End Fed Half Wave
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Hi All,
Here's a question for the antenna gurus among the group. It's about the best way to deploy an end fed half wave antenna. First of all, I assume most would say to put the entire antenna up in the air as high as possible, and in a horizontal plane. I understand the advantage of doing that. However, what about a situation where you only have one support? My first inclination would be to deploy the antenna like a sloper, with the far end at the top of the support, and the other end at, or near, the rig. I started wondering, though, about where the maximum radiation occurs. In a half wave antenna, the current max is more or less in the center of the antenna. So, would it be better to get the center of the antenna as high as possible (taking advantage of the one support you might have), and then maybe bending the other half back downwards, sort of in inverted vee fashion? That would be as opposed to just running the antenna up in a straight line to the top of the support, thus possibly only getting the center about half as high as the top of the support. Here's a more definitive description of what I am thinking about, and compares to the situation I have. I have a pole that goes up approx. 40 feet. If I deploy the EFHW in sloper fashion, with one end near the ground close to the rig, the center of the antenna would only be at approx. 20 feet. Also, On 40 meters (the band I would be using), the pole would need to be some 50+ feet from the rig. Alternatively, what if I move the center of the antenna up closer to the top of the pole, and have the rest of the antenna slope back down to another tie point? Wouldn't this be apt to work better, even though I have created something similar to an inverted vee? I know a couple of RVer's who do something similar. They have two poles in use, one of which is much taller. They deploy their antenna so that the mid point of the antenna is near the top of the tallest pole, then over to another shorter pole, and then back down that 2nd pole vertically--almost a somewhat slanted "U" shape. Their results seem to be decent, but I don't know if there is a better way to do it. Their method condenses the lateral space required to deploy the antenna, thus fitting within most RV sites. I don't know exactly what this does to the impedance at the feed point, but they use tuners to resolve any mismatch. The pole I have is somewhat taller than either of the ones they use. Anyway, I assume I could do the sloper approach without creating any serious issues, but I'm curious about what others think of the "vee" approach to get the antenna center higher. I appreciate any suggestions. Dave W7AQK ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I have a similar antenna.
I would use the inverted "V" or "L" configuration. You want the center of the antenna as high as possible. Mine is an inverted "L", but the far end actually is about 20 feet below the center, which is 50 feet high. The maximum radiation is where the current is greatest, a quarter wave from the far end, which has no current. Mine works quite well for a single wire. I made it a little more than a half wave at the lowest frequency, so I can use a remote tuner at the base for other bands. I feed it against a less than great radial system for all bands, but for a half wave, this might not be very important. The base is 140 feet from my shack, fed with coax in a conduit. I also have a 43 foot vertical, which I can select by remote switch. Except on 20 M, the inverted "L" usually works better. 73, Rick K7MW On Sep 22, 2014, at 2:49 PM, <[hidden email]> wrote: > Hi All, > > Here's a question for the antenna gurus among the group. It's about the best way to deploy an end fed half wave antenna. > > First of all, I assume most would say to put the entire antenna up in the air as high as possible, and in a horizontal plane. I understand the advantage of doing that. However, what about a situation where you only have one support? My first inclination would be to deploy the antenna like a sloper, with the far end at the top of the support, and the other end at, or near, the rig. I started wondering, though, about where the maximum radiation occurs. In a half wave antenna, the current max is more or less in the center of the antenna. So, would it be better to get the center of the antenna as high as possible (taking advantage of the one support you might have), and then maybe bending the other half back downwards, sort of in inverted vee fashion? That would be as opposed to just running the antenna up in a straight line to the top of the support, thus possibly only getting the center about half as high as the top of the support. > > Here's a more definitive description of what I am thinking about, and compares to the situation I have. I have a pole that goes up approx. 40 feet. If I deploy the EFHW in sloper fashion, with one end near the ground close to the rig, the center of the antenna would only be at approx. 20 feet. Also, On 40 meters (the band I would be using), the pole would need to be some 50+ feet from the rig. Alternatively, what if I move the center of the antenna up closer to the top of the pole, and have the rest of the antenna slope back down to another tie point? Wouldn't this be apt to work better, even though I have created something similar to an inverted vee? > > I know a couple of RVer's who do something similar. They have two poles in use, one of which is much taller. They deploy their antenna so that the mid point of the antenna is near the top of the tallest pole, then over to another shorter pole, and then back down that 2nd pole vertically--almost a somewhat slanted "U" shape. Their results seem to be decent, but I don't know if there is a better way to do it. Their method condenses the lateral space required to deploy the antenna, thus fitting within most RV sites. I don't know exactly what this does to the impedance at the feed point, but they use tuners to resolve any mismatch. The pole I have is somewhat taller than either of the ones they use. > > Anyway, I assume I could do the sloper approach without creating any serious issues, but I'm curious about what others think of the "vee" approach to get the antenna center higher. > > I appreciate any suggestions. > > Dave W7AQK > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by w7aqk
