shorter radials are used, then loss increases and the directivities (gains) of these patterns would be reduced -- but the radiation pattern shapes would remain the same. Many amateur radio operators consider only the far-field pattern of a monopole antenna as shown by NEC and in textbooks, without realizing that this is not the shape of the radiation leaving the monopole. It leads to the concept of a takeoff angle where radiation apparently was maximum from that monopole. However the elevation field radiated by a monopole always is maximum in the horizontal plane, and always is less than that at the elevation of an assumed takeoff angle. A NEC analysis including the surface wave from the monopole will show this. Some of that low-angle radiation can reach the ionosphere and produce skywave service, even though according to a NEC far-field analysis, the fields are approaching zero at those low angles. This doesn't mean that radiation at and near the takeoff angle does not provide significant skywave service, but it does mean that significant skywave service can be generated by radiation at much lower angles than commonly believed. http://i62.photobucket.com/albums/h85/rfry-100/MWElPatComparison.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Guy Olinger wrote: It IS TECHNICALLY TRUE what you say, no argument, but of little use since you don't get to keep it, UNLESS you can get it over salt water, or off a mountain top. ... I can only spend take-home pay, and I can only make QSO's with the take-home pattern. I don't see anything wrong with using the take-home takeoff angle as the item of conversation -- it's the one you get to use. Note in the link below that the value of the surface wave at 1 km at an elevation of 50 meters is about 110 uV/m, which is not much less than the 113 uV/m field shown by the NEC far-field analysis at the peak of the space wave at 1 km. Also note that the surface wave field at 1 km in the horizontal plane exceeds the peak field of the space wave at 1 km in the NEC far-field analysis for the alleged takeoff angle of this radiator, per my opening post in this thread. These NEC analyses are based on 5 mS/m real earth, not a perfect ground plane. A point elevated 50 meters above a plane surface from another point 1 km away on that plane surface has an elevation angle of 2.86 degrees. And while the calculated space wave is not much above zero field at that elevation and distance, the surface wave has a much higher value there. Unless that propagation path is obstructed by some physical object, nothing prevents such low-angle waves from traveling on to the ionosphere, which under the right conditions will result in their reflections returning to the earth as skywave. Monopole radiation at such low angles is part of its take-home pattern that also can make DX QSOs. http://i62.photobucket.com/albums/h85/rfry-100/Space_Surface_Wave_Compare.gif ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
And your point is ?? That is not the only place where substitute arithmetic will produce a different figure. You can do the same with ground losses in the immediate vicinity, where if you do anything except the Norton-Sommerfield estimations you come up with a different figure. NOBODY has possession of the perfect computation. From where a lot of us sit, THE WHOLE THING is an approximation of sorts. Only what happens out there is natural law. What we are doing is trying to invent formulas that match what is observed. Are we actually under the impression that someone has put down the absolute equations? To allow that in our thinking is perilously close to scientific arrogance. Until someone comes up with the undisputable system of everything that explains gravity, all those piles of contradictions in stellar observations, and the huge mass of not-properly-explained observations and simply lays out how radio works, we need to have the humility that our formulas are the best of our approximations TODAY. Tomorrow may be an entirely different bucket. Dark matter, dark energy...we're having a VERY hard time making our equations stretch around the universe. Radio propagation, what goes on in space between two distanced physical occurrences is part of that stuff out there they can't get under control. 73, Guy. On Sun, May 6, 2012 at 11:10 AM, Richard Fry r...