Re: Topband: Inverted L with elevated radials for topband
When it comes to elevated radials, the amount of guys who have strong opinions on the subject are many - and unfortunately the amount of objective data behind those strong opinions is generally not existent. On the other hand, the N6LF work is one of the few well documented objective works available. You won't go wrong drawing your radial design based on the N6LF graphs. As far as the performance and feedpoint question goes, build the best ground you can and then cook up the match network based on the measured values. 73/jeff/ac0c alpha-charlie-zero-charlie www.ac0c.com On 3/5/20 5:43 PM, Grant Saviers wrote: comments in line On 3/5/2020 10:02, Gabriel - EA6VQ via Topband wrote: I have some doubts about installing and inverted L with elevated radials for 160m. I have been searching in Google and find some contradictory information, so I would appreciate very much if you can help me with your own experience. As noted by others, N6LF has a wealth of modeled and measured data on elevated radials. antennasbyn6lf.com The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole placed on top of a 3m (10 ft) high small tower with the horizontal part of the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away. Two to four tuned elevated radials can be placed, although they will have to be bent due to space restrictions. By "tuned" do you mean resonant 130ft +/-? Again N6LF has data for 2 to 16 elevated radials, and with more they can be shorter. Also see his paper in Antenna Compendium 8 re inductively loading for shorter radials. I had only 2 75ft radials on a 52' mast. Now the doubts: What impedance can I expect at the feed point with this configuration? Having the radials as high as possible will minimize ground losses and decease Z. With 2x at 10ft plan on 25 to 30 ohms. How to match it in order to feed it with a 50 ohm cable? Some pages say that no match is required, only a choke. Other pages say a hairpin is necessary as the impedance can be too low. So other say that a tuner at the base is required? I am confused L SWR losses on 160 are so low that a 2:1 doesn't cost many db's. Too keep your amplifier happier I use a 50::25 ohm transmission line transformer. make it or buy it. A good choke is a must. Make the K9YC 4" #31 choke. What performance for DX can be achieved by this antenna? Is it really good or do you have some better suggestion for a really small lot where no ground radials are possible? You won't do better with anything else. More radials will improve it slightly. Would it be worth to use a higher fiberglass pole, let's say 4 m (13 ft) higher, in order to lengthen the vertical section of the L? Would the difference be noticeable? The taller the better but probably less than 1 db gain. Anyone has real experience setting up this antenna with elevated radials? Most information I can find on Internet is related to ground mounted antennas. Read all of what Rudy N6LF says, and you will be an expert. Grant KZ1W Thanks in advance! 73. Gabriel - EA6VQ _ 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 with elevated radials for topband
I havent experimented on top band but I have tried elevated radials on 80M ¼ verticals. I had one in Houston Texas that worked wonderfully elevated 8 radials at about 10 ft. Ground conductivity in Houston was about as good as anywhere in the US. I tried doing the same thing at 2 different QTHs in Vermont and both were very disappointing. I gave up on elevated radials for 80 and 160M. My experience has been that ground conductivity matters for a small number of elevated radials. I have been much happier with 48 ¼ wave ground radials. Ed N1UR _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L with elevated radials for topband
I second this. Wes N7WS On 3/5/2020 4:43 PM, Grant Saviers wrote: Read all of what Rudy N6LF says, and you will be an expert. Grant KZ1W _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L with elevated radials for topband
"Sooner or later everything old is new again" (Stephen King) February 1922 QST page 30 The 1BCG antenna used for the transatlantic tests was a T cage over a radial counterpoise. The antenna is hung between two pipe masts 230 feet apart, and 108 and 75 feet high, respectively. The two horizontal sections of the T-vertical are each 50 feet long. The vertical section is 70 feet over the top of the counterpoise. The elevated counterpoise consisted of thirty 60 foot wires The operating frequency was 1500 kilocycles http://p1k.arrl.org/pubs_archive/4361 73 Frank W3LPL - Original Message - From: "Bill Stewart" To: "Gabriel - EA6VQ" Cc: "topband" Sent: Thursday, March 5, 2020 8:13:08 PM Subject: Re: Topband: Inverted L with elevated radials for topband Hi Gabriel, These comments will be of little help as far as the technical info on the subject antenna and is a far cry from an excellently constructed antenna but it is very practicalin my opinion of course. However, I do use an Inv. L with a four wire counterpoise...or elevated