Re: Topband: Best wire antenna for roof top location.
Hi John,9V1VV You are absolutely right...the main issue for operating topband is how to get better and better S/N...finding a quiet place whenever possible...and luckily...after that ...be a though one like a dog hound in the night till morning...hearing for a new one ... hi hi Best of luck for all of the 160M operator Nuradi YB0UNC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of JC Sent: Saturday, August 15, 2015 8:55 PM To: 'John Davies'; topband@contesting.com Subject: Re: Topband: Best wire antenna for roof top location. All of us have tried separate small loop receive antennas, both passive and active, with only marginal improvements. Noise cancelling antennas don't work due to the myriad of noise sources in built-up areas. Short Beverages are a waste of time as well. Bottom line is it is hardly worth bothering. After you have worked the few big guns in EU and the JAs, Aussies and Russians on top band there is a quantum leap to the rest of the world, all due to noise. John 9V1VV Hi John I understand how frustrating it is when you need to hear on the transmit antenna. I started listening top-band back in 1970, I was able to work my first DX in 1972 and it took me 20 years to work 100 countries. After moving to a quiet location in 1990, I worked 9V1XQ in 1994 with 579 and using a vertical with almost no radials, my back yard was 20 x 10 m... The good news is that there is a solution for rooftop location. I have been working on developing the Horizontal Waller Flag since 2009 and there are two HWF in downtown Sao Paulo, Brazil. One at PY2XB and another at PY2AAZ. Fabio's location is PY2AAZ-15 - 23°35.12' S 46°40.16' W - GG66PJ99QM Fred, PY2XB, has several pictures on QRZ.com. The Horizontal WF has two identical horizontal flags cancelling each other, the rejection of manmade noise is above 40 db at the direction of maximum gain. The antenna directive gain is excellent, 11,5 db RDF. But the power gain is very low -55 db. There is over 20 db increase in SNR. The antenna already optimized and the amplifiers still have some option under test, the final system will only be available next year. I am running very late on my final tests. This season there is almost no signal to use, it has been hard to hear Europe on 160m. Very poor conditions. Next year you can expect few articles on QST for those who want to build them, if you google HWF N4IS or NX4D (http://nx4d10.wix.com/waller-flag) you can find presentations and pdfs about the project. I will offer a commercial optimized version next year. Some DX expeditions will use the HWF from roof top as well. With the HWF the 160, 80, 40 and 30m bands are quiet as 20m, it is a difference experience. Regards JC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location.
All of us have tried separate small loop receive antennas, both passive and active, with only marginal improvements. Noise cancelling antennas don't work due to the myriad of noise sources in built-up areas. Short Beverages are a waste of time as well. Bottom line is it is hardly worth bothering. After you have worked the few big guns in EU and the JAs, Aussies and Russians on top band there is a quantum leap to the rest of the world, all due to noise. John 9V1VV Hi John I understand how frustrating it is when you need to hear on the transmit antenna. I started listening top-band back in 1970, I was able to work my first DX in 1972 and it took me 20 years to work 100 countries. After moving to a quiet location in 1990, I worked 9V1XQ in 1994 with 579 and using a vertical with almost no radials, my back yard was 20 x 10 m... The good news is that there is a solution for rooftop location. I have been working on developing the Horizontal Waller Flag since 2009 and there are two HWF in downtown Sao Paulo, Brazil. One at PY2XB and another at PY2AAZ. Fabio's location is PY2AAZ-15 - 23°35.12' S 46°40.16' W - GG66PJ99QM Fred, PY2XB, has several pictures on QRZ.com. The Horizontal WF has two identical horizontal flags cancelling each other, the rejection of manmade noise is above 40 db at the direction of maximum gain. The antenna directive gain is excellent, 11,5 db RDF. But the power gain is very low -55 db. There is over 20 db increase in SNR. The antenna already optimized and the amplifiers still have some option under test, the final system will only be available next year. I am running very late on my final tests. This season there is almost no signal to use, it has been hard to hear Europe on 160m. Very poor conditions. Next year you can expect few articles on QST for those who want to build them, if you google HWF N4IS or NX4D (http://nx4d10.wix.com/waller-flag) you can find presentations and pdfs about the project. I will offer a commercial optimized version next year. Some DX expeditions will use the HWF from roof top as well. With the HWF the 160, 80, 40 and 30m bands are quiet as 20m, it is a difference experience. Regards JC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location.
