Re: Topband: Topband Digest, Vol 113, Issue 8
- Original Message - From: topband-requ...@contesting.com To: topband@contesting.com Sent: Saturday, May 05, 2012 7:00 PM Subject: Topband Digest, Vol 113, Issue 8 Send Topband mailing list submissions to topband@contesting.com To subscribe or unsubscribe via the World Wide Web, visit http://lists.contesting.com/mailman/listinfo/topband or, via email, send a message with subject or body 'help' to topband-requ...@contesting.com You can reach the person managing the list at topband-ow...@contesting.com When replying, please edit your Subject line so it is more specific than Re: Contents of Topband digest... Today's Topics: 1. Re: Fwd: radals fer 160m vertcal (Jim WA9YSD) 2. Re: Fwd: radals fer 160m vertcal (ZR) 3. Re: Fwd: radals fer 160m vertcal (Charlie Young) 4. Re: Fwd: radals fer 160m vertcal (Richard Fry) 5. Re: Fwd: radals fer 160m vertcal (James Rodenkirch) 6. Radials on top band (John Harden) 7. Re: Fwd: radals fer 160m vertcal (Mike Waters) -- Message: 1 Date: Sat, 5 May 2012 07:00:08 -0700 (PDT) From: Jim WA9YSD wa9...@yahoo.com Subject: Re: Topband: Fwd: radals fer 160m vertcal To: Top Band topband@contesting.com Message-ID: 1336226408.63699.yahoomail...@web111714.mail.gq1.yahoo.com Content-Type: text/plain; charset=iso-8859-1 Keep in mind this Sole purpose of a BC station is to get coverage of about 60 miles running 5KW day time and 1 KW night time with no fad and quality signal not to work DX. I read in some posts or on some web site that it does not matter if the ends are tied to a ground rod or not.??Note then ends not at the base of the vertical. My backyard is only 35 by 36 feet.??You guys only think you have a small back yard.??Compare it with this one. The City water pipe system sure works as the good ground I guess so does the neighbors plumbing cause their house in only 8 feet from mine :-) Jim K9TF ? Stay on course, fight a good fight, and keep the faith.?Jim K9TF/WA9YSD -- Message: 2 Date: Sat, 5 May 2012 10:34:06 -0400 From: ZR z...@jeremy.mv.com Subject: Re: Topband: Fwd: radals fer 160m vertcal To: Richard Fry r...@adams.net, topband@contesting.com Message-ID: F637FEFE70F444C692A62D16142B015F@computer1 Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original There have been several reports of established AM stations that the FCC gave permission to replace a decayed or destroyed inground radial system with elevated radials or an elevated mesh/radial arrangement. In all the cases I read the FS measurements exceed the original and power had to be reduced to the original level. Carl KM1H - Original Message - From: Richard Fry r...@adams.net To: topband@contesting.com Sent: Saturday, May 05, 2012 8:07 AM Subject: Re: Topband: Fwd: radals fer 160m vertcal James Rodenkirch wrote: What about radials above the ground? This link http://www.commtechrf.com/documents/nab1995.pdf leads to a paper by Clarence Beverage with some real-world results for monopoles with elevated wires used as a counterpoise. Here is a quote from it: \ \The antenna system consisted of a lightweight, 15 inch face tower, 120 feet in height, with a base insulator at the 15 foot elevation and six elevated radials, a quarter wave in length, spaced evenly around the tower and elevated 15 feet above the ground. The radials were fully insulated from ground and supported at the ends by wooden tripods. Power was fed to the system through a 200 foot length of coaxial cable with the cable shield connected to the shunt element of the T network and to the elevated radials. A balun or RF choke on the feedline was not employed and the feedline was isolated from the lower section of the tower. The system operated on 1580 kHz at a power of 750 watts. The efficiency of the antenna was determined by radial field intensity measurements along 12 radials extending out to a distance of up to 85 kilometers. The measured RMS efficiency was 287 mV/m for 1 kW, at one kilometer, which is the same measured value as would be expected for a 0.17 wave tower above 120 buried radials. / / So while such elevated installations are rare for AM broadcast stations, their performance has been measured to be about the same as when using an r-f ground consisting of 120 buried wires, each 1/4-wave long (free space length). These elevated systems are readily modeled using NEC-2. However the radiation patterns shown by a typical NEC far-field analysis do not accurately show the fields actually launched by them, or by any vertical radiator with its base near the earth, because they do not include the surface wave. The fields radiated in and near the horizontal plane by any vertical monopole of 5/8 wavelength height and less are the greatest fields it radiates in the
Re: Topband: Parasitic Elements with 160m Verticals (was radals fer 160m vertcal)
