On 12/28/2011 6:18 PM, Jim Lux wrote:
> For a given voltage at the feedpoint, the current in the tree will be
> 1/30,000th that in wire. The power dissipated is that squared.. or, in
> other words, negligible.
> This is a fascinating observation...
Indeed it is.
> IN other places, we've discovered that trees are like soil (similar
> conductivity and epsilon), and we know that laying an antenna on the
> ground doesn't work all that well. However, that's the difference
> between half of the space being occupied by the lossy medium and just a
> tree's worth.
When thinking about attenuation in a forest, it should be remembered
we're talking about a DENSE forest, a lot of big trees relatively close
together, and some of those studies you've cited are talking about
jungles. This is very different from hanging a wire in/near a single
tree or a few trees. A very dense forest like mine, or the pine forests
of the American South East, are somewhat analogous to the lossy soil.
> To compare.. if I put two 8 foot rods into the soil 10 meters apart,
When I've measured resistance between two rods a few yards apart in the
loamy soil of my redwood forest, the lowest DC R I've seen is on the
order of 30 ohms. This is with a Simpson 260.
Thanks for a VERY interesting post, and the digging that's behind it.
I'll be chewing on it for a while, and I suspect others will too!
73, Jim K9YC
TowerTalk mailing list