Re: Topband: Question - optimum number of radials
The r-f loss at the operating frequency in a set of buried radials varies with the conductivity and permittivity of the earth in which they are buried. The NEC4.2 study below shows that for poor earth conditions (within about 1/2WL from the base of the monopole), the number and length of buried radials needed to maintain an r-f loss of a few ohms in the ground return rises from that needed for more conductive earth. In the case of AM broadcast stations, the use of 120 buried radials each 1/4-wavelength (in free space) produces a ground system loss of 2 ohms or less. This is true no matter what are the characteristics of the the earth in which those 120 radials are buried. For a 1/4-wave, unloaded monopole with 35 ohms of radiation resistance and 2 ohms of ground system loss, antenna system radiation efficiency is 35/37 = 95% of the applied power (approx). The FCC requires that a minimum inverse distance groundwave field of 241 mV/m is produced by an applied power of 1 kW at at a distance of 1 km by even the lowest class of AM station (Class C). A perfect 1/4-wave monopole driven against a perfect ground plane produces about 313 mV/m for those conditions. A typical installation using an unloaded 1/4-wave monopole driven against 120 x 1/4-wave buried radials produces about 306 mV/m for those conditions -- which field is consistent with a monopole system with a radiation efficiency of 95%. The 241 mV/m minimum field required for Class C AM stations could be produced by a 1/4-wave monopole+ground system with about 59% efficiency. Class A AM stations such as WLW, WJR, WGN etc are required to generate an inverse distance groundwave field of 362 mV/m at 1 km for 1 kW of applied power. This cannot be done with a 1/4-wave monopole. Most of the Class A stations use monopole heights ranging from 180 to 195 degrees. WJR, Detroit uses a 195-deg monopole system that produces about 403 mV/m at 1 km for 1 kW of applied power. At their licensed transmitter power of 50 kW, that field becomes 403 x SQRT(50) = 2.85 V/m, approx. http://i62.photobucket.com/albums/h85/rfry-100/10m_Vert32Buried_Radials.jpg RF _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
That's a lot of good information, Richard! Thanks for sharing! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard Fry Sent: Friday, February 14, 2014 7:00 AM To: topband@contesting.com Subject: Re: Topband: Question - optimum number of radials The r-f loss at the operating frequency in a set of buried radials varies with the conductivity and permittivity of the earth in which they are buried. The NEC4.2 study below shows that for poor earth conditions (within about 1/2WL from the base of the monopole), the number and length of buried radials needed to maintain an r-f loss of a few ohms in the ground return rises from that needed for more conductive earth. In the case of AM broadcast stations, the use of 120 buried radials each 1/4-wavelength (in free space) produces a ground system loss of 2 ohms or less. This is true no matter what are the characteristics of the the earth in which those 120 radials are buried. For a 1/4-wave, unloaded monopole with 35 ohms of radiation resistance and 2 ohms of ground system loss, antenna system radiation efficiency is 35/37 = 95% of the applied power (approx). The FCC requires that a minimum inverse distance groundwave field of 241 mV/m is produced by an applied power of 1 kW at at a distance of 1 km by even the lowest class of AM station (Class C). A perfect 1/4-wave monopole driven against a perfect ground plane produces about 313 mV/m for those conditions. A typical installation using an unloaded 1/4-wave monopole driven against 120 x 1/4-wave buried radials produces about 306 mV/m for those conditions -- which field is consistent with a monopole system with a radiation efficiency of 95%. The 241 mV/m minimum field required for Class C AM stations could be produced by a 1/4-wave monopole+ground system with about 59% efficiency. Class A AM stations such as WLW, WJR, WGN etc are required to generate an inverse distance groundwave field of 362 mV/m at 1 km for 1 kW of applied power. This cannot be done with a 1/4-wave monopole. Most of the Class A stations use monopole heights ranging from 180 to 195 degrees. WJR, Detroit uses a 195-deg monopole system that produces about 403 mV/m at 1 km for 1 kW of applied power. At their licensed transmitter power of 50 kW, that field becomes 403 x SQRT(50) = 2.85 V/m, approx. http://i62.photobucket.com/albums/h85/rfry-100/10m_Vert32Buried_Radials.jpg RF _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