radials if you prefer. Mine is approximately 50ft vertical and rest horiztotal, a quarter wave. The horizontal part is about 50 feet high and fairly flat. The antenna is completely covered over with tall pine trees. The CP wires go off from the base/feed point 10ft off the ground and at approximately 90 degrees apart. Each CP wire is about ten feet high and some are supported on tree trunks, others have some PVC posts for support and seems the CP wire lengths are a bit shorter than a 1/4 wave lgth, but my memory may not be too good on this part. I feed it with RG8X...I only run 100 watts(CW) on 160no need for big coax in my case. I just used a door-knob cap between the vert and CP at the basecan't remember the value but think I just experimented until I got the SWR goodalso think I did some trimming on the CP wires. I have had very good success with this antenna. With 100 watts I have been able to work several DXped. stns in the Pacific, JA. This season I have worked nearly 80 EU, Carib and Pac. stations. I had a lot of fun in the recent ARRL CW test. No, I don't get every station I call, but enough to keep me happy. The purist, with all their instruments and computer programs would laugh at my version, but it seems to be an easy antenna to get working and, at least in my case, a decent antenna. (I also use it for receiving...works well there too). Try iteasy to put up and if it don't work, go on to something elsehi. GL & 73 de Bill K4JYS/NC - Original Message - From: "topband" To: "topband" Sent: Thursday, March 5, 2020 1:02:07 PM Subject: Topband: Inverted L with elevated radials for topband I have some doubts about installing and inverted L with elevated radials for 160m. I have been searching in Google and find some contradictory information, so I would appreciate very much if you can help me with your own experience. The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole placed on top of a 3m (10 ft) high small tower with the horizontal part of the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away. Two to four tuned elevated radials can be placed, although they will have to be bent due to space restrictions. Now the doubts: What impedance can I expect at the feed point with this configuration? How to match it in order to feed it with a 50 ohm cable? Some pages say that no match is required, only a choke. Other pages say a hairpin is necessary as the impedance can be too low. So other say that a tuner at the base is required? I am confused L What performance for DX can be achieved by this antenna? Is it really good or do you have some better suggestion for a really small lot where no ground radials are possible? Would it be worth to use a higher fiberglass pole, let's say 4 m (13 ft) higher, in order to lengthen the vertical section of the L? Would the difference be noticeable? Anyone has real experience setting up this antenna with elevated radials? Most information I can find on Internet is related to ground mounted antennas. Thanks in advance! 73. Gabriel - EA6VQ _ 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 with elevated radials for topband
On 3/5/2020 11:26 AM, Mike Waters wrote: Many hams --including myself-- have had very good results using only a few elevated radials. Yes. One of the key factors is the height of the radials. N6BT, who has done a LOT of work with elevated radials on topband, told me that 18 ft is a minimum height. After my first tower (120 ft) was up, I had sloping wires rigged to points about 60 ft from the tower base, insulated from the tower and fed from the base against elevated radials. The tower has about ten on-ground radials to improves its performance as a reflector. I had started out based on Rudy's early work with much lower elevation and wasn't satisfied with the result -- I had directivity, but the gain was poor. When I raised them to 18=20 ft (gull wing from about 3 ft at the feedpoint), I started seeing the few dB of gain that NEC predicted. A few other important points. The ends of the radials are a high voltage point, so must be carefully insulated. Second, Rudy emphasizes that four elevated radials is a minimum, and twice that number is better. He also observes that they work better if current distribution between them is equal, that current distribution can be varied by variations in the soil underneath them, and that cutting them slightly shorter than a quarter wave minimizes those variations. These are slides for a talk I've given about 160M antennas and counterpoise/radial systems, all based on good work by others. http://k9yc.com/160MPacificon.pdf 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L with elevated radials for topband
