Re: [Elecraft] Need help from an EZNec user on a horizontal loop question
My current antenna is an Inverted L 1/2 wavelength long at 80 meters and is direct fed. That length puts the voltage "loop" (maximum) at the rig, so the counterpoise requirements are minimal on 80. The L is 40 feet vertical and 80 feed horizontal. That puts the current max near the bend on the "flat top" for high efficiency. I have my own Homebrew L-Net tuner on a shelf above the rig that will handle the huge voltages experienced at exactly 1/2 wave, but by finagling the length the impedance can be brought into range of the K3s/KAT500 tuners without a huge loss in efficiency. However note that the antenna terminates right in the shack so you need to be concerned about meeting safe RF exposure limits, especially if running more than 100 watts on the higher bands. I use mine with good results on 160 through 20 meters. 73, Ron AC7AC -Original Message- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm Sent: Sunday, January 1, 2017 6:44 PM To: Terry Brown; elecraft@mailman.qth.net Subject: Re: [Elecraft] Need help from an EZNec user on a horizontal loop question Terry, Have you considered an 80 meter inverted L? It takes up little real estate for the radiator, but does require putting down a ground screen at the base of the inverted L. If you do not wish to bury 32 radials for a ground screen, consider using resonant elevated radials. Two elevated radials running in opposing directions will do the job nicely. Put the elevated radials above ground by about 10 feet to keep them out of the range of humans and deer and other things running into them and causing harm. If there are horse riders who will be riding through your property, you may want to increase the height to 15 feet. 73, Don W3FPR On 1/1/2017 4:55 PM, Terry Brown wrote: > I am moving from my current QTH where I have a horizontal loop up > about > 35-40 ft. that is a bit longer than 1 wavelength on 80. I feed it at > one corner with 450 ohm twin lead connected to a 4:1 voltage balun, > then coax to my rig. I can tune all the ham bands either barefoot to > my K2 or KX3 and the KXPA100 using their internal tuners. > __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to r...@elecraft.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Need help from an EZNec user on a horizontal loop question
On Sun,1/1/2017 6:44 PM, Don Wilhelm wrote: It takes up little real estate for the radiator, but does require putting down a ground screen at the base of the inverted L. To avoid confusion about how antennas work, it's best to call this a counterpoise, and leave the word "ground" out of it. The first function of a counterpoise is to provide a path for return current. The earth is a terrible path, because it's basically a big resistor, so it burns a lot of transmitter power, leaving less for the antenna to radiate. Radials are a nearly ideal form of counterpoise, because they not only provide a low resistance source for return current, but they also shield the antenna from lossy earth. In addition to the very good solution that Don described, there are other possibilities. K2AV has designed what he calls a "folded" counterpoise that fits on a pretty small lot. Google to find details. His original design was for 160m, but it can be scaled for 80M. I've given several talks to ham clubs about "getting on 160 from a small lot." It's mostly about antennas and counterpoise systems. http://k9yc.com/160MPacificon.pdf For 80M, divide the dimensions by 2. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Need help from an EZNec user on a horizontal loop question
Terry, Have you considered an 80 meter inverted L? It takes up little real estate for the radiator, but does require putting down a ground screen at the base of the inverted L. If you do not wish to bury 32 radials for a ground screen, consider using resonant elevated radials. Two elevated radials running in opposing directions will do the job nicely. Put the elevated radials above ground by about 10 feet to keep them out of the range of humans and deer and other things running into them and causing harm. If there are horse riders who will be riding through your property, you may want to increase the height to 15 feet. 73, Don W3FPR On 1/1/2017 4:55 PM, Terry Brown wrote: I am moving from my current QTH where I have a horizontal loop up about 35-40 ft. that is a bit longer than 1 wavelength on 80. I feed it at one corner with 450 ohm twin lead connected to a 4:1 voltage balun, then coax to my rig. I can tune all the ham bands either barefoot to my K2 or KX3 and the KXPA100 using their internal tuners. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Need help from an EZNec user on a horizontal loop question