@adams.net wrote: Guy Olinger wrote: It IS TECHNICALLY TRUE what you say, no argument, but of little use since you don't get to keep it, UNLESS you can get it over salt water, or off a mountain top. ... I can only spend take-home pay, and I can only make QSO's with the take-home pattern. I don't see anything wrong with using the take-home takeoff angle as the item of conversation -- it's the one you get to use. Note in the link below that the value of the surface wave at 1 km at an elevation of 50 meters is about 110 uV/m, which is not much less than the 113 uV/m field shown by the NEC far-field analysis at the peak of the space wave at 1 km. Also note that the surface wave field at 1 km in the horizontal plane exceeds the peak field of the space wave at 1 km in the NEC far-field analysis for the alleged takeoff angle of this radiator, per my opening post in this thread. These NEC analyses are based on 5 mS/m real earth, not a perfect ground plane. A point elevated 50 meters above a plane surface from another point 1 km away on that plane surface has an elevation angle of 2.86 degrees. And while the calculated space wave is not much above zero field at that elevation and distance, the surface wave has a much higher value there. Unless that propagation path is obstructed by some physical object, nothing prevents such low-angle waves from traveling on to the ionosphere, which under the right conditions will result in their reflections returning to the earth as skywave. Monopole radiation at such low angles is part of its take-home pattern that also can make DX QSOs. http://i62.photobucket.com/albums/h85/rfry-100/Space_Surface_Wave_Compare.gif ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
On 05/06/2012 11:10 AM, Richard Fry wrote: Unless that propagation path is obstructed by some physical object, nothing prevents such low-angle waves from traveling on to the ionosphere, which under the right conditions will result in their reflections returning to the earth as skywave. The problem is that radiation does not just have an amplitude, it also has a phase angle. At certain ground resistances, the ground wave and the low angle sky wave will cancel each other out, which moves the angle of radiation up. None of this is anything you really have to worry about. Top band is a lot like camping: you do not need to outrun the bear, you only have to outrun the other campers. If you can get vaguely reasonable gain at 10-20 degrees takeoff angle, you have outrun the other campers. -- All rights reversed. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Rik van Riel wrote: The problem is that radiation does not just have an amplitude, it also has a phase angle. At certain ground resistances, the ground wave and the low angle sky wave will cancel each other out, which moves the angle of radiation up. If that were true, the low-angle radiation would not move up to create a lobe centered on a takeoff angle. But in any case, the graphic linked below (Terman) does not show a lack of radiation from a monopole at elevation angles between 1 and 5 degrees. http://i62.photobucket.com/albums/h85/rfry-100/TermanFig55.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
In 2006 Tom Rauch, W8JI mentioned the disappointment with 3/8 wave vertical antennas and Carl mention today abut how BCB stations migrated from 5/8 wave and 1/2 wave antennas. I added to Tom's rejoinder that several AM stations spent considerable amounts of money with the Franklyn design which was claimmed to lay more radiation at lower angles. This is possible if the two is insulated and a phasing device is place between the upper and lower tower sections. Presumably it can be accomplished even with reduced height or a squashed design of the true Franklyn. Admittedly I have yet to hear of any TB'er to use this. However a 3db signal enhancement at low angles in all directions may be something to consider. I would also wonder if putting to much RF below the critical angle (since DX-ers) are not particularly interest in ground wave coverage and need sky wave instead) would be detrimental. There are times when a higher angle take off is the difference between being heard or not especially, I think, during SR/SS Grey line enhancements, and maybe on some skews and spotlights. I post the Franklyn information just the same for those who may have missed the original post. Herb Schoenbohm, KV4FZ Quoting Tom Rauchw...