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Inverted VEE Yagi antenna
Rick wrote:
I am seeking opinions as to the performance of such an antenna The opinion is it will be a great antenna. The modeling facts a It will give you approx. 11 dbi gain, and 13 db f/b. It will have a feedpoint Z at resonance (7.025 MHz) of 33.3+j0. The gain will vary from 11.24 dbi at 7 MHz to10.2 at 7.2 . . . Try deleting the parasitic element and see what the gain of just the driven element is. The difference between this and the Yagi gain is the gain relative to a single element at the same height. This is a more meaningful measure of gain than dBi for this application. Roy Lewallen, W7EL |
#2
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Inverted VEE Yagi antenna
On Mon, 12 Nov 2007 18:54:14 -0800, Roy Lewallen wrote:
Try deleting the parasitic element and see what the gain of just the driven element is. Ok, I did. The gain at 7 MHz went from 11.2 to 7.22 dbi, at 30 degrees elevation angle. Rick K2XT |
#3
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Inverted VEE Yagi antenna
On Nov 13, 8:05 am, (Rick) wrote:
On Mon, 12 Nov 2007 18:54:14 -0800, Roy Lewallen wrote: Try deleting the parasitic element and see what the gain of just the driven element is. Ok, I did. The gain at 7 MHz went from 11.2 to 7.22 dbi, at 30 degrees elevation angle. Rick K2XT That seems more reasonable... Heck, a NBS yagi with 3 elements only gives about 9.4 dbi plus or minus. MK |
#4
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Inverted VEE Yagi antenna
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#5
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Inverted VEE Yagi antenna
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#6
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Inverted VEE Yagi antenna
On Nov 13, 5:16 pm, Roy Lewallen wrote:
That's the gain of an NBS Yagi in free space. It's more like 13 or so over ground, depending on height and ground characteristics. Comparing the gain of one antenna over ground to another (for example a dipole) in free space is a trick often used by antenna manufacturers to fool naive people. Both must be in the same environment for a comparison to be meaningful. Roy Lewallen, W7EL I missed the part where he said it was modeled 23 m over ground.. But then you have to wonder about the ground quality used. Thats why I always quote antenna gain using free space numbers.. I often forget that some people don't always do this... :-/ Gives a level playing field that works for anyone no matter where they are. I never quote gain numbers including ground effects unless I specifically mention it due to some reason. And thats very rare. So I tend to constantly think in terms of free space gain most of the time if I'm thinking or talking about antennas not mounted in any specific location. One can always add the effects of ground themselves if they desire that for their local QTH. MK |
#7
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Inverted VEE Yagi antenna
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#8
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Inverted VEE Yagi antenna
so even if you point both a W8JK and dipole or W8JK and
Yagi in the direction of the same distant station, you might not see the predicted gain difference because of the different elevation patterns. ************************************************** *********** You might even think you have one way propagation.... denny -the devil made me do it- k8do |
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