On Mon,9/22/2014 2:49 PM, [hidden email] wrote:
> It's about the best way to deploy an end fed half wave antenna. Not necessarily the "best" way, but here's a really good feeding method if you have a suitable sky hook! Also look at N6LF's ideas, on his website. Google to find it. http://k9yc.com/VerticalDipole.pdf 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by w7aqk
Dave,
There are two ways to approach a response, a discussion of the theory or a practical implementation. I usually worry more about the practical. So, here goes. A half wave antenna in a perfectly vertical position radiates energy at low angles with little to no energy radiated upward. a 1/2 antenna that is horizontal at a height of 1/4 wave radiates energy at high angle and very little to the horizon. Everything else is somewhere in between. The question you need to answer is do you want to work DX or local nets. Your antenna configuration should follow that answer. The physical construction of the antenna is more a matter of what you can install. For instance, do you have the trees in the correct location to hang the antenna horizontally? Do you have a support high enough to make your antenna vertical. Do you have only one possible support that is not high enough to go vertical requiring an inverted Vee configuration? Typically, the physical problems are far greater than the theoretical. My suggestion is that you install the antenna in a manner that will keep it from falling and as far from your station as possible. Figure out whether you are going to chase DX or nets, and then change the antenna configuration to maximize that. There is no single perfect antenna nor is there a perfect single configuration. Everything with antennas is a compromise, so stick one up and see what happens. 73, Barry K3NDM ----- Original Message ----- From: [hidden email] To: "elecraft" <[hidden email]> Sent: Monday, September 22, 2014 5:49:41 PM Subject: [Elecraft] End Fed Half Wave Hi All, Here's a question for the antenna gurus among the group. It's about the best way to deploy an end fed half wave antenna. First of all, I assume most would say to put the entire antenna up in the air as high as possible, and in a horizontal plane. I understand the advantage of doing that. However, what about a situation where you only have one support? My first inclination would be to deploy the antenna like a sloper, with the far end at the top of the support, and the other end at, or near, the rig. I started wondering, though, about where the maximum radiation occurs. In a half wave antenna, the current max is more or less in the center of the antenna. So, would it be better to get the center of the antenna as high as possible (taking advantage of the one support you might have), and then maybe bending the other half back downwards, sort of in inverted vee fashion? That would be as opposed to just running the antenna up in a straight line to the top of the support, thus possibly only getting the center about half as high as the top of the support. Here's a more definitive description of what I am thinking about, and compares to the situation I have. I have a pole that goes up approx. 40 feet. If I deploy the EFHW in sloper fashion, with one end near the ground close to the rig, the center of the antenna would only be at approx. 20 feet. Also, On 40 meters (the band I would be using), the pole would need to be some 50+ feet from the rig. Alternatively, what if I move the center of the antenna up closer to the top of the pole, and have the rest of the antenna slope back down to another tie point? Wouldn't this be apt to work better, even though I have created something similar to an inverted vee? I know a couple of RVer's who do something similar. They have two poles in use, one of which is much taller. They deploy their antenna so that the mid point of the antenna is near the top of the tallest pole, then over to another shorter pole, and then back down that 2nd pole vertically--almost a somewhat slanted "U" shape. Their results seem to be decent, but I don't know if there is a better way to do it. Their method condenses the lateral space required to deploy the antenna, thus fitting within most RV sites. I don't know exactly what this does to the impedance at the feed point, but they use tuners to resolve any mismatch. The pole I have is somewhat taller than either of the ones they use. Anyway, I assume I could do the sloper approach without creating any serious issues, but I'm curious about what others think of the "vee" approach to get the antenna center higher. I appreciate any suggestions. Dave W7AQK ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jim Brown-10
------------ ORIGINAL MESSAGE ------------(may be snipped)
On Mon, 22 Sep 2014 16:21:09 -0700, k9yc wrote: > >Not necessarily the "best" way, but here's a really good feeding method >if you have a suitable sky hook! Also look at N6LF's ideas, on his >website. Google to find it. > >http://k9yc.com/VerticalDipole.pdf > >73, Jim K9YC REPLY: Very clever, just might try this myself. This is basically a variation on the ancient coaxial sleeve antenna, with a choke substituting for the separate sleeve. Nice! 50+ years ago I used the original coaxial sleeve antenna on six meters when I had a Tech license and it worked well. Thanks for the idea. 73, Bill W6WRT ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Rick Dettinger-3
I agree. I would just add that if you use an inverted L or V configuration, be sure the included angle is 90 degrees or greater. Otherwise there will be some cancellation of radiation from the two legs. As a thought experiment, consider what would happen if you reduced the angle to 0. That would make the antenna into a parallel line which wouldn't radiate at all.
