Oregonian Haruspex wrote:
On 2014-10-15 22:04:30 +0000, said:
How much control do you have over the local ground or nearby objects?
Depends on your location, really. Some to lots, in general. It's
possible to change your local ground (especially directly under the
antenna) with soil emendation and moisture control though this is never
even considered or mentioned in any amateur or professional radio texts
as far as I have seen.
How much control do you have over the design of an antenna you are
designing?
Some to lots, depending on your budget and the space available.
On the contrary, first you analyze the antenna, then add nearby objects
to the model and adjust the ground conditions to your real ones.
I suppose that's one way. It seems unnecessarily slow and methodical
though, especially as most (all?) models are either terrible at
accounting for enarby objects, or fail to do so entirely. So you take
your rough model and start trying to account for trees, the local
topography, and pretty soon it's two years later and you haven't even
bought your antenna supplies let alone run the coax because you're
still trying to account for what happens when the geese fly over the
antenna in November.
Yeah, sure.
I guess some people are just slower than others.
I few things I might point out.
If you are conerned about nearby objects you only have to model them once.
In the real world most nearby objects can be ignored; most either have
an insignificant effect on an antenna or an effect in one direction only.
If there is a field full of 10M tall poles surrounding you, they will effect
your 40M vertical, but this is not a likely situation.
The time required to get an antenna "right" through modeling is in
general much less than the time it takes through cut and try, even
with things like antenna analyzers and it wastes a lot less material.
--
Jim Pennino