Halo John, 9V1VV Thanks for your experience shared re-the topband operation Same story on what has happened so far with my inv.V antenna on 160m at my office and QTH. Just would like to hear every suggestion in detail from all the topband guru's here and...try another experience on the roof top of a hi-rise building...do hope I got lucky and could get better S/N therehi hi Best 73, Nuradi, YB0UNC / KU2B -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of John Davies Sent: Friday, August 14, 2015 6:58 AM To: topband@contesting.com Subject: Topband: Best wire antenna for roof top location. From: coupe...@hotmail.com To: topband@contesting.com Subject: Re: Best wire antenna for roof top location. Date: Thu, 13 Aug 2015 23:55:30 + 9V operations are similar to Jakarta, with huge noise problems in an urban environment. Over the past 15 years there have only been three or four 9V ops on 160. The most successful was Bob 9V1GO who claimed 100 DXCC entities over a few seasons. However, these were internet assisted. He tried everything and eventually ended up with a long wire sloper from his high rise apartment down to ground level, using the building water pipes as a counterpoise. His efforts took hundreds or even thousands of hours to achieve. Another was Pete 9V1PC (SK) who tried an inverted L from a high-rise, with the top section 30 feet above the roof and the vertical section sloping a bit down to the ground. Noise killed him. He tried a 1/4 wave vertical from the roof on a helium balloon but his neighbours threatened to report him to the police, so he gave up after a few nights. Using 1KW he got out fine but could only hear S9 noise. He got many angry emails from ops around the world because he could not hear them. I was on a few years ago using a full length dipole above the roof, far too low of course, but with 500 Watts it got out OK. Noise again was the problem. I worked 40 DXCC entities but after many nights of listening to static I gave up. Life is too short. All of us have tried separate small loop receive antennas, both passive and active, with only marginal improvements. Noise cancelling antennas don't work due to the myriad of noise sources in built-up areas. Short Beverages are a waste of time as well. Bottom line is it is hardly worth bothering. After you have worked the few big guns in EU and the JAs, Aussies and Russians on top band there is a quantum leap to the rest of the world, all due to noise. John 9V1VV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location.
Has anyone tried merely dropping a lightweight wire over the side of the building as a receive-only antenna? That might get it away from the plane of interference from the equipment at the top. On Fri, Aug 14, 2015 at 11:26 PM, John Davies coupe...@hotmail.com wrote: Hello Nuradi. Please don't let my post discourage your efforts. There is a lot of satisfaction gained in trying out different ideas. You may have more success than we had. 73 John Sent from my Mi phone On Aug 15, 2015 6:23 AM, Nuradi yb0...@gmail.com wrote:br type=attributi Halo John, 9V1VV Thanks for your experience shared re-the topband operation Same story on what has happened so far with my inv.V antenna on 160m at my office and QTH. Just would like to hear every suggestion in detail from all the topband guru's here and...try another experience on the roof top of a hi-rise building...do hope I got lucky and could get better S/N therehi hi Best 73, Nuradi, YB0UNC / KU2B -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of John Davies Sent: Friday, August 14, 2015 6:58 AM To: topband@contesting.com Subject: Topband: Best wire antenna for roof top location. From: coupe...@hotmail.com To: topband@contesting.com Subject: Re: Best wire antenna for roof top location. Date: Thu, 13 Aug 2015 23:55:30 + 9V operations are similar to Jakarta, with huge noise problems in an urban environment. Over the past 15 years there have only been three or four 9V ops on 160. The most successful was Bob 9V1GO who claimed 100 DXCC entities over a few seasons. However, these were internet assisted. He tried everything and eventually ended up with a long wire sloper from his high rise apartment down to ground level, using the building water pipes as a counterpoise. His efforts took hundreds or even thousands of hours to achieve. Another was Pete 9V1PC (SK) who tried an inverted L from a high-rise, with the top section 30 feet above the roof and the vertical section sloping a bit down to the ground. Noise killed him. He tried a 1/4 wave vertical from the roof on a helium balloon but his neighbours threatened to report him to the police, so he gave up after a few nights. Using 1KW he got out fine but could only hear S9 noise. He got many angry emails from ops around the world because he could not hear them. I was on a few years ago using a full length dipole above the roof, far too low of course, but with 500 Watts it got out OK. Noise again was the problem. I worked 40 DXCC entities but after many nights of listening to static I gave up. Life is too short. All of us have tried separate small loop receive antennas, both passive and active, with only marginal improvements. Noise cancelling antennas don't work due to the myriad of noise sources in built-up areas. Short Beverages are a waste of time as well. Bottom line is it is hardly worth bothering. After you have worked the few big guns in EU and the JAs, Aussies and Russians on top band there is a quantum leap to the rest of the world, all due to noise. John 9V1VV _ 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: Best wire antenna for roof top location.
Hello Nuradi. Please don't let my post discourage your efforts. There is a lot of satisfaction gained in trying out different ideas. You may have more success than we had. 73 John Sent from my Mi phone On Aug 15, 2015 6:23 AM, Nuradi yb0...@gmail.com wrote:br type=attributi Halo John, 9V1VV Thanks for your experience shared re-the topband operation Same story on what has happened so far with my inv.V antenna on 160m at my office and QTH. Just would like to hear every suggestion in detail from all the topband guru's here and...try another experience on the roof top of a hi-rise building...do hope I got lucky and could get better S/N therehi hi Best 73, Nuradi, YB0UNC / KU2B -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of John Davies Sent: Friday, August 14, 2015 6:58 AM To: topband@contesting.com Subject: Topband: Best wire antenna for roof top location. From: coupe...@hotmail.com To: topband@contesting.com Subject: Re: Best wire antenna for roof top location. Date: Thu, 13 Aug 2015 23:55:30 + 9V operations are similar to Jakarta, with huge noise problems in an urban environment. Over the past 15 years there have only been three or four 9V ops on 160. The most successful was Bob 9V1GO who claimed 100 DXCC entities over a few seasons. However, these were internet assisted. He tried everything and eventually ended up with a long wire sloper from his high rise apartment down to ground level, using the building water pipes as a counterpoise. His efforts took hundreds or even thousands of hours to achieve. Another was Pete 9V1PC (SK) who tried an inverted L from a high-rise, with the top section 30 feet above the roof and the vertical section sloping a bit down to the ground. Noise killed him. He tried a 1/4 wave vertical from the roof on a helium balloon but his neighbours threatened to report him to the police, so he gave up after a few nights. Using 1KW he got out fine but could only hear S9 noise. He got many angry emails from ops around the world because he could not hear them. I was on a few years ago using a full length dipole above the roof, far too low of course, but with 500 Watts it got out OK. Noise again was the problem. I worked 40 DXCC entities but after many nights of listening to static I gave up. Life is too short. All of us have tried separate small loop receive antennas, both passive and active, with only marginal improvements. Noise cancelling antennas don't work due to the myriad of noise sources in built-up areas. Short Beverages are a waste of time as well. Bottom line is it is hardly worth bothering. After you have worked the few big guns in EU and the JAs, Aussies and Russians on top band there is a quantum leap to the rest of the world, all due to noise. John 9V1VV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Best wire antenna for roof top location.
