Re: Topband: Inverted L improvements - Part 3
> I think theoretical is 32 ohms or so, Theoretical impedance for a full height 1/4 wave vertical is 32 Ohms. An inverted L (also "T" or other top loaded antenna) will be less depending on the height of the vertical section and how much the horizontal section slopes downward. 73, ... Joe, W4TV On 2019-01-16 8:00 PM, Jamie WW3S wrote: I read recently, maybe on this forum, that 32 ft radials were "long enough" if thats all you could get.I thought they needed to be longer as well, mine for my inv L are 132 ft long, but "bent" to keep them in my lot size.when we were talking about the feedpoint impedance of my L, thats when someone suggested that more radials 32 ft long, would be better than fewer radials that were longer Mike, get rid of the 15' cable, try to measure the impedance with as short a piece of coax as possible, as close to the feedpoint as possible.thats what got me recently...ideal impedance will be mid to upper 30 ohmsI think theoretical is 32 ohms or so, add a few ohms for the ground.the more radials you add, the lower it will get - Original Message - From: "Mike Smith VE9AA" To: topband@contesting.com Sent: Wednesday, January 16, 2019 7:32:09 PM Subject: Re: Topband: Inverted L improvements - Part 3 Hi Todd and thanks for answering so quickly. I am no expert. (I'm an Electronics Engineering Technologist and a ham for 40+ yrs,fwiw) I won't debate the exact numbers on that table by K3LC referenced by K9YC, (they are experts) but I will tell you that it makes me go "hmmm" (as in a mild doubting tone) A 42' radial on 160m is only something like 1/12th of a wavelength long. (pretty short) AM Broadcasters talk about the point of diminishing returns for on-ground radials being around 120 (or is it 240?) for full sized 1/4wl radials. That would be the equivalent of ~15,240feet on 160m. You've laid out aprox 1260feet of wire (give or take).so aprox 1/12th or .08% of optimum. It's just not a lot of wire for a 160m antenna. I have 2x 160m antennas here. One with about 7500' of wire on/in the ground and another with 2 raised radials (tuned, raised, 1/4wl each) and I can tell you the one with 7500' of wire under it always works better in true A/B comparisons. Not by a lot, but it's noticeable. I can't imagine you're anywhere' s near optimum. I know "tone" doesn't come across in emails and postings, so I am not saying this all in a sarcastic or snarky tone. Just as a "matter of fact" type tone. With what you've described, it's probably as good as you'll get if you have a typical small city lot and average soil. You could play around with chicken wire, tying your pool and well casing, fence, metal garden shed and neighbours dog-run ,in to give you just as much conductive material under the antenna as humanly possible or you can accept the limitations of a small lot. Personally, I don't give up easy..if it were me, I'd buy another couple thousand feet of wire and put it down. Something is just not right. I'll let the *REAL* experts chime in, but my experience (such as it is), tells me you're warming the ground or there's something else going on we aren't yet aware of. (ginormous metal bldg. next door, hi). GL with it Todd. I hope there is an epiphany~! truly. Mike VE9AA Hi Mike, Yes, it is a space issue. The presentation I was referring to is http://audiosystemsgroup.com/160MPacificon.pdf where it has a table the references a paper by K3LC that has "Optimum Use of Wire On/In Ground Over Average Soil" and it lists 12 radials at 42' each to essentially use a 500' spool of wire. I had more wire than that but not much more room. I could run out a few wires in few directions to about 100' if that might help. I did use the antenna for a couple of evenings with only 12 radials and yesterday I tacked on the additional 18. That is why that decision was made. I didn't think that SWR curve was good at all. But another guy just emailed me and said that the BCB filter is probably messing up those readings and they aren't accurate. I can take SWR readings from my radio (in the shack) with the filter not in line. Maybe that will show different values but it will be attached to a 150' long piece of coax after the choke. 73, Todd - NR7RR Mike, Coreen & Corey Keswick Ridge, NB _ 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: Inverted L improvements - Part 3