@contesting.com: / Some of the biggest failure antennas I have used were 5/8th/ / wave verticals at broadcast stations. We loaded one AM tower/ / that happened to be a 5/8th wave on 160, and it was poor/ / compared to a short vertical./ The balloon lengths has increased my curiosity in learning what principles are working here. Theoretically, very low angle radiation could be obtained by a balloon supported long wire with controlled current distribution. (ARRL Antenna Compendium Vol. 2 pp. 132-135) As I mentioned before in my case the 5/8 vertical 308 foot insulated tower, totally surrounded by sea water was a big disappointment on 160 meters. I tried it for 5 years and the lower antennas were always noticeably better. I once worked for KUOM which shared a tall tower with KSTP 1500 kHZ in Minneapolis. Stan Hubbard, owner of KSTP was convinced to erect a Franklin antenna design which was supposed to modify the current distribution on tall towers to lay out a stronger ground wave then the 1/4 wave or smaller AM radiators. All the theory, the engineer and construction cost, sort of like a Ringo Ranger for the broadcast band were very disappointing. Years of A/B testing driving across the Dakotas, WCCO (although lower in frequency) was the king of signals from the Twin Cities by a significant margin. Both were 50KW clear channel stations. (KSTP bragged 100KW Effective Radiated Power) Some claimed this was due to sky wave and ground wave out of phase arrivals in which case the Franklyn actaully redued the sky-wave component, at least in theory. The Franklin concept can be found in Jasik's First Edition Antenna Engineering Handbook pp. 4-35 and 4-36. A traditional Franklin was two half waves stacked end to end and fed in phase. KNBC (Los Angles)built one in 1949 as a means of lowering the angle of radiation, but used a 550 foot tower since at 680 Khz a true Franklin would have been 1500 feet tall. They were apparently able to design a much shorter structure since their top portion was top loaded with a capacity hat and only 150 feet tall. (Put KNBC Franklin Antenna in your search engine for some awesome pictures of this antenna.) Did it actually improve coverage for KNBC? Are they still using it today? It would be interesting to learn if any AM stations still use the Franklin design and if the shortened Franklin (ala KNBC) has any merit for consideration on 160 meters as a shortened gain low angle DX antenna As far as I have been able to find out, collinear verticals below VHF are just not worth the effort, but that is not what the books tell us. Yet in practice a 1/4 to 3/8 wave appear to be the best topband performers for all the reasons stated in previous posts. (The 3/8 wave if converted to an Inverted L was popular in the 60's as it provided a 50 to 60 ohm feed point with just some inductive reactance to tuned out to actually resonate the wire as a 1/4 wave. In an inverted L configuration there is radiation in both the horizontal and vertical portion. I mention this since this would be a totally different antenna then a bottom feed 3/8 wave vertical tower.) Herb Schoenbohm, KV4FZ On 5/6/2012 12:31 PM, ZR wrote: The BCB stations migrated from 1/2 and 5/8 wave antennas, diamond shaped towers, and mountain tops by the early to mid 30's as they started to understand how things worked...or didnt. Carl KM1H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
One has to be careful with 5/8 wavelength verticals. A radiator that is physically 5/8 wavelength is already electrically too tall. That is why a 300 foot BC tower would not work well at low angles on 160. There are too things to considers one is that towers have velocity factor just like coax and the other is guy wires and anything else attached to the tower will have a loading effect. The size of the tower face also has an effect. I knew someone who without doing the necessary engineering built a 225 degree BC radiator and had horrible results because he did not take the above factors into consideration. It is difficult to say what a safe physical height might be without fairly precise modelling. A significant number of 50KW former clear channel stations use 195 degree radiators. Part of the logic is that above that height a minor high angle lobe becomes significant and causes sky wave cancellation of the ground wave which is a concern to broadcasters. But the other point is that 195 degrees is far enough away from 225 degrees that the mechanics of the install is not important unless that tower is also supporting some beam antennas. There is one true Franklin on the BC band in Sacramento CA. There are several other sectionalized radiators in service but the generally tend to be high maintenance. On 5/6/12 5:07 PM, Herb Schoenbohm wrote: In 2006 Tom Rauch, W8JI mentioned the disappointment with 3/8 wave vertical antennas and Carl mention today abut how BCB stations migrated from 5/8 wave and 1/2 wave antennas. I added to Tom's rejoinder that several AM stations spent considerable amounts of money with the Franklyn design which was claimmed to lay more radiation at lower angles. This is possible if the two is insulated