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#1
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V Beam, do they work?
I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain. Has anyone seen a successful model anyplace of a two or three wave V with good gain?? 73 Tom |
#2
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V Beam, do they work?
wrote in message oups.com... I've been modeling V beams off and on for a few years now, and never can seem to get one that has useful gain. Has anyone seen a successful model anyplace of a two or three wave V with good gain?? 73 Tom Hi Tom, I have a model of a 5 wavelength 24MHz Vee beam in AO- I can send the file if it is useful to you. AO reports 11dBi free space gain. Included angle appears to be 44 degrees. Dale W4OP |
#3
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V Beam, do they work?
Dale Parfitt wrote: wrote in message oups.com... I've been modeling V beams off and on for a few years now, and never can seem to get one that has useful gain. Has anyone seen a successful model anyplace of a two or three wave V with good gain?? 73 Tom Hi Tom, I have a model of a 5 wavelength 24MHz Vee beam in AO- I can send the file if it is useful to you. AO reports 11dBi free space gain. Included angle appears to be 44 degrees. I don't have AO Dave, so a description will work. That sounds like the problem I am seeing. With a 3-5 WL long V, I have about the same gain as a three element Yagi. But I'll still try to model your antenna with 5wl legs and 44 degree angle. Thanks. |
#4
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V Beam, do they work?
wrote in message oups.com... Dale Parfitt wrote: wrote in message oups.com... I've been modeling V beams off and on for a few years now, and never can seem to get one that has useful gain. Has anyone seen a successful model anyplace of a two or three wave V with good gain?? 73 Tom Hi Tom, I have a model of a 5 wavelength 24MHz Vee beam in AO- I can send the file if it is useful to you. AO reports 11dBi free space gain. Included angle appears to be 44 degrees. I don't have AO Dave, so a description will work. That sounds like the problem I am seeing. With a 3-5 WL long V, I have about the same gain as a three element Yagi. But I'll still try to model your antenna with 5wl legs and 44 degree angle. Thanks. Hi Tom et al, This is from the AO library: F=24.94 The vertex is at the origin: 0,0 X,Y of 1st leg is 185.44', -74.92' #12 wire X,Y of 2nd leg is 185.44', 74.92' #12 wire Fed at the origin and modeled in free space AO reports Z= 255- J706 Forward gain= 11.34dBi F/B 2.70dB Hope this is useful, Dale W4OP |
#6
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V Beam, do they work?
Thanks guys. I tried the models and they still look poor. Let me
explain a bit... What is "good" gain? More than a 3 element yagi. What frequency? Well, I was trying 160, 80 and 40. I have a 300ft support at one point, and a bunch of 100ft trees a good distance away across open fields (maybe 800 feet). How high? Anything up to 300 ft at the feedpoint. Try this at 10 MHz. Dimensions in feet. That antenna almost equals a three element yagi in gain, but the 3 ele yagi has a HPBW of 60 degrees. The V beam has a HPBW of 18 degrees. Not so good. Even if I try two V beams, one inside the other, I can only get 3dB more gain. I was wondering if I was missing something, because I keep hearing stories about how good big V beams work. |
#7
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V Beam, do they work?
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#8
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V Beam, do they work?
I was just reading about them in the antenna handbook. The v-beam is better than a dipole and is directional, but the same wire bent half-way out to make a rombic seems to add more gain. you might look into it. Buck N4PGW On 22 Mar 2006 17:40:02 -0800, wrote: I've been modeling V beams off and on for a few years now, and never can seem to get one that has useful gain. Has anyone seen a successful model anyplace of a two or three wave V with good gain?? 73 Tom -- 73 for now Buck N4PGW |
#9
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V Beam, do they work?
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#10
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V Beam, do they work?
On Fri, 24 Mar 2006 12:04:51 -0500, Dave wrote:
wrote: SNIPPED It looks like a simple antenna, has a good reputation, but it doesn't look very useful for anything. Unless there is a combination I'm missing. 73 Tom I've never worked with a Vee antenna. But, while stationed at Hill AFB, Utah we used two of them back to back to make a Rhombic :-) to support the South East Asia phone patch nets during the Vietnam conflict. Fixed point to point communication [We had an LP that was used for stateside COMMs] My understanding is that a narrow beam is formed along the axis [centerline] of the Vee. In a standing wave antenna, the beam is bi-directional. In a terminated antenna, traveling wave, the pattern is unidirectional. The narrow beam width reduces interference from undesired directions. Tom is correct. Vee beams and rhombics have horrible sidelobes that make them in my estimation highly overrated. The vee is not completely bi-directional, a couple of dB FB is not uncommon. A vee, just like a rhombic can be terminated to increase the FB. If the legs are long enough it -is- a traveling-wave antenna and is somewhat self-terminating. The claim for broadband gain is also suspect. There are optimum parameters that are not frequency independent Of course I can't fault VK5MC's three-stack rhombic that gave me my two-meter WAC :-) Total wavelength and included angle have significant impact on performance. Of course. |
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