Re: Topband: Inverted J antennas?
Awesome. Thank you very much Dave ! Mike, Coreen & Corey Keswick Ridge, NB From: Dave Cuthbert [mailto:telegraph...@gmail.com] Sent: January 11, 2021 5:59 PM To: Mike Smith VE9AA Subject: Re: Topband: Inverted J antennas? Okay, over "medium" GND (0.005S/13) it has the same elevation pattern shape as any vertical. If you wonder about the radiation efficiency, EZNEC using NEC-2 reports loss of 6dB. This is with two 1/4 wavelength radials 5' above GND. I think that once the radials are 10' above GND NEC-2 and NEC-4 will agree. On Mon, Jan 11, 2021 at 11:46 AM Mike Smith VE9AA wrote: Hi Dave and thank you. That was quick. I guess I should’ve been clearer with my question. What does the elevation pattern look like please? Mike, Coreen & Corey Keswick Ridge, NB From: Dave Cuthbert [mailto:telegraph...@gmail.com] Sent: January 11, 2021 5:35 PM To: Mike Smith VE9AA Cc: topband Subject: Re: Topband: Inverted J antennas? Hi Mike, your inverted-J in EZNEC shows a radiation resistance at 1850kHz of 10 ohms. It is resonant at 1800kHz. With the 50' vertical wire removed it is resonant at 2.7MHz and has a radiation resistance at 1850kHz of 11 ohms. Dave KH6AQ On Mon, Jan 11, 2021 at 10:52 AM Mike Smith VE9AA wrote: Has anyone modeled an inverted J on 160m ? (almost an inverted U, really) I currently have only one left (the other half of my 2-el array blew down and I've been lazy to replace it) and it "works" but not as good as it could I think if I had better supports (ie: taller trees, wider yard). I am quite constrained on my property boundaries, so it goes up crookedly and also at a slight angle about 60', over maybe 35'in broad arc and then nearly straight down vertically 40', with the far end maybe only 10' off the ground (just like an inverted J or U). It has 2 full size 1/4wl radials 180* apart raised up about 6' off the ground. The radials are perpendicular to the direction the far end of the vertical is headed..which is to say, the 'vertical' is not directly above any part of the radials. (a little bit like an Aki-special but not nearly as 'good', hi) What concerns me MOST is the far end is mostly vertical on its way down and it being barely off the ground at the far end. I can't do anything now that there's a foot of snow down in the woods with lots of rocks sitting right on top of the ground (too dangerous to walk.especially on a bit of slanted ground,) however if I believed I could do better by keeping the far end up off the ground some more, I might re-route it somehow in the spring. Because of the lack of trees I doubt I could get anything resembling a true inverted L, but I might be able to zig-zag the far end here and there in the tree tops and some branches on its way back to earth a little bit to keep the far end away from the ground some more. Has anyone done any modeling of this type of antenna or even have anecdotal evidence to share? p.s.- at times it works gangbusters..fr'instance I was testing it the other day at 0.9watts (900mW) and it was still daylight here and about 45mins before SS in New England and 2 skimmers (about 340miles/550kms away) picked me up at 2-9dB..maybe that only means it's a cloud warmer? Tnx in advance. CU (all of a sudden) on Top Band. Mike VE9AA , NB Mike, Coreen & Corey Keswick Ridge, NB _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted J antennas?
Hi Dave and thank you. That was quick. I guess I should’ve been clearer with my question. What does the elevation pattern look like please? Mike, Coreen & Corey Keswick Ridge, NB From: Dave Cuthbert [mailto:telegraph...@gmail.com] Sent: January 11, 2021 5:35 PM To: Mike Smith VE9AA Cc: topband Subject: Re: Topband: Inverted J antennas? Hi Mike, your inverted-J in EZNEC shows a radiation resistance at 1850kHz of 10 ohms. It is resonant at 1800kHz. With the 50' vertical wire removed it is resonant at 2.7MHz and has a radiation resistance at 1850kHz of 11 ohms. Dave KH6AQ On Mon, Jan 11, 2021 at 10:52 AM Mike Smith VE9AA wrote: Has anyone modeled an inverted J on 160m ? (almost an inverted U, really) I currently have only one left (the other half of my 2-el array blew down and I've been lazy to replace it) and it "works" but not as good as it could I think if I had better supports (ie: taller trees, wider yard). I am quite constrained on my property boundaries, so it goes up crookedly and also at a slight angle about 60', over maybe 35'in broad arc and then nearly straight down vertically 40', with the far end maybe only 10' off the ground (just like an inverted J or U). It has 2 full size 1/4wl radials 180* apart raised up about 6' off the ground. The radials are perpendicular to the direction the far end of the vertical is headed..which is to say, the 'vertical' is not directly above any part of the radials. (a little bit like an Aki-special but not nearly as 'good', hi) What concerns me MOST is the far end is mostly vertical on its way down and it being barely off the ground at the far end. I can't do anything now that there's a foot of snow down in the woods with lots of rocks sitting right on top of the ground (too dangerous to walk.especially on a bit of slanted ground,) however if I believed I could do better by keeping the far end up off the ground some more, I might re-route it somehow in the spring. Because of the lack of trees I doubt I could get anything resembling a true inverted L, but I might be able to zig-zag the far end here and there in the tree tops and some branches on its way back to earth a little bit to keep the far end away from the ground some more. Has anyone done any modeling of this type of antenna or even have anecdotal evidence to share? p.s.- at times it works gangbusters..fr'instance I was testing it the other day at 0.9watts (900mW) and it was still daylight here and about 45mins before SS in New England and 2 skimmers (about 340miles/550kms away) picked me up at 2-9dB..maybe that only means it's a cloud warmer? Tnx in advance. CU (all of a sudden) on Top Band. Mike VE9AA , NB Mike, Coreen & Corey Keswick Ridge, NB _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted J antennas?