On 02/14/2014 09:15 AM, Charlie Cunningham wrote: That's a lot of good information, Richard! Thanks for sharing! 73, Charlie, K4OTV The whole topic of radials as it applies to me on my small lot is put in as many as you can. The same probably applies to others on small lots. On top band I do not have room in *any* direction for a quarter wavelength radial..not even one. In some directions a quarter wavelength radial wire might be bent to fit but that begins the many compromises. Obviously that setup would have the antenna in one corner of the lot so there would be no radials at all in one or two directions. So.. no quarter wave radials at all. I have been buying small spools of wire and will be adding them to whatever puny little radial field I DO have. As soon as the ice and snow is gone (maybe in June?) I will be elevating my wire antenna the rest of the way to the treetops and adding in the radial wires. In the process of elevating the antenna I will learn to be ace with a rod n reel grin. The whole point of that exercise is to *miss* the tree and go over the top. So far I've only ever tried to *hit* a spot out on the water. It's not hard to hit the water wink. I didn't do too badly finding a particular spot on the water with the bait. But the tree top is not over there. It's up there. 73, Bill KU8H _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Question - optimum number of radials
Besides optimim number(s), I wonder if there is supporting analysis for the connection of the radial ends?? I have around 80 elevated radials that range from 50 foot lengths, running east and west, and 25 foot lengths running north and south (all of that a function of being geographically challenged). I have not tied the bitter ends togethernever really thought about it when I put the radial field together but seem to recall reading something about tieing the ends together and having a well bounded complete grid underthe antenna. Thoughts? I tend to think it wouldn't hurt... 72, Jim Rodenkirch K9JWV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
While Tom touched on the subject yesterday the subject of an individuals ground conductivity has to be stressed, continuously it seems. The FCC maps arent perfect and hams usually dont have the options of perfect siting for their verticals as do many of the BC stations. Home developers often remove all of the good topsoil and sell it. They back fill with rocky sand and whatever else is cheap or worthless and finish with a skimcoat of real topsoil just thick enough to grow grass. My own attempt with 60-65 quarter wave radials 30 years ago at another home were dismal since the ground was pure sand left behind by the glaciers with a fresh water table about 4' down. Great for mixing concrete and drainage only. After I installed a 2X4 fence mesh around the base and out 50' could I reliably work DX. Going to elevated radials here on a granite hill in the same town saved a lot of work and works very well. Carl KM1H _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
Hi, Bill Well, like you, I also live on a fairly small city lot with way too much bedrock coming up to the surface and a long concrete driveway, so buried radials just aren't feasible for me! So I hung my inverted L in a tall tulip poplar in one corner of the lot and I ran two elevated resonant radials down the fence lines - elevated about 5-6 feet. I worked good stuff all over the world including JA and Indian Ocean, and VK6. If I could hear 'em, I could work 'em! BEST thing I EVER did for myself was to build a KAZ terminated receiving loop for the low-bands 160-30m, so I could HEAR more! Worked great!! And no, I didn't have 100 buried radials, but just a few elevated resonant radials will produce very effective results for the transmit antenna! 73 Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill Cromwell Sent: Friday, February 14, 2014 10:02 AM To: topband@contesting.com Subject: Re: Topband: Question - optimum number of radials On 02/14/2014 09:15 AM, Charlie Cunningham wrote: That's a lot of good information, Richard! Thanks for sharing! 73, Charlie, K4OTV The whole topic of radials as it applies to me on my small lot is put in as many as you can. The same probably applies to others on small lots. On top band I do not have room in *any* direction for a quarter wavelength radial..not even one. In some directions a quarter wavelength radial wire might be bent to fit but that begins the many compromises. Obviously that setup would have the antenna in one corner of the lot so there would be no radials at all in one or two directions. So.. no quarter wave radials at all. I have been buying small spools of wire and will be adding them to whatever puny little radial field I DO have. As soon as the ice and snow is gone (maybe in June?) I will be elevating my wire antenna the rest of the way to the treetops and adding in the radial wires. In the process of elevating the antenna I will learn to be ace with a rod n reel grin. The whole point of that exercise is to *miss* the tree and go over the top. So far I've only ever tried to *hit* a spot out on the water. It's not hard to hit the water wink. I didn't do too badly finding a particular spot on the water with the bait. But the tree top is not over there. It's up there. 73, Bill KU8H _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