From: coupe...@hotmail.com To: topband@contesting.com Subject: Re: Best wire antenna for roof top location. Date: Thu, 13 Aug 2015 23:55:30 + 9V operations are similar to Jakarta, with huge noise problems in an urban environment. Over the past 15 years there have only been three or four 9V ops on 160. The most successful was Bob 9V1GO who claimed 100 DXCC entities over a few seasons. However, these were internet assisted. He tried everything and eventually ended up with a long wire sloper from his high rise apartment down to ground level, using the building water pipes as a counterpoise. His efforts took hundreds or even thousands of hours to achieve. Another was Pete 9V1PC (SK) who tried an inverted L from a high-rise, with the top section 30 feet above the roof and the vertical section sloping a bit down to the ground. Noise killed him. He tried a 1/4 wave vertical from the roof on a helium balloon but his neighbours threatened to report him to the police, so he gave up after a few nights. Using 1KW he got out fine but could only hear S9 noise. He got many angry emails from ops around the world because he could not hear them. I was on a few years ago using a full length dipole above the roof, far too low of course, but with 500 Watts it got out OK. Noise again was the problem. I worked 40 DXCC entities but after many nights of listening to static I gave up. Life is too short. All of us have tried separate small loop receive antennas, both passive and active, with only marginal improvements. Noise cancelling antennas don't work due to the myriad of noise sources in built-up areas. Short Beverages are a waste of time as well. Bottom line is it is hardly worth bothering. After you have worked the few big guns in EU and the JAs, Aussies and Russians on top band there is a quantum leap to the rest of the world, all due to noise. John 9V1VV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Guy and jim, No, I'm not missing anything -- did you miss my words first approximation in my description of the model? That model was a feasibility study, not intended or accepted (by me, at least) as a predictor of actual performance of an antenna on a building that we known nothing more than a few dimensions. You are missing my point, which is that, depending on the nature of the building roof and structure, a horizontal antenna MIGHT be a very good one, and is worth trying. 73, Jim K9YC On Tue,8/11/2015 12:08 PM, Guy Olinger K2AV wrote: No. You'd be missing the essential point which has to do with the shape of the tool and whether it was remotely suited to the problem. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Okay guys - when email starts getting this specific and personal - the rest of the list is really not interested in it. Please take this debate off the list. Thanks. Tree On Wed, Aug 12, 2015 at 8:16 AM, Jim Brown j...@audiosystemsgroup.com wrote: Guy and jim, No, I'm not missing anything -- did you miss my words first approximation in my description of the model? That model was a feasibility study, not intended or accepted (by me, at least) as a predictor of actual performance of an antenna on a building that we known nothing more than a few dimensions. You are missing my point, which is that, depending on the nature of the building roof and structure, a horizontal antenna MIGHT be a very good one, and is worth trying. 73, Jim K9YC On Tue,8/11/2015 12:08 PM, Guy Olinger K2AV wrote: No. You'd be missing the essential point which has to do with the shape of the tool and whether it was remotely suited to the problem. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Ah, perfection. Sadly, EZNEC does not provide that set of options. If I could build that model, I would. But I can't. I will take this first approximation, understanding its limitations. Brown's 99th law -- never let perfect be the enemy of good. We don't know the nature of that roof, so modeling several possibilities and using the result to TRY things seems like a pretty good approach to me. 73, Jim K9YC On Tue,8/11/2015 12:42 AM, Guy Olinger K2AV wrote: In order to estimate your hypothesis you need to create a building shaped cage of dielectric wrapped, resistively loaded, interconnected wires. It is necessary to bookkeep in the model that the roof, as conductor, is connected to a vertical conducting face on four sides and then to ground. These faces electrically are at least in the quarter to half wavelength range vertically and can radically effect the appearance of the roof as conductor. These faces can have significant radiation. These faces can be the majority radiator with the dipole serving mainly as a matching device to the building as majority radiator. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Hi Jim, I must respectfully disagree. And warn any reader that using NEC ground media to simulate a conductive roof is a very troubled procedure with significant issues. Using the first media to simulate an elevated conductive plane for any purpose is a problem. Using it to simulate radials is simply the ubiquitous recurring error (out of a class of errors) that W7EL specifically lists as the example in self defense. You are putting forth a rare invocation of this same NEC weakness. In order to estimate your hypothesis you need to create a building shaped cage of dielectric wrapped, resistively loaded, interconnected wires. It is necessary to bookkeep in the model that the roof, as conductor, is connected to a vertical conducting face on four sides and then to ground. These faces electrically are at least in the quarter to half wavelength range vertically and can radically effect the appearance of the roof as conductor. These faces can have significant radiation. These faces can be the majority radiator with the dipole serving mainly as a matching device to the building as majority radiator. It is not inconceivable that the combination could function more like a big dummy load. 73, Guy K2AV On Monday, August 10, 2015, Jim Brown j...