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#1
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Modeling the effect of a tower
How do you guys model the parasitic effects of
a tower? With its base in concrete, it is neither floating nor grounded. Is there some sort of modeling rule for such? For instance, if a vertical with sloping radials is mounted on a tower with the radials insulated from the tower, the tower still has an effect. If we model the tower as mininec grounded, it has some extreme effects which may not be realistic. -- 73, Cecil http://www.w5dxp.com |
#2
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Modeling the effect of a tower
Cecil Moore wrote in news:6F0Ih.1335$FG1.829
@newssvr27.news.prodigy.net: How do you guys model the parasitic effects of a tower? With its base in concrete, it is neither floating nor grounded. Is there some sort of modeling rule for such? For instance, if a vertical with sloping radials is mounted on a tower with the radials insulated from the tower, the tower still has an effect. If we model the tower as mininec grounded, it has some extreme effects which may not be realistic. I know that some assert that a metal tower structure in concrete foundations is effectively earthed for lightning protection, wouldn't you also have some form of additional lightning protection that the RF effects would be important to include in your model? Owen |
#3
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Modeling the effect of a tower
Owen Duffy wrote:
I know that some assert that a metal tower structure in concrete foundations is effectively earthed for lightning protection, wouldn't you also have some form of additional lightning protection that the RF effects would be important to include in your model? I have no additional lightning protection. I just want to gather thoughts on modeling a concrete based tower located within the fields of an antenna. Modeling it connected to mininec ground just doesn't seem to provide realistic results. -- 73, Cecil http://www.w5dxp.com |
#4
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Modeling the effect of a tower
Cecil Moore wrote:
How do you guys model the parasitic effects of a tower? With its base in concrete, it is neither floating nor grounded. Is there some sort of modeling rule for such? For instance, if a vertical with sloping radials is mounted on a tower with the radials insulated from the tower, the tower still has an effect. If we model the tower as mininec grounded, it has some extreme effects which may not be realistic. I'll be a bit glib here.. I wouldn't use mininec to model it, just because it doesn't do a good job for those sorts of things. Hie thee to NEC4, which is specifically designed to deal with antennas near, on, touching, partially and fully immersed in the ground. And even then, you can get bitten. in practical terms, the impedance to "ground" of a concrete base is very low.. large contact area with the soil, reasonably good conductivity of the concrete itself (compared to soil, and especially compared to air). if that level of subtle detail is important, you need some sort of Finite element or finite differences code. When I want to assess the sensitivity with something like NEC, I start by just modeling the "widget" with a single wire, or maybe, a few wires. Then, see how much difference it makes to change that simplified model a bit (maybe move it a few inches or change the length a bit). if it doesn't make much difference, there's not much interaction, and the inaccuracy of the simple model will be small. |
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