Yeah, just a few elevated resonant radials can work wonders as you have discovered, Carl! And rock does get in the way of buried radials!! The models teach that elevated resonant radials should work very well! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Sent: Friday, February 14, 2014 10:46 AM To: Tom W8JI Cc: topband@contesting.com Subject: Re: Topband: Question - optimum number of radials While Tom touched on the subject yesterday the subject of an individuals ground conductivity has to be stressed, continuously it seems. The FCC maps arent perfect and hams usually dont have the options of perfect siting for their verticals as do many of the BC stations. Home developers often remove all of the good topsoil and sell it. They back fill with rocky sand and whatever else is cheap or worthless and finish with a skimcoat of real topsoil just thick enough to grow grass. My own attempt with 60-65 quarter wave radials 30 years ago at another home were dismal since the ground was pure sand left behind by the glaciers with a fresh water table about 4' down. Great for mixing concrete and drainage only. After I installed a 2X4 fence mesh around the base and out 50' could I reliably work DX. Going to elevated radials here on a granite hill in the same town saved a lot of work and works very well. Carl KM1H _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
I would expect it to work OK with 75 ohm cable. An open-circuited 1/4 wave line looks like a short at its sending end and you would be looking for a null as the line reaches a 1/4 wavelength, so I would expect the method to work fine with 75 ohm line. In fact, the 50 or 75 ohm line, if we consider it to be lossless would be operating at infinite VSWR so I wouldn't think the modest difference in characteristic impedance would make any real difference. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of map...@windstream.net Sent: Friday, February 14, 2014 12:18 AM To: topband@contesting.com Subject: Topband: Palomar R-X Noise Bridge I have a question about using the noise bridge. I have used it cut stubs to 1/4 wavelength using 52 ohm cable with no problems. I now need some stubs using 75 ohm cable which I have on hand. Will the same procedure work for 75 ohm that works for 52 ohm cable, or will the different impedance need to be accounted for. I started to cut cable and this question came to me. My first thought is that it will work fine, but I am not sure. I did some searches on the web but found nothing about it. Any help would be appreciated. Thanks, Pat Armstrong KF5YZ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
I used a noise bridge to cut all the RG-11 stacked yagi and phased verticals phasing lines as well as harmonic stubs here when running a 2 station single op contest, before SO2R. Using the station receiver also works well as the backround noise null is easily heard. I did that several times when a 9V battery was dead and compared results later, they were right on. Carl KM1H - Original Message - From: map...@windstream.net To: topband@contesting.com Sent: Friday, February 14, 2014 12:18 AM Subject: Topband: Palomar R-X Noise Bridge I have a question about using the noise bridge. I have used it cut stubs to 1/4 wavelength using 52 ohm cable with no problems. I now need some stubs using 75 ohm cable which I have on hand. Will the same procedure work for 75 ohm that works for 52 ohm cable, or will the different impedance need to be accounted for. I started to cut cable and this question came to me. My first thought is that it will work fine, but I am not sure. I did some searches on the web but found nothing about it. Any help would be appreciated. Thanks, Pat Armstrong KF5YZ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: A simple question about EWE
Hello,brethren-in-low-bands, Anyone who has had experience with EWE antennas please share the wealth of your knowledge: 1. How critical are the physical parameters of the aerial, e.g. if I go 3 meters high and 13 meters long? 2. Any suggestions on the change impedance with the change of physical size? I would highly appreciate any comments and suggestions. And thanks to those of you who guided me through the maze of beverages design. CU on TB Temporarily bound to 100 watts, Alex HC2AO -HD2A-HD2RAE-HD8A ex UA4WAE -- ALEXEY OGORODOV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
Null depth is a function of cable loss. Heliax produces the deepest null, small diameter coax (RG-59, RG-58) is quite poor 75 vs. 50 ohm should make no difference. 73 Frank W3LPL - Original Message - From: Charlie Cunningham charlie-cunning...@nc.rr.com To: map...@windstream.net, topband@contesting.com Sent: Friday, February 14, 2014 4:16:30 PM Subject: Re: Topband: Palomar R-X Noise Bridge I would expect it to work OK with 75 ohm cable. An open-circuited 1/4 wave line looks like a short at its sending end and you would be looking for a null as the line reaches a 1/4 wavelength, so I would expect the method to work fine with 75 ohm line. In fact, the 50 or 75 ohm line, if we consider it to be lossless would be operating at infinite VSWR so I wouldn't think the modest difference in characteristic impedance would make any real difference. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of map...@windstream.net Sent: Friday, February 14, 2014 12:18 AM To: topband@contesting.com Subject: Topband: Palomar R-X Noise Bridge I have a question about using the noise bridge. I have used it cut stubs to 1/4 wavelength using 52 ohm cable with no problems. I now need some stubs using 75 ohm cable which I have on hand. Will the same procedure work for 75 ohm that works for 52 ohm cable, or will the different impedance need to be accounted for. I started to cut cable and this question came to me. My first thought is that it will work fine, but I am not sure. I did some searches on the web but found nothing about it. Any help would be appreciated. Thanks, Pat Armstrong KF5YZ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: TO7CC