I read recently, maybe on this forum, that 32 ft radials were "long enough" if thats all you could get.I thought they needed to be longer as well, mine for my inv L are 132 ft long, but "bent" to keep them in my lot size.when we were talking about the feedpoint impedance of my L, thats when someone suggested that more radials 32 ft long, would be better than fewer radials that were longer Mike, get rid of the 15' cable, try to measure the impedance with as short a piece of coax as possible, as close to the feedpoint as possible.thats what got me recently...ideal impedance will be mid to upper 30 ohmsI think theoretical is 32 ohms or so, add a few ohms for the ground.the more radials you add, the lower it will get - Original Message - From: "Mike Smith VE9AA" To: topband@contesting.com Sent: Wednesday, January 16, 2019 7:32:09 PM Subject: Re: Topband: Inverted L improvements - Part 3 Hi Todd and thanks for answering so quickly. I am no expert. (I'm an Electronics Engineering Technologist and a ham for 40+ yrs,fwiw) I won't debate the exact numbers on that table by K3LC referenced by K9YC, (they are experts) but I will tell you that it makes me go "hmmm" (as in a mild doubting tone) A 42' radial on 160m is only something like 1/12th of a wavelength long. (pretty short) AM Broadcasters talk about the point of diminishing returns for on-ground radials being around 120 (or is it 240?) for full sized 1/4wl radials. That would be the equivalent of ~15,240feet on 160m. You've laid out aprox 1260feet of wire (give or take).so aprox 1/12th or .08% of optimum. It's just not a lot of wire for a 160m antenna. I have 2x 160m antennas here. One with about 7500' of wire on/in the ground and another with 2 raised radials (tuned, raised, 1/4wl each) and I can tell you the one with 7500' of wire under it always works better in true A/B comparisons. Not by a lot, but it's noticeable. I can't imagine you're anywhere' s near optimum. I know "tone" doesn't come across in emails and postings, so I am not saying this all in a sarcastic or snarky tone. Just as a "matter of fact" type tone. With what you've described, it's probably as good as you'll get if you have a typical small city lot and average soil. You could play around with chicken wire, tying your pool and well casing, fence, metal garden shed and neighbours dog-run ,in to give you just as much conductive material under the antenna as humanly possible or you can accept the limitations of a small lot. Personally, I don't give up easy..if it were me, I'd buy another couple thousand feet of wire and put it down. Something is just not right. I'll let the *REAL* experts chime in, but my experience (such as it is), tells me you're warming the ground or there's something else going on we aren't yet aware of. (ginormous metal bldg. next door, hi). GL with it Todd. I hope there is an epiphany~! truly. Mike VE9AA Hi Mike, Yes, it is a space issue. The presentation I was referring to is http://audiosystemsgroup.com/160MPacificon.pdf where it has a table the references a paper by K3LC that has "Optimum Use of Wire On/In Ground Over Average Soil" and it lists 12 radials at 42' each to essentially use a 500' spool of wire. I had more wire than that but not much more room. I could run out a few wires in few directions to about 100' if that might help. I did use the antenna for a couple of evenings with only 12 radials and yesterday I tacked on the additional 18. That is why that decision was made. I didn't think that SWR curve was good at all. But another guy just emailed me and said that the BCB filter is probably messing up those readings and they aren't accurate. I can take SWR readings from my radio (in the shack) with the filter not in line. Maybe that will show different values but it will be attached to a 150' long piece of coax after the choke. 73, Todd - NR7RR 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 L improvements - Part 3
Hi Todd and thanks for answering so quickly. I am no expert. (I'm an Electronics Engineering Technologist and a ham for 40+ yrs,fwiw) I won't debate the exact numbers on that table by K3LC referenced by K9YC, (they are experts) but I will tell you that it makes me go "hmmm" (as in a mild doubting tone) A 42' radial on 160m is only something like 1/12th of a wavelength long. (pretty short) AM Broadcasters talk about the point of diminishing returns for on-ground radials being around 120 (or is it 240?) for full sized 1/4wl radials. That would be the equivalent of ~15,240feet on 160m. You've laid out aprox 1260feet of wire (give or take).so aprox 1/12th or .08% of optimum. It's just not a lot of wire for a 160m antenna. I have 2x 160m antennas here. One with about 7500' of wire on/in the ground and another with 2 raised radials (tuned, raised, 1/4wl each) and I can tell you the one with 7500' of wire under it always works better in true A/B comparisons. Not by a lot, but it's noticeable. I can't imagine you're anywhere' s near optimum. I know "tone" doesn't come across in emails and postings, so I am not saying this all in a