Topband: WG: AW: Low Dipoles
I used a dipole at 103ft and an elevated GP (top loaded tower) fed at 70ft with full size resonance and two elevated straight radials for the last couple of years. Foreground is sloping towards North America and Japan. Most of the time the vertical is the better antenna beyond 3000km and almost identical in signal strength with the dipole to the northern east coast stations. It never happened that a DX station was stronger on the dipole then on the vertical on receive. Even within Europe and with path length extending 800km and with a vertical at the other station sometimes the vertical is the better antenna. 73 Peter -Original-Nachricht- Betreff: Re: Topband: Low Dipoles Datum: 2020-12-17T23:49:41+0100 Von: "Jim Brown" An: "topband@contesting.com" On 12/17/2020 1:27 PM, Roger Kennedy wrote: > > I do take offence at people suggesting that I am somehow lying about the > results I have always had with a 160m Dipole at 50ft ! I don't see where anyone is saying you're lying, Roger. In terms of people doing their own DIRECT comparisons against a Vertical at > the same QTH, I believe the problem is that the Dipole is usually above (or > near) a decent Radial system. That will have the effect of lowering the > Antenna, and therefore making it only fire at very high angles. A radial system would be only a small part of the story for a horizontal wire, potentially reducing loss in the soil under the antenna; the major contribution of height is formation of the pattern from the reflection in the far field. > > A Dipole that is above poor ground, and without any wires underneath it, I > believe will "think" it's much higher The property that aligns with that thinking is the Skin Depth at the frequency of interest. W8JI has noted that can be in the range of 60 ft (don't recall the specific numbers he cited -- it's a long time since I read it). I haven't studied the relationship between soil conductivity and skin depth. , and probably therefore be more > efficient at lower radiation angles. The strength of the first reflection increases with increased soil conductivity. The shape of the resulting vertical pattern depends on both the strength of that reflection and the electrical height of the antenna, taking skin depth into account. Lousy soil where that reflection is formed would weaken its strength. I'd be interested to hear Frank's thoughts on this from an analytical point of view. But the bottom line for situations such as yours (and mine when I lived in Chicago) is that any antenna is better than no antenna, but the reason we study how antennas work is to make the most of our situation, which includes, but is not limited to, real estate, our surroundings, available or possible skyhooks, local noise, and our resources (money, friends to help, physical and mental abilities). 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Low Dipoles
On 12/17/2020 1:27 PM, Roger Kennedy wrote: I do take offence at people suggesting that I am somehow lying about the results I have always had with a 160m Dipole at 50ft ! I don't see where anyone is saying you're lying, Roger. In terms of people doing their own DIRECT comparisons against a Vertical at the same QTH, I believe the problem is that the Dipole is usually above (or near) a decent Radial system. That will have the effect of lowering the Antenna, and therefore making it only fire at very high angles. A radial system would be only a small part of the story for a horizontal wire, potentially reducing loss in the soil under the antenna; the major contribution of height is formation of the pattern from the reflection in the far field. A Dipole that is above poor ground, and without any wires underneath it, I believe will "think" it's much higher The property that aligns with that thinking is the Skin Depth at the frequency of interest. W8JI has noted that can be in the range of 60 ft (don't recall the specific numbers he cited -- it's a long time since I read it). I haven't studied the relationship between soil conductivity and skin depth. , and probably therefore be more efficient at lower radiation angles. The strength of the first reflection increases with increased soil conductivity. The shape of the resulting vertical pattern depends on both the strength of that reflection and the electrical height of the antenna, taking skin depth into account. Lousy soil where that reflection is formed would weaken its strength. I'd be interested to hear Frank's thoughts on this from an analytical point of view. But the bottom line for situations such as yours (and mine when I lived in Chicago) is that any antenna is better than no antenna, but the reason we study how antennas work is to make the most of our situation, which includes, but is not limited to, real estate, our surroundings, available or possible skyhooks, local noise, and our resources (money, friends to help, physical and mental abilities). 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Low Dipoles
I do take offence at people suggesting that I am somehow lying about the results I have always had with a 160m Dipole at 50ft ! Several people on this Forum have already stated how my current Signal on 160m compares favourably with other regular British DXers, all of whom use decent Vertical Antennas. If you don't believe them, then you can compare my signal reports on NA RBN sites with all the other Gs on the band at the same time. (I have set up my RBN to do that automatically) Again, you will see that, on average, there is very little difference between mine and theirs. (sometimes I am a little stronger, sometimes they are) Equally the good results I have always had working DX stations in Contests, or getting through Pileups to DX-peditions speak for themselves. And there's nothing special about my current QTH or Antenna. I have been working all over the world on Top Band since 1969, and ALWAYS with either a Horizontal Half Wave Dipole or an End Fed Half Wave, at around 50ft. In terms of people doing their own DIRECT comparisons against a Vertical at the same QTH, I believe the problem is that the Dipole is usually above (or near) a decent Radial system. That will have the effect of lowering the Antenna, and therefore making it only fire at very high angles. A Dipole that is above poor ground, and without any wires underneath it, I believe will "think" it's much higher, and probably therefore be more efficient at lower radiation angles. Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Low Dipoles
On 12/17/2020 12:28 PM, Mike Smith VE9AA wrote: I've had low (30-40' up) 160m dipoles in essentially 3 QTH's.and always had inverted L's to do A/B realtime comparisons. I'd define a dipole as "low" if it were less than 1/4 wavelength; I had one at 120 ft, less than a quarter wave. The virtue of having it lower than that, of course, is that it further suppresses low angle, potentially reducing local noise. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Low Dipoles
I've had low (30-40' up) 160m dipoles in essentially 3 QTH's.and always had inverted L's to do A/B realtime comparisons. .Here up on a good sized hill (660'ASL), rocky excuse for soil. (14+ yrs) .At previous QTH, 30' ASL, wet swampy soil in most directions. (12+ yrs) .At CY9AA, surrounded by salt water in 360* (< 2 weeks of operation) In ~30 years of Topbanding, only *once*, at the swampy QTH did the low dipole outperform my inverted L's on transmit. There was one greyline opening to 9M6 that he was 539 or something on the low dipole and inaudible on the inverted L. Even on St. Paul's (N.) island-CY9AA (1997) completely surrounded by salt water mere feet away from the antenna, it sucked really bad on 160m and the balloon vertical kicked its butt 100% of the time. At this ridgetop QTH where I've been extremely active the past 16+ yrs contesting and DXing at no time did I see various 'low' dipoles ever outperform inverted L's on 160m transmit. (every once in a blue because of an arcing transformer or someone welding in the local area, the dipole might be quieter on RX, but it's exceedingly rare) I tend to view peoples claims about low dipoles with a huge grain of salt.especially when they have no antenna to compare it to. YMMV CU (all of a sudden) (in the RAC Winter? in the Stew?) Mike VE9Antenna Antenna Mike, Coreen & Corey Keswick Ridge, NB _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: History
Hi I have posted a bit of my story on the site. Maybe some of our American friends will be interested in: My first USA pile up on TOPBAND (27.01.1997 ). 11 QSOs = 100 % QSLs http://www.topband.in.ua/members/uy0zg/ I had then : Антенна Delta-Loop W2EGH, PA-200 w . QTH - The central part of the city of Nikolaev Nick, UY0ZG http://www.topband.in.ua _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Wednesday CW DX Activity Night
Conditions were great into Arizona for me,, Worked 24 EU with 20 being ATNO !!! Thanks to all who called me!! Happy Holidays Tom N7GP ex WA8WZG On 2020-12-17 12:34, Roger Kennedy wrote: Great to hear so many CW stations on the band last night . . . and conditions were good too ! I came on for about an hour from 0100Z, and worked stations in Arkansas, Colorado, Arizona, Montana, New Mexico, Oregon, Saskatchewan and Alberta, so pretty pleased with that. Here's to next Wednesday ! 73 Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Wednesday CW DX Activity Night
Great to hear so many CW stations on the band last night . . . and conditions were good too ! I came on for about an hour from 0100Z, and worked stations in Arkansas, Colorado, Arizona, Montana, New Mexico, Oregon, Saskatchewan and Alberta, so pretty pleased with that. Here's to next Wednesday ! 73 Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