Has anyone heard or worked these guys on 80 or 160? 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: TO7CC
Jim, N6SS in AZ worked him a few days ago at our SS on 80m. They were on 80m RTTY yesterday at SS and workable in AZ. I don't do RTTY, so still looking for them, They were also on yesterday at SS on 160m but no one west of W5 land heard or worked them. Its going to be difficult with the Contest starting later today. Ray, N6VR On Fri, Feb 14, 2014 at 10:21 AM, Jim Brown j...@audiosystemsgroup.comwrote: Has anyone heard or worked these guys on 80 or 160? 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: TO7CC
They have been on 160/80 almost every day, so far I have not heard a peep on 160, seems they are on for their sunset and then move to 80. Right now at 1700Z they are 579 at my sunrise peak on 3510 Think they start on 160 about 1400-1430Z 73 Merv K9FD/KH6 Has anyone heard or worked these guys on 80 or 160? 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: RF ground radials
In reference to all the ground radial postings; A link to a source of RF ground radial links, all in one place without having to search the web, links are always updated. -73- http://www.rossradio.net/ + Today's Topics: 1. Re: TO7CC (Ray Benny) 2. Ice (Tom W8JI) 3. Re: Ice (Mike Waters) 4. Re: Ice (Charlie Cunningham) 5. Re: Power stayed on! (Gary Smith) 6. Re: NQ4I (Mike Waters) 7. Re: Power stayed on! (ZR) 8. Question - optimum number of radials (DALE LONG) 9. Re: Question - optimum number of radials (Mike Waters) 10. Re: Question - optimum number of radials (Joe Subich, W4TV) 11. Re: Ice (n0...@juno.com) 12. Re: Ice (Gary and Kathleen Pearse) 13. Re: Question - optimum number of radials (Tom W8JI) 14. Re: Question - optimum number of radials (Brad Rehm) 15. Re: Question - optimum number of radials (Tom W8JI) 16. Re: Question - optimum number of radials (Dan Maguire) 17. Palomar R-X Noise Bridge (map...@windstream.net) 18. Re: Question - optimum number of radials (Richard Fry) 19. Re: Question - optimum number of radials (Charlie Cunningham) 20. Re: Question - optimum number of radials (Bill Cromwell) 21. Question - optimum number of radials (James Rodenkirch) 22. Re: Question - optimum number of radials (Carl) 23. Re: Palomar R-X Noise Bridge (Carl) 24. Re: Question - optimum number of radials (Charlie Cunningham) 25. Re: Question - optimum number of radials (Charlie Cunningham) -- Message: 1 Date: Thu, 13 Feb 2014 12:35:12 -0700 From: Ray Benny rayn...@cableone.net Cc: topband@contesting.com topband@contesting.com, f6...@sfr.fr Subject: Re: Topband: TO7CC Message-ID: CAC716YZb4xTKXcygPJcz2afMom=dt-b-2bplzkpho-pe7v_...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Heard TO7CC at our SS yesterday on 80m CW - 0100z, until about 0130z. You worked K6XT, but I was there too. Will be looking for you on 80m CW at or Sunset this evening, about 0100z and later. 73, tnx, Ray, N6VR On Thu, Feb 13, 2014 at 7:35 AM, Doug Renwick ve...@sasktel.net wrote: I haven't heard them or seen spots on 160 or 80 for the west coast around 1400 UTC give or take. Doug -Original Message- Try to focuse our work on top band each time as possible. Every nights ops are there. At the end of FT5ZM QRG back quiet but dont Forget that another guys still on fr?quences for you. Finaly team stay on the Island untill sunday morning. D?pending cndx Est coast stations Can be ear half and more after SR. In FR time around 2H30 AM. Last night have strong noise even on 80 didn't log much qso in lows bands. TO7CC team _ Topband Reflector Archives - http://www.contesting.com/_topband --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband -- Message: 2 Date: Thu, 13 Feb 2014 15:32:53 -0500 From: Tom W8JI w...@w8ji.com To: topband@contesting.com Subject: Topband: Ice Message-ID: EE168A8969984EEAB34FD00755CF9ABD@MAIN Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original The ice that fell off my Yagi's typically measures about 1 thick off the largest pieces, and 1/2 thick on the smaller thicknesses. I'm going to assume the thick pieces are from the bottoms, so that's probably like 3/4 inch radial ice. We lost power just before sunset last night.The power lines are a mess on my road, I'd guess they use maybe 400 ft spans, so they broke in multiple places. I expect days before we have commercial power. All of my Yagis sprung back except the 40 meter antenna. The ice dropped off one side of the top antenna, so it rotated the elements enough to look pretty ugly. The bottom 40M Yagi lived just fine until big chunks of ice kept banging it, and then one side of one element bent. Many ropes snapped. The next time I need to remember to go out and release tension **before** the ice hits. Once it started icing, none of the ropes running through pulleys could be released. I have not looked at Beverages and in woods and fields, but I have a lot of tree and building damage so I expect some chain saw and receiving antenna work. All in all not bad for such a large amount of ice. 73 Tom -- Message: 3 Date: Thu, 13 Feb 2014 14:47:50 -0600 From: Mike Waters mikew...