sarcastic or snarky tone. Just as a "matter of fact" type tone. With what you've described, it's probably as good as you'll get if you have a typical small city lot and average soil. You could play around with chicken wire, tying your pool and well casing, fence, metal garden shed and neighbours dog-run ,in to give you just as much conductive material under the antenna as humanly possible or you can accept the limitations of a small lot. Personally, I don't give up easy..if it were me, I'd buy another couple thousand feet of wire and put it down. Something is just not right. I'll let the *REAL* experts chime in, but my experience (such as it is), tells me you're warming the ground or there's something else going on we aren't yet aware of. (ginormous metal bldg. next door, hi). GL with it Todd. I hope there is an epiphany~! truly. Mike VE9AA Hi Mike, Yes, it is a space issue. The presentation I was referring to is http://audiosystemsgroup.com/160MPacificon.pdf where it has a table the references a paper by K3LC that has "Optimum Use of Wire On/In Ground Over Average Soil" and it lists 12 radials at 42' each to essentially use a 500' spool of wire. I had more wire than that but not much more room. I could run out a few wires in few directions to about 100' if that might help. I did use the antenna for a couple of evenings with only 12 radials and yesterday I tacked on the additional 18. That is why that decision was made. I didn't think that SWR curve was good at all. But another guy just emailed me and said that the BCB filter is probably messing up those readings and they aren't accurate. I can take SWR readings from my radio (in the shack) with the filter not in line. Maybe that will show different values but it will be attached to a 150' long piece of coax after the choke. 73, Todd - NR7RR Mike, Coreen & Corey Keswick Ridge, NB _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L improvements - Part 3
Hi Mike, Yes, it is a space issue. The presentation I was referring to is http://audiosystemsgroup.com/160MPacificon.pdf where it has a table the references a paper by K3LC that has "Optimum Use of Wire On/In Ground Over Average Soil" and it lists 12 radials at 42' each to essentially use a 500' spool of wire. I had more wire than that but not much more room. I could run out a few wires in few directions to about 100' if that might help. I did use the antenna for a couple of evenings with only 12 radials and yesterday I tacked on the additional 18. That is why that decision was made. I didn't think that SWR curve was good at all. But another guy just emailed me and said that the BCB filter is probably messing up those readings and they aren't accurate. I can take SWR readings from my radio (in the shack) with the filter not in line. Maybe that will show different values but it will be attached to a 150' long piece of coax after the choke. 73, Todd - NR7RR _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L improvements - Part 3
".have attached 30 insulated wire radials each 42' in length (as suggested in a K9YC presentation referencing a K3LC study in the NCJ) laying on the ground roughly evenly distributed. The paper said that 12 radials would be "adequate" but I had room and materials for 30 so that's what I laid out.." ".I measured the SWR curve and it starts at 2.0 @ 1800 and bottoms around 1.4 @ 1840 but it doesn't rise above 2.0 again until 1940. That is far too broad, right? Lots of loss somewhere still?..." I believe it's way, wy too broad of an SWR Todd. I think all your power is going to warm worms (or whatever lives in the ground where you are this time of year). I'm curious. Why did you use only 42' long radials? If it's space limitations, I understand. Not all of us live in the country. My $$ is on a poor ground system. The "vertical" part sounds good. GL with this.I've been following along. Mike VE9AA Mike, Coreen & Corey Keswick Ridge, NB _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Inverted L improvements - Part 3
