Re: Topband: Accuracy of modeling of 160m verticals
Hi Roger I used a dipole for several years too. Actually took me 20 years to work my first DXCC on 160m from SPaulo Brazil using them.. Here is the thing, your horizontal dipole is not 100% horizontal polarized. It is only 50% horizontal and 50% vertical. You can see it on EZENEC selecting 3 D and NO TOTAL FIELD, just red for vertical and green for horizontal field. Even a perfect straight line dipole, without the feed line, is 50 % vertical and 50% horizontal, Vertical along the wire like a Beverage antenna, and broadside horizontal. If the ends are close to the ground like an inverted V the, the vertical polarization take off angle will be lower than the horizontal one. However you have a feed line and without an excellent BALUN, very hard to find one for 160m, your feed line is a vertical antenna by itself, and the vertical polarized wave on your dipole will have a lower take off angle is all directions. Any vertical antenna is 100 % vertical, but all horizontal antennas close to the ground are not 100% horizontal. On 160m all antennas are very close to the ground. If you have a tower or any other vertical structure near your dipole, guess what , it will be feed by the dipole and irradiate vertical as well. Always use both polarization on EZNEC to understand what the antenna is doing. 73's JC N4IS -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Roger Kennedy Sent: Thursday, November 08, 2018 4:51 AM To: topband@contesting.com Subject: Topband: Accuracy of modeling of 160m verticals Exactly! How can you know what your ground is REALLY like, especially when you go underground? (and even if you knew, how could you model it?) I'm really not interested in trying to get an accurate model. It's just that I have ALWAYS used a horizontal Dipole at just 50ft for working DX on Top Band. Yet I've always done pretty well - most people on here tell me my signal is comparable with most of the other EU signals, who all use decent verticals. Now I'm pretty sure that most 160m DX propagation ISN'T as low angle as most people think (like it usually is on 80m) . . . but equally I believe that my Dipoles simply CAN'T be the "cloud warmers" that the theoretical plots from EZNEC etc predict! About 20 Years ago I actually did a load tests on SSB with a good friend of mine who had a full sized vertical and 50 radials (this was over a period of months) . . . we made sure we were running the same power, and each night we did this, we got critical comparison reports from dozens of stations right across North America . . over 80% said we were the same strength! Roger G3YRO -Original Message- From: Richard (Rick) Karlquist [mailto:rich...@karlquist.com] Sent: 08 November 2018 00:00 To: Roger Kennedy; topband@contesting.com Subject: Re: Topband: Accuracy of modeling of 160m verticals If you really want to get accurate ground modeling, you need to follow N6LF's procedure. He installs low dipoles at various heights over his ground and measures their impedance and resonant frequency. He then models them on NEC4 and tweaks the ground parameters to get the model to agree with the measured data. This is repeated on each band of interest. The other problem is that the ground may not be homogeneous, in either the horizontal direction or the vertical direction. Not to mention seasonal moisture effects. If you can manage a low dipole, there is a good chance you reconfigure it as a T-top loaded vertical with a few elevated radials. That is likely lead to a worthwhile improvement in performance over any kind of ground. 73 Rick N6RK On 11/7/2018 3:19 PM, Roger Kennedy wrote: > > Actually, I'm rather sceptical about the accuracy of theoretical > antenna modelling software generally on 160m. (as per my recent > discussion on a well-known Forum) > > I'm not convinced that the various programs (which all seem to give > different projections) properly take into account the different kind > of REAL ground under the antenna . . . particularly with a low Dipole > like I use - which is equivalent to a 20m Dipole just 3ft off the > ground ! (and therefore the ground has a HUGE effect on the antenna) > > Roger G3YRO > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Accuracy of modeling of 160m verticals
Exactly! How can you know what your ground is REALLY like, especially when you go underground? (and even if you knew, how could you model it?) I'm really not interested in trying to get an accurate model. It's just that I have ALWAYS used a horizontal Dipole at just 50ft for working DX on Top Band. Yet I've always done pretty well - most people on here tell me my signal is comparable with most of the other EU signals, who all use decent verticals. Now I'm pretty sure that most 160m DX propagation ISN'T as low angle as most people think (like it usually is on 80m) . . . but equally I believe that my Dipoles simply CAN'T be the "cloud warmers" that the theoretical plots from EZNEC etc predict! About 20 Years ago I actually did a load tests on SSB with a good friend of mine who had a full sized vertical and 50 radials (this was over a period of months) . . . we made sure we were running the same power, and each night we did this, we got critical comparison reports from dozens of stations right across North America . . over 80% said we were the same strength! Roger G3YRO -Original Message- From: Richard (Rick) Karlquist [mailto:rich...@karlquist.com] Sent: 08 November 2018 00:00 To: Roger Kennedy; topband@contesting.com Subject: Re: Topband: Accuracy of modeling of 160m verticals If you really want to get accurate ground modeling, you need to follow N6LF's procedure. He installs low dipoles at various heights over his ground and measures their impedance and resonant frequency. He then models them on NEC4 and tweaks the ground parameters to get the model to agree with the measured data. This is repeated on each band of interest. The other problem is that the ground may not be homogeneous, in either the horizontal direction or the vertical direction. Not to mention seasonal moisture effects. If you can manage a low dipole, there is a good chance you reconfigure it as a T-top loaded vertical with a few elevated radials. That is likely lead to a worthwhile improvement in performance over any kind of ground. 