and a phasing device is place between the upper and lower tower sections. Presumably it can be accomplished even with reduced height or a squashed design of the true Franklyn. Admittedly I have yet to hear of any TB'er to use this. However a 3db signal enhancement at low angles in all directions may be something to consider. I would also wonder if putting to much RF below the critical angle (since DX-ers) are not particularly interest in ground wave coverage and need sky wave instead) would be detrimental. There are times when a higher angle take off is the difference between being heard or not especially, I think, during SR/SS Grey line enhancements, and maybe on some skews and spotlights. I post the Franklyn information just the same for those who may have missed the original post. Herb Schoenbohm, KV4FZ Quoting Tom Rauchw...@contesting.com: / Some of the biggest failure antennas I have used were 5/8th/ / wave verticals at broadcast stations. We loaded one AM tower/ / that happened to be a 5/8th wave on 160, and it was poor/ / compared to a short vertical./ The balloon lengths has increased my curiosity in learning what principles are working here. Theoretically, very low angle radiation could be obtained by a balloon supported long wire with controlled current distribution. (ARRL Antenna Compendium Vol. 2 pp. 132-135) As I mentioned before in my case the 5/8 vertical 308 foot insulated tower, totally surrounded by sea water was a big disappointment on 160 meters. I tried it for 5 years and the lower antennas were always noticeably better. I once worked for KUOM which shared a tall tower with KSTP 1500 kHZ in Minneapolis. Stan Hubbard, owner of KSTP was convinced to erect a Franklin antenna design which was supposed to modify the current distribution on tall towers to lay out a stronger ground wave then the 1/4 wave or smaller AM radiators. All the theory, the engineer and construction cost, sort of like a Ringo Ranger for the broadcast band were very disappointing. Years of A/B testing driving across the Dakotas, WCCO (although lower in frequency) was the king of signals from the Twin Cities by a significant margin. Both were 50KW clear channel stations. (KSTP bragged 100KW Effective Radiated Power) Some claimed this was due to sky wave and ground wave out of phase arrivals in which case the Franklyn actaully redued the sky-wave component, at least in theory. The Franklin concept can be found in Jasik's First Edition Antenna Engineering Handbook pp. 4-35 and 4-36. A traditional Franklin was two half waves stacked end to end and fed in phase. KNBC (Los Angles)built one in 1949 as a means of lowering the angle of radiation, but used a 550 foot tower since at 680 Khz a true Franklin would have been 1500 feet tall. They were apparently able to design a much shorter structure since their top portion was top loaded with a capacity hat and only 150 feet tall. (Put KNBC Franklin Antenna in your search engine for some awesome pictures of this antenna.) Did it actually improve coverage for KNBC? Are they still using it today? It would be interesting to learn if any AM stations still use the
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
WHO-AM (1040 KHz) still uses the modified Franklin. Their 50KW covers the entire state of Iowa + during the day and goes international at night. On 05/06/2012 11:31 AM, ZR wrote: The BCB stations migrated from 1/2 and 5/8 wave antennas, diamond shaped towers, and mountain tops by the early to mid 30's as they started to understand how things worked...or didnt. Carl KM1H -- R. Kevin Stover AC0H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
In the early 1930s, both WSM and WLW had spent a considerable amount of time optimizing their Blaw-Knox tower heights by monitoring skywave at a distance of a couple hundred miles. By trial and error, they came up with their targets of approximately 190 degrees which is also validated in NEC modeling. This results in the most field strength at zero degrees elevation while simultaneously minimizing high-angle lobes. Tower heights for some notable stations in electrical degrees: WSM = 192.3 degrees WLW = 189.3 WLS = 189.8 WGN = 195.0 WSCR (was WMAQ) = 181.0 WJR = 194.7 WABC = 180.3 WSB = 179.3 WBBM = 194.1 WHAM = 177.1 WOAI = 193.2 KYW = 180.0 KNX = 193.5 AVG: 187.7 electrical degrees. Paul, W9AC - Original Message - From: W2XJ w...@nyc.rr.com To: he...