comments in line On 3/5/2020 10:02, Gabriel - EA6VQ via Topband wrote: I have some doubts about installing and inverted L with elevated radials for 160m. I have been searching in Google and find some contradictory information, so I would appreciate very much if you can help me with your own experience. As noted by others, N6LF has a wealth of modeled and measured data on elevated radials.antennasbyn6lf.com The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole placed on top of a 3m (10 ft) high small tower with the horizontal part of the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away. Two to four tuned elevated radials can be placed, although they will have to be bent due to space restrictions. By "tuned" do you mean resonant 130ft +/-? Again N6LF has data for 2 to 16 elevated radials, and with more they can be shorter. Also see his paper in Antenna Compendium 8 re inductively loading for shorter radials. I had only 2 75ft radials on a 52' mast. Now the doubts: What impedance can I expect at the feed point with this configuration? Having the radials as high as possible will minimize ground losses and decease Z. With 2x at 10ft plan on 25 to 30 ohms. How to match it in order to feed it with a 50 ohm cable? Some pages say that no match is required, only a choke. Other pages say a hairpin is necessary as the impedance can be too low. So other say that a tuner at the base is required?I am confused L SWR losses on 160 are so low that a 2:1 doesn't cost many db's. Too keep your amplifier happier I use a 50::25 ohm transmission line transformer. make it or buy it. A good choke is a must. Make the K9YC 4" #31 choke. What performance for DX can be achieved by this antenna? Is it really good or do you have some better suggestion for a really small lot where no ground radials are possible? You won't do better with anything else. More radials will improve it slightly. Would it be worth to use a higher fiberglass pole, let's say 4 m (13 ft) higher, in order to lengthen the vertical section of the L? Would the difference be noticeable? The taller the better but probably less than 1 db gain. Anyone has real experience setting up this antenna with elevated radials? Most information I can find on Internet is related to ground mounted antennas. Read all of what Rudy N6LF says, and you will be an expert. Grant KZ1W Thanks in advance! 73. Gabriel - EA6VQ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L with elevated radials for topband
My experience too, Bill! The very first time I tried my inverted-L with the two elevated radials etc., I broke a number of pile-ups in a contest with 100 watts! At that time, I did not have an amplifier that covered 160m. After that, for awhile I made a game out of turning down the power output to 50 watts or less. I finally understood why some hams love QRP. :-) 73, Mike W0BTU On Thu, Mar 5, 2020, 2:13 PM Bill Stewart wrote: > ... > These comments will be of little help as far as the technical info on the > subject antenna and is a far cry from an excellently constructed antenna > but it is very practicalin my opinion of course. > > However, I do use an Inv. L with a four wire counterpoise...or elevated > radials if you prefer. Mine is approximately 50ft vertical and rest > horiztotal, a quarter wave. The horizontal part is about 50 feet high > and fairly flat. The antenna is completely covered over with tall pine > trees. The CP wires go off from the base/feed point 10ft off the ground and > at approximately 90 degrees apart. Each CP wire is about ten feet high and > some are supported on tree trunks ... I only run 100 watts(CW) on 160no > need for big coax in my case. I have had very good success with this > antenna. With 100 watts I have been able > to work several DXped. stns in the Pacific, JA. This season I have worked > nearly 80 EU, Carib and Pac. stations. I had a lot of fun in the recent > ARRL CW test. ... > Try iteasy to put up and if it don't work, go on to something > elsehi. > GL & 73 de Bill K4JYS/NC > > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L with elevated radials for topband
Hi Gabriel, There is too many variables in your antenna setup to determine the expected impedance. I have built and measured several inverted L's with/without elevated radials and/or sloping top wires. So I will refrain from putting out estimations, other than guesses from what I learned during the last 30yrs. What I do know: Fact: an inverted L with 1/8 vertical and 1/8 straight horizontal offers a radiation resistance Rs=18 Ohm. No more. Fact: Antenna impedance (Z)= Rs+Rg. Rground refers to energy not radiated but lost in the radials to ground. Your Antenna Analyzer/VNA will offer at resonance (find the frequency at which Xc=0) is Z. You now have two unknown variables(Rs and Rg) and one measured value Z Fact: Z, SWR_usable_Bandwidth, Rground, Rs and any device to match it all to 50 Ohm are variables which can be a challenge. But don't sweat it. Fact: making the vertical part higher v.s. sloping wire=> get the sloping wire up. That is much more effective. My experience: - A straight horizontal L-part is just to about impossible; at 1/8 length any wire will droop in the middle and lower Rs substantially. Spent two days measuring just that when I had two 23m HD tubular towers. - A sloping single top wire quickly lowers the Rs. In your setup I would expect it to be between 11 and 13 Ohm - knowing that guestimated value; when your analyzer shows Z=40 Ohm SWR=great at resonance (Xc=0) one can calculate the ground losses Rg=40-12=28Ohm. That will be with 4 radials on ground probably. A nice SWR but effectivity is 12/40= 30% the other 28/40-70% of the power goes into ground. - Good SWR does not mean the antenna is 'really good'. But don't seat it, sometimes you have limited options. And you have to start somewhere. - Elevated radials: been there. 