@audiosystemsgroup.com wrote: Actually, what he says is not use the high level media to model a RADIAL system. While playing with this model, I changed the characteristics of the higher level media to have far less conductivity. The result suggested that my model was good for what I was trying to understand -- that is, the very low far field lobe was unaffected by the conductivity of the high level media (that is, the roof). 73, Jim K9YC On Mon,8/10/2015 6:48 PM, Guy Olinger K2AV wrote: There is a rather stern W7EL caution in the EZNEC doc about using two ground media. He particularly nixes using the inner media as sea water to mimic a high conductive surface. _ Topband Reflector Archives - http://www.contesting.com/_topband -- Sent via Gmail Mobile on my iPhone _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
I hope Nuradi's rooftop antenna installation doesn't proceed like this: https://www.youtube.com/watch?v=IU7eSAw3IZs 73 Frank W3LPL _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
I'm still laughing !! Ollie did try a safety idea when he tied a rope around his waist in case he fell. Who would have thought the brick chimney would come crashing down ?HIHIHI thanks Frank ! Bob K6UJ On Aug 10, 2015, at 9:31 AM, donov...@starpower.net wrote: I hope Nuradi's rooftop antenna installation doesn't proceed like this: https://www.youtube.com/watch?v=IU7eSAw3IZs 73 Frank W3LPL _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
It might be fun to drive around Culver City for a while and find some of those old buildings. The houses are a lot closer together now, but most of the originals are probably still there. 'JK On Monday, August 10, 2015 9:31 AM, donov...@starpower.net donov...@starpower.net wrote: I hope Nuradi's rooftop antenna installation doesn't proceed like this: https://www.youtube.com/watch?v=IU7eSAw3IZs 73 Frank W3LPL _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Hi Bud, Thanks for comments. I used sea water in the model to correspond to your copper plate example. I also tried other less conductive mediums for the roof as a sanity check. What changes is the strength of the high angle stuff. No surprise that a dipole 5 ft above a conductive surface would be a train wreck both as a radiator and as a match. I just looked at an 80M dipole 20 and 30 ft above that sea water roof. Feedpoint Z about 15 ohms at 20 ft, about 30 ohms at 30 ft. Narudi's shack is on the roof, so a feedline will be short enough that a 3:1 mismatch on 80M should not be an issue with RG8. Obviously, a different conclusion if his shack was on the first floor, with 400 ft of coax running to it. If you change the roof medium to less conductive, feedpoint Z is about 28 ohms for an 80M dipole 20 ft above the roof. I understand the goal of your 5 ft high antenna in the example for a domestic contest. Narudi is in Jakarta, and his objective is CQWW. I still think the major issue will be RX noise. 73, Jim K9YC On Mon,8/10/2015 5:08 AM, W2RU - Bud Hippisley wrote: Jim — I’m not sure you’re “missing” anything from a theoretical standpoint. Some comments from a practical standpoint, however: 1. In my dormitory roof example, our objective was to work W/VE — most of whom were very close to us, hence very high angle. We might well have had a great DXing pattern; I just wasn’t “into” DXing back then. 2. In a two-medium model such as the one you’re describing below, the relatively small inner medium (the roof of Narudi’s building directly beneath the dipole) sets the feedpoint impedance of the dipole, which will be very low because the dipole height above Narudi’s roof is very low when measured as a fraction of a wavelength on 80 meters. This leads to what I call “super-gain” models which can have the far field “boost” you describe but which are extremely difficult to realize in practice, due to the difficulty of matching such low impedance feedpoints without substantial feedline or antenna matching unit losses. For brevity in my initial posting I didn’t mention that the low-Z feedpoint on 80 and 40 made it impossible to properly match our dormitory dipole with just the pi-network output of the 813 rig. 3. You say you used sea water as your inner medium. I’m not sure I’d equate a rooftop with sea water — even “my” rooftop with a solid sheet of copper flashing under the tar and gravel. I think having a dipole really close to a rooftop tends to compress the entire dipole pattern because of losses in that “ground” system directly beneath the dipole. So, overall, I think the _pattern_ you got from your model is probably not too horribly off, but the overall efficiency and gain of a real-world implementation of that antenna system is not the greatest. Bud, W2RU On Aug 10, 2015, at 1:56 48AM, Jim Brown j...@audiosystemsgroup.com wrote: On Sat,8/8/2015 10:36 AM, W2RU - Bud Hippisley wrote: but, with the usual wire sag, the feedpoint was about 5 feet above the gravel. We weren’t worried, because the roof was at least 70 feet above the surrounding terrain. Hmmm! Let's remind ourselves of Nuradi's situation. The roof is 110m high, 45m x 33 m. Corner to corner is less than a wavelength on 80M, more than a wavelength on 40M, but the distance to a corner from a wire strung between the two corners is less than a quarter wave on 80M, less than a half wave on 40. Assuming an ideal conductor on the roof, it's going to act as a reflector going upward, but the low angle pattern will be determined in the far field. I've not worked before with two ground media, so I pulled out W7EL's instructions for doing so. I built a very simple model attempting to roughly simulate Nuradi's situation. I'm running NEC2 with EZNEC Pro5. The