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4nec2 advice sought...
Greetings to one and all,
Hopefully someone will be able to advise me on the following, being very new to NEC modelling I've hit a stumbling block. As part of my Masters dissertation (In RF Engineering) I am working on developing an N element antenna array in the V/UHF area of the spectrum for a field system (non-amateur). It's nothing that's not really been done before, but I'm taking the practical 'ham' approach to it. Anyway this is only background to my question, and is not really too relevant. I decided to have a go with some modelling software before actually building an array ad testing it. It just so happens that I had installed 4nec2 many moons ago though I'd never used it. For some reason I had it in my head that modelling an antenna was difficult. Well I'm sure it takes a lot of thought to do a complex model, and the simple models I've done so far have been quite a learning curve, but a fun one at that. Anyway, I have modelled what is essentially a 4-square above ground and so on, which is fine. The next stage was to make the array out of dipoles. This went fine when modelling in free space, centring around z=0. I get lovely 3D plots etc, wonderful! Now I want to model this dipole arrangement as if it was mounted on a tower, i.e. not at z=0. So I move all the elements up to the correct height and add in a real earth (which adds itself at z=0). That much is fine. When I then run the model the radiation plots are still all centred on z=0. Now, logic says to me that the radiation should be coming from the driven antenna elements rather than a point on the ground beneath them. Am I missing something really simple here? Many thanks in advance. :-) -- 73, Iain M0PCB/AD5XI |
4nec2 advice sought...
Hi Iain
You are displaying the far field radiation pattern, not the close-up energy density... ie the antenna and height above ground is very small compared to the radiation pattern being displayed. Cheers Bob Iain Kelly wrote: Now, logic says to me that the radiation should be coming from the driven antenna elements rather than a point on the ground beneath them. Am I missing something really simple here? Many thanks in advance. :-) |
4nec2 advice sought...
Bob Bob wrote:
Hi Iain You are displaying the far field radiation pattern, not the close-up energy density... ie the antenna and height above ground is very small compared to the radiation pattern being displayed. Cheers Bob Aha, so it's just a matter of scale in the plot then? That's what was confusing me. My mind was looking to directly compare the 3D pattern generated with the antenna structure. It makes a bit more sense now. Cheers, -- 73, Iain M0PCB/AD5XI |
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