I expect the losses are related to current not voltage. The current of my
antenna is in the vertical section for the most part and loss would would
have to happen there as coupled to the nearest tree. The current would have
to flow to ground so I seriously doubt if the resistance of the trunk is low
enough to conduct any significant current to ground. Any loss in the top hat
where the voltage is probably would amount to much power; the current has
already flowed in the vertical section where I want it to.>>>>
While I'm sure you are right about losses, and the losses are probably
somewhat small, it isn't for the reason above. The real reason is a tree has
such high resistance it can't sap (pardon) most of your TX power.
The same things that make a tree a terrible (or virtually nonexistent)
antenna also cause it to not have significant effect unless the electric
field is right into the tree, or it is a pretty thick woods. The problem is
no one really know how much loss there really is.
But................ the antenna is a closed system. A high resistance to
ground at the high voltage end of things can cause just as much loss as a
low series resistance at the current end of things. It **isn't ** that
current has already flowed past where you wanted it. It isn't that because
it flowed, losses at the top do not matter. Losses at the voltage point
certainly do matter. You can create a pretty poor antenna if you terminate
the open end of a short antenna in a resistance.
The real reason antennas in trees make people happy is the loss in the
system making them happy is not really noticeable to them. I can't notice 6
dB loss at times, unless with an A-B test or by measuring things.
73 Tom
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Topband Reflector
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