4 resonant elevated radials is possible, but difficult to measure correctly such that all four behave similar. We had them at 4m height. Higher is better, more is better. - If you lengthen the L-part so the total becomes 50 to 54m and tune out that extra length using a series Cap at the feedpoint, you can raise the Z. We did it with our 4 elevated radials and got a Z=34 Ohms which was nice to use a W2FMI 32:50 Ohm transformer. - Radials; put down about 30-50pcs with 25 to max 30m length. Want to lower Rground more effectively? Go to 120 radials at longer lengths, OR - Additionally put lengths of chicken wire directly under the vertical. Do not try to make length in a start config like radials; instead just closely cover straight lengths, make a square. It does not have to make electrical contact (it will help a bit but not the effort worth). Been there, measured it. - At a good setup you probably will have a Z= 12+15=27 Ohms (there it is I did make an estimation!) my point here: - You will need a matching device / transformer (one toroid <500W, two or three at 1K5) to get from the guestimation value to connect it to your 50 Ohms coax feeder into the shack. - There will be many other voices from other people having less/similar/more/different experience. My tips: - Don't sweat it. At 1/8 vertical part, even with a sloping wire, one can make a good signal. Even at some crooked elevated radials. - Read Low Band Dx'ing by ON4UN; it tells you how to do it, both in KISS mode as well as freaking nerd-mode. There will not be a great difference unless you have the hardware AND lots of real estate. - Use an antenna analyzer which shows Xc, Z and SWR; the cheapest Rig Expert or any like is best in the field (no MFJ). I have had several different ones in the past 20yrs. - Use a portable VNA if you must, but only if you have the experience how to use it. Or have someone come over to do that . No Smith chart crap; that's for nerds and NOT effective in the field, unless you use smith charts on a daily basis. - Measure at the antenna, using a pigtail coax to about 0,5 to 1m length. Yes one can measure it in the shack using professional network analyzers/ VNA's etc. when the feedline is properly calibrated out. Been there. A friend has a large HP in his shack. In the end we prefer that small but very practical Rig Expert. Happy experimenting! 73 Mark, PA5MW -Original Message- From: Topband On Behalf Of Gabriel - EA6VQ via Topband Sent: Thursday, March 05, 2020 19:02 PM To: topband@contesting.com Subject: Topband: Inverted L with elevated radials for topband I have some doubts about installing and inverted L with elevated radials for 160m. I have been searching in Google and find some contradictory information, so I would appreciate very much if you can help me with your own experience. The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole placed on top of a 3m (10 ft) high small tower with the horizontal part of the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away. Two to four tuned elevated radials can be placed, al
Re: Topband: Inverted L with elevated radials for topband
Hi Gabriel, These comments will be of little help as far as the technical info on the subject antenna and is a far cry from an excellently constructed antenna but it is very practicalin my opinion of course. However, I do use an Inv. L with a four wire counterpoise...or elevated radials if you prefer. Mine is approximately 50ft vertical and rest horiztotal, a quarter wave. The horizontal part is about 50 feet high and fairly flat. The antenna is completely covered over with tall pine trees. The CP wires go off from the base/feed point 10ft off the ground and at approximately 90 degrees apart. Each CP wire is about ten feet high and some are supported on tree trunks, others have some PVC posts for support and seems the CP wire lengths are a bit shorter than a 1/4 wave lgth, but my memory may not be too good on this part. I feed it with RG8X...I only run 100 watts(CW) on 160no need for big coax in my case. I just used a door-knob cap between the vert and CP at the basecan't remember the value but think I just experimented until I got the SWR goodalso think I did some trimming on the CP wires. I have had very good success with this antenna. With 100 watts I have been able to work several DXped. stns in the Pacific, JA. This season I have worked nearly 80 EU, Carib and Pac. stations. I had a lot of fun in the recent ARRL CW test. No, I don't get every station I call, but enough to keep me happy. The purist, with all their instruments