Thanks to everyone that has written to me on the reflector and via email. I've read everything you've written and hopefully your efforts have helped me or guided me towards getting this antenna working better. I've made some changes, bought some equipment/parts and built some stuff per all of your advise. So I have some new observations and data and a few more questions. I'd really just like to get this playing better for the 160m CW contest in a couple of weeks. First, so I could use my antenna analyzer (by knocking down the 27.5KW AM station just down the road) I bought a DLW Associates BCB brickwall filter customized to have a strong dip at 1210kHz. It works great all across the BC band and my transciever is happier and I can use it out at the antenna to help the Comet CAA-500 analyzer actually make measurements. I also ordered the 2.4" #31 toroids and some RG400 as suggested at the often referenced K9YC website. I will build the choke as directed but for now I am using a DX Engineering Maxi-Core feedline choke that is supposedy effective to 160m but they provide no data sheet. I'll get the parts for the K9YC designed choke this week and will substitute that right away. The antenna (freshly measured and rehung) has a near-ground mounted feed point. The insulated 14g THHN wire is a total of 135' in length. It goes straight vertical for 90', makes a 90 degree bend and runs horizontally for 45'. It is well insulated at the end and it does not touch any trees at any point. I have attached 30 insulated wire radials each 42' in length (as suggested in a K9YC presentation referencing a K3LC study in the NCJ) laying on the ground roughly evenly distributed. The paper said that 12 radials would be "adequate" but I had room and materials for 30 so that's what I laid out. Here are some measurements I made and I can take others you may wish to see. My analyzer does not sign the reactance value. R=50 X=27 SWR=1.7 @ 1813 MHz then also R=50 and X=21 SWR=1.5 @ 1890 MHz The lowest X value I could obtain is X=5 with R=35 SWR=1.4 @ 1845 MHz This is with a 15' piece of coax from the feedpoint to the choke then a very short jumper to the BCB filter then a short jumper to the analyzer. I'll be able to put the choke right at the feedpoint (if that will make a difference) when the toroid/RG400 arrives. I measured the SWR curve and it starts at 2.0 @ 1800 and bottoms around 1.4 @ 1840 but it doesn't rise above 2.0 again until 1940. That is far too broad, right? Lots of loss somewhere still? So, that's where I am. It has worked US coast to coast, easily to Alaska and Hawaii and to N. Cook. It is being heard in VK and I worked half a dozen JAs all with 100 watts but I still think it has many problems. This is definitely an improvement thanks to all of your tips and advise but what can I reasonably do to make it better or am I at diminishing returns? I'm willing to put some more time and energy into it and also take more measurements if that would help. Any ideas? 73, Todd - NR7RR _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: elevated radial
Hello You want the elevated radials as high as possible. 3 meters is probably as low as you would want. 5 meters would probably be optimum. To be effective, the radials would need to be resonant, and you would need at least two, preferably four. The current on each radial should be equal. Any vegetation under the radials may have some effect. Hopefully the corn is down and harvested before the 160 meter DX season starts. As was suggested, the K2AV folded counterpoise, when installed as Guy suggests, is a good compromise that has enabled many hams to get on 160 Meters when they are in locations that are not radial friendly Peter K1ZJH _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: elevated radial
Hello Anton I thoroughly recommend the K2AV folded counterpoise that I use (248 countries wkd on 160 in 6 years). Read k2av.com. He suggests that it might be equivalent to 4 elevated radials. The counterpoise is easy to construct yourself. The balun is available from balundesigns.com or easy to construct yourself too. It would be very useful if you have an antenna analyser for final matching. Contact me off reflector if you want help with. 73 John G3XHZ Sent from my iPhone > On 16 Jan 2019, at 03:12, donov...@starpower.net wrote: > > Hello Anton, > > > One elevated wire will work, more than one will work much better. > > > Elevated wires must be near resonant length, a good starting point > is to make your wire about 125 feet (38 meters) long > > > Good luck! > > > 73 > Frank > W3LPL > > > > > > > - Original Message - > > From: "Anton Moehammad via Topband" > To: topband@contesting.com > Sent: Wednesday, January 16, 2019 3:07:07 AM > Subject: Topband: elevated radial > > Hello All,I wondering if You can give me advice about some unclear thing for > my second attempt 160m antenna. I can put a vertical antenna but > unfortunately there is no way I can lay down my ground in or on the ground > the best I can is put the ground wire at least 3m above average ground > because its an corn field, is there anything I need to worry or pay attention > about it ?with my 80m inverted V antenna my S meter go as high as S9 for > 160m. any advice. I live in YB land and this is my second attempt to be on > air on 160 any advice will appreciate. > thank You. > Anton > _ > 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