Have Topbanders used parasitic elements? Yes, there are several parasitic arrays in use on the band. Mine started out in 1998 as a K3LR array (described in ON4UN's Low band antennas book) with a central tower as the driven element and four sloping t-shaped parasitic wire elements giving three elements in each of four directions. Two of the elements in line are used as a director or reflector and the other two left floating. I later added a loaded 90-ft tower as a second director element toward Europe (4 elements total to Europe). Each of the original 5 elements has 120 1/4 wave radials laid on the ground (now mostly invisible, sunk in slightly) -- shorter where they intersect at a midpoint and are bonded to adjacent radials.. Some more details at www.aa1k.us under 160 TX array. KC1XX has one at his contest super station, described here: http://www.kc1xx.com/antennas/160_array.pdf K0HA has one that has proven quite effective from his Nebraska QTH: http://k0ha.com/160m/160m.html. My first recollection of the sloping reflector idea was in an article VE2CV wrote in the Sept. 1984 QST. 4X4NJ (now K7NJ) used parasitic elements on a loaded tower to produce a consistently big signal, described in a Feb. 1985 QST article. K4ERO's article on sloping reflectors appeared in the ARRL Antenna Compendium Vol. 4. N6LF covers them in an article in the March/April 2003 issue of NCJ, available here: http://rudys.typepad.com/ant/files/antenna_array_single_support.pdf. There's a good list of additional references at the end of that article. 73/Jon AA1K ___ 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: Topband Digest, Vol 113, Issue 8
This post is the best evidence ever that Top Posting is a good Idea. Bill--W4BSG - Original Message - From: gw3jxn gw3...@tiscali.co.uk To: topband@contesting.com Sent: Sunday, May 06, 2012 3:27 AM Subject: Re: Topband: Topband Digest, Vol 113, Issue 8 - Original Message - From: topband-requ...@contesting.com To: topband@contesting.com Sent: Saturday, May 05, 2012 7:00 PM Subject: Topband Digest, Vol 113, Issue 8 Send Topband mailing list submissions to topband@contesting.com To subscribe or unsubscribe via the World Wide Web, visit http://lists.contesting.com/mailman/listinfo/topband or, via email, send a message with subject or body 'help' to topband-requ...@contesting.com You can reach the person managing the list at topband-ow...@contesting.com When replying, please edit your Subject line so it is more specific than Re: Contents of Topband digest... Today's Topics: 1. Re: Fwd: radals fer 160m vertcal (Jim WA9YSD) 2. Re: Fwd: radals fer 160m vertcal (ZR) 3. Re: Fwd: radals fer 160m vertcal (Charlie Young) 4. Re: Fwd: radals fer 160m vertcal (Richard Fry) 5. Re: Fwd: radals fer 160m vertcal (James Rodenkirch) 6. Radials on top band (John Harden) 7. Re: Fwd: radals fer 160m vertcal (Mike Waters) -- Message: 1 Date: Sat, 5 May 2012 07:00:08 -0700 (PDT) From: Jim WA9YSD wa9...@yahoo.com Subject: Re: Topband: Fwd: radals fer 160m vertcal To: Top Band topband@contesting.com Message-ID: 1336226408.63699.yahoomail...@web111714.mail.gq1.yahoo.com Content-Type: text/plain; charset=iso-8859-1 Keep in mind this Sole purpose of a BC station is to get coverage of about 60 miles running 5KW day time and 1 KW night time with no fad and quality signal not to work DX. I read in some posts or on some web site that it does not matter if the ends are tied to a ground rod or not.??Note then ends not at the base of the vertical. My backyard is only 35 by 36 feet.??You guys only think you have a small back yard.??Compare it with this one. The City water pipe system sure works as the good ground I guess so does the neighbors plumbing cause their house in only 8 feet from mine :-) Jim K9TF ? Stay on course, fight a good fight, and keep the faith.?Jim K9TF/WA9YSD -- Message: 2 Date: Sat, 5 May 2012 10:34:06 -0400 From: ZR z...@jeremy.mv.com Subject: Re: Topband: Fwd: radals fer 160m vertcal To: Richard Fry r...@adams.net, topband@contesting.com Message-ID: F637FEFE70F444C692A62D16142B015F@computer1 Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original There have been several reports of established AM stations that the FCC gave permission to replace a decayed or destroyed inground radial system with elevated radials or an elevated mesh/radial arrangement. In all the cases I read the FS measurements exceed the original and power had to be reduced to the original level. Carl KM1H - Original Message - From: Richard Fry r...