and computer programs would laugh at my version, but it seems to be an easy antenna to get working and, at least in my case, a decent antenna. (I also use it for receiving...works well there too). Try iteasy to put up and if it don't work, go on to something elsehi. GL & 73 de Bill K4JYS/NC - Original Message - From: "topband" To: "topband" Sent: Thursday, March 5, 2020 1:02:07 PM Subject: Topband: Inverted L with elevated radials for topband I have some doubts about installing and inverted L with elevated radials for 160m. I have been searching in Google and find some contradictory information, so I would appreciate very much if you can help me with your own experience. The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole placed on top of a 3m (10 ft) high small tower with the horizontal part of the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away. Two to four tuned elevated radials can be placed, although they will have to be bent due to space restrictions. Now the doubts: What impedance can I expect at the feed point with this configuration? How to match it in order to feed it with a 50 ohm cable? Some pages say that no match is required, only a choke. Other pages say a hairpin is necessary as the impedance can be too low. So other say that a tuner at the base is required?I am confused L What performance for DX can be achieved by this antenna? Is it really good or do you have some better suggestion for a really small lot where no ground radials are possible? Would it be worth to use a higher fiberglass pole, let's say 4 m (13 ft) higher, in order to lengthen the vertical section of the L? Would the difference be noticeable? Anyone has real experience setting up this antenna with elevated radials? Most information I can find on Internet is related to ground mounted antennas. Thanks in advance! 73. Gabriel - EA6VQ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Inverted L with elevated radials for topband
Many hams --including myself-- have had very good results using only a few elevated radials. This question contains an answer with a NEC 4.2 plot comparing the efficiency of earth vs. elevated radials: https://ham.stackexchange.com/questions/9823/how-does-the-performance-of-elevated-radials-differ-from-that-of-buried-radials From the publications of N6LF (Dr. Rudy Severns) and others, they can be almost the same. Please scroll past the table and graphs down to the "Relevant links" section at https://web.archive.org/web/20180815154501/http://w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html and you can read more proof. However, *you cannot ground the elevated radials,* AND *you must use a proper ferrite choke balun on the coax feedline right at the antenna feedpoint*. At https://web.archive.org/web/20170703105635/http://www.w0btu.com/160_meters.html scroll down to the section "The W0BTU 160 Meter Inverted-L Antenna" for very important details about how to use elevated radials effectively. One missing detail there is that these are "gull-wing" radials. That is, they slope up at a 45° angle from the feedpoint to 10'. Sorry there are no photos there. 73, Mike W0BTU On Thu, Mar 5, 2020, 12:12 PM Gabriel - EA6VQ via Topband < topband@contesting.com> wrote: > I have some doubts about installing and inverted L with elevated radials > for > 160m. I have been searching in Google and find some contradictory > information, so I would appreciate very much if you can help me with your > own experience. > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Inverted L with elevated radials for topband
I have some doubts about installing and inverted L with elevated radials for 160m. I have been searching in Google and find some contradictory information, so I would appreciate very much if you can help me with your own experience. The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole placed on top of a 3m (10 ft) high small tower with the horizontal part of the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away. Two to four tuned elevated radials can be placed, although they will have to be bent due to space restrictions. Now the doubts: What impedance can I expect at the feed point with this configuration? How to match it in order to feed it with a 50 ohm cable? Some pages say that no match is required, only a choke. Other pages say a hairpin is necessary as the impedance can be too low. So other say that a tuner at the base is required?I am confused L What performance for DX can be achieved by this antenna? Is it really good or do you have some better suggestion for a really small lot where no ground radials are possible? Would it be worth to use a higher fiberglass pole, let's say 4 m (13 ft) higher, in order to lengthen the vertical section of the L? Would the difference be noticeable? Anyone has real experience setting up this antenna with elevated radials? Most information I can find on Internet is related to ground mounted antennas. Thanks in advance! 73. Gabriel - EA6VQ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