Vic, k2vco > On Sep 23, 2014, at 2:20 AM, Rick Dettinger <[hidden email]> wrote: > > I have a similar antenna. > I would use the inverted "V" or "L" configuration. You want the center of the antenna as high as possible. > Mine is an inverted "L", but the far end actually is about 20 feet below the center, which is 50 feet high. The maximum radiation is where the current is greatest, a quarter wave from the far end, which has no current. Mine works quite well for a single wire. I made it a little more than a half wave at the lowest frequency, so I can use a remote tuner at the base for other bands. I feed it against a less than great radial system for all bands, but for a half wave, this might not be very important. The base is 140 feet from my shack, fed with coax in a conduit. I also have a 43 foot vertical, which I can select by remote switch. Except on 20 M, the inverted "L" usually works better. > > 73, > Rick K7MW > > > > > >> On Sep 22, 2014, at 2:49 PM, <[hidden email]> wrote: >> >> Hi All, >> >> Here's a question for the antenna gurus among the group. It's about the best way to deploy an end fed half wave antenna. >> >> First of all, I assume most would say to put the entire antenna up in the air as high as possible, and in a horizontal plane. I understand the advantage of doing that. However, what about a situation where you only have one support? My first inclination would be to deploy the antenna like a sloper, with the far end at the top of the support, and the other end at, or near, the rig. I started wondering, though, about where the maximum radiation occurs. In a half wave antenna, the current max is more or less in the center of the antenna. So, would it be better to get the center of the antenna as high as possible (taking advantage of the one support you might have), and then maybe bending the other half back downwards, sort of in inverted vee fashion? That would be as opposed to just running the antenna up in a straight line to the top of the support, thus possibly only getting the center about half as high as the top of the support. >> >> Here's a more definitive description of what I am thinking about, and compares to the situation I have. I have a pole that goes up approx. 40 feet. If I deploy the EFHW in sloper fashion, with one end near the ground close to the rig, the center of the antenna would only be at approx. 20 feet. Also, On 40 meters (the band I would be using), the pole would need to be some 50+ feet from the rig. Alternatively, what if I move the center of the antenna up closer to the top of the pole, and have the rest of the antenna slope back down to another tie point? Wouldn't this be apt to work better, even though I have created something similar to an inverted vee? >> >> I know a couple of RVer's who do something similar. They have two poles in use, one of which is much taller. They deploy their antenna so that the mid point of the antenna is near the top of the tallest pole, then over to another shorter pole, and then back down that 2nd pole vertically--almost a somewhat slanted "U" shape. Their results seem to be decent, but I don't know if there is a better way to do it. Their method condenses the lateral space required to deploy the antenna, thus fitting within most RV sites. I don't know exactly what this does to the impedance at the feed point, but they use tuners to resolve any mismatch. The pole I have is somewhat taller than either of the ones they use. >> >> Anyway, I assume I could do the sloper approach without creating any serious issues, but I'm curious about what others think of the "vee" approach to get the antenna center higher. >> >> I appreciate any suggestions. >> >> Dave W7AQK >> >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [hidden email] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Barry K3NDM
On Mon,9/22/2014 6:08 PM, [hidden email] wrote:
> A half wave antenna in a perfectly vertical position radiates energy at low angles with little to no energy radiated upward. a 1/2 antenna that is horizontal at a height of 1/4 wave radiates energy at high angle and very little to the horizon. Everything else is somewhere in between. Right on. I've addressed this in considerable detail in http://k9yc.com/VertOrHorizontal-Slides.pdf 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by w7aqk
Hi All,
Thanks for all the helpful, and thoughtful, responses. I've gone ahead and deployed the EFHW more or less as described, and did make a few contacts last night just running 10 watts with the KX3. I even made a couple of SSB contacts, which I don't often try and do when running QRP. I did make it to the east coast (from here on the Oregon coast), so that was encouraging. Hi. Some asked (suggested) I just use a standard dipole or inverted vee, which I often do. It's just that I happen to have a PAR end fed with me, and wanted to give it a try. This one is the higher power version, so later I may hook up the KXPA100 and see how it goes. An inverted vee might have been a better choice, except I don't really have all that much space. I did hear several European stations on 40 last night, but I wasn't expecting to catch any of them, and didn't!!! Hi. The best part of all of this tinkering is that it confirms how useful my 40 ft. Wonderpole can be. It certainly gives me a lot of viable options for getting on the air in tight places. Of all the collapsible poles that I have, and I do have a bunch of them, the Wonderpole is the most versatile. I actually have two of them, but one is here with me in the motorhome, and the other is at home. Anyway, it is the easiest, and most effective, pole for RVing and portable operating. It collapses to 8 ft., so it is easy to transport--not a backpacking pole, but otherwise very manageable. I've even used one of W6MMA's YP-3 portable beams with this pole at about 30 ft., or a bit less. The top section is still 3/4 inch diameter, so I just use one of the lower sections with an even larger diameter, then "Armstrong it" for rotation. It's a sturdy rascal! That doesn't get me a particularly great take-off angle, but it works! Dave W7AQK ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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