Hi Mike, your inverted-J in EZNEC shows a radiation resistance at 1850kHz of 10 ohms. It is resonant at 1800kHz. With the 50' vertical wire removed it is resonant at 2.7MHz and has a radiation resistance at 1850kHz of 11 ohms. Dave KH6AQ On Mon, Jan 11, 2021 at 10:52 AM Mike Smith VE9AA wrote: > Has anyone modeled an inverted J on 160m ? (almost an inverted U, really) > > > > I currently have only one left (the other half of my 2-el array blew down > and I've been lazy to replace it) and it "works" but not as good as it > could > I think if I had better supports (ie: taller trees, wider yard). I am > quite > constrained on my property boundaries, so it goes up crookedly and also at > a > slight angle about 60', over maybe 35'in broad arc and then nearly straight > down vertically 40', with the far end maybe only 10' off the ground (just > like an inverted J or U). > > It has 2 full size 1/4wl radials 180* apart raised up about 6' off the > ground. The radials are perpendicular to the direction the far end of the > vertical is headed..which is to say, the 'vertical' is not directly above > any part of the radials. > > (a little bit like an Aki-special but not nearly as 'good', hi) > > > > What concerns me MOST is the far end is mostly vertical on its way down and > it being barely off the ground at the far end. > > > > I can't do anything now that there's a foot of snow down in the woods > with > lots of rocks sitting right on top of the ground (too dangerous to > walk.especially on a bit of slanted ground,) however if I believed I could > do better by keeping the far end up off the ground some more, I might > re-route it somehow in the spring. Because of the lack of trees I doubt I > could get anything resembling a true inverted L, but I might be able to > zig-zag the far end here and there in the tree tops and some branches on > its > way back to earth a little bit to keep the far end away from the ground > some > more. > > > > Has anyone done any modeling of this type of antenna or even have anecdotal > evidence to share? > > > > p.s.- at times it works gangbusters..fr'instance I was testing it the other > day at 0.9watts (900mW) and it was still daylight here and about 45mins > before SS in New England and 2 skimmers (about 340miles/550kms away) picked > me up at 2-9dB..maybe that only means it's a cloud warmer? > > > > Tnx in advance. > > > > CU (all of a sudden) on Top Band. > > > > Mike VE9AA , NB > > > > > > Mike, Coreen & Corey > > Keswick Ridge, NB > > > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Inverted J antennas?
Has anyone modeled an inverted J on 160m ? (almost an inverted U, really) I currently have only one left (the other half of my 2-el array blew down and I've been lazy to replace it) and it "works" but not as good as it could I think if I had better supports (ie: taller trees, wider yard). I am quite constrained on my property boundaries, so it goes up crookedly and also at a slight angle about 60', over maybe 35'in broad arc and then nearly straight down vertically 40', with the far end maybe only 10' off the ground (just like an inverted J or U). It has 2 full size 1/4wl radials 180* apart raised up about 6' off the ground. The radials are perpendicular to the direction the far end of the vertical is headed..which is to say, the 'vertical' is not directly above any part of the radials. (a little bit like an Aki-special but not nearly as 'good', hi) What concerns me MOST is the far end is mostly vertical on its way down and it being barely off the ground at the far end. I can't do anything now that there's a foot of snow down in the woods with lots of rocks sitting right on top of the ground (too dangerous to walk.especially on a bit of slanted ground,) however if I believed I could do better by keeping the far end up off the ground some more, I might re-route it somehow in the spring. Because of the lack of trees I doubt I could get anything resembling a true inverted L, but I might be able to zig-zag the far end here and there in the tree tops and some branches on its way back to earth a little bit to keep the far end away from the ground some more. Has anyone done any modeling of this type of antenna or even have anecdotal evidence to share? p.s.- at times it works gangbusters..fr'instance I was testing it the other day at 0.9watts (900mW) and it was still daylight here and about 45mins before SS in New England and 2 skimmers (about 340miles/550kms away) picked me up at 2-9dB..maybe that only means it's a cloud warmer? Tnx in advance. CU (all of a sudden) on Top Band. Mike VE9AA , NB Mike, Coreen & Corey Keswick Ridge, NB _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
