Topband: Effect of Trees

[Jim Brown]

On Sun, 3 Dec 2006 10:20:55 -0800, Michael Tope wrote:

>I am
>running about 1KW, but I still feel like I am running 
>barefoot. There may be a number of reasons for this:

You might also add 

1) The very nice antenna systems of some big 160 stations. Take a 
look at the links for K9DX and N6RO, for example. 

2) It's worth running HFTA on your site.

3) The high noise levels at the other end. 

I'm in a redwood forest, and own 8.5 acres of it, so this issue is 
of great interest to me as well. The short answer, based on what 
I've read and learned from others is that the absorption from 
trees increases more or less with frequency. I have two wires up 
for 160 -- a top-loaded vertical very similar to yours with 30 
radials 67 ft long, and a horizontal dipole at 100 ft. Both work 
pretty well. The ends of the dipole are within 5 ft of the trees 
that are holding it up. The vertical is near the middle of the 
clearing (roughly 250 ft diameter) that surrounds our house. 
There's a nice stand of five 70 ft birches within about 20 feet of 
the vertical. The radial system is far from symmetrical -- most of 
the radials are within an arc of roughly 200 degrees because there 
are buildings and landscaping in the way of the other directions. 

My site works pretty well on the low bands, six meters is sort of 
ok except for the ridge noted below, but is awful at VHF and UHF. 
We have NO cell phone coverage here, even though we're at 2,000 
ft. My neighbor, WA6NMF, has done some research on this. He says, 
at cell phone frequencies, "think -3dB/tree." I've seen similar 
comments from someone who installs/engineers cell sites and has 
tried to make them work in pine forests. 

My greatest challenge on HF are a couple of ridges within about 
1/2 mile that are roughly 200 ft above me and extend from roughly 
straight north down to about 160 degrees or so. This makes low 
angle radiation a challenge to the east coast, EU, AF, the 
Carribean, and South America. HFTA is really useful in figuring 
out what to do about this with horizontal antennas, but I don't 
know of an equivalent tool for vertically polarized antennas. 

73,

Jim Brown K9YC