Topband: Effect of trees- tree appreciation

[Tom W8JI]

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