@adams.net To: topband@contesting.com Sent: Saturday, May 05, 2012 8:07 AM Subject: Re: Topband: Fwd: radals fer 160m vertcal James Rodenkirch wrote: What about radials above the ground? This link http://www.commtechrf.com/documents/nab1995.pdf leads to a paper by Clarence Beverage with some real-world results for monopoles with elevated wires used as a counterpoise. Here is a quote from it: \ \The antenna system consisted of a lightweight, 15 inch face tower, 120 feet in height, with a base insulator at the 15 foot elevation and six elevated radials, a quarter wave in length, spaced evenly around the tower and elevated 15 feet above the ground. The radials were fully insulated from ground and supported at the ends by wooden tripods. Power was fed to the system through a 200 foot length of coaxial cable with the cable shield connected to the shunt element of the T network and to the elevated radials. A balun or RF choke on the feedline was not employed and the feedline was isolated from the lower section of the tower. The system operated on 1580 kHz at a power of 750 watts. The efficiency of the antenna was determined by radial field intensity measurements along 12 radials extending out to a distance of up to 85 kilometers. The measured RMS efficiency was 287 mV/m for 1 kW, at one kilometer, which is the same measured value as would be expected for a 0.17 wave tower above 120 buried radials. / / So while such elevated installations are rare for AM broadcast stations, their performance has been measured to be about the same as when using an r-f ground consisting of 120 buried wires, each 1/4-wave long (free space length). These elevated systems are readily modeled using NEC-2. However the radiation patterns shown by a typical NEC far-field analysis do not accurately show the fields actually launched by
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
Topband: Question about antenna bandwidth
If I were to extend my 1/4-wave inverted-L to a 3/8-wave L, and tune out the inductance with a fixed capacitor at the base, what would this do to the broadbandedness of the antenna? Inquiring minds... Rob / KD8WK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Question about antenna bandwidth
On 2012-05-06, at 2:42 PM, Rob Stampfli wrote: If I were to extend my 1/4-wave inverted-L to a 3/8-wave L, and tune out the inductance with a fixed capacitor at the base, what would this do to the broadbandedness of the antenna? Hi Rob, The 2:1 SWR points on my extended 3/8-wave inverted L elements are about 70-KHz apart...I have no idea what those points might be in a regular 1./4-wave vertical. ~73~ de Eddy VE3CUI - VE3XZ ___ 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
Topband: VB: Monopole Radiation Patterns, takeoff angles
-Ursprungligt meddelande- Från: Lennart M [mailto:lennart.michaels...@telia.com] Skickat: den 6 maj 2012 19:43 Till: 'Guy Olinger K2AV' Ämne: Topband: Monopole Radiation Patterns, takeoff angles 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.K2AV Well guys! I still recall having two different MW verticals erected in the 1970's. ( for ship to shore traffic). They were exactly the the same layout. 30.5 m high with a wide cage and a 120 x 100 m ground wire counterpoise. They had a broad band filter making the antennas useful for 1.7-3-5 MHZ. Both antennas were located very close to sea. One was close (50 m) to the Streats separating Sweden from Denmark and the other one was on the east coast of Skane the south part of Sweden. We actually measured the field strength from each of the antennas and found they were equal. Never the less I did some Ham radio from both positions and found out that the one being closer to Denmark worked out consistently better than the one on on the east coast of Skane. My Helmer in commercial antennas, buried long ago, told me that the difference might be due to the Geomagnetic field between those two positions. We checked that out and there was a difference! He might be right, but the only correct answer is: Pick your QTH, invest money in ground system for your antennas antenna and invest in a good rx antenna system. Easily said... Difficult for most of us! 73 Len SM/BIC ___ 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
Re: Topband: Parasitic Elements with 160m Verticals
I have been using a five element array of 1/8th wave (43ft) verticals since 2006 on Top band. I feel this is the lower limit to maintain radiation efficiency as each element is at or near 12.5 Ohms impedance. The array is set up in a rectangle such that there 4 elements broadside E/W and and 3 elements in-line NW, SW,SE and NE. They are all identical top loaded sloping T verticals and matched by UN-UN transformers. The key to their success is low loss matching and low loss ground systems. The center element has 120 .27 wavelength radials and the exterior 4 elements all have than 60 .27 wavelength radials. This system has done very well for me in making up for less than optimum operator skills in the low power category of competition. The advantages are lower initial cost and single person maintenance. Bob, W7RH -- Bob Kile, W7RH DM35OS -- “There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves.” Will Rogers ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