@gmail.com To: topband topband@contesting.com Subject: Re: Topband: Ice Message-ID: ca+fxyxihu-ca4h2vmtpwna0eaeejee4nziyigfhs0vhcn6p...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 The last ice storm surely would have taken down my 160m inverted-L, had it not been for the counterweight at the end. (It's made from #16 THHN, not very strong.) The pulley did not completely ice up, apparently because it moved every so often as ice
Re: Topband: Palomar R-X Noise Bridge
- Original Message - From: donov...@starpower.net To: topband@contesting.com Sent: Friday, February 14, 2014 11:42 AM Subject: Re: Topband: Palomar R-X Noise Bridge Null depth is a function of cable loss. ** Yup Heliax produces the deepest null, small diameter coax (RG-59, RG-58) is quite poor ** The highest VF and lowest loss produces the deepest null but also the least deep null bandwidth due to the higher Q. I used CATV RG-11 for my stubs and could get a good 25 dB+ null compared to about 12dB for RG-58. I had to add pieces for CW contests on some bands. The 25dB was sufficient to operate on any other band and put the TX phase noise in the noise. Carl KM1H 75 vs. 50 ohm should make no difference. 73 Frank W3LPL - Original Message - From: Charlie Cunningham charlie-cunning...@nc.rr.com To: map...@windstream.net, topband@contesting.com Sent: Friday, February 14, 2014 4:16:30 PM Subject: Re: Topband: Palomar R-X Noise Bridge I would expect it to work OK with 75 ohm cable. An open-circuited 1/4 wave line looks like a short at its sending end and you would be looking for a null as the line reaches a 1/4 wavelength, so I would expect the method to work fine with 75 ohm line. In fact, the 50 or 75 ohm line, if we consider it to be lossless would be operating at infinite VSWR so I wouldn't think the modest difference in characteristic impedance would make any real difference. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of map...@windstream.net Sent: Friday, February 14, 2014 12:18 AM To: topband@contesting.com Subject: Topband: Palomar R-X Noise Bridge I have a question about using the noise bridge. I have used it cut stubs to 1/4 wavelength using 52 ohm cable with no problems. I now need some stubs using 75 ohm cable which I have on hand. Will the same procedure work for 75 ohm that works for 52 ohm cable, or will the different impedance need to be accounted for. I started to cut cable and this question came to me. My first thought is that it will work fine, but I am not sure. I did some searches on the web but found nothing about it. Any help would be appreciated. Thanks, Pat Armstrong KF5YZ _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: TO7CC
Heard bits and dits on 160 last night my sunset gray line, but noise from snow was too great for solid copy. Worked them at 0100 on 80 on Wednesday. Not strong, but workable. They have said that they will operate through their night if there is an opening on 80 and/or 160. 73, Ken - K4XL On Fri, Feb 14, 2014 at 12:30 PM, Merv Schweigert k...@flex.com wrote: They have been on 160/80 almost every day, so far I have not heard a peep on 160, seems they are on for their sunset and then move to 80. Right now at 1700Z they are 579 at my sunrise peak on 3510 Think they start on 160 about 1400-1430Z 73 Merv K9FD/KH6 Has anyone heard or worked these guys on 80 or 160? 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: TO7CC
On 2/14/2014 11:04 AM, Kenneth Grimm wrote: They have said that they will operate through their night if there is an opening on 80 and/or 160. They need to understand grey line propagation to work NA on 160 and 80, and to realize that there's an opening to Zone 3/4 around their sunset and our sunrise. FT5ZM did that to great advantage, working Zone 4/5 around 4/5 sunset and Zone 3/4 at sunrise. According to ClubLog, they made 3,571 Qs on Topband, of which 784 were to North America! 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: TO7CC
Jim, Your points about understanding grey line propagation is right. I know that they have been on almost everyday working just that. If you have a great circle map located on your QTH you will see a very great difference in paths between FT5ZM and TO7CC. FT5ZM was almost a East West path and TO7CC is North South Path right through the intensity of the auroral oval a much more difficult path by far. So I don't think I can expect to hear TO7CC as easily as I did FT5ZM. Rich K7ZV On 2/14/2014 11:04 AM, Kenneth Grimm wrote:the They have said that they will operate through their night if there is an opening on 80 and/or 160. They need to understand grey line propagation to work NA on 160 and 80, and to realize that there's an opening to Zone 3/4 around their sunset and our sunrise. FT5ZM did that to great advantage, working Zone 4/5 around 4/5 sunset and Zone 3/4 at sunrise. According to ClubLog, they made 3,571 Qs on Topband, of which 784 were to North America! 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
