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#1
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Long inverted V not working well, why?
On Sat, 12 May 2007 08:02:52 -0400, "Rick (W-A-one-R-K-T)"
wrote: I just put up an inverted V that is up about 70 feet in the center and about 15 feet at the ends. Each leg is about 130 feet long, or about 260 feet overall, which is right around a half wave for 160 meters. It is fed with ladder line and an LDG auto-tuner. I also have a dipole antenna that's up about 17 feet and is a half wave for certain MARS / CAP frequencies above the 75 meter band, hence it's a bit short for 75 meters. That antenna is coax fed and goes through a different LDG auto-tuner which allows me to use it on 75/80 meters with a good match. The long and high inverted V doesn't work any better than the short and low dipole, and in some cases doesn't work as well. I have checked all the connections on the inverted V and even did a continuity check from each side of the ladder line, up through the feed point, out each leg to the end of each leg, and all seems OK. I have tried switching auto-tuners (taking the one that's on the coax-fed dipole and putting it on the inverted V) with no discernible difference. Seems very strange. Any ideas that might account for why the V doesn't work better? http://www.cebik.com/wire/vang.html |
#2
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Long inverted V not working well, why?
On Sat, 12 May 2007 06:42:30 -0700, Danny Richardson wrote:
http://www.cebik.com/wire/vang.html Good morning, Danny. Thanks for the pointer. That one was a real eye opener. I always thought that any angle 90 degrees or greater at the feedpoint was OK. I think mine is something like about 100 degrees. I'll see if I can raise the ends up a bit and see what difference that makes. |
#3
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Long inverted V not working well, why?
On Sat, 12 May 2007 10:37:13 -0400, Rick (W-A-one-R-K-T) wrote:
Thanks for the pointer. That one was a real eye opener. I always thought that any angle 90 degrees or greater at the feedpoint was OK. I think mine is something like about 100 degrees. Actually I just calculated it out and it's more like around 130 degrees, or each leg is just 25 degrees down from horizontal. So, according to Cebik that should be pretty good. |
#4
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Long inverted V not working well, why?
Rick (W-A-one-R-K-T) wrote:
On Sat, 12 May 2007 10:37:13 -0400, Rick (W-A-one-R-K-T) wrote: Thanks for the pointer. That one was a real eye opener. I always thought that any angle 90 degrees or greater at the feedpoint was OK. I think mine is something like about 100 degrees. Actually I just calculated it out and it's more like around 130 degrees, or each leg is just 25 degrees down from horizontal. So, according to Cebik that should be pretty good. What is the length of your feedline? -- 73, Cecil http://www.w5dxp.com |
#5
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Long inverted V not working well, why?
On Sat, 12 May 2007 12:47:32 -0500, Cecil Moore wrote:
What is the length of your feedline? That I don't know at the moment. I downloaded your imax.exe program and ran some numbers. There sure aren't very many numbers that are good for all bands 160 through 10. No doubt my feedline is wrong for a lot of frequencies, made more clear by the fact that there are a few frequencies where my LDG autotuner can't find a match. However, how much does the feedline length matter IF the autotuner is able to find a good match point? I can get 1.5:1 or better from everywhere in the 160 and 80 meter bands, and the high end of the 40-meter band (on the low end I can't get below about 2:1). I'm about to go outside and try some different feedline lengths. |
#6
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Long inverted V not working well, why?
Rick (W-A-one-R-K-T) wrote:
No doubt my feedline is wrong for a lot of frequencies, made more clear by the fact that there are a few frequencies where my LDG autotuner can't find a match. However, how much does the feedline length matter IF the autotuner is able to find a good match point? Some impedances are outside the matching range and some impedances are barely inside the matching range. Some of the latter may not be a "good" match point. I model my antenna systems to get a ballpark idea of what impedance I am up against and use an antenna analyzer to fine tune the system. -- 73, Cecil http://www.w5dxp.com |
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