@vitelcom.net; topband@contesting.com Sent: Sunday, May 06, 2012 6:04 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc One has to be careful with 5/8 wavelength verticals. A radiator that is physically 5/8 wavelength is already electrically too tall. That is why a 300 foot BC tower would not work well at low angles on 160. There are too things to considers one is that towers have velocity factor just like coax and the other is guy wires and anything else attached to the tower will have a loading effect. The size of the tower face also has an effect. I knew someone who without doing the necessary engineering built a 225 degree BC radiator and had horrible results because he did not take the above factors into consideration. It is difficult to say what a safe physical height might be without fairly precise modelling. A significant number of 50KW former clear channel stations use 195 degree radiators. Part of the logic is that above that height a minor high angle lobe becomes significant and causes sky wave cancellation of the ground wave which is a concern to broadcasters. But the other point is that 195 degrees is far enough away from 225 degrees that the mechanics of the install is not important unless that tower is also supporting some beam antennas. There is one true Franklin on the BC band in Sacramento CA. There are several other sectionalized radiators in service but the generally tend to be high maintenance. On 5/6/12 5:07 PM, Herb Schoenbohm wrote: In 2006 Tom Rauch, W8JI mentioned the disappointment with 3/8 wave vertical antennas and Carl mention today abut how BCB stations migrated from 5/8 wave and 1/2 wave antennas. I added to Tom's rejoinder that several AM stations spent considerable amounts of money with the Franklyn design which was claimmed to lay more radiation at lower angles. This is possible if the two is insulated and a phasing device is place between the upper and lower tower sections. Presumably it can be accomplished even with reduced height or a squashed design of the true Franklyn. Admittedly I have yet to hear of any TB'er to use this. However a 3db signal enhancement at low angles in all directions may be something to consider. I would also wonder if putting to much RF below the critical angle (since DX-ers) are not particularly interest in ground wave coverage and need sky wave instead) would be detrimental. There are times when a higher angle take off is the difference between being heard or not especially, I think, during SR/SS Grey line enhancements, and maybe on some skews and spotlights. I post the Franklyn information just the same for those who may have missed the original post. Herb Schoenbohm, KV4FZ Quoting Tom Rauchw...@contesting.com: / Some of the biggest failure antennas I have used were 5/8th/ / wave verticals at broadcast stations. We loaded one AM tower/ / that happened to be a 5/8th wave on 160, and it was poor/ / compared to a short vertical./ The balloon lengths has increased my curiosity in learning what principles are working here. Theoretically, very low angle radiation could be obtained by a balloon supported long wire with controlled current distribution. (ARRL Antenna Compendium Vol. 2 pp. 132-135) As I mentioned before in my case the 5/8 vertical 308 foot insulated tower, totally surrounded by sea water was a big disappointment on 160 meters. I tried it for 5 years and the lower antennas were always noticeably better. I once worked for KUOM which shared a tall tower with KSTP 1500 kHZ in Minneapolis. Stan Hubbard, owner of KSTP was convinced to erect a Franklin antenna design which was supposed to modify the current distribution on tall towers to lay out a stronger ground wave then the 1/4 wave or smaller AM radiators. All the theory, the engineer and construction cost, sort of like a Ringo Ranger for the broadcast band were very disappointing. Years of A/B testing driving across the Dakotas, WCCO (although lower in frequency) was the king of signals from the Twin Cities by a significant margin. Both were 50KW clear channel stations. (KSTP bragged 100KW
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
And your point is ?? That is not the only place where substitute arithmetic will produce a different figure. I ran a 4Nec2 (with NEC/4.2 engine) surface wave plot for a 160m 1/4-wave vertical radiator over a field of 60 radials with average ground conductivity. Input power = 1.5KW. 4Nec2 was first set to analyze field strength at 10 km or 60 wavelengths on 160m.That's way out there... http://72.52.250.47/images/160m.jpg Next, I ran a simulation of the far field plot for the same radiator: http://72.52.250.47/images/160m-1.jpg The far filed shows zero field strength at zero elevation. By contrast, the surface wave analysis shows that the field strength never drops below 12.2 mV/m at any elevation, including zero elevation. I'm just the messenger Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