first ground medium is sea water, with a radius 120 ft (it's a rectangular building so that's an approximation. The second medium is Very Poor: cities, industrial, and it's at -360 ft. Yes, I'd like to elevate the first medium and have the second medium at 0 ft, but EZNEC won't let me do that. I simulated 40M and 80 dipoles in the range of 20-30 ft. What I got was a two lobe vertical pattern -- a VERY strong, very narrow low angle lobe, and a broad upward lobe whose strength depends on the height of the dipole above the roof. Very low (5 ft) makes the bottom lobe VERY narrow and VERY low (about 2 degrees) and makes the high lobe a lot weaker. Yes, it's a poor antenna -- IF its low to the roof. But if it's up 20-30 ft, a horizontally polarized wire looks like a nice DX antenna. What am I missing? And, like I said before and several others added -- all that stuff on the roof is likely to be mondo noisy. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
On Mon,8/10/2015 5:53 AM, Tom W8JI wrote: A dipole on a real tall building roof is worth a try (because it is so simple and easy), but it is not a simple predictable system. Tom, I agree with this post on all counts. What's actually there can be difficult to predict or even know, so anything that can be installed reasonably easily is worth a try. Yes, an end-fed wire loaded against the building as a counterpoise is certainly worth trying. This one of those situations where you must try the various options to see what works. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Hallo Frank,W3LPL It's very funny 'old' film...hi hi Thanks for remind me...just dreaming how to break the 160m-S9 noise as what has happened so far in my House and office using an 1/2 lambda inv.V with about 100 ft. apex and 33ft. only end WITHOUT receiving antenna . GBUs all... Nuradi, YB0UNC/KU2B -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of donov...@starpower.net Sent: Monday, August 10, 2015 11:32 PM To: topband@contesting.com Subject: Re: Topband: Best wire antenna for roof top location I hope Nuradi's rooftop antenna installation doesn't proceed like this: https://www.youtube.com/watch?v=IU7eSAw3IZs 73 Frank W3LPL _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Actually, what he says is not use the high level media to model a RADIAL system. While playing with this model, I changed the characteristics of the higher level media to have far less conductivity. The result suggested that my model was good for what I was trying to understand -- that is, the very low far field lobe was unaffected by the conductivity of the high level media (that is, the roof). 73, Jim K9YC On Mon,8/10/2015 6:48 PM, Guy Olinger K2AV wrote: There is a rather stern W7EL caution in the EZNEC doc about using two ground media. He particularly nixes using the inner media as sea water to mimic a high conductive surface. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
There is a rather stern W7EL caution in the EZNEC doc about using two ground media. He particularly nixes using the inner media as sea water to mimic a high conductive surface. (EZNEC doc)--- Using Two Ground Media The ground may be broken into two media, each having its own conductivity and dielectric constant (relative permittivity). The second medium can be at a different height, but must be at the same level or below the first medium. The media can be arranged in parallel slices or concentric rings. One use of two media would be to model an antenna on a lake surrounded by land. A very important thing to understand is that the second medium is used only for far field pattern calculations, and is ignored for all other purposes. Be careful when using two media, and keep the following in mind: Even if you place the antenna over the second medium, EZNEC will always use the ground constants and height (z = 0) of the first medium for calculation of the impedances and currents. The second medium is used only for far field calculations. Near Field and Ground Wave calculations assume that the first medium is of infinite extent, and ignores the second medium. The effect of the second medium is taken into account only in a very simplified way. The vertical pattern is generated by tracing rays direct from the antenna and reflected from the ground. When a second medium is used, the ground reflection ray is determined by whichever medium it strikes the top of. The ray does not penetrate either medium, and diffraction or similar effects aren't considered. Because of this, a highly conductive inner medium and normally conductive outer medium is not a good model of a ground radial system, and shouldn't be used for this purpose. Buried wires in EZNEC Pro/4 will always be treated as though they're immersed wholly in the first medium. ---(end EZNEC doc)- The effect of this is to render any use of ground to represent the roof of a building as potentially grossly inaccurate, particularly as applies to building loss. The simplest way to summarize is that NEC x.x cannot model this situation without creating a presumptive model of the building using resistively loaded wires. Can be done, but a real pain in the *ss. Even then the question remains as to WHAT values to assign to anything. This is one place where anecdota from trusted sources and other considerations besides pattern are far more valuable decision tools. Noise and lots of lossy conductors beneath would get me away from the roof for low bands. Personally, in that situation, I would try an FCP on the roof as counterpoise and then pull a wire down and out at a 45 degree angle. End feed the wire at the roof against the FCP. The FCP would couple the roof far less than a single wire, and have far less pickup from from horizontal conductors below. I would make the wire 5/16 wave on 160 which would get the current max on the sloping