On 2/14/2014 10:55 AM, Carl wrote: The highest VF and lowest loss produces the deepest null but also the least deep null bandwidth due to the higher Q. Not always -- stubs made with higher Vf cables are longer, so in my experience they come out about the same for attenuation and bandwidth. The only way to get a deeper null (with the reduction in bandwidth you have noted), is to reduce the RF resistance -- this means larger diameter coax and a more robust shield, like hard line. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
Makes sense. The lower the return-loss, the deeper the null! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Brown Sent: Friday, February 14, 2014 4:17 PM To: topband@contesting.com Subject: Re: Topband: Palomar R-X Noise Bridge On 2/14/2014 10:55 AM, Carl wrote: The highest VF and lowest loss produces the deepest null but also the least deep null bandwidth due to the higher Q. Not always -- stubs made with higher Vf cables are longer, so in my experience they come out about the same for attenuation and bandwidth. The only way to get a deeper null (with the reduction in bandwidth you have noted), is to reduce the RF resistance -- this means larger diameter coax and a more robust shield, like hard line. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
- Original Message - From: Jim Brown j...@audiosystemsgroup.com To: topband@contesting.com Sent: Friday, February 14, 2014 4:16 PM Subject: Re: Topband: Palomar R-X Noise Bridge On 2/14/2014 10:55 AM, Carl wrote: The highest VF and lowest loss produces the deepest null but also the least deep null bandwidth due to the higher Q. Not always -- stubs made with higher Vf cables are longer, so in my experience they come out about the same for attenuation and bandwidth. The only way to get a deeper null (with the reduction in bandwidth you have noted), is to reduce the RF resistance -- this means larger diameter coax and a more robust shield, like hard line. 73, Jim K9YC Isnt that what lowest loss means? At least that was my intention. On 6M Ive used a 7/8 Heliax stub to kill harmonics getting into the police system 200' away. Carl KM1H _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Still in search of resonance
List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Sorry Carl, I hit the send button before responding..Now. I believe that first #14 wire is a bit small. I do not believe that you will find a 50ohmZ and X=0 point. I have 80ft of Rohn 45G with a Telrex 20M546 at 80ft, 3el on 15 at 90 and 3el on 10 at 100ft. I shunt feed the tower for 160 with a tap at 35ft using 1/2 EMT Conduit. At the end of the shunt rod I have a 500pf Vacuum Variable to the tower base and a 500pf Vacuum in series from the shunt rod to the Coax. I can and did tune the Vacuum Caps to VSWR 1:1 at 1830kHz. I did this in 1991 and it gets out very well. It hears good but my noise is over S9 with it. DXCC on 160 is 192 cmfd. 73 de Price W0RI near St. Louis List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Is the single 14AWG too thin causing goofy readings? Absolutely! Treating the Sky Needle and the #12 wire as a folded dipole and using 8 for the diameter of the tower, you have a 16:1 step-up with the single #14 wire. If you made a cage of 4 or 6 wires with a 6 to 8 diameter, back of the envelope calculations say the impedance with the 67' tap point would be much closer to 50 Ohms *and* the bandwidth would be much wider. Even three parallel wires spaced 12 or so would have a much greater effective diameter and would reduce the step-up you see by a great deal. Of course, if all you can do is a single #14 wire, use an Omega match or an L-network to bring the impedance down to 50 Ohms. 73, ... Joe, W4TV On 2/14/2014 6:14 PM, Carl Braun wrote: List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Thanks Dean The one I'm looking at is the old heathkit with the various coil plug ins. The kit comes with a coil that goes down to 1.600. Is there another one you can recommend that may go down further? ON4UN says my tower should be close to 115 degrees others say closer to 140 degrees Thanks for your input. I agree with you wholeheartedly. Carl AG6X Sent from my iPhone On Feb 14, 2014, at 3:32 PM, dospi...@q.com dospi...@q.com wrote: Hello Carl: My suggestion is the same as the first time you were on about this. Obtain... beg borrow steal or buy a meter that will read down into the BC band. You NEED to know where it is resonant.. All the esoteric nonsense about resistance and reactance are meaningless unless you know the frequencies at which the readings are obtained! You might find the damn thing is 1:1 at 1356 kc.. At this point you are shooting in the dark in a dark room.. You may or may not have an adequate ground system, but that doesn't lessen the need to know what it is you have... and you don't. 73 GL Dean W5PJR Tijeras, NM - Original Message - From: Carl Braun carl.br...@lairdtech.com To: 160 topband@contesting.com Sent: Friday, February 14, 2014 4:14:42 PM Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