While you design and experiment with a new loop: Install a reduced size dipole for 80. My rule of thumb, which has worked for many quickie antennas is to use insulated #14 wire and close-wind on a 2" white PVC pipe a length of wire that is twice the length of that removed from the antenna. You will loose some bandwidth, but you will be on the air. Comment about the proposed loop: If the overall physical size is a little short - you are using tuned feed, so it will not make for that big a loss. It also does not have to be square - five or six sides will do fine - just get as much open space inside the loop as possible. Proximity to the roof means proximity to the RFI from the house. Nothing scientific or big worded here - just things that work that are based on my experience over the years. Bill W2BLC - K-Line __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Need help from an EZNec user on a horizontal loop question
Terry what is the size of your roof line perimeter? Mel, K6KBE From: Terry Brown <n...@comcast.net> To: elecraft@mailman.qth.net Sent: Sunday, January 1, 2017 1:55 PM Subject: [Elecraft] Need help from an EZNec user on a horizontal loop question I am moving from my current QTH where I have a horizontal loop up about 35-40 ft. that is a bit longer than 1 wavelength on 80. I feed it at one corner with 450 ohm twin lead connected to a 4:1 voltage balun, then coax to my rig. I can tune all the ham bands either barefoot to my K2 or KX3 and the KXPA100 using their internal tuners. My new QTH will not have the real estate to do what I can now. I was hoping someone who is well versed with the EZNec antenna program could give me an idea of how well what I think I can build, will work. I will have a yagi for 10-15-20. I am particularly concerned that I may not be able to tune 80. I have a Sunday CW qso with a group of great guys on 80 and want to keep participating. Here is the info on the new horizontal loop: The east side will be 54 ft. long and be 2 ft. above my roof at a 35 ft. height. That leg of the loop will be over a roof that slopes away for about 8 feet. The west side will be 78 ft. long and up 20 ft. The remaining north and south sides will be 38-40 feet each of the same length. This will give a loop a bit longer than 200 ft. I plan to feed it again on a corner, the NE corner when it is two feet from the roof and I can run the twin lead down the side of the house to my shack. I know this will be predominantly a cloud burner, but that is fine on 40 and 80. My concern is being able to tune it on the 80, 40, 30, 17, and 24 meter ham bands. My lot is only 80 by 100 so a doublet on 80 will not work without folding it in several locations. I have loved my loop and would love to be able to continue using one. The fact that it is horizontally polarized is so nice for being able to work weak stations without a lot of noise. If anyone could help me with the analysis of this antenna, I would appreciate it. 73's, Terry, N7TB __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to farrerfo...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] Need help from an EZNec user on a horizontal loop question
I am moving from my current QTH where I have a horizontal loop up about 35-40 ft. that is a bit longer than 1 wavelength on 80. I feed it at one corner with 450 ohm twin lead connected to a 4:1 voltage balun, then coax to my rig. I can tune all the ham bands either barefoot to my K2 or KX3 and the KXPA100 using their internal tuners. My new QTH will not have the real estate to do what I can now. I was hoping someone who is well versed with the EZNec antenna program could give me an idea of how well what I think I can build, will work. I will have a yagi for 10-15-20. I am particularly concerned that I may not be able to tune 80. I have a Sunday CW qso with a group of great guys on 80 and want to keep participating. Here is the info on the new horizontal loop: The east side will be 54 ft. long and be 2 ft. above my roof at a 35 ft. height. That leg of the loop will be over a roof that slopes away for about 8 feet. The west side will be 78 ft. long and up 20 ft. The remaining north and south sides will be 38-40 feet each of the same length. This will give a loop a bit longer than 200 ft. I plan to feed it again on a corner, the NE corner when it is two feet from the roof and I can run the twin lead down the side of the house to my shack. I know this will be predominantly a cloud burner, but that is fine on 40 and 80. My concern is being able to tune it on the 80, 40, 30, 17, and 24 meter ham bands. My lot is only 80 by 100 so a doublet on 80 will not work without folding it in several locations. I have loved my loop and would love to be able to continue using one. The fact that it is horizontally polarized is so nice for being able to work weak stations without a lot of noise. If anyone could help me with the analysis of this antenna, I would appreciate it. 73's, Terry, N7TB __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