wire away from the building. Use a trifilar winding on a T400A-2 #2 powdered iron core, and then an autotuner. Given my band use on 160 (low end CW only), I would use a tank circuit tuner tuned at 1.83 MHz. Not having coax running up to the sloping wire, not fed as a doublet, would allow a far less visible installation and a durable pull on the wire. When I was a freshman in college we strung #12 copperweld-like wire *between* two dormitories, and fed an 80m halfwave off center, one of those Heath double bifilar coil baluns hanging off the wire connected to RG59 down to a window on second floor, and used it on 80, 40 and 20. The wire had very secure mount at either end and supported the weight without problem. Was a killer antenna. The dormitories were right at the edge of a ridge line looking out over the Kentucky Blue Grass region. That was a four story building down to the ground, which went 100 feet to the northwest and then quickly dropped 150-200 feet to the Blue Grass plain below. The high view was from southwest to northwest to northeast. Could see 25 miles out to the horizon for 180 degrees. You could see the incoming weather from the northwest hours ahead of time. Will give you that was one wire off a building that depended on location, location, location. 73, Guy K2AV On Mon, Aug 10, 2015 at 2:00 PM, Jim Brown j...@audiosystemsgroup.com wrote: Hi Bud, Thanks for comments. I used sea water in the model to correspond to your copper plate example. I also tried other less conductive mediums for the roof as a sanity check. What changes is the strength of the high angle stuff. No surprise that a dipole 5 ft above a conductive surface would be a train wreck both as a radiator and as a match. I just looked at an 80M dipole 20 and 30 ft above that sea water roof. Feedpoint Z about 15 ohms at 20 ft, about 30 ohms at 30 ft. Narudi's shack is on the roof, so a feedline will be short enough that a 3:1 mismatch on 80M should not be an issue with RG8. Obviously, a different
Re: Topband: Best wire antenna for roof top location
Hmmm! Let's remind ourselves of Nuradi's situation. The roof is 110m high, 45m x 33 m. Corner to corner is less than a wavelength on 80M, more than a wavelength on 40M, but the distance to a corner from a wire strong between the two corners is less than a quarter wave on 80M, less than a half wave on 40. Assuming an ideal conductor on the roof, it's going to act as a reflector going upward, but the low angle pattern will be determined in the far field. A dipole on a real tall building roof is worth a try (because it is so simple and easy), but it is not a simple predictable system. First, any conductor approaching a resonant length in the near field is a real problem for antenna pattern modification. Second, another issue is absorption from everything in the building. Third, there is likely noise. A building is generally a real complicated mess of long conductors that run both horizontally and vertically, and thick lossy dielectrics of all types. A building typically cannot be modeled as a flat sheet the dimensions and height of the building roof. On receiving, a building is typically full of multiple noise sources. There can be buildings that work OK through luck, and they are generally OK on frequencies where the antenna can be a long distance in fractional wavelengths away from the building wiring, but they are almost never anything like a pole or mast support for pattern, and they are rarely good for noise. Usually it is a better idea to get the wire out away from things that might be problems, or at least put a nearfield null in the direction of the problem. I had a friend who managed a high rise apartment building on a hill. We never could get a good 80 horizontal antenna on the roof, but it was killer on 20 meters and up (he had a 20-30 ft tower on the roof). The only thing that seemed to work well on 80 was a wire hung off the side out away from the building. We used the metal flashing as a ground, and end-fed a real Zepp antenna. It was like a J-pole laid on its side. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Jim — I’m not sure you’re “missing” anything from a theoretical standpoint. Some comments from a practical standpoint, however: 1. In my dormitory roof example, our objective was to work W/VE — most of whom were very close to us, hence very high angle. We might well have had a great DXing pattern; I just wasn’t “into” DXing back then. 2. In a two-medium model such as the one you’re describing below, the relatively small inner medium (the roof of Narudi’s building directly beneath the dipole) sets the feedpoint impedance of the dipole, which will be very low because the dipole height above Narudi’s roof is very low when measured as a fraction of a wavelength on 80 meters. This leads to what I call “super-gain” models which can have the far field “boost” you describe but which are extremely difficult to realize in practice, due to the difficulty of matching such low impedance feedpoints without substantial feedline or antenna matching unit losses. For brevity in my initial posting I didn’t mention that the low-Z feedpoint on 80 and 40 made it impossible to properly match our dormitory dipole with just the pi-network output of the 813 rig. 3. You say you used sea water as your inner medium. I’m not sure I’d equate a rooftop with sea water — even “my” rooftop with a solid sheet of copper flashing under the tar and gravel. I think having a dipole really close to a rooftop tends to compress the entire dipole pattern because of losses in that “ground” system directly beneath the dipole. So, overall, I think the _pattern_ you got from your model is probably not too horribly off, but the overall efficiency and gain of a real-world implementation of that antenna system is not the greatest. Bud, W2RU On Aug 10, 2015, at 1:56 48AM, Jim Brown j...@audiosystemsgroup.com wrote: On Sat,8/8/2015 10:36 AM, W2RU - Bud Hippisley wrote: but, with the usual wire sag, the feedpoint was about 5 feet above the gravel. We weren’t worried, because the roof was at least 70 feet above the surrounding terrain. Hmmm! Let's remind ourselves of Nuradi's situation. The roof is 110m high, 45m x 33 m. Corner to corner is less than a wavelength on 80M, more than a wavelength on 40M, but the distance to a corner from a wire strung between the two corners is less than a quarter wave on 80M, less than a half wave on 40. Assuming an ideal conductor on the roof, it's going to act as a reflector going upward, but the low angle pattern will be determined in the far field. I've not worked before with two ground media, so I pulled out W7EL's instructions for doing so. I built a very simple model attempting to roughly simulate Nuradi's situation. I'm running NEC2 with EZNEC Pro5. The first ground medium is sea water, with a radius 120 ft (it's a rectangular building so that's an approximation. The second medium is Very Poor: cities, industrial, and it's at -360 ft. Yes, I'd like to elevate the first medium and have the second medium at 0 ft, but EZNEC won't let me do that. I simulated 40M and 80 dipoles in the range of 20-30 ft. What I got was a two lobe vertical pattern -- a VERY strong, very narrow low angle lobe, and a broad upward lobe whose strength depends on the height of the dipole above the roof. Very low (5 ft) makes the bottom lobe VERY narrow and VERY low (about 2 degrees) and makes the high lobe a lot weaker. Yes, it's a poor antenna -- IF its low to the roof. But if it's up 20-30 ft, a horizontally polarized wire looks like a nice DX antenna. What am I missing? And, like I said before and several others added -- all that stuff on the roof is likely to be mondo noisy. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
On Sat,8/8/2015 10:36 AM, W2RU - Bud Hippisley wrote: but, with the usual wire sag, the feedpoint was about 5 feet above the gravel. We weren’t worried, because the roof was at least 70 feet above the surrounding terrain. Hmmm! Let's remind ourselves of Nuradi's situation. The roof is 110m high, 45m x 33 m. Corner to corner is less than a wavelength on 80M, more than a wavelength on 40M, but the distance to a corner from a wire strong between the two corners is less than a quarter wave on 80M, less than a half wave on 40. Assuming an ideal conductor on the roof, it's going to act as a reflector going upward, but the low angle pattern will be determined in the far field. I've not worked before with two ground media, so I pulled out W7EL's instructions for doing so. I built a very simple model attempting to roughly simulate Nuradi's situation. I'm running NEC2 with EZNEC Pro5. The first ground medium is sea water, with a radius 120 ft (it's a rectangular building so that's an approximation. The second medium is Very Poor: cities, industrial, and it's at -360 ft. Yes, I'd like to elevate the first medium and have the second medium at 0 ft, but EZNEC won't let me do that. I simulated 40M and 80 dipoles in the range of 20-30 ft. What I got was a two lobe vertical pattern -- a VERY strong, very narrow low angle lobe, and a broad upward lobe whose strength depends on the height of the dipole above the roof. Very low (5 ft) makes the bottom lobe VERY narrow and VERY low (about 2 degrees) and makes the high lobe a lot weaker. Yes, it's a poor antenna -- IF its low to the roof. But if it's up 20-30 ft, a horizontally polarized wire looks like a nice DX antenna. What am I missing? And, like I said before and several others added -- all that stuff on the roof is likely to be mondo noisy. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
On Aug 8, 2015, at 10:58 22AM, Tom W8JI w...@w8ji.com wrote: Large buildings are not towers or poles. Buildings have a significant amount of large conductive metallic things and noise generating junk inside. If the building has wiring and large connected metallic things under the horizontal antenna, it will act like a reflector. If the antenna is somewhat low to the roof (less than 1/4 wave or more above the roof), the elevation pattern won't be much different than a low dipole over flat earth. Most of the radiation will be beamed straight up. Even with a 400 ft high building, a horizontal antenna a fraction of wave over the roof can be very disappointing. Many years ago, at the start of my sophomore year in college, a classmate and I decided to operate CW Sweepstakes from my room in a 5-story dormitory. The dormitory footprint was a long, skinny rectangle with brick parapets rising 10 feet above the rooftop at the four corners of the building. We had easy access to the roof, which was flat with a tar and gravel surface, so we strung an 80-meter center-fed dipole diagonally across the roof between two opposing parapets — but, with the usual wire sag, the feedpoint was about 5 feet above the gravel. We weren’t worried, because the roof was at least 70 feet above the surrounding terrain. We had a single-813 transmitter that ran 500 watts input at a time when the legal limit was 1 KW input. It was far more power than I was accustomed to, since my home station transmitter at that time was a Heath DX-40, running about a tenth as much power. I was expecting “great things” in this contest, but it was one of the most disappointing outings I’ve ever participated in — we struggled for every QSO the entire weekend! A few days after the contest we learned from the head of the college maintenance department that underneath all that tar and gravel was a solid sheet of copper! Moral of the story: Believe what Tom tells you — especially his final sentence above! Bud, W2RU _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
Nuradi, how about halfwave sloping dipoles hung digonally from the top of the building? Some 30 years ago at YU1EXY we had contest shack at top of 60m tall building with student's dormitory. In spite the building was in the middle of city noise, sloping dipoles played extremely well. Later we replaced sloping dipoles with sloped yagis for 80m (3 el toward NW (USA) and 2 el toward NE (Japan). With halfwave sloping dipole we managed to QSO KH6 on 160m, very though contact from this part of Europe. Maybe building acted as kind of reflector on this band... 73, Mirko, S57AD 2015-08-08 1:52 GMT+02:00 Nuradi yb0...@gmail.com: Dear all, In preparation of this coming WW big contest, I plan to install wire antenna on a roof top of a 33rd storey building (about 110metres above the ground) for operating on the 160M, 80M and 40M band. The building roof top rectangular size about 45 metres long (from NWtoN-326.8 degress to SEtoS-146.8degrees) and 33 metres wide (fromNEtoE-56.8 degrees to SWtoW-236.8 degrees) located in centre of Jakarta city. The roof top have plenty of cellulair microwave operator antennas (operating in 5GHz and above ALSO one TV operator with around 400MHz working freq.) and there are also two SelfSupportingTower-15metres high, on each end of the long side of the building. There is also one-SST belong to theTV operator which is about 50 metres high, located on the SE end of the roof top. Good grounding terminal is available as it's used for grounding all the communication antennas/equipments. I have my own room in the centre of the roof top where we put all our indoor microwave devices and routers/switch. Prefereable wire antenna is lazy 'laying'H or quad, dipole, slope.. I appreciate verymuch any suggestion, input from all, regarding the best wire antenna for this site to be used in the 160M, 80M and 40M band. Thankyou very much indeed in advance. Regards, Nuradi, YB0UNC / KU2B Cellulair +62811138378 _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Best wire antenna for roof top location
I agree with Mirko...sloping dipoles is the best choice for Nuradi location...THE LOW BAND DXING book is very clear. If SEA WATER is close it is better. 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla - Original Message - From: Mirko S57AD miroslav.sibi...@amis.net To: Nuradi yb0...@gmail.com Cc: topband@contesting.com Sent: Saturday, August 08, 2015 3:03 PM Subject: Re: Topband: Best wire antenna for roof top location Nuradi, how about halfwave sloping dipoles hung digonally from the top of the building? Some 30 years ago at YU1EXY we had contest shack at top of 60m tall building with student's dormitory. In spite the building was in the middle of city noise, sloping dipoles played extremely well. Later we replaced sloping dipoles with sloped yagis for 80m (3 el toward NW (USA) and 2 el toward NE (Japan). With halfwave sloping dipole we managed to QSO KH6 on 160m, very though contact from this part of Europe. Maybe building acted as kind of reflector on this band... 73, Mirko, S57AD 2015-08-08 1:52 GMT+02:00 Nuradi yb0...@gmail.com: Dear all, In preparation of this coming WW big contest, I plan to install wire antenna on a roof top of a 33rd storey building (about 110metres above the ground) for operating on the 160M, 80M and 40M band. The building roof top rectangular size about 45 metres long (from NWtoN-326.8 degress to SEtoS-146.8degrees) and 33 metres wide (fromNEtoE-56.8 degrees to SWtoW-236.8 degrees) located in centre of Jakarta city. The roof top have plenty of cellulair microwave operator antennas (operating in 5GHz and above ALSO one TV operator with around 400MHz working freq.) and there are also two SelfSupportingTower-15metres high, on each end of the long side of the building. There is also one-SST belong to theTV operator which is about 50 metres high, located on the SE end of the roof top. Good grounding terminal is available as it's used for grounding all the communication antennas/equipments. I have my own room in the centre of the roof top where we put all our indoor microwave devices and routers/switch. Prefereable wire antenna is lazy 'laying'H or quad, dipole, slope.. I appreciate verymuch any suggestion, input from all, regarding the best wire antenna for this site to be used in the 160M, 80M and 40M band. Thankyou very much indeed in advance. Regards, Nuradi, YB0UNC / KU2B Cellulair +62811138378 _ 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: Best wire antenna for roof top location
Dear all, In preparation of this coming WW big contest, I plan to install wire antenna on a roof top of a 33rd storey building (about 110metres above the ground) for operating on the 160M, 80M and 40M band. The building roof top rectangular size about 45 metres long (from NWtoN-326.8 degress to SEtoS-146.8degrees) and 33 metres wide (fromNEtoE-56.8 degrees to SWtoW-236.8 degrees) located in centre of Jakarta city. The roof top have plenty of cellulair microwave operator antennas (operating in 5GHz and above ALSO one TV operator with around 400MHz working freq.) and there are also two SelfSupportingTower-15metres high, on each end of the long side of the building. There is also one-SST belong to theTV operator which is about 50 metres high, located on the SE end of the roof top. Good grounding terminal is available as it's used for grounding all the communication antennas/equipments. I have my own room in the centre of the roof top where we put all our indoor microwave devices and routers/switch. Prefereable wire antenna is lazy 'laying'H or quad, dipole, slope.. I appreciate verymuch any suggestion, input from all, regarding the best wire antenna for this site to be used in the 160M, 80M and 40M band. Thankyou very much indeed in advance. Regards, Nuradi, YB0UNC / KU2B Cellulair +62811138378 _ Topband Reflector Archives - http://www.contesting.com/_topband