There seems to be some confusion, Carl! First of all, since the gamma match (regardless of the diameter of the gamma rod) is a shorted transmission line, less than 1/4 wavelength it WILL have series inductive reactance that you will need to tune out with a series variable capacitance. Second, I don't understand the R readings that you are reporting at various tap points with the MFJ, that come down when you apply the series C. That suggests to me that what you are reporting as R is R+jX or [R+jX], and it's coming down as you tune out the series reactance jX. If you find a tap point that results in 50 ohms real when you use the series-C to make X=0, that IS the 50 ohm tap point that you are looking for. You will NOT find a point that gives you 50 ohms real without the series C to tune out the inductive reactance, Other opinions notwithstanding, you CAN do the gamma match with 14 ga. wire, The only effect of using a thin gamma rod or gamma wire is to increase the losses a bit in the gamma, and to increase the inductance per unit length of the gamma. Finally, take care. That you don't have enough broadcast signal on the Sky needle to screw up the MFJ readings. ON additional note: In some cases guys use a shorter gamma that resultsn in a resistive real part LESS than 50 ohms. In this case only a portion of the series inductance is cancelled with the series C and theremainin inductive reactance is used in conjunction with a shunt variable C to form an L-network to match the real part UP to 50 ohms! Sounds like you are hitting all around it, Carl. Just remember that what you are searching for is R=50, and X=0, or R+jX = 50 + j0. GL! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband
Re: Topband: Still in search of resonance
Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance - BTW Resonance
Well, of course not, Tom! I need to be more precise and keep in mind the audience on this Reflector, and that you are always lurking out there in the weeds to chide and chastise me! Of course devices that are pure real over the frequency range of interest would not be resonant! I guess I was thinking of the more general case.like Carl's gamma match whose impedance would consist of a real and imaginary part, in which case I stand by my assertion. Touche! Mea culpa! -Original Message- From: Tom W8JI [mailto:w...@w8ji.com] Sent: Friday, February 14, 2014 9:10 PM To: Charlie Cunningham; 'Carl Braun'; 'Joe Subich, W4TV' Cc: topband@contesting.com Subject: Re: Topband: Still in search of resonance - BTW Resonance Subject: Re: Topband: Still in search of resonance - BTW Resonance BTW Resonance = X=0 or jX = j0 So my dummy load is resonant, and the resistors in my resistor bins are all resonant? :-) _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
On 2/14/2014 2:17 PM, Carl wrote: Isnt that what lowest loss means? At least that was my intention. I must not have written clearly enough. I was not questioning the low loss, only that the high Vf was the way to get it. You DO get the low loss by going to larger coax, (like the 7/8-in hard line), but it's the fact that it's LARGER and has lower RF resistance, NOT the higher Vf. Think of it this way -- The higher Vf cable has less attenuation per ft because the higher Vf allows the center conductor to be larger. But a stub made with foam coax with Vf = 0.84 must be 27% longer than one with with a solid dielectric and Vf =.66. If those coaxes are the same diameter and of comparable quality, the stub attenuation and Q will be nearly the same. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
All generally true, I expect, but I also believe that dielectric constant and dielectric losses also figure in and the lowest loss lines would be filled with air, dry nitrogen or evacuated. I expect those would likely be the lowest loss AND highest velocity factor cases. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Brown Sent: Friday, February 14, 2014 9:42 PM To: 'TopBand' Subject: Re: Topband: Palomar R-X Noise Bridge On 2/14/2014 2:17 PM, Carl wrote: Isnt that what lowest loss means? At least that was my intention. I must not have written clearly enough. I was not questioning the low loss, only that the high Vf was the way to get it. You DO get the low loss by going to larger coax, (like the 7/8-in hard line), but it's the fact that it's LARGER and has lower RF resistance, NOT the higher Vf. Think of it this way -- The higher Vf cable has less attenuation per ft because the higher Vf allows the center conductor to be larger. But a stub made with foam coax with Vf = 0.84 must be 27% longer than one with with a solid dielectric and Vf =.66. If those coaxes are the same diameter and of comparable quality, the stub attenuation and Q will be nearly the same. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance - BTW - Update!