I think Carl may have his time line backwards. In the 20s and early 30s many stations used various forms of wire antennae including dipoles and various cage designs. During the 30s Dr Brown and colleagues studied and tested various vertical radiators and ground systems. The result of that work remains the underpinning of most MW radiators and a substantial amount of it ultimately became part of FCC rules and standards in many other parts of the world. Some stations continued with their wire antenna into the 40s and some paid a penalty of having stations moved into the natural nulls of a dipole. On 5/6/12 6:18 PM, Kevin wrote: WHO-AM (1040 KHz) still uses the modified Franklin. Their 50KW covers the entire state of Iowa + during the day and goes international at night. On 05/06/2012 11:31 AM, ZR wrote: The BCB stations migrated from 1/2 and 5/8 wave antennas, diamond shaped towers, and mountain tops by the early to mid 30's as they started to understand how things worked...or didnt. Carl KM1H -- R. Kevin Stover AC0H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
At the prior QTH the shunt fed tower with a 4 el 10-20M Christmas tree was resonant at 1520KHz and worked gangbusters. While this was only around 107* vs 90* I see no reason that a bit taller would work as well. The question is at what point is too much? I do know the 2:1 BW was very narrow but the last year I was there the ARRL 160M CW contest was won and a good portion of the band was used. As usual no tuner was used, just a modified amp pi net. With the L including significant high angle it could be an excellent all around antenna. If instead of an L a 2 wire top hat replaced it that high angle is cancelled. I need 2 antennas to cover high and low angles however at times even somewhat locals tell me I have an aurora sound on the verticals. Under those band conditions I do well into the auroral region and possibly by the very low angle part of the signal running below the ionized layer and getting less attenuation. Gray line remains mysterious as at that prior QTH I was the first New England station to work JA on 160 and worked 3 that morning with that 107* vertical. Now that its rather commonplace Ive done it more with the 180' high inverted vee. Maybe its because the 2 elements are broadside to JA and the pattern is a figure 8 with less gain than endfire. Its all guesswork! Carl KM1H - Original Message - From: Herb Schoenbohm he...@vitelcom.net To: topband@contesting.com Sent: Sunday, May 06, 2012 5:07 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc In 2006 Tom Rauch, W8JI mentioned the disappointment with 3/8 wave vertical antennas and Carl mention today abut how BCB stations migrated from 5/8 wave and 1/2 wave antennas. I added to Tom's rejoinder that several AM stations spent considerable amounts of money with the Franklyn design which was claimmed to lay more radiation at lower angles. This is possible if the two is insulated and a phasing device is place between the upper and lower tower sections. Presumably it can be accomplished even with reduced height or a squashed design of the true Franklyn. Admittedly I have yet to hear of any TB'er to use this. However a 3db signal enhancement at low angles in all directions may be something to consider. I would also wonder if putting to much RF below the critical angle (since DX-ers) are not particularly interest in ground wave coverage and need sky wave instead) would be detrimental. There are times when a higher angle take off is the difference between being heard or not especially, I think, during SR/SS Grey line enhancements, and maybe on some skews and spotlights. I post the Franklyn information just the same for those who may have missed the original post. Herb Schoenbohm, KV4FZ Quoting Tom Rauchw...@contesting.com: / Some of the biggest failure antennas I have used were 5/8th/ / wave verticals at broadcast stations. We loaded one AM tower/ / that happened to be a 5/8th wave on 160, and it was poor/ / compared to a short vertical./ The balloon lengths has increased my curiosity in learning what principles are working here. Theoretically, very low angle radiation could be obtained by a balloon supported long wire with controlled current distribution. (ARRL Antenna Compendium Vol. 2 pp. 132-135) As I mentioned before in my case the 5/8 vertical 308 foot insulated tower, totally surrounded by sea water was a big disappointment on 160 meters. I tried it for 5 years and the lower antennas were always noticeably better. I once worked for KUOM which shared a tall tower with KSTP 1500 kHZ in Minneapolis. Stan Hubbard, owner of KSTP was convinced to erect a Franklin antenna design which was supposed to modify the current distribution on tall towers to lay out a stronger ground wave then the 1/4 wave or smaller AM radiators. All the theory, the engineer and construction cost, sort of like a Ringo Ranger for the broadcast band were very disappointing. Years of A/B testing driving across the Dakotas, WCCO (although lower in frequency) was the king of signals from the Twin Cities by a significant margin. Both were 50KW clear channel stations. (KSTP bragged 100KW Effective Radiated Power) Some claimed this was due to sky wave and ground wave out of phase arrivals in which case the Franklyn actaully redued the sky-wave component, at least in theory. The Franklin concept can be found in Jasik's First Edition Antenna Engineering Handbook pp. 4-35 and 4-36. A traditional Franklin was two half waves stacked end to end and fed in phase. KNBC (Los Angles)built one in 1949 as a means of lowering the angle of radiation, but used a 550 foot tower since at 680 Khz a true Franklin would have been 1500 feet tall. They were apparently able to design a much shorter structure since their top portion was top loaded with a capacity hat and only 150 feet tall. (Put KNBC Franklin Antenna in your search engine for some
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Carl has nothing backwards, best do your research the next time. - Original Message - From: W2XJ w...@nyc.rr.com To: topband@contesting.com Sent: Sunday, May 06, 2012 7:40 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc I think Carl may have his time line backwards. In the 20s and early 30s many stations used various forms of wire antennae including dipoles and various cage designs. During the 30s Dr Brown and colleagues studied and tested various vertical radiators and ground systems. The result of that work remains the underpinning of most MW radiators and a substantial amount of it ultimately became part of FCC rules and standards in many other parts of the world. Some stations continued with their wire antenna into the 40s and some paid a penalty of having stations moved into the natural nulls of a dipole. On 5/6/12 6:18 PM, Kevin wrote: WHO-AM (1040 KHz) still uses the modified Franklin. Their 50KW covers the entire state of Iowa + during the day and goes international at night. On 05/06/2012 11:31 AM, ZR wrote: The BCB stations migrated from 1/2 and 5/8 wave antennas, diamond shaped towers, and mountain tops by the early to mid 30's as they started to understand how things worked...or didnt. Carl KM1H -- R. Kevin Stover AC0H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2411/4981 - Release Date: 05/06/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
Subject: Date: From: Reply-To: To: Having worked in the business over 54 years with LW MW and SW transmission systems up to 2 megawatts and having built numerous MW arrays to 12 towers I would respectfully suggest a quick check of fundamental broadcast history. Google is your friend. BTW most early stations broadcast from rooftops, not mountain tops, and some diamond towers (Blau Knox) are still in service at legendary stations. On 5/6/12 9:40 PM, ZR wrote: Carl has nothing backwards, best do your research the next time. - Original Message - From: W2XJw...@nyc.rr.com To:topband@contesting.com Sent: Sunday, May 06, 2012 7:40 PM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc I think Carl may have his time line backwards. In the 20s and early 30s many stations used various forms of wire antennae including dipoles and various cage designs. During the 30s Dr Brown and colleagues studied and tested various vertical radiators and ground systems. The result of that work remains the underpinning of most MW radiators and a substantial amount of it ultimately became part of FCC rules and standards in many other parts of the world. Some stations continued with their wire antenna into the 40s and some paid a penalty of having stations moved into the natural nulls of a dipole. On 5/6/12 6:18 PM, Kevin wrote: WHO-AM (1040 KHz) still uses the modified Franklin. Their 50KW covers the entire state of Iowa + during the day and goes international at night. On 05/06/2012 11:31 AM, ZR wrote: The BCB stations migrated from 1/2 and 5/8 wave antennas, diamond shaped towers, and mountain tops by the early to mid 30's as they started to understand how things worked...or didnt. Carl KM1H -- R. Kevin Stover AC0H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2411/4981 - Release Date: 05/06/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
