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Good answer, its actually close to what I was looking for. I might have actually said this above, but an antenna model in freespace shows where an antenna is directly putting its signal, while an antenna modeled over an earth shows where the signal goes after the earth has played its part. IMHO, knowing what the antenna is doing with said radiation is the whole point of modeling. That being said, I was surprised that your freespace models in mmana-gal only had half a horizon, like an earth was present, yet they clearly said freespace. When I model freespace in 4nec2 I get a full 360 degree view of the vertical pattern. I wonder if there is a setting in mmana-gal to change that? There are times when you want the antenna to put a signal lower than the horizon. RF steering for a repeater on top of a mountain for example, you want to steer its output to the town/city down in the valley, not go straight out and overshoot it. Also, in general, any time where you are determining how well an antenna works locally, depending on how its mounted you want to see the 0 degree mark, and in many cases the area just below the horizon.

If there is anything within two wavelengths of an antenna, I would assume that to some extent it is affecting the antenna's impedance, and by extension SWR. If the antenna is longer than a half wavelength then this reach is actually further than two wavelengths. When I purchased my first VNA, one that could scan through a bunch of frequencies, I noticed that on the CB band a car passing over 30 feet away would affect SWR as it passed by, it would increase SWR by .2 before dropping back to normal, and hte next scan this bump would be gone. It actually took me a while to figure out the cause. Another thing that affected the SWR curve was birds that when they flew right by the antenna. Of course these things affect the radiation pattern as well, and sometimes you will be surprised by how much, while others you will be surprised by how little.

The DB

<blockquote data-quote="The DB" data-source="post: 777399" data-attributes="member: 21346">Good answer, its actually close to what I was looking for.&nbsp; I might have actually said this above, but an antenna model in freespace shows where an antenna is directly putting its signal, while an antenna modeled over an earth shows where the signal goes after the earth has played its part.&nbsp; IMHO, knowing what the antenna is doing with said radiation is the whole point of modeling.&nbsp; That being said, I was surprised that your freespace models in mmana-gal only had half a horizon, like an earth was present, yet they clearly said freespace.&nbsp; When I model freespace in 4nec2 I get a full 360 degree view of the vertical pattern.&nbsp; I wonder if there is a setting in mmana-gal to change that?&nbsp; There are times when you want the antenna to put a signal lower than the horizon.&nbsp; RF steering for a repeater on top of a mountain for example, you want to steer its output to the town/city down in the valley, not go straight out and overshoot it.&nbsp; Also, in general, any time where you are determining how well an antenna works locally, depending on how its mounted you want to see the 0 degree mark, and in many cases the area just below the horizon.If there is anything within two wavelengths of an antenna, I would assume that to some extent it is affecting the antenna&#039;s impedance, and by extension SWR.&nbsp; If the antenna is longer than a half wavelength then this reach is actually further than two wavelengths.&nbsp; When I purchased my first VNA, one that could scan through a bunch of frequencies, I noticed that on the CB band a car passing over 30 feet away would affect SWR as it passed by, it would increase SWR by .2 before dropping back to normal, and hte next scan this bump would be gone.&nbsp; It actually took me a while to figure out the cause.&nbsp; Another thing that affected the SWR curve was birds that when they&nbsp; flew right by the antenna.&nbsp; Of course these things affect the radiation pattern as well, and sometimes you will be surprised by how much, while others you will be surprised by how little.The DB</blockquote>

[QUOTE="The DB, post: 777399, member: 21346"] Good answer, its actually close to what I was looking for. I might have actually said this above, but an antenna model in freespace shows where an antenna is directly putting its signal, while an antenna modeled over an earth shows where the signal goes after the earth has played its part. IMHO, knowing what the antenna is doing with said radiation is the whole point of modeling. That being said, I was surprised that your freespace models in mmana-gal only had half a horizon, like an earth was present, yet they clearly said freespace. When I model freespace in 4nec2 I get a full 360 degree view of the vertical pattern. I wonder if there is a setting in mmana-gal to change that? There are times when you want the antenna to put a signal lower than the horizon. RF steering for a repeater on top of a mountain for example, you want to steer its output to the town/city down in the valley, not go straight out and overshoot it. Also, in general, any time where you are determining how well an antenna works locally, depending on how its mounted you want to see the 0 degree mark, and in many cases the area just below the horizon. If there is anything within two wavelengths of an antenna, I would assume that to some extent it is affecting the antenna's impedance, and by extension SWR. If the antenna is longer than a half wavelength then this reach is actually further than two wavelengths. When I purchased my first VNA, one that could scan through a bunch of frequencies, I noticed that on the CB band a car passing over 30 feet away would affect SWR as it passed by, it would increase SWR by .2 before dropping back to normal, and hte next scan this bump would be gone. It actually took me a while to figure out the cause. Another thing that affected the SWR curve was birds that when they flew right by the antenna. Of course these things affect the radiation pattern as well, and sometimes you will be surprised by how much, while others you will be surprised by how little. The DB [/QUOTE]

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