By the way, Carl, you indicated that whe you were tapped at 90', the real part was 60 ohms when you tuned ou't the series reactance with th;e series capacitor!! Gee!! That ain't a bad match!! Should result in about 1.2:1 VSWR when fed with 50 ohm cable!! Not bad at all and certainly not enough VSWR to cause any significant excess loss (over flat-loss) even on a very long run of coax feeding the gamma match!! You were essentially done at that point and you should have just stopped there and bolted everything down!! You could probably find the 50 ohm j0 tap point somewhere below 90 ' , but if those are the only four tap points that are available, then 90' is the one that you want! The 14 ga wire isn't causing goofy readings and your radial field is probably OK as well! (operator head-spacing problem??) GL - move the tap back to 90' and be done! And you can't do a gamma match to shunt feed that tower without a series-c in the gamma arm! No way! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Tom and all Thanks for the responses. I was under the assumption that I would find a 50 ohm tap on the tower but with a lot of reactance requiring a cap that would tune out the X but leave the 50 ohm resistive value in place. I knew my tap was too low at 46' when I saw less than 50 ohms with the variable cap in place. Same thing when I tapped the tower at 90' and I saw the lowest R at 68 ohms with the 160pf only partially meshed. With all of the information presented in this thread it appears my best bet is to tap the tower at the 67' level while playing with the larger (1050pf) variable in series to see what my results are. I have never used the larger cap with the tap at 90' or 67'...only the smaller 160pf variable. More experimentation tomorrow if I don't burn out the Skyneedle motor with all the up and down. Thanks and details to follow. Carl AG6X Sent from my iPhone On Feb 14, 2014, at 6:01 PM, Tom W8JI w...@w8ji.com wrote: Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
On 2/14/2014 7:00 PM, Charlie Cunningham wrote: All generally true, I expect, but I also believe that dielectric constant and dielectric losses also figure in and the lowest loss lines would be filled with air, dry nitrogen or evacuated. I expect those would likely be the lowest loss AND highest velocity factor cases. If you run the equations, you find that below about 1 GHz, the losses are all copper losses. Dielectric loss is a few percent of the total loss in the 500 MHz range. The benefit of a foam dielectric at HF and VHF is that it allows the center conductor to be larger for a given shield diameter. But the improvement in loss of a foam dielectric coax below 1 GHz is entirely due to the center conductor being larger. BTW -- the relevant equation is on each Times data sheet. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance Update 2
Well, if those 4 discrete tap points are the only ones that you have available, Carl, you likely won't find one that give that gives you 50 ohms real. So the best that you can do is pick the one that falls closest to 50 ohms real when you tune out the series inductive reactance with the capacitor. Even if the 90' point gives you 68 ohms real, that's not too bad - about 1.4:1 VSWR. If the 67' tap gives you less than 50 ohms real, you could add a shunt C back to GND at the base of the tower the and readjust the series C to only cancel a portion of the inductive reactance, leaving the remainder to work against the shunt C to form an L-network to transform the real part up to 50 ohms. By alternating back and forth adjusting the series and shunt capacitors, you should be able to bring the feedpoint VSWR to 1:1. Note that whatever the tap point, if the real part of the impedance is LESS than 50 ohms, a shunt C will be required. GL, 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 11:52 PM To: Tom W8JI Cc: 160 Subject: Re: Topband: Still in search of resonance Tom and all Thanks for the responses. I was under the assumption that I would find a 50 ohm tap on the tower but with a lot of reactance requiring a cap that would tune out the X but leave the 50 ohm resistive value in place. I knew my tap was too low at 46' when I saw less than 50 ohms with the variable cap in place. Same thing when I tapped the tower at 90' and I saw the lowest R at 68 ohms with the 160pf only partially meshed. With all of the information presented in this thread it appears my best bet is to tap the tower at the 67' level while playing with the larger (1050pf) variable in series to see what my results are. I have never used the larger cap with the tap at 90' or 67'...only the smaller 160pf variable. More experimentation tomorrow if I don't burn out the Skyneedle motor with all the up and down. Thanks and details to follow. Carl AG6X Sent from my iPhone On Feb 14, 2014, at 6:01 PM, Tom W8JI w...@w8ji.com wrote: Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Palomar R-X Noise Bridge
Thanks, Jim Well, I confess that most of my professional work has been near or above 1 GHz Thanks for tip about the Times datasheets! 73, Charlie,K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Brown Sent: Saturday, February 15, 2014 12:16 AM To: 'TopBand' Subject: Re: Topband: Palomar R-X Noise Bridge On 2/14/2014 7:00 PM, Charlie Cunningham wrote: All generally true, I expect, but I also believe that dielectric constant and dielectric losses also figure in and the lowest loss lines would be filled with air, dry nitrogen or evacuated. I expect those would likely be the lowest loss AND highest velocity factor cases. If you run the equations, you find that below about 1 GHz, the losses are all copper losses. Dielectric loss is a few percent of the total loss in the 500 MHz range. The benefit of a foam dielectric at HF and VHF is that it allows the center conductor to be larger for a given shield diameter. But the improvement in loss of a foam dielectric coax below 1 GHz is entirely due to the center conductor being larger. BTW -- the relevant equation is on each Times data sheet. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