73 Rick N6RK On 11/7/2018 3:19 PM, Roger Kennedy wrote: > > Actually, I'm rather sceptical about the accuracy of theoretical > antenna modelling software generally on 160m. (as per my recent > discussion on a well-known Forum) > > I'm not convinced that the various programs (which all seem to give > different projections) properly take into account the different kind > of REAL ground under the antenna . . . particularly with a low Dipole > like I use - which is equivalent to a 20m Dipole just 3ft off the > ground ! (and therefore the ground has a HUGE effect on the antenna) > > Roger G3YRO > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Accuracy of modeling of 160m verticals
Actually, I'm rather sceptical about the accuracy of theoretical antenna modelling software generally on 160m. (as per my recent discussion on a well-known Forum) I'm not convinced that the various programs (which all seem to give different projections) properly take into account the different kind of REAL ground under the antenna . . . particularly with a low Dipole like I use - which is equivalent to a 20m Dipole just 3ft off the ground ! (and therefore the ground has a HUGE effect on the antenna) Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Accuracy of modeling of 160m verticals
So true, my AM broadcast station location with 120 330ft radials does not hold a candle to the same InvL antenna at the beach with two radials. I am about a mile inland from the beach. Too far for any help. 73 Merv K9FD Molokai Island Hawaii Hi Ignacy, Salt water is very special! In a salt water environment potentially the entire Fresnel zone -- where as much a 6 dB of gain is obtained from ground reflection -- is in a highly conductive environment. Low angle radiation from a vertical with a salt water Fresnel Zone is much better than from an inland vertical. In a inland location only a very small fraction of the Fresnel Zone is covered by conductive radials. 73 Frank W3LPL - Original Message - From: "Ignacy Misztal" To: topband@contesting.com Sent: Tuesday, November 6, 2018 8:45:28 PM Subject: Topband: Accuracy of modeling of 160m verticals A number of articles analyzed 160m verticals by simulation. Once the height was lambda/8 and the number of radials >= 16 (buried) or >=4 (elevated), the difference in gain was at most a few db. I operated the 2017 Stew contest from a northern beach of St George Island, FL. The antenna was inv L about 55 ft vertical and 90 ft horizontal,. with one 70ft radial elevated 5 ft. The performance was astounding. EU was heard one hr before the sunset, in bright sun..During the contest, EU were only slightly weaker than the US. A special point was easily working a DL with 100W while a well known contester using high power 100 miles inland could not work it. So it seemed that the salt-water enhancement was like 15 db, not a few. I wonder whether simulations are inaccurate with respect to radials/soil type or is salt water special? Ignacy, NO9E _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Accuracy of modeling of 160m verticals
Hi Ignacy, Salt water is very special! In a salt water environment potentially the entire Fresnel zone -- where as much a 6 dB of gain is obtained from ground reflection -- is in a highly conductive environment. Low angle radiation from a vertical with a salt water Fresnel Zone is much better than from an inland vertical. In a inland location only a very small fraction of the Fresnel Zone is covered by conductive radials. 73 Frank W3LPL - Original Message - From: "Ignacy Misztal" To: topband@contesting.com Sent: Tuesday, November 6, 2018 8:45:28 PM Subject: Topband: Accuracy of modeling of 160m verticals A number of articles analyzed 160m verticals by simulation. Once the height was lambda/8 and the number of radials >= 16 (buried) or >=4 (elevated), the difference in gain was at most a few db. I operated the 2017 Stew contest from a northern beach of St George Island, FL. The antenna was inv L about 55 ft vertical and 90 ft horizontal,. with one 70ft radial elevated 5 ft. The performance was astounding. EU was heard one hr before the sunset, in bright sun..During the contest, EU were only slightly weaker than the US. A special point was easily working a DL with 100W while a well known contester using high power 100 miles inland could not work it. So it seemed that the salt-water enhancement was like 15 db, not a few. I wonder whether simulations are inaccurate with respect to radials/soil type or is salt water special? Ignacy, NO9E _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Accuracy of modeling of 160m verticals
A number of articles analyzed 160m verticals by simulation. Once the height was lambda/8 and the number of radials >= 16 (buried) or >=4 (elevated), the difference in gain was at most a few db. I operated the 2017 Stew contest from a northern beach of St George Island, FL. The antenna was inv L about 55 ft vertical and 90 ft horizontal,. with one 70ft radial elevated 5 ft. The performance was astounding. EU was heard one hr before the sunset, in bright sun..During the contest, EU were only slightly weaker than the US. A special point was easily working a DL with 100W while a well known contester using high power 100 miles inland could not work it. So it seemed that the salt-water enhancement was like 15 db, not a few. I wonder whether simulations are inaccurate with respect to radials/soil type or is salt water